documented - University of Oxford

PHOTOGRAPHS 

Front cover 

Acacia karroo in flower in a sorghum field in the Umguza Valley near Bulawayo, Zimbabwe 

(Photograph I.H.W. Bickle) 

Back cover 

Above: People of Ntabazinduna Communal Area in Zimbabwe nurture and prune the Acacia 

karroo to provide shade and fodder for their livestock 

Below: Goats browsing Acacia karroo near Queenstown in South Africa where, properly 

managed, the trees make a valuable contribution to increasing productivity of the range in this 

environment 

Oxford Forestry Institute 

South Parks Road 

Oxford OXl 3RB 

United Kingdom 

Telephone: 

Fax: 

Email: 

+44 (0)1865 275 000 

+44 (0)1865 275 074 

richard.barneS@plants.ox.ac.uk

TROPICAL FORESTRY PAPERS 

No. 32 

Acacia karroo 

MONOGRAPH 

AND 

ANNOTATED BIBLIOGRAPHY 

R. D. Barnes, D. L. Filer and S. J. Milton 

Oxford Forestry Institute 

Department of Plant Sciences 

University of Oxford 

1996

ISBN 0 85074 138 6 

ISSN 0141 9668 

Printed and bound in Great Britain by Nuffield Press, 21 Nuffield Way, Abingdon, Oxon OX14 lRL

PREFACE 

It is one oflife's many anomalies that a tree species that now epitomises the concept of multi-purpose trees and shrubs should 

have been the subject ofconsiderable research on its eradication as a weed. Until the last decade, Acacia karroo was considered 

a major threat to pastures and farmland in southern Africa and little was known of its genetic variation, or of its management 

and productivity. Largely as a result of work at the Oxford Forestry Institute, and Dr Barnes in particular, we now have a much 

fuller appreciation of the species as a valuable and manageable resource, offering a wide range of marketable and domestic 

products as well as a number of characteristics that improve the soil and social environments. 

This monograph provides an annotated bibliography of all the relevant literature and a critical monograph on the species, one 

ofthe most widespread and important ofall the Acacia species. The authors have considerable experience in the field, laboratory 

and library that permit them to produce such an integrative review with excellent field photographs and computer generated 

maps. The monograph will be of value to rural development specialists, agriculturalists, foresters and extension workers 

throughout the dry zones of Africa, particularly in the southern half of the continent where the species is indigenous. It will 

stimulate further research and development of the species for enhanced socioeconomic productivity of the tree itself and of the 

crops, animals and environments that it supports. 

J Burley 

Director, Oxford Forestry Institute 

iii

TABLE OF CONTENTS 

ACKNOWLEDGEMENTS ix. 

INTRODUCTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1 

NOMENCLATURE AND TAXONOMY 2 

The place ofAcacia ka"oo in the genus Acacia 2 

Nomenclature 2 

Vernacular names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3 

Botanical description 3 

Representative specimens 6 

Related species 10 

Natural hybrids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 10 

GENETIC VARIATION 10 

Morphological variation 10 

Biochemical variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 13 

Sampling variation for genetic evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 13 

REPRODUCTIVE BIOLOGY . . . . . . .. 13 

Cytology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 13 

Sporogenesis, embryology and pollination 15 

Breeding system 15 

Pollinating and seed dispersal agents 15 

DISTRmUTION AND ECOLOGY 16 

Natural distribution 16 

Ecology 16 

Climate 16 

Soils 16 

Vegetation types and succession . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 17 

Associatedfungi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 17 

Rhizobia 18 

GROWTH HABITS 18 

Life cycle 18 

Growth patterns 19 

Flower and fruit phenology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 20 

PREDATORS, DISEASES AND HARMFUL PHYSICAL AGENCIES 20 

Biotic factors 20 

Anirrza.ls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 20 

Insects 20 

Parasitic plants andfungi 21 

Abiotic factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 21 

Fire 21 

Drought 22 

Frost 22 

PRODUCTS AND USES 22 

Wood 22 

Anatomy 22 

Fuelwood 22 

Round and sawn wood 23 

Pulp 23 

Bark 25 

Gum 25 

History, specifications and trade 25 

Chemistry 26 

Collection and marketing 26 

Ot1le.r uses for gwn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 26 

Fodder 27 

Medicine and food 29 

Soil amelioration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 29 

v

vi 

ESTABLISHMENT, YIELD AND MANAGEMENT 29 

Establishment 30 

Seed collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 30 

Seed storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 30 

Seed pretreatf11,(!.nt 30 

Nursery 30 

Planting 31 

Yield and management 31 

Wood 31 

Browse 34 

Control ofinvasion 36 

CONCLUSIONS AND FUTURE RESEARCH 37 

ANNOTATED BIBLIOGRAPHy 39 

AUTHOR INDEX 75 

LIST OF TABLES 

Table 1 Provenances of Acacia karroo collected by the Oxford Forestry Institute 

for genetic evaluation in the international African Acacia trials network 14 

Table 2 Acacia karroo: kraft pulping tests: handsheet properties compared with 

Eucalyptus grandis 24 

Table 3 Acacia karroo: dissolving pulp yields, viscosity, brightness and kappa 

compared with three Australian acacias 24 

Table 4 Proximate nutritional and mineral analyses ofAcacia karroo foliage and 

pods from the Cape Province in South Africa . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 28 

Table 5 An analysis ofpercentage of leaf nitrogen (%N), nitrogen 15 ratio e 5 N) 

and carbon 13 ratio ( l3 C) for leaf samples from Acacia karroo compared 

with Acacia erioloba, A.fleckii, A. nilotica ssp. kraussiana, A. tortilis ssp. 

heteracantha and Faidherbia albida . . . . . . . . . . . . . . . . . . . . . .. 28 

LIST OF FIGURES 

Figure 1 Acacia karroo. Botanical drawings ofbranchlets, leaves, stipular spines, 

pods and glands 4 

Figure 2 Acacia karroo. Botanical drawings ofbranchlets, leaves, pinnules, glands, 

flowers and pods 5 

Figure 3 Leaves from six-month-old seedlings of ten provenances ofAcacia karroo ..... 11 

Figure 4 Acacia karroo,A. rehmanniana andA. karroo xA. rehmanniana hybrid. 

Botanical drawings ofbranchlets, leaves, pinnules, glands and flowers . . . . . . . .. 12 

Figure 5 flowering and fruiting phenology ofAcacia karroo 32 

Figure 6 Relationship between basal area at breast height and total over-bark volume 

to 5 cm minimum branch diameter for a stand ofAcacia karroo 32 

Figure 7 Relationship between basal area at ankle height and total over-bark volume 

to 5 cm minimum branch diameter for a stand ofAcacia karroo 32 

Figure 8 Total wood volume production per year in cubic metres and the annual rainfall 

during the life of a natural stand ofAcacia karroo 33 

Figure 9 Total cumulative wood volume in cubic metres and the number of stems that 

contributed to that volume in each year during the life of a natural stand of 

Acacia karroo 33

LIST OF PLATES 

Plate 1 

Plate 2 

Plate 3 

Plate 4 

Plate 5 

Plate 6 

A Typical yellow flowers 

B Pale flowers from Bazaruto Island, Mozambique 

C Spines from the coastal dune forests in Zululand 

D Inflated spines from eastern Zimbabwe 

E Unopened pods 

F Dehisced pods with seeds still suspended by the funicle 

A Bark characteristic of the coastal dune forests 

B Bark characteristic of the main range 

C Putative natural hybrid with A. rehmanniana 

D Rowers ofA. karroo (left), A rehmanniana (right) and the 

natural hybrid between them (centre) 

E Seedlings of the Bazaruto Island, Mozambique, provenance at six months 

F Seedlings of the Jedibe Island, Botswana, provenance at six months 

G Seedlings of ten provenances at six months from sowing 

A Distribution plotted from herbarium specimens ofprecisely known origin 

B Seed collection localities for genetic evaluation trials 

A Frequency of the peroxidase band M in an electrophoretic study of 63 

populations that cover the entire natural range 

B Frequency of the peroxidase band K in an electrophoretic study of 63 

populations that cover the entire natural range 

A In scrub near the coast in the eastern Cape Province of South Africa 

B On the beach on Bazaruto Island in Mozambique 

C In the coastal dune forest ofZululand, South Africa 

D On black vertisols in the Umguza Valley, Matabeleland, Zimbabwe 

E On a salt-encrusted island in the inland Okavango Delta in Botswana 

F In the Bokaap district of Cape Town 

G In the Kalahari Gemsbok National Park in South Africa 

A Lush perennial Panicum maximum pasture beneath the trees 

B The trees follow A. erioloba in being among the first to flush at the end of the 

dry season 

C Foliage and flowers in reach are heavily browsed by domestic and wild animals 

D The species nodulates early and prolifically 

E Intensive root system on a tree uprooted in the coastal sand dunes 

F The parasitic mistletoe, Viscum sp., is conspicuous after it has been killed by a 

heavy frost while the tree has survived 

G Extensive root system exposed ofa tree growing near a river in a black vertisol 

vii

viii 

Plate 7 Acacia ka"oo 

A Gum exudation from the inner bark associated with wood-boring insect 

activity 

B The larvae of a number of Cerambycid beetles bore in the sterns 

C The thin continuous line of marginal parenchyma can be distinguished in 

transverse section of the wood from the aliform parenchyma associated with 

the vessels 

D The chambered cells of the marginal parenchyma are crystalliferous 

E Drought and wood boring insects stimulate gum production at the end of 

the dry season 

F The marginal parenchyma has been shown, by wounding experiments, to be 

laid down annually during the dry season 

G The crystals in the marginal parenchyma have been identified as calcium 

oxalate by scanning proton microprobe 

H The fungus Ravenelia macowaniana on pods: the galls are inhabited by an 

assemblage of microlepidoptera 

Plate 8 Acacia ka"oo 

A Gum being weighed before purchase at a buyer's factory in Bulawayo, 

Zimbabwe 

B Tapping gum from the stem for laboratory analysis 

C Gum collectors queuing at the factory door in Bulawayo, Zimbabwe, 

to sell their loads 

D Pure stands established to rehabilitate coastal dunes after the forest has 

been removed for the mining of titanium 

E The species is a preferred frrewood in all parts of its range 

F A young stand in the Umguza Valley near Bulawayo, Zimbabwe, pruned 

to let in light for grasses and to give access for domestic stock 

G The only green grass after a drought in what would normally be lush green 

pasture is under the trees where the shade and soil fertility provide a suitable 

environment for the more nutritious and deeper-rooted perennial grasses such 

as Panicum maximum

ACKNOWLEDGEMENTS 

It would not be possible 10 thank individually all the people and organizations who have assisted us at the various stages of the 

conduct of Project R4526 - Acacia karroo: evaluation and assembly of genetic resources - under which the production of 

this monograph and armotated bibliographyhas been funded. We are very grateful to them all for the help and infonnation they 

have given and for their interest. In particular we should like to thank the following:- 

for logistical support and permission to carry out research - Zimbabwe Forestry Commission; Department of National 

Parks and Wildlife Management, Zimbabwe; Natal Parks Board; Richards Bay Minerals; National Parks Board of South 

Africa; Sappi Forests; Direccao Nacional De F10restas E Fauna Bravia, Mozambique; Ministry of Agriculture, Water and 

Rural Development, Namibia; Umguza Valley Estates, Zimbabwe; National Herbarium and Botanical Gardens, Zimbabwe; 

Forestry Research Institute ofMalawi; kwaZulu Bureau ofNatural Resources; lYSIS, Swaziland; Department of Agriculture, 

Zambia; Forestry Association of Botswana; 

for assistance in preparation ofthe annotated bibliography - Richard Dean, Catherine Dorey, Kristina Plenderleith; 

for the botanical drawings - Rosemary Wise; 

for assistance with the maps - William Hawthome; 

for assistance in seed collection - Jennifer Bickle, Peter Brain, Paul Clegg, Richard Dean, Derek Donald, Christopher Fagg, 

John Garikayi, Herta Kolberg, Kenneth Ngwarayi, Richard Seward, Frank Woodvine, Gerrit van Wyk; 

for permission to publish selected abstracts - CAB International, Wallingford, OXIO 8DE, UK; 

for stimulating ideas and discussion - Jonathan Timberlake, Tom Muller and Jennifer Bickle; 

for critical review ofthe text - Jeff Burley, Jonathan Timberlake, Dick Willan; 

for final editing and formatting - Liz Pearce. 

We gratefully acknowledge the help of the Botanical Research Institute in Pretoria for generously providing the computerized 

infonnation on the botanical specimens ofAcacia karroo held in South Mrican herbaria. Without this we would not have been 

able to complete the distribution and phenological studies. 

We thank Or. Peter Brain particularlyfor the great enthusiasm with which he agreed to extend his original leaf peroxidase study 

ofAcacia karroo and the industry and interest with which he has analyzed all the leaf samples we have sent him. The results 

of this work are summarized here but are being published in full elsewhere. 

Many of our colleagues at the Oxford Forestry Institute have given us support and this has been much appreciated. The 

assistance we have received from Christopher Fagg throughout the project both in the field and with specimen entry in 

BRAHMS has been invaluable. The studies of!an Gourlay and Julie Smith on the productivity studies and of Stephen Harris 

and Phanuel Oballa on the isozymes have been particularly valuable contributions to the knowledge on Acacia karroo; the 

results oftheir work are quoted here but are being formally published elsewhere. 

The project was funded through the Forest Research Programme of the Overseas Development Administration of the 

Government of the United Kingdom. 

ix

Woodlands are a crucial component of farming systems in 

the communal lands of Africa. Increasing population 

pressure and devastating droughts have brought about 

deforestation and severe land degradation in the dry zones of 

the continent. Rural populations in these areas face great 

hardships and are becoming increasingly vulnerable to 

climatic change. hnproving their quality of life is dependent 

on increasing yields from cultivated crops, on realizing more 

of the potential for livestock production and on providing 

wood for fuel and poles. This can be done most effectively 

by developing and promoting the use of trees in 

agrisilvopastoral systems. 

The useful species in the original climax tree communities 

in the savanna woodlands are rapidly disappearing. Even 

given favourable conditions, they would take many years to 

re-establish themselves. Attempts to remedy the situation 

with exotic species have met with limited success. It is 

among the indigenous pioneers that there is greatest 

potential now to increase productivity from both arable and 

non-arable land. 

As pioneers, species of the genus Acacia are unrivalled by 

any other group of trees and shrubs in the combined 

importance of their distribution throughout the seasonally 

dry to arid regions of the continent, their varied ecologies, 

their ability to colonize and rehabilitate degraded sites and 

their relatively fast growth. They are commonly found 

throughout the continent and are of great ecological and 

socio-economic importance; they have evolved over the 

millennia with the larger herbivores for which they provide 

highly nutritious fodder and which, as a result, disperse the 

seeds; and, traditionally, rural man and his livestock have 

exploited these trees for many purposes. 

Acacia karroo is foremost among the acacias in southern 

Africa as regards both range and uses. It occurs in 

Zimbabwe, Botswana, Swaziland, Lesotho, Namibia, South 

Africa, Mozambique, Zambia, Malawi and the south of 

Angola. It varies from a shrub to a tree more than 20 m in 

height and grows from sea level to 1800 m on soils ranging 

INTRODUCTION 

Introduction 

from pure unconsolidated sand to heavy clays with an annual 

rainfall from 1500 mm down to less than 200 mm where 

ground water is available along drainage lines and around 

pans and dams. The species fixes nitrogen, provides shade, 

stabilizes sand dunes and disturbed areas and is resistant to 

drought, frost, fire and salinity. The leaves, flowers, pods 

and its parasitic mistletoes are excellent fodder, it yields a 

high quality clear gum with many uses and it is a good bee 

tree in that it provides quantities of pollen and nectar and 

can flower three or four times a year. The wood is an 

excellent fuel, the bark can be used for tanning, the inner 

bark makes good cord and the sawn timber can be used for 

general purposes. A. karroo is therefore very much a 

multipurpose tree with great potential for increasing 

productivity in agroforestry and silvopastoral systems over 

a wide range ofsites in the dry zones of the tropics and subtropics. 

Ithas been described as being an asset on any farm. 

This Tropical Forestry Paper is based principally on the 

work done on Project R4526 - Acacia karroo: evaluation 

and assembly of genetic resources at the Oxford Forestry 

Institute (OFI) in the Department of Plant Sciences, 

University of Oxford. The project was funded by the 

Forestry Research Programme (FRP) of the Overseas 

Development Administration (ODA) of the Government of 

the United Kingdom. One objective of the project was to 

supply seed for genetic evaluation of the species across its 

entire range; this collection has now been completed and the 

seed is available from the OFI. A second objective was to 

develop BRAHMS, the Botanical Research And Herbarium 

Management System; the taxonomic treatment and 

distribution maps contained in this publication are products 

of this database. The third major objective was to conduct 

a literature search on the species and to disseminate all 

knowledge available. That is accomplished in this 

monograph and annotated bibliography. The monographic 

part of the paper summarizes all the information that has 

been compiled on the species whereas the abstracts in the 

bibliography provide a path for the reader to focus on 

specific aspects. 

Oxford Forestry Institute Tropical Forestry Paper No. 32

Vernacular names 

muBayamhondoro (Shona); Butema (Kalanga); Gaba 

(Kalanga); Mimosa thorn (English); Mooka (Tswana); 

Mookana (bush) (Tswana); isiNga (Ndebele); Orusu 

(Herero); Soetdoring (Afrikaans); Sweet thorn (English); 

muUnga (Shona); umuNga (Zulu). (Timberlake, 1980; 

Wild et al., 1972). 

[References:- 27,67,233,258] 

Botanical description (Modified from Ross (1979» 

Habit a shrub to 2 ID, often several-stemmed, or a tree 25 m 

high, crown typically somewhat rounded or flattened; 

sometimes tree very slender, spindle-like and sparsely 

branched. Bark longitudinally fissured, reddish-brown to 

dark brown or black and rough or pale greyish-white or 

greyish-brown and smooth, the latter often with scattered 

persistent spines; smaller branches «50 mm) roughish, 

rusty red, sometimes with some grey, discontinuous, peeling 

striations and persisting thorns; young branchlets bright 

green, typically glabrous but occasionally densely 

pubescent, eglandular or with small inconspicuous reddish 

sessile glands, epidermis flaking off to expose a dark 

rusty-red non-powdery inner layer or sometimes smooth and 

persistent. Stipules spinescent, in pairs, mostly 0.4-7 (10) 

cm long but sometimes to 25 cm long and then usually 

slightly fusiform-inflated and up to c. 1 cm in diameter, 

remaining distinct to the base and not confluent, straight or 

slightly curved or deflexed. Leaves typically glabrous but 

occasionally densely pubescent: petiole 0.5-1.8 cm long, 

adaxial gland usually present; rachis (0) 1-5 (9) cm long, 

with a gland at the junction of each or some pinnae pairs; 

pinnae (1) 2-6 (13) pairs; rachillae (1) 1.5-4 (7.2) cm long; 

leaflets 5-15 (27) pairs per pinna, (2.8) 3.5-8 (12.5) x 1-2.5 

(5) mm, linear to obovate-oblong, eglandular, apex rounded 

to subacute but not spinulose mucronate, usually glabrous 

sometimes pubescent beneath. Inflorescences on the 

current season's growth, capitate, fascicled or solitary on 

axillary peduncles, sometimes aggregated into more or less 

leafless terminal "racemes"; peduncles 0.7-2.4 (4) cm long, 

usually glabrous; involucel 113 - Y2 way up the peduncle. 

Flowers bright yellow. Calyx 1.25-2 mm long, glabrous 

throughout or apices oflobes pubescent. Corolla 2.5-3 mm 

long, glabrous or almost so. Pods brown, (4) 5-10.5 (21) x 

0.5-0.7 (1.1) cm, linear, usually more or less falcate, usually 

± constricted between the seeds, often distinctly, mostly 

glabrous but at times densely tomentellous, sometimes 

inconspicuously glandular. Seeds (3.5) 4.5-6.5 (9) x (2) 3-4 

(7) mm, elliptic, lenticular or sometimes ± quadrate, 

compressed; areole 3-5.5 (7) x 2-3.5 (4.5) mm. (See 

Figures 1-4; Plates lA-F and 2A-B). 

little has been published on the root morphology of Acacia 

karroo. Exposure ofroot systems has shown that it can vary 

with site conditions from being extensive in heavy soils as 

seen on eroded river banks (Plate 6F) (Bayer, 1943) to 

Nomenclature and taxonomy 

being intensive on coastal dunes (Plate 6E). It is alTIOng the 

first trees to flush in the spring at the end of the dry season 

and it can maintain a luxuriant green crown even when the 

rains fail which suggests that it can exploit soil moisture 

reserves at great depth (Plate 6B). 

A. karroo occupies a diverse range of habitats and is 

consequently exceedingly variable. There is evidence that 

the variation is regional; plants in various parts of the 

species' geographical range often having a different "look" 

(Ross, 1971b). "Typical" A. karroo grows in the Karoo and 

in the drier parts ofthe Cape Province as a shrub (Plate 5A) 

or tree with dark rough bark, usually 2-3 pinnae pairs per 

leaf, and 6-12 pairs of leaflets per pinna that are 4.0-8.0 x 

1.5-2.5 mm. Apart from the "typical" form, a number of 

other entities are recognizable within the species. Some of 

the more important are listed below. 

1. The white-barked trees or shrubs with short spines, 

4-7 (13) pinnae pairs per leaf and 12-18 (27) pairs of 

smaller, narrower leaflets per pinna (Acacia natalitia) 

which are found chiefly in the eastern Cape, Natal, 

Swaziland, the eastern Transvaal, Zimbabwe and 

Mozambique. A. hirtella, described from the Natal coast, is 

similar but differs in having pubescent young branchlets, 

leaves, leaflets and peduncles. 

2. The small slender shrubs up to 1 m high found in the 

eastern Cape in the vicinity of the Kei River mouth. A local 

entity of which Dyer 4502 (K; PRE) is typical. 

3. The "fire-resistant" shrubs found in the Nongoma 

District of Zululand (Acacia inconflagrabilis). 

4. The slender, sparingly branched trees up to 6 m high 

found in Zululand, particularly in the Hluhluwe and 

Umfolozi Game Reserves and in the corridor linking them 

("spindle" Acacia karroo). A "spindle" growth form also 

occurs near the Loskop Dam in the Transvaal. Plants 

typically have bright reddish-brown minutely flaking bark, 

glaucous foliage, large flattened + discoid petiolar glands 

and a large gland at the junction of each or most pinnae 

pairs. Ward 2123 and Codd 9616 are representative. 

5. The large trees with greyish-white bark, spines up to 

25 cm long and long moniliform pods found along the 

Zululand coast from the mouth of the Tugela River 

northwards into Mozambique (Plates 5C and 8D). Plants 

are confined to a narrow belt and occur on the coastal plain, 

among the coast dunes, in the mouths of river estuaries and 

around the shore ofthe fresh water Lake Sibaya. The plants, 

which usually form very dense pure stands and are often 

dominant to the exclusion of other trees, often act as 

pioneers in stabilising loose sand dunes, especially in 

disturbed areas and in patches of regenerating dune forest. 

Unlike in "typical" A. karroo, the paired spines often persist 

on the trunk (Plate 2A). Gerstner 4526 and Strey 4960 are 

representative. 


83 

Nomenclature and taxonomy 5 

Figure 2 Acacia karroo. A - Pod (xO.65) Bames Rn 3183. Bl - Pod (xO.65); B2 - Flowers (xO.65); B3 - Pinnule (x4); 

B4 - Leaf (xO.65); B5 - Branchlet with leaf and stipular spines (xO.65); Barnes Rn 4436. C - Pod (xO.65) Bames RD 1909. 

D - Flowers (xO.65) Fagg CW 482. E - Flowers (xO.65) Bames RD 509. Fl - Leaf (xO.65); F2 - Pinnule (x4); Barnes RD 

3183. G - Branchlet with leafand stipular spines (xO.65) Barnes RD 3151. H - Branchlet with leaf and stipular spines (xO.65) 

FaggCW 474. 


6 ACACIA KARROO Monograph & Annotated Bibliography 

6. On the Transvaal highveld from Pretoria eastwards 

there is a local tendency for the production of a sparse 

indumentum on the young branchlets, leaves, peduncles and 

pods (Acacia karroo var. transvaalensis). However, 

occasionally this tendency is so extreme, for example, at 

Steelpoort, as to completely alter the general appearance of 

the plants. Indeed, the latter, for example Codd 6702 and 

Ross 2089, 2094, bear a strong superficial resemblance to 

A. gerrardii. 

7. On the island of Bazaruto in the Bazaruto 

archipelago in Mozambique, what has been up to now 

recognized as Acacia karroo has pale yellowish bark, rather 

like that on the Zululand coast, and pale lemon-yellow 

flowers. Bames RD 4436 (PHO) is representative. (See 

Plates 1B and 5B). 

'Ibe extremes ofeach of these variants are usually distinctive 

and attract immediate attention. For example, six well 

defined intra-specific groups were distinguished in a study 

of selected natural populations of Acacia karroo using 

numerical taxonomic methods and a combination of 38 traits 

measured on seedlings raised under controlled conditions 

(Swartz, 1982). After a discussion of the morphology, 

distribution and ecological characteristics of the six groups, 

the author suggested that the groups should have subspecific 

status. More recently, the taxonomic history of A. natalitia 

was investigated from its description in the early 19th 

century to its amalgamation with A. karroo Hayne (von 

Breitenbach, 1989). The diffusion of the original A. karroo 

concept by the inclusion of A. natalitia and various other 

clearly differing forms .is considered undesirable. It is 

considered that, with its whitish bark, small thorns, more 

finely divided leaves, lemon-yellow candle-like 

inflorescences and longer, more constricted pods, A. 

natalitia at least can be sufficiently well distinguished from 

A. karroo to justify its reinstatement as a separate taxon. 

However, as stated by Ross (1979), all these variants appear 

to be linked to the "central Acacia karroo gene-pool" by 

numerous and varied intermediate stages that become 

progressively less distinct until it becomes difficult to 

delimit each variant clearly. Consequently, many specimens 

are difficult to assign to a particular variant with any degree 

of certainty. In the absence of more detailed sampling and 

taxonomic studies, therefore, it remains preferable to regard 

A. karroo as an inherently variable polymorphic species in 

which no formal infraspecific categories are recognized 

rather than to fragment the species into a number of 

somewhat arbitrary infraspecific taxa. Recent molecular 

studies (Bames et al., 1994), however, suggest that the 

island populations of the Bazaruto archipelago may be an 

exception. 

A few flowers often develop in the involucel on the peduncle 

in Acacia karroo giving the appearance of a smaller 

secondary capitulum below the main one. These 

involucelate flowers usually develop before those in the 

main capitulum. Gordon-Gray and Ward (1974 and 1975), 

Barnes, R.D., Filer, D.L. & Milton, SJ. 

found a wide range in the number, size and structure of these 

sterile involucelate flowers and suggested that, opening as 

they do before the flowers in the main capitulum, "and being 

both visually and olfactorily attractive", they "may perhaps 

attract pollinating animals" so that visiting patterns are 

already established when the bisexual flowers of the capitate 

head open. 

[References:- 27,43, 55, 67, 93, 94, 174, 179, 194, 233, 

243,258] 

Representative specimens 

ANGOLA. HUILA: Dec 1859, WILN? 1833, (K); Sa da Bandeira, 14 0 

55'S 13 0 

30'E, 31 Jan 1967, HENRIQUES C 1070, (LISC); Sa da 

Bandeira, Bata Bbata, 10 Dec 1961, SANTOS R 680, (K); 

Tchivinguiro,21 Dee 1961, BARBOSA G 9727, (K); Viriambundo,27 

Feb 1972, CLARA couro 165, (SRGH). 

BOTSWANA. CENTRAL: SeJeka Ranch, 23 0 0'S 27 0 50'E, 24 Nov 

1977, HANSEN OJ 3291, (K, PRE); NGAMILAND: Nokaneng Flab, 

19 o 40'S 22 0 

12'E, 8 Apr 1975, ASTLE WL 7396, (SRGH); NORTH: 

Locality?, 19 0 

31'S 22 °49'E, 21 Jan 1977, SMITH PA 1879, (K, PRE, 

SRGH); SOUTH EAST: Gaberones, 24 o 40'S 25 0 

55'E, 3 Jan 1979, 

KREUlENAR 516, (pRE, SRGH); Gaberones dam, 24 0 

44'S 25 0 

54'E, 

26 Dee 1975, MOTT PJ 854, (SRGH); Honye, 24 °55'S 24 0 

42'E, 21 

Nov 1979, TIMBERIAKEJR2047, (SRGH); Kanye, 24 0 

59'S 25 0 

19'E, 

22 Jan 1979, TIMBERLAKE JR 1923, (SRGH); Mahalapye, 23 0 

4'S 

26°50'E, 11 Apr 1962, YALALA AM 338, (K, SRGH); Mmathethe,28 

Feb 1977, MOTT PJ 1080, (SRGH); Sebele, 3 Mar 1987, LONG DG & 

RAEDAH20, (K); TULI BLOCK: Beers farm, Sep 1945, MILLER OB 

B1375, (PRE). 

LESOTHO. UNKNOWN: Berea" DIEIERLENA 185, (PRE); Koloni, 

Jan 1953, JACOT-GUILLARM 1496, (PRE); Mafeteng dist., 29 0 

49'S 

27° 14'E, Dec 1933, GERSTNER JJ 209, (PRE). 

MALAWI. BLANTYRE: Michim Mtn, 1 Ju11980, MORRIS B 1156, 

(MAL); Michim Reserve, 8 Dee 1983, BANDA CS 18, (MAL); 

NdirandePlantation, 15 o 45'S 35 0 3'E, 12 Mar 1969, MSINKHU JB 9, 

(MAL, SRGH); Walala,7 Nov 1989, FAGG CW 477, (pHD, K, MAL); 

CHIRADZULU: ChiradmJu Mtn, 15 °41'S 35 °9'E, 11 May 1980, 

BRUMMI1TRK & PATEL IH 15618, (K, MAL); DEDZA: DOOza, 14 0 

24'S 34 °20'E, 22 Apr 1970, BRUMMI1TRK 10035, (K, MAL, SRGH); 

DedzahiDs, 3 Ju11936, BURTT-DAVY J 6042, (K); Linthipe, 14 0 

16'S 

34 0 15'E, 9 Dec 1988, FAGG CW 448, (PHD, K, MAL); Mpampa,1 

Dec 1941, ClEMENTS JB 851, (MAL); MULANJE: Fort Lister Gap, 

15°51'S 35 0 O'E, 9 Aug 1958, CHAPMAN JD 625, (MAL, SRGH); 

NTCHISI: Samson Sonkho, 15 0 15'S 35 o 49'E, 9 Sep 1966, DOWNIE 

HUTCHESON & LAMB 92, (MAL); ZOMBA: Namadzi, 1900, 

CHAPMAN JD & EG 8326, (K, MO); Njuli, 18 Dee 1980, CHAPMAN 

JD &PATELIH5498, (K); Thondwe, 15 0 28'S 35 0 15'E, 14 Jan 1981, 

SA LUBENIAJ 2880, (SRGH). 

MOZAMBIQUE.GAZA: 13 Sep 1968, MYRE M, DUANTEA & ROSE 

N 4943, (LISC); Macia, 25 0 19'5 33 o 15'E, 16 Jul 1947, PEDRO & 

PEDROGAO 1460, (K, SRGH); INHAMBANE: Bazamto Island, 21 0 

32'S 35 °29'E, 200et 1958, MOGG AOD 28528, (SRGH); MANICA 

ESOFALA: Chbnoio, 19 0 

0'S 33 0 

23'E, 2 Mar 1948, MENDONCA FA 

585, (K); Macequece, 18 0 58'S 32 o 58'E, 25 Mar 1948, MENDONCA 

FA 728, (K); Serra de Sumba, 25 Mar 1948, GARCIA 728, (EA); 

Spungabera, 20 °29'S 32 o 45'E, 15 Nov 1943, TORRE AR 6202, (K); 

MAPUTO: BeJa Vista, 26°21'S 32 °40'E, 10 Dee 1962, LEMOS F & 

BALSINHAS A 285, (SRGH); Bela vista, Ponta de Ouro, 10 Dee 1961, 

DElEMOS F &BALSINHAS A 285, (K); Goba, 26 °12'S 32 0 I1'E, 23 

Dec 1944, MENDONCA FA 3481, (K); Inhaca Island, 26 0 2'S 32 0 

58'E, 1 Mar 1963, MOGG AOD 32000, (K, SRGH); Matutuine, 32 0 

54'S 26 0 

45'E, 15 Nov 1979, JAN DE KONING 7622, (K); Mt. Inhaca, 

12 Aug 1980, JANSEN PCM &DE KONINGJ 7428, (K); Namaacha, 

26 0 0'S 33 0 10'E, 2 Mar 1948, TORRE AR 7456, (K); Planicies da 

Polna, Nov 1940, HORNBY 996, (LISC); PoJana, 12 Mar 1947,


30 °40'E, 5 May 1977, CANTP s.n., (EA, SRGH); Motorashanga, 17 0 

10'S 30 0 

42'E, 14 Jun 1991, FAGG CW 1, (PHO); MAKONI: 

Baddeley, 18 0 20'S 32 0 9'E, 28 Feb 1991, BARNES RD 2760, (PH0 , 

SRGH); Rosape, 18 0 

32'S 32 0 

7'E, 29 Dec 1952, MUNCH R 404, 

(SRGH); Rosape, 18 0 

32'S 32 °7'E, 10 Dee 1966, CORBYHDL 1689, 

(SRGH); MARONDERA: 21 Dec 1966, CORBY HDL 1701, (K, 

SRGH); MASVINGO: Fort Victoria, 20 0 5'S 30 0 50'E, 1 Jun 1932, 

CUTHBER1S0NA 5858, (SRGH); Zimbabwe NP, 20 °18'S 30 0 57'E, 

2 Nov 1970, CHIPARAWASHA 0 103, (SRGH); MATOBO: Hope 

FOlBltain Mssn, 20 0 16'S 28 0 39'E, 21 Apr 1973, NORRGRANN G 342, 

(SRGH); MAZOWE: Mazoe Dam, 17 0 31'S 31 °4'E, 24 May 1934, 

GIlllIAND HB 200, (HIO, K); MUTARE: Odanzi river valley, 1915, 

TEAGUE Al 509, (K); Old UmtaU Mssn, 18 0 51'S 32 0 39'E, 29 Dec 

1967, BIEGELHM2461, (SRGH); Penhalonga, 18 0 53'S 32 °4I'E, 20 

lan 1945, HOPKlNS 13228, (SRGH); Penhalonga, 18 0 53'S 32 0 41'E, 

21 Dec 1964, CORBY HDL 1198, (SRGH); NDANGA: Apr 1953, 

VINCENT V 197, (PHO); NYAMANDHLOVU: 19 0 

40'S 27 0 

50'E, 1 

May 1959, ARMITAGE FB 56/59, (SRGH); NYANGA: Nyamaropa 

Reserve, 18 0 0'S 32 °50'E, 25 Jul 1966, CORBYHDL 1626, (SRGH); 

Vdu Dam, 18 0 ITS 32 0 42'E, 17 Jan 1988, BARNES RD 510, 

SHURUGWI: 1917, WALTERS lAS 2353, (K); WEDZA: Wedza 

Mountain, 18 0 45'S 31 °35'E, 22 May 1968, RUSHWORTHlE 1072, 

(SRGH). 

[References:- 27, 179] 

Related species 

The glandular podded Acacia species (Acacia borleae, A. 

exuvialis, A. nebrownii, A. permixta, A. swazica, A. 

tenuispina and A. torrei) in southern Africa are all related 

to A. karroo. A. karroo differs from them all in lacking 

spinulose-mucronate leaflet apices and glandular pods. 

Acacia seyal is also closely related to A. karroo, but differs 

in having powdery bark and the "ant-galls" (when present) 

confluent and distinctly bilobed basally. The northern limit 

of distribution of A. karroo in Africa corresponds roughly 

with the southern limit of distribution of A. seyal. 

[References:- 87, 169, 173, 174, 176, 177, 179, 208, 243] 

Natural hybrids 

On the Springbok Flats north of Pretoria small shrubby 

plants occur which can be distinguished from Acacia 

tenuispina only with difficulty. Some of the plants have a 

similar growth form to A. tenuispina but as they lack 

spinulose-mucronate leaflet apices and glandular pods they 

are referred to A. karroo. Some collectors have suggested 

that the plants may be hybrids between A. karroo and A. 

tenuispina. Burtt Davy 4075 and Codd 7040 are 

representative. (Ross, 1979). 

On the Umguza Valley Estates near Bulawayo in 

Zimbabwe, a tree has been found in a mixed population of 

Acacia karroo and A. rehmanniana that has taxonomic 

characteristics that are intermediate between the two species 

(Barnes et al., 1994) (Plates 2C-D). The habit is more 

similar to A. karroo but the stem colour is closer to the 

reddish brown of A. rehmanniana; the pubescence of the 

branchlets, leaf rachis and leaflets is intermediate between 

Barnes, R.D., Filer, D.L. & Milton, S.J. 

A. karroo (glabrous) and A. rehmanniana (densely 

pubescent); the leaf is glandular (as are the leaves of both A. 

karroo and A. rehmanniana) with an average 11 pairs of 

pinnae (A. karroo average 4 and A. rehmanniana 30) and 

25 pairs of leaflets per pinna (A. karroo average 10 and A. 

rehmanniana average 36); the leaflets are closely spaced on 

the rachis but not overlapping (the leaflets ofA. karroo are 

distinctly spaced on the rachis whereas those of A. 

rehmanniana overlap); the flowers are lemon-yellow (A. 

karroo yolk }ellow andA. rehmanniana creamy-white); the 

tree bears no pods. Leaf peroxidase analyses of samples 

from this tree and from neighbouring trees ofA. karroo and 

A. rehmanniana indicated that the tree could be a hybrid 

between these two species; A. nilotica, also a neighbour, 

was ruled out as a possible parent by this analysis (Brain, 

pers. comm.) 1 Barnes RD 3651 (PHO, SRGH) is 

representative. 


GENETIC VARIATION 

Morphological variation 

The extent to which the morphological variation, described 

under the botanical description above, over the range of 

Acacia karroo is due to genetic differences can be 

determined only through the establishment of comparative 

field trials in which the effects of environment can be 

controlled. The extremes of environment over which the 

species is indigenous will in itself have a profound effect on 

the morphology of the tree; but, it would be surprising if 

these environments themselves have not induced significant 

genetic adaptive responses in A. karroo. 

In a numerical taxonomic evaluation of Acacia karroo in 

southern Africa (Swartz, 1982), 38 characters were used in 

an analysis that distinguished between six well defined 

intra-specific groups. Seedlings of these groups cultivated 

under controlled conditions similarly showed morphological 

variation, indicating that the groups were genetically fixed. 

In a range-wide study (Barnes et al., 1994), material is now 

being raised for provenance trials and early results confirm 

that there is substantial morphological variation in the 

seedlings and that it is under genetic control (Figure 3; 

Plates 2E-G). This material is to be used for the 

establishment of international provenance evaluation trials 

that will provide information on the genetic control of 

variation of field characteristics within and between 

populations. This information will be important for devising 

optimum strategies for domestication and breeding but it 

will only provide pointers for the taxonomist. Whether there 

are grounds for sub-division of the taxon will depend upon 

1Dr Peter Brain, 14 Richmond Avenue, Kloof 3610, South Africa

showing that there are discontinuities in the variation and 

this will require much more intensive sampling in selected 

parts of the species' range. 

[References:- 25, 27, 208] 

Biochemical variation 

Twelve populations of Acacia karroo, covering its entire 

range, were surveyed for 12 allozyme systems (aspartic 

aminotransferase, alcohol dehydrogenase, diaphorase, alphaesterase, 

beta-esterase, glucose-6 phosphoglucose 

dehydrogenase, glutamate dehydrogenase, malate 

dehydrogenase (mdh), malate dehydrogenase (mdhp), 

menadione reductase, 6-phosphogluconate dehydrogenase 

and shikimate dehydrogenase) (Oballa, 1993). All 

expressed a high level of genetic diversity. Ninety-eight 

percent of the isozyme loci were polymorphic with an 

average of 3.7 alleles per locus. The total gene diversity 

was 88 %, higher than that reported for most plant species. 

The mean genetic identity was 90% and the coefficient of 

gene differentiation was estimated at 5%; this indicated a 

low divergence between populations. Cluster analysis 

grouped the populations into three phylogenetic groups, the 

northern, the southern and the south-central-eastern (Oballa, 

1993). 

More recently, seed collections have been made from two 

Acacia karroo populations, one on the island of Bazaruto 

and one on the island of Magaruque, both in the Bazaruto 

archipelago off the coast of Mozambique. The same 12 

allozyme systems were run for this material and they showed 

these populations to be profoundly different from all others, 

including those on the island of Inhaca off Maputo and those 

on the Zululand Coast (B ames et aI., 1994). This makes 

these populations of great interest both taxonomically and 

genetically. 

In a study of variation of the leaf peroxidases of Acacia 

karroo (Brain 1986 and 1989; Barnes et al. 1994; Brain et 

al., in prep.), two zones of activity, one fast and one slow, 

were found. The most anodally migrating zone was scored 

and five bands were found in this region, labelled from the 

cathode as K, L, M, N, O. Across all populations, the 

frequencies of the M (.38) and N (.32) bands were much 

greater than those of bands K (0.1), L (0.1) and 0 (.10). 

The analysis of this huge data set, 4,322 individual trees 

from 63 populations representing the complete range of the 

species, indicated strong regional concentrations of 

particular types. The K band has a high frequency in the 

south (Karoo) but is absent from Zululand and Natal (Plate 

4B); band L is more frequent in the western part of the 

species' range; and there is virtual fixation of the M band in 

the coastal populations of Zululand and Mozambique (Plate 

4A). The latter is one of the most significant findings 

because M is not fixed in populations just to the west of the 

dunes with which the A. karroo on the dunes could 

interbreed; therefore it is likely that there is some selective 

Genetic variationlReproductive biology 13 

advantage associated with the M "allele" and, should this 

prove to be so, it would be one of the first instances where 

an adaptive trait had been associated with a chemical 

substance under monogenic control. Cluster analysis 

suggested the presence of these three groups. Variability 

appeared to be highest under the most adverse climatic 

conditions of low temperatures and low rainfall. 

[References:- 25, 27, 35, 36, 37a, 3Th, 148] 

Sampling variation for genetic evaluation 

A sampling strategy has been devised to select provenances 

from which to collect seed for international provenance 

trials of Acacia karroo (Bames et al., 1994). A 

combination ofgeographic, climatic, edaphic, ecological and 

morphological considerations was used to select 

provenances together with the evidence from the 

biochemical studies described above; the latter provided the 

only hard information on genotypic, as opposed to 

phenotypic, variation. On the basis of these data, a sampling 

strategy was devised that was likely to ensure that most of 

the genetic diversity of A. karroo would be contained in the 

provenance trials. Since the biochemical studies showed 

that the majority of variation occurred within (80%) rather 

than between (20%) populations, it was considered 

appropriate to sample large numbers of trees per population 

and to restrict the number of populations that were sampled. 

All the peroxidase alleles and most genotypes could be 

obtained by sampling very few populations; but if sampling 

had been restricted to the coastal areas where M is fixed, it 

would have been possible to miss out entirely on 80% of the 

genetic variation at this locus. 

The map (Plate 3B) shows the localities of the seed 

collections made for the international provenance trials in 

relation to the natural distribution of Acacia karroo (Plate 

3A). Details of the localities are given in Table 1. 

[References:- 25, 26, 27, 37b] 

Cytology 

REPRODUCTIVE BIOLOGY 

The chromosome number of Acacia karroo was first 

reported under the species' original name of A. horrida as 

2n=4x=52 (Ghimpu, 1929). However, some acacias have 

variable chromosome numbers and as no cytological survey 

had been undertaken to determine possible variation with 

ecotype in this very variable species, a study based on 

cytological evidence from ten populations was recent!y 

undertaken (Oballa, 1993; Oballa and Olng'otie, 1994). A. 

karroo was again found to be a tetraploid consisting of only 


k 

A 

B 

C 

Typical yellow flowers 

Pale flowers from Bazaruto Island, Mozambique 

Spines from the coastal dune forests in Zululand 

Plate 1 Acacia luuToo (left to right sequence) 

D 

E 

F 

Inflated spines from eastern Zimbabwe 

Unopened pods 

Dehisced pods with seeds still suspended by the funiCle

Plate 4 

VI) 

11 

Acacia luuToo peroxidase distribution 

ral 

o + 

C') 

1000 IQ( 

Frequency of the peroxidase bands M (map A above) and K (map B below) in an electrophoretic study of Acacia karroo 

from 63 populations that rover its entire natural range. There are five bands, K, L, M, Nand 0, in the fast zone of this 

isozyme system in the species. The black portion of the vertical yellow bar represents the relative proportion of individuals 

that exhibit the band. Band M is almost fixed in the coastal dune populations of Zululand on the east coast of south Africa 

and in the coastal populations of Mozambique. The frequency of K is highest in a cluster of populations in the Karoo region 

of South Mrica. (Data from Brain et al., in press) 

20 

30 S 

+ 

35 S 

P tl 

"IJ 

(J 

g 

o 

tl 

Sl 

si

one cytotype with a chromosome number of 2n = 52. The 

tetraploid status was further supported by evidence from the 

isozyme inheritance patterns which also indicated that the 

species is a segmental tetraploid. 

[References:- 88, 148, 149, 238] 

Sporogenesis, embryology and pollination 

The sporogenesis and embryology of Acacia karroo have 

been fully described (Bala, 1978). Four microspore mother 

cells are formed in each lobe of the anther and each of these 

gives rise to 16 microspores. The young ovule is 

orthotropous at frrst gradually becoming anatropous. The 

archesporium appears as a single cell and is hypodermal in 

origin; it cuts off parietal tissue on the upper side and forms 

the megaspore mother cell which divides into two dyad cells 

which give rise to a linear tetrad of megaspores. Two polar 

nuclei are suspended in the centre of the embryo sac by 

means of cytoplasm and the three antipodal cells. The first 

division of the embryo is transverse, the second vertical and 

later divisions irregular. The cotyledons are differentiated 

when the proembryo is of a massive type. The endosperm 

follows the nuclear type ofdevelopment; it is not completely 

reabsorbed by the developing embryo and a little endosperm 

remains in the mature seed. 

Acacia karroo have protandrous flowers, with stigmas 

unreceptive at anthesis, but receptive at five days after 

anther dehiscence (Sedgeley and Harbard, 1993). 

[References:- 23, 58, 165] 

Breeding system 

The existence in Acacia karroo of trees that are entirely 

male suggests a tendency towards out-crossing; and the 

preponderance of male flowers in the population ensures 

abundant pollen (Oballa, 1993). It has been suggested that 

it is a generally self-incompatible species that exhibits a 

combination of clinal and discontinuous variation in 

response to climatic factors (Burley et al., 1986). These are 

pronounced characteristics ofA. karroo across its range and 

this supports the suggestion that the species is outcrossing. 

'. In some acacias, including A. karroo in which it is 16 

(Robbertse, 1974b; Coetzee, 1955), the number of pollen 

grains in a polyad corresponds closely to the number of 

ovules (Kenrick and Knox, 1984). It has been suggested 

that the balance is maintained in Angiosperms to ensure 

successful pollination of all ovules in a single flower by a 

single polyad (Kress, 1981). 

Reproductive biology 15 

An intensive study was undertaken in one population to 

investigate the breeding system of Acacia karroo (Oballa, 

1993). Estimates of genetic parameters in this population 

indicated that the species has a mixed mating system. The 

multilocus outcrossing rate was estimated at 0.88; single 

locus outcrossing estimates were heterogeneous ranging 

from 0.53 to 1.00. The mean outcrossing rate was 0.72. 

This indicated that the species was predominantly outcrossing 

in this population but at the same time quite a high 

level ofselfing did occur; however, the estimated biparental 

inbreeding was higher than actual selfing which suggested 

the presence of some correlated mating. In the absence of 

similar studies in other populations and of any estimate of 

inbreeding depression, it was not possible to assess the 

likely effect that inbreeding might have in biasing 

provenance comparisons in the evaluation trials. 

Nevertheless, the relatively high degree of out-crossing in 

this population suggests that the effects of inbreeding are not 

likely to be so profound as to necessitate taking each 

provenance through a generation of outcrossing to release it 

from these before genetic evaluation is undertaken. 

[References:- 27,43,58, 116, 122, 148, 162, 187] 

Pollinating and seed dispersal agents 

Although eight pollen grains were found per 7 cm 2 on 

vaselined slides exposed for 24 hours on a warm, windy day 

in a flowering community (Coetzee, 1955), Acacia karroo 

is zoomophilous, principally insect-pollinated. This might 

be expected with the strong colouration of the inflorescence 

and the heavy pollen grains (Oballa, 1993). Isolated plants 

often bear no fruits (Gerstner, 1948). Huge numbers of 

insects of many species visit the flowers throughout the 

flowering period. No comprehensive list of pollinating 

insect species has been found but no doubt they include 

species in the orders Coleoptera, Lepidoptera, Hymenoptera 

and Diptera. 

It has been noted that in the bright yellow inflorescences of 

Acacia karroo, small sterile involucelate flowers develop as 

a small secondary capitulum on the peduncle before the 

main fertile flowers open (Ross, 1979; Coe and Coe, 1987). 

It has been suggested that these may serve to attract 

pollinating insects, to ensure that they have already 

established visiting patterns by the time that the fertile 

flowers open (Coe and Coe, 1987). 

Although the pods are dehiscent on the tree, they are not 

explosively so (Plates E-F) and dispersal is principally by 

cattle and other herbivores ingesting and voiding through 

their dung. 

[References:- 56, 58, 87, 93, 94, 179] 



DISTRIBUTION AND ECOLOGY 

Natural distribution 

Full details of all botanical specimens of Acacia karroo held 

in all the major herbaria in which the species is likely to be 

housed, have been logged into the BRAHMS database 

(B arnes et al., 1994). These herbaria included those in 

Pretoria (National Herbarium, South Africa), Cape Town 

(Compton Herbarium, South Africa), Harare (National 

Herbarium and Botanical Gardens, Zimbabwe), Windhoek 

(National Herbarium, Namibia), Zomba (National 

Herbarium, Malawi), Nairobi (National Herbarium, Kenya), 

Lisbon (The Herbarium, Portugal), Kew (The Herbarium, 

United Kingdom), Oxford (the Forest Herbarium, United 

Kingdom), and Paris (Musee National d'Histoire Naturelle, 

France). The data were used to produce the natural 

distribution map given on Plate 3A. It is apparent that there 

are two unexplained gaps in the distribution, one in southern 

Angola and the other in Mozambique south of the Bazaruto 

archipelago. It is not clear whether the gaps are due to the 

species not occurring there or whether they are due to undercollection. 

Geographically Acacia karroo is the most widespread tree 

in southern Africa. It occurs in every country of the 

Southern African Development Community (SADC) region 

excluding Tanzania where the species is replaced by the 

taxonomicallyand ecologically similar A. seyal. Within the 

region, however, there are isolated populations that might be 

expected to have had the opportunity to diverge genetically. 

Most notable among these are the island populations off the 

coast ofMozambique, particularly those on the islands of the 

Bazaruto archipelago which are the most distant from the 

mainland. Also isolated are the populations on the islands 

in the Okavango Delta in Botswana. On a larger scale, the 

populations of northern Namibia, southern Angola, Zambia, 

Zimbabwe and Malawi are all separated from the main 

South African population and each other by arid zones 

mainly associated with the deep, dry, hot valleys of the 

major rivers. 

[References:- 3,27, 78,124,134,137,178,179,180,199] 

Ecology 

Climate 

Acacia karroo occurs naturally over an extraordinary range 

of climates with rainfall distribution ranging from summer 

maximum, through evenly distributed, to winter maximum 

(Plates SA-G). In each of these zones, mean annual rainfall 

can vary from 200 to over 1500 mm. Mean annual 

temperatures are also variable with a high of 24°C on 

Bazaruto to a low of 12°C in the Karoo; on the Zululand 

coast the maximum daily temperature may rise to 40°C and 

Barnes, R.D" Filer, D.L. & Milton, SJ. 

the relative humidity seldom falls below 50% (Venter, 

1971). The species survives all but the most severe frosts 

in southern Africa (c. -12°C in Matabeleland, Zimbabwe) 

which is one of the factors that explains its ubiquity in the 

region except at the cold high altitudes in Lesotho, the only 

country in the world with no land below 1000 m. It also 

tolerates wind and salt spray from the sea on the coast 

(Venter, 1971) (Plates 5-B). Timberlake 2 describes A. 

karroo in Zimbabwe as a catholic species but not ubiquitous 

and seldom found below 1000 m (at which altitude the mean 

annual temperature would not exceed about 22°C); it is 

common on degraded lands in the lower rainfall areas. 

[References:- 3, 12,27,29,70,71, 133, 137, 190, 199, 

237,239] 

Soils 

The range ofsoil types on which Acacia karroo occurs is no 

less remarkable than the variability of the climates in which 

it can thrive. Over much of its inland range it tends to be 

restricted to the heavier soils and it is one of the very few 

species that grows on the heavy, black, hydromorphic, 

cracking vertisols with high pH (Coetzee et al., 1976; Kooij 

et al., 1991;) (Plate 5D); but it will thrive on deep alluvial 

clay-loam soils (du Preez and Venter, 1990) in river valleys, 

on shales (Roberts, 1966) and even on acid soils (Pous and 

Tidmarsh, 1937). In Zimbabwe, A. karroo forms stands on 

heavier-textured alluvium and is very common on red clay 

soils along watercourses and on shallow red clay soils from 

metasediments and metavolcanics; in high rainfall areas it 

occurs widely on clay-rich soils; it is generally an indicator 

of soils that are nutrient-rich (Timberlake et al., 1993). In 

the more tropical part of its range, A karroo needs 

somewhat eutrophic, nutrient-rich (particularly calciumrich) 

soil conditions for good establishment; consequently it 

is not found in the miombo woodland except on the more 

clay-rich soils (Timberlake, pers. comm.)2. In arid South 

Africa, A. karroo occurs along drainage lines and round 

pans (Milton, 1991). At the other extreme, it thrives on the 

unconsolidated bare drift sands of the coastal dunes in 

Zululand (Venter, 1971; Mentis and Ellery, 1994; Weisser 

and Muller, 1983) (Plates 5C and 8D). The species is 

tolerant ofextremely saline conditions and is found growing 

on the beach below high spring tide level on the island of 

Bazaruto in Mozambique (Plate 5B) and on salt (probably 

sodium carbonate) encrusted islands of the Okavango Delta 

in Botswana (Barnes, 1994). Tolerance of this wide range 

of edaphic conditions may be in part due to the extremely 

dense and robust rooting habit (Barnes, 1994) (Plates 6E 

and 6F). A. karroo is intolerant of levels of arsenic of over 

10,000 parts per million (Wild, 1974). 

[References:- 2,27,59,69,70, 100, 120, 129, 131, 134, 

156,159,170,190,194,199,234,239,251,257,258] 

2J.R. Timberlake, 3 Rue des Heurs, Fortunes Gate, Bulawayo, Zimbabwe

Vegetation types and succession 

Acacia karroo occurs in everyone of the nine main 

phytochoria (White, 1983) in southern Africa (Plate 3A); it 

is absent only from the Mroalpine zone on the highest 

mountains in the region. It is also present in all seven of 

Rutherford and Westfall's (1986) Biomes and it is listed as 

a typical constituent in five of the seven main veld types of 

South Africa (Acocks, 1988) particularly in the savanna, 

karoo and coastal dune forest. It occupies a successional 

position between the tropical forest and the bushveld 

(Acocks, 1988; Venter, 1971) but it grows in riverine 

communities (Dean et al., 1990; Drummond, 1981; Kooij 

et. al., 1991) even into very arid environments provided 

there is an assured supply of underground water (Acocks, 

1988; Carr, 1965). Large specimens of A. karroo are 

reputed to be indicators of underground water (Leistner, 

1967). It has been reported as occurring along rivers in 26 

of30 vegetation types sampled in arid and semi arid parts of 

South Africa (Acocks, 1976) where its comparative 

tolerance offrost often gives it an advantage over other tree 

species. 

Acacia karroo is an adaptable species that is expanding its 

range particularly under the disturbed ecological conditions 

that result from human activity in southern Africa today. In 

South Africa it is spreading eastward up the valleys into the 

higher parts of the Karoo and beyond into what has 

previously been grassveld, and also westward from the 

valley bushveld of the east coast rivers right up into the 

surviving temperate forests of the mountains in the eastern 

Cape Province and the Transkei; it is also invading the open 

savannas of the Transvaal and Natal (Acocks, 1988). These 

expansions are usually associated with bad veld grazing 

management practices although climatic deterioration 

cannot be ruled out as being at least a contributory factor in 

its spread. ' 

Acacia ka"OO is a pioneer with a maximum life of about 40 

years (Gourlay and Barnes, 1994). It flowers precociously 

and produces large quantities of seed. It is well adapted to 

establishing itself with no shade, shelter or protection from 

grass fires. However, where A. karroo invades following 

disturbance, the correlation between tree density and pasture 

condition is not linear; this indicates that there may be a 

threshold condition below which a dramatic increase in trees 

is likely (Friedel, 1987). Under undisturbed conditions, 

many other woody plants germinate beneath the canopy and 

they and various parasitic mistletoes and root parasites may 

subsequently kill the pioneer. Marked changes have taken 

place in dune vegetation near Richards Bay in Zululand that 

have been due mainly to secondary successions resulting 

from protection by forest plantation activities. It is 

estimated that under the existing favourable climatic 

conditions it takes some dune grassland only 25-60 years to 

develop into mature A. karroo woodland and a further 

30-150 years to proceed to secondary dune forest (Weisser 

and Marques, 1979). 

Distribution and ecology 17 

Despite it being a pioneer, there are often environmental 

conditions that allow Acacia karroo stands to regenerate 

themselves; these may be naturally imposed, for example by 

local soil or climatic conditions, or they may be the result of 

human interference, for example through over-grazing or 

forest clearance. In these circumstances, there is often the 

development of an understorey of perennial, palatable and 

nutritious grasses (e.g. Panicum maximum, Cenchrus 

ciliaris, Digitaria pentzii, Cynodon incompletus) that thrive 

on the environmental benefits that stem from the species' 

ability to use water and nutrients from depth and to fix 

nitrogen (Roberts, 1963; Acocks, 1988) (Plate 6A). 

Shading by the A. karroo canopy may also reduce soil 

surface temperature and evaporation making conditions 

more suitable for drought susceptible grasses. On the 

southern coast of the Cape Province, South Africa, where 

there is year-round rainfall of 725 mm, A. karroo is 

restricted to deep, sandy soils on river banks, the 

understorey is trampled by antelope seeking shade beneath 

the trees and the vegetation is consequently dominated by 

the grass Cynodon dactylon (Grobler and Marais, 1967). 

On alluvial clay-loam soils, understorey shrubs in A. karroo 

woodland near the Vaal River in the Transvaal can include 

members of the genera Rhus, Ehretia, Protasparagus, 

Diospyros, Maytenus, Ziziphus, Lycium and, Celtis (Du 

Preez and Venter, 1990; van der Walt, 1980) among which 

may be the species that ultimately succeed A. karroo (Potts 

and Tidmarsh, 1937). In the Orange Free state, A. karroo 

occurs in valley bottoms, on riverbanks and in steep ravines 

where soils tend to be saline. The A. karroo-dominated 

woodland has an understorey of shrubs and grasses but, in 

the uplands, it occurs on black vertisols associated with rock 

outcrops, and the understorey is grass (Kooij et al., 1991). 

In Zimbabwe, A. karroo is generally the predominant tree 

species on heavy black vertisols, derived from calcium-rich 

basaltic and mafic rocks. The ability of its root system to 

survive the root-shear associated with tie severe cracking of 

these soils in the dry season ensures its permanent 

dominance. 

[References:- 1,2,27, 38,44, 59, 60, 65, 67, 69, 73, 84, 

96,100,104,119,120,124,129,131,140,159,169,180, 

189,200,234,237,239,250,251] 

Associatedfungi 

Many species offungi have been isolated from the leaf litter 

and soil beneath Acacia karroo communities. In the Eastern 

Transvaal, a total of 858 sporulating cultures representing 

76 genera and 144 species were recovered from the soil 

under A. karroo communities (Papendorf 1976). The 

majority were fungi imperfecti, with a limited number of 

zygomycetes and ascomycetes. No oomycetes or 

basidiomycetes were recorded. The most abundant genera 

were Penicillium and Aspergillus with Hyalotiella 

transvaalensis, Arxiella terrestris, Arthrocladium 

caudatum, Veronaea simplex, Exophiala brunnea and 



Melanophoma karroo specifically identified (Papendorf, 

1967 and 1969; Papendorf and Du Toit, 1967). The 

greatest concentration ofindividuals and species occurred in 

the swface la}efs; numbers decreased with increasing depth. 

The nature of this mycoflora suggests a close correlation 

with the existing plant cover. 

[References:- 89, 127, 128, 151, 152, 153, 154, 159,207] 

Rhizobia 

Nodulation in the Mimosoideae is far more common than it 

is in the Caesalpinioideae but it is by no means universal 

(Sprent, 1995). Nodulation is very common among the 

acacias but, even in this genus, it cannot be assumed. There 

is great diversity in both host and rhizobia symbioses in the 

acacias. It has been found that the fastest growing acacia 

rhizobia are those from the most desiccation and salt tolerant 

isolates. This suggests that there could considerable scope 

for improvement through selection. 

During the course of a genetic evaluation project on Acacia 

karroo (Barnes et al., 1994), seedlings of six African 

Acacia species (A. karroo, A. tortilis, A. senegal, A. 

nilotica, A. erioloba and Faidherbia (Acacia) albida) were 

raised in six nurseries in different environments throughout 

Zimbabwe and nodules collected for a study on rhizobia 

technology. The specific objectives of the project were "to 

isolate, identify and test the effectiveness and 

competitiveness of Rhizobium strains and produce inocula 

for six Zimbabwean Acacia species (Sutherland et al., 

1994). Of all six species, A. karroo nodulated most freely 

in the nurseries. The nodules on each species were 

morphologically different, those on A. karroo being typically 

a slightly pear-shaped cylinder in shape and light to medium 

brown in colour (Barnes et al., 1994). Only A. karroo and 

A. tortilis ssp. heteracantha seedlings showed significant 

increase in dry weight when harvested four months after 

inoculation (Sutherland et al., 1994); a strategy of applying 

a mixed inoculum was effective on these species and was 

recommended. Considerable difficulty was experienced in 

preventing deterioration of the rhizobia in culture and in 

achieving nodulation. It is expected that the problems in 

preventing deterioration will be resolved now that it is 

realized that tropical tree rhizobia are stressed when grown 

on a medium developed for temperate field crop rhizobia; 

while able to survive on this medium, they lose their 

symbiosis plasmids. The difficulties in effecting nodulation 

were overcome when it was realized that relatively high 

light levels are required for effective nodulation in acacias. 

The prospect, therefore, of cost-effective inoculation of 

acacias is relatively good for tree establishment in dry areas. 

Nevertheless, inoculation trials will be costly and imprecise 

until there is better experimental control of the genetic 

constitution ofthe host plants. The future is seen as lying in 

rhizobia research linked to a tree selection and breeding 

programme (Sutherland et al., 1994). 


During the research being conducted on the genetics and 

rhizobia ofAcacia karroo, leaf samples were collected from 

trees of this species and from five other Acacia species 

growing sympatrically with it for laboratory analysis to 

compare their efficiency in fixing atmospheric nitrogen and 

in ground water usage (Barnes et al., 1994). Foliage 

samples from the six species were collected from Umguza 

Valley Estates in Zimbabwe and the resultant analysis of the 

percentage ofnitrogen and stable isotope ratios are given in 

Table 5, page 28. The data suggest that A. karroo fixes 

more atmospheric nitrogen than A. erioloba or A. tortilis 

ssp. heteracantha but not as much as A. jleckii, A. nilotica 

or Faidherbia albida. On the other hand, A. karroo is less 

efficient in its water use than all the above species except A. 

tortilis ssp. heteracantha. 

[References:- 27, 112, 192,206,209] 

Life cycle 

GROWTH HABITS 

The pods of Acacia karroo ripen between February and 

June (Figure 5, page 32). They open on the tree and the 

seeds are suspended by a thin, thread-like funicle which 

becomes brittle as it dries (Plate IF). The seeds fall, or are 

eaten by animals or birds, before the pods drop from the tree 

two or three months later and are dispersed by wind, water 

and in the dung of cattle and other mammals (Story, 1952). 

The heavy, sound, seed falls first very often leaving many 

lighter, damaged, bruchid-infested seed still suspended from 

the pods by their funicIes after all the sound seed has gone. 

There is evidence that seed remains viable for up to seven 

years when buried in the soil (Du Toit, 1972); seeds from 

herbarium sheets have been found to be viable after 57 years 

(Story, 1952). The seeds have water impermeable 

dormancy and can remain damp for 29 months without 

germinating or rotting; but once the seed coat is penetrated, 

germination takes place in three or four days. Establishment 

is prejudiced by desiccation (Du Toit, 1967), severe frost 

(Carr, 1976), soil compaction (Friedel, 1987), grass 

competition and browsing animals (Comins,1962). 

Story (1952) found that only about 10% of Acacia karroo 

seed that has not passed through an animal germinates 

during the frrst 14 months after sowing. He found that 

seedlings in cultivated ground had >90% survival rate and 

reached 42 cm in 18 months, whereas only 5% of seedlings 

in grassland survived and were only 10 cm high after 18 

months. Seedlings were resistant to browsing, but all 

seedlings


Flower and fruit phenology 

Shoot growth, shoot mortality and the abundance of flowers, 

fruit and leaves were observed on seven Acacia species 

including A. karroo for 13 months at Nylsvley, Transvaal, 

South Africa (Milton, 1987). In this study it was found that 

A. karroo bears flowers only on green extending shoots and 

flowers throughout the growing season as the new shoots are 

produced. Flowers are most abundant between December 

and February. Pods ripen in winter; they are thin-walled and 

split open while still on the tree when the seeds dangle from 

the pocl on their funicles. In Zimbabwe the flowering period 

may last from November to late April with individual trees, 

and sometimes whole populations, flowering three or four 

times in the year particularly in sunny spells following 

periods of heavy rain. Flowering is always on the current 

season's growth (Barnes et al., 1994). 

Information on phenological variation between populations 

ofAcacia karroo cannot be obtained without making regular 

observations in many populations over long periods. The 

extent to which this variation is under genetic control can 

only be determined from field provenance trials. An attempt 

has been made to extract as much information as possible on 

this subject from the herbarium sheet data logged into the 

Oxford Forestry Institute's database BRAHMS (Barnes et 

al., 1994). Most of these sheets had been assessed for 

flowering and fruiting status. Although there was some 

difficulty in merging different assessor's categories, the 

overall phenological picture for flowering and fruiting for 

the species was produced by plotting the number of 

specimens categorized as "buds and flowers" and "mature 

fruits" against month as shown in Figure 5, page 32. 

Because the species covers such a large area, the data was 

first partitioned into latitudinal bands but this did not 

indicate that even the most northerly populations within the 

tropics flowered or fruited at different times from those in 

the winter rainfall areas of the Cape. 

[References:- 27, 124, 131, 133] 

PREDATORS, DISEASES AND 

HARMFUL PHYSICAL AGENCIES 

Biotic factors 

Animals 

Acacia karroo is an important browse tree for many wild 

and domestic herbivores. The effects of browsing on the 

subsequent growth and metabolism of the tree are discussed 

under fodder in the section on yield and management q.v. 

During drought periods, the foliage of Acacia karroo trees 

is often the only browse available. Drought also promotes 

gum exudations on the stem. Although severe drought in the 


Karoo may reduce flowering, the flowers are more 

conspicuous in dry periods when they escape storm damage 

and they then become attractive to herbivores (Plate 6C). 

Those higher up in the crown are eaten by monkeys and 

many species of birds; monkeys and galagos (Galagidae) 

(Anderson and Pinto, 1980) eat the gum. 

Peak breeding of birds in Acacia karroo woodland near 

Pietermaritzburg in Natal, South Africa, coincided with the 

rapid spring increase in insect biomass (Earle, 1981). 

[References:- 11,39,65,76, 118, 121, 135, 133, 134, 137, 

139, 146,215,218,219] 

Insects 

There is a great wealth of insect life associated with the 

African acacias. It has been speculated that no other genus 

in the semi-arid environments of the continent has as many 

insects associated with it (Ross, 1975b). The caterpillars of 

various moths feed on and destroy the leaves, scale insects 

infest the twigs, the bark and woody tissues are riddled with 

the holes and tunnels of boring insects while the flowers are 

visited by numerous species of bees, wasps and flies and 

beetles voraciously consume the seed. 

In a checklist of insects found attacking trees and shrubs 

growing in South Africa (SAPPRI, 1970), many are listed as 

attacking Acacia karroo. In the order Coleoptera these 

include species from the families Bostrychidae (larval borers 

in drybranches and stem), Bruchidae (adults and larvae feed 

in seed), Cerambycidae (larval borers in the stem, adults 

ringbark shoots when feeding (Plate 7B)), Lamiinae (adults 

debark trees, feed in seed pods, feed on leaves and flowers; 

larvae bore in weak trees), Colydiidae (predate on boring 

beetles), Curculionidae (leaf feeders) and Scolytidae (bark 

beetles). In the order Hemiptera (sap-suckers) these include 

species from the families Asterolecaniidae, Coccidae, 

Diaspididae, Lacciferidae and Pseudococcidae. In the order 

Lepidoptera (leaf feeders) these include species from the 

families Arctiidae, Cossidae, Geometridae (mainly leaf 

feeders and some wood borers (Plate 7A)), Lasiocampidae, 

Limacodidae, Lycaenidae, Lymantriidae, Noctuidae, 

Notodontidae, Psychidae, Pyralidae, Saturniidae and 

Sphingidae (Taylor, 1949, 1951, 1953 and 1965). In the 

order Thysanoptera these include species from the Thripidae 

(sap suckers). In the order Homoptera (foliage feeder) these 

include species from the Psyllidae (Webb, 1974). 

Many species ofthe family Bruchidae parasitize seeds of the 

acacias including Acacia karroo and since their activity can 

seriously affect reproduction in the species, an account of 

the life cycle of a bruchid follows from Southgate (1978). 

The female beetle lays an egg on a ripening or, more rarely, 

a ripe pod. The larva bores through the pod wall and 

burrows into a ripening seed within which it creates a 

chamber. In its final stages the larva eats away the outer 

layers of the seed until only a thin shell of testa remains. 

After pupation, the beetle emerges through the testa. In a

few species the larva leaves the seed and pod, drops to the 

ground on a silk thread, and pupates in the soil beneath the 

tree. Early indications from phytochemical investigations 

indicate that the concentrations of certain amino acids 

(pipecolic acid and some heteropoly-saccharides) determine 

if a bruchid larva can survive in a seed (Southgate, 1978). 

Predation can destroy the viability of up to 90% of the seed. 

In a study of the monophagous psyllid Acizzia russellae 

(Homoptera) and its hymenopterous parasites, seasonal 

patterns in psyllid numbers were found to follow fluctuations 

in nitrogen levels on individual trees of Acacia karroo on 

which it is the most consistently abundant herbivore; it feeds 

on the foliage and shows preference for young leaves for 

oviposition. No effect of stress or leaf hardness was clearly 

discerned. Cutting of trees altered the characteristics of the 

subsequent regenerative growth so as to allow massive 

psyllid infestations to develop, thus showing the critical 

importance of the host plant quality in determining 

population levels in this insect (Webb, 1974; Webb and 

Moran, 1974). 

Acacia karroo is often subjected to severe attacks by the 

ps){:hid wattle bagworm, Kotochaliajunodii (Ross, 1979). 

Large trees can be defoliated and killed. 

Acacia karroo is resistant to attack by termites throughout 

its life. It has been suggested that the calcium oxalate 

crystals in the wood and tissues of tropical trees, including 

A. karroo, make them less palatable to termites (Prior and 

Cutler, 1992). 

A community of small moths is closely associated with the 

galls caused by the rust fungus Ravenelia macowaniana 

pazschke on the flowers and fruits of Acacia karroo 

(ChOWll, 1993) (Plate 7H). Larvae of seven species of these 

microlepidoptera were found to be associated with 

R. macowaniana near Pretoria and Bloemfontein in South 

Africa and an additional seven species have been found in 

the Eastern Cape region of the country (Mcgeoch, 1993). 

The size and diversity of the larval assemblages in these 

galls are considered to be potential indicators of habitat 

quality (Mcgeoch and Kruger, 1994); they will be used to 

monitor climatic changes due to global warming, and 

changes in environmental quality caused by pollution and 

habitat loss. Significant differences have already been 

observed in highly disturbed as opposed to undisturbed 

natural areas in the Pretoria region (ChoWll, 1993). 

Gall-like swellings sometimes develop on the stipulate 

thorns of Acacia karroo (Hocking, 1970). An ant, 

Cataulacus rugosus, nests in these hollow spines (Gerstner, 

1948). 

[References:- 50, 56,63,66,71,79,85,87, 109, 110, 127, 

128,141,143,146,159,161,179,181,191,210,211, 

212,213,245,246,247,248] 

Parasitic plants andfungi 

Predators, diseases and harmful physical agencies 21 

Mistletoe species richness in southern Africa is correlated 

with host nitrogen levels. Acacias (27 mg g-l N) support 24 

species in this region (Dean et al., 1994). The crowns of 

Acacia karroo trees are characteristically parasitized by 

various mistletoes particularly during the tree's decline 

towards the end ofits life (Plate 6F). Earlier infestations can 

occur during drought periods or after severe frosts when the 

trees are under stress. Species of mistletoe recorded on A. 

karroo include Loranthus dregei, Moquinella rubra, 

Viscum capense, V. continuum, V. obscurum, and V. 

rotundifolium (Venter, 1971; van der Walt, 1980; Archer, 

1982; Midgeley and Joubert, 1991; Dean et al., 1994). 

Root parasites such as Sarcophyte sanguinea (Visser, 

1981) have been recorded on Acacia karroo and may kill 

the pioneer (Weisser and Marques, 1979; Bews, 1917). 

The rust fungus Ravenelia macowaniana is specific to 

Acacia karroo (Mcgeoch, 1993). The inflorescences and 

young pods can be heavily infested causing gall-like growths 

that inhibit seed production (Potts and Tidmarsh, 1937) 

(Plate 7H). 

[References:- 13,28,33,64,89,110,127,128,130,151, 

152,153,154,159,207,209,230,237,239,242,250] 

Abiotic factors 

Fire 

Acacia karroo is well adapted to establishing itself with no 

shade, shelter or protection from grass fires (Bews, 1917). 

However, all seedlings less than eight weeks old, about 10 

cm high"can be killed by fire. By twelve months, when the 

seedlings are 35 cm high, there is die-back following a burn 

but they re-sprout from the base and each gives rise to 3-4 

stems (Story, 1952). Later, A. karroo will respond 

favourably to a very severe burn producing a dense multi 

stemmed thicket within a season or two (Henderson, 1987; 

Guilloteau, 1958). 

Withholding fire, in combination with overstocking, has 

been responsible for the marked increase of Acacia karroo 

in various parts ofSouth Africa. Overstocking has eased or 

removed competitive effects of grass on the tree seedlings 

and has reduced grass fuel loads and hence fire frequency. 

This has accelerated succession to a mixed thorn scrub 

climax (Phillips, 1936). Fire intensity is an important 

component of the fire regime and its effect on the grass 

sward and bush were investigated in the Eastern Cape 

thornveld. Research indicated that fire intensity had no 

effect on the recovery of grass after a burn. Conversely it 

had a marked effect on the topkill of bush to a height of 2 m. 

The results provide valuable guidelines for the use of fire in 

controlling bush encroachment (Trollope and Tainton, 1986). 



[References:- 33,34, 101, 106, 146, 158, 199, 236] 

Drought 

Acacia karroo has a deep taproot and is independent of 

surface moisture where underground water is available. The 

species is drought resistant but cannot withstand desiccation 

and loss of water from the protoplasm. The seedlings are 

sensitive to desiccation because they are fairly slow growing 

and have a high temperature and moisture requirement for 

growth. Any factor that causes rapid drying of topsoil or 

delays root development will be deleterious to the seedlings 

(Du Toit, 1966). Once established the trees are drought 

resistant (Cunliff, 1975; Henderson, 1987). 

An ecological study has been made of modes of plant 

adaptation to the extreme conditions ofdrought, evaporation 

and temperature that occur in the Natal thornveld. Attention 

is drawn to the extensive root system of most thomveld 

trees, including Acacia karroo, and to the water relations 

(specific conductivity, osmotic pressure, transpiration rate, 

etc.) of woody plants growing in this environment. The 

transpiration rate of thornveld trees is normally high but is 

subject to sharp fluctuations. As compared with forest trees, 

the trees of the thomveld show a much greater latitude of 

functional response to environmental changes (Bayer, 1943) 

[References:- 29,62,70, 106, 136,214,219,220] 

Frost 

Young plants ofAcacia karroo are said to be frost sensitive 

(Carr, 1976) but, once established, the trees are moderately 

resistant (Cunliff, 1975; Henderson, 1987). A frost of -10°C 

may cause defoliation but does not kill the trees. However, 

there are occasionally (once in 50 to 100 years) much more 

severe frosts in its natural range and, on these occasions, 

whole stands oflarge trees in frost hollows and river valleys 

may be completely killed. The extent of frost damage is also 

likely to be dependent upon the environment and state of 

growth ofthe tree. For example, trees planted in the central 

strip of a dual carriageway in a Johannesburg suburb in the 

highveld region of South Africa proved to be much more 

frost-resistant than those in adjacent gardens (Carr, 1977). 

Acacia karroo is more resistant to frost than A. nilotica 

(West, 1951) Faidherbia albida,A. galpinii andA. tonilis 

but not as resistant as A. erioloba. 

A severe frost (c. -12°C) that occurred in the Umguza 

Valley in Zimbabwe only defoliated trees ofAcacia karroo 

but killed the parasitic Viscum sp. mistletoes (Plate 6F). 

[References:- 27, 45, 46, 62, 106, 253] 


Wood 

Anatomy 

PRODUCTS AND USES 

In end section, growth rings and rays ofAcacia karroo are 

well defined, vessels numerous, medium to large, arranged 

along the growth ring parenchyma (Plate 7C). Clear gum 

deposits are present (Plate 7A) and parenchyma is aliformconfluent 

and associated with the vessels (Plate 7C). 

(Goldsmith and Carter, 1981; Kromhout, 1975). Rays are 

1-3 seriate but a significant negative correlation was found 

between latitude and ray height of A. karroo wood 

specimens collected in different parts of South Africa 

(Robbertse et al., 1980). 

Although early work has suggested that Acacia karroo 

wood showed discontinuous rings and indistinct boundary 

parenchyma (Lilly, 1977), it has subsequently been shown 

that marginal parenchyma bands and crystalliferous chains 

do define growth phases in African Acacia species and may 

therefore be useful for age determination (Gourlay and 

Kanowski, 1991) (Plates 7D and 7F-G). In a later study on 

A. karroo (Gourlay and Barnes, 1994), seasonal growth 

rings in the anatomy were confirmed as narrow bands of 

marginal parenchyma filled with long crystal chains (Plates 

7D and 7G) and the number of bands was shown to 

correspond closely to the known ages of the trees. There 

was further confirmation that they were annual in that the 

width of the growth rings was correlated with annual 

rainfall. The bands were laid down during the dry winter 

season when stem diameter growth ceased. The crystals 

were subsequently identified as calcium oxalate through the 

use of a scanning proton microprobe (Gourlay and Grime, 

1994) (Plate 7G). When tree roots take up salty water, 

excess calcium ions must be removed to maintain its water 

balance. These are combined with oxalic acid to produce 

insoluble calcium oxalate which is stored as large prismatic 

crystals in the wood (Prior and Cutler, 1992). 

[References:- 27, 92, 96, 97, 98, 99, 123, 125, 147, 161, 

170] 

Fuelwood 

Acacia karroo is a preferred fuelwood almost everywhere it 

occurs (e.g. Bembridge and Tarlton, 1990) (Plate 8E). The 

only exceptions to this are where slow-growing species such 

as Colophospermum mopane and Combretum imberbe 

occur; but where such old-growth species have disappeared 

and dependence is on fast-growing pioneers, A. karroo is 

unrivalled for its sustained high temperature and cleanburning 

traits. It burns brightly and evenly with little smoke 

and no odour. It produces good coals and little ash. It splits 

easily and, once dried, it does not easily absorb moisture

Dissolving pulp tests have also been conducted on Acacia 

karroo. Its pulping properties are inferior to the three 

Australian acacias with which it is compared in the Table 3; 

A. mearnsii is extensively used for dissolving pulp in South 

Africa and sets the standard by which A. karroo should be 

judged. In addition, it had more spots and a relatively higher 

percentage of shives (21 %). 

[References:- 27] 

Bark 

Bark from the roots of Acacia karroo is used to make twine 

and rope (Archer, 1988) and bark is used in the construction 

of the traditional Nama mat house (Archer, 1989a). A dye 

is extracted from the bark by the Nama people (Archer, 

1989b). The bark of the stem contains up to 19% tannin 

and is used for tanning leather to which it imparts a red 

colour (Timberlake, 1980). It is also used for making twine 

(Wehmer, 1935; Watt and Breyer-Brandwijk, 1962). 

[References:- 14, 16, 194,233,244, 249, 258] 

Gum 

History, specifications and trade 

The historical and present day uses of gum arabic have been 

comprehensively described (Allison, 1993). It is an ancient 

article of international commerce and, among other things, 

it has been used in the mixing of inks and paints, in 

adhesives, cosmetics, perfumery and in medicine. It is a 

unique multi-functional food additive for which 80% of the 

world annual production is used. Its modern day use is 

principally as an emulsifier, flavouring agent, stabilizer, 

humectant, surface finishing agent and thickener in the food 

and pharmaceutical industries. It retards sugar 

crystallization which is an important property. It also has 

potential uses in other industries. 

The following is an extract from the JECFA (Joint 

FAOIWHO Expert Committee on Food Additives) 1990 

Specifications For Identity and Purity ofFood Additives as 

they refer to gum arabic (syn. acacia gum, arabic gum, INS. 

No. E414). 

"Gum arabic is defined as a dried exudation obtained from 

the stems and branches of Acacia senegal (L) Willd. or 

closely related species [it is not made clear whether closely 

related means taxonomically or chemically related]. It 

consists mainly of high molecular weight polysaccharides 

and their calcium, magnesium and potassium salts which, on 

hydrolysis, yield arabinose, galactose, rhamnose and 

glucuronic acid. The article of commerce may be further 

specified as to viscosity. Unground gum arabic occurs as 

white or yellowish white spheroidal tears of varying size or 

as angular fragments. It is also available commercially in 

Products and uses 25 

the form of white to yellowish white flakes, granules, 

powder or spray-dried." 

Specifications have been developed by the Committee to 

identify the substance that has been toxicologically tested, to 

ensure that the substance is of the quality required for safe 

use in foods and to encourage good manufacturing practice. 

The increase in the consumption of convenience foods has 

led to an increase in the use of gum and, at the same time, 

the concern about a healthy diet has stimulated interest in 

thickeners of natural origin. Nevertheless, irregularity of 

supply and fluctuating prices have caused gum arabic to lose 

out to synthetic substitutes on the world market with the 

result that annual gum production has dropped from about 

70,000 tons in the 1960s to 25,000 tons today. The current 

(1995) prices are US$4,200 per ton for ordinary grade, 

US$4,650 per ton for hand-picked nodules and US$5,2oo 

per ton for kibbled ordinary grade ex-Port Sudan from 

which 85% ofthe world production is supplied. Gum arabic 

exports constitute 10-15% of the total foreign currency 

earnings of Sudan. It is interesting that the value of the soil 

ameliorating action of the acacia trees on the arable land on 

which millet crops are grown is estimated to be worth more 

in terms of grain exported from Sudan than is the gum 

(Hassan, pers. comm.)4. Gum arabic is therefore potentially 

a valuable product. With improved quality control and a 

more reliable supply, it could provide a cash income for 

many more resource-poor farmers in Africa. 

Gums from at least ten species of Mrican acacias as well as 

those from other genera, e.g. Combretum and Albizia, have 

been sources of what is marketed as gum arabic. This has 

given rise to considerable controversy in the trade although 

it is now widely accepted under the joint WHOIFAO 

directive, 1989, that the source should be Acacia senegal 

and the 18 species (mostly occurring in Somalia) belonging 

to the A. senegal complex, i.e. those with spicate 

inflorescences and three prickles at or near the nodes 

(Allison, 1993). However, because the gum is collected 

from wild trees by rural people, mixing with gum from 

species outside this group occurs and cannot be detected 

although they might be distinguishable pure. On their own, 

gum from these species would not be acceptable for use in 

foodstuffs and for pharmaceuticals because it would be held 

that they were not toxicologically cleared, a process that 

might be prohibitively expensive for a single species. Even 

in pure form, the chemical constitution of the gums of 

Acacia species from such widely disparate groups as the 

Gummiferae and the Vulgares merge at the boundaries 

indicating that there are some that could be regarded as 

closely related gums in regulatory terms; this could include 

species such as A. seyal and A. karroo (Jurasek et al., 

1993). The situation in regard to A. karroo is most 

unsatisfactory in that it is used regionally as a substitute for 

4professoc Hassan Osman A-Nour, Forests National Corporation, P.O.Box 

658, Khartoum, Sudan 


Detergents. Surfactants, which are responsible for reducing 

the surface tension of water, have specific structural features 

and gum was found unsuitable as a substitute to these products. 

Glue industry. Tylose and emulsions are major ingredients; 

Tylose is used to adjust viscosity. The disadvantage of using 

gum solution itself is that the glue does not dry quickly. 

Stockfeeds industry. Most of the local formulations use 

molasses and starch (also an ingredient) as binders. Gum 

solution was rejected by National Foods on cost and because it 

lacked the molasses flavour. 

Printing industry. The printing industry in Zimbabwe is 

provided with a complete dye carrier which possibly contains 

gums e.g. Guar. Presentation of gum to such customers was 

difficult as they always asked for a match to that carrier. 

Inkindustry. Printing works are already using gum ofAcacia 

karroo. 

Pharmaceutical industry. This industry is looking for a 

microbiologically clean and high quality binder. This is difficult 

to provide until such time as local processors can purify their 

gum to the desired standard. 

Mining industry. Rotation is by hydropbillic and hydrophobic 

flocculation and these are achieved by specialized chemicals. 

Thickeners and emulsifiers are used as lubricants during the 

drilling stage. The main disadvantage of gum solution is the 

slow increase in viscosity with increase in solids. Guar Gum is 

used for the flotation of chelite and tungsten; gum acacia could 

be tried for a range of minerals. 

Pottery industry. A number of pottery companies are already 

using A. karroo gum as a glazing agent. 

Traditionally, Acacia karroo gum is mixed with cattle dung 

for sealing the floors of dwellings (Archer, 1988). 

[References:- 15] 

Fodder 

The foliage, flowers, green pods and parasitic mistletoes of 

Acacia ka"OO are important sources of browse for livestock 

and game in southern Mrica (Plate 6C and back cover). 

When consumption ofA. karroo browse and grass by goats 

was measured in woodland in the Eastern Cape Province of 

South Africa (Teague, 1989a), A. karroo was preferred to 

grass and selected almost exclusively when available at high 

leaf densities. Grass was consumed in significant amounts 

only when approximately 50% of the available A. karroo 

leafhad been consumed. Total intake of browse plus grass 

was lower during the period when the goats changed from 

consuming mostly A. karroo to consuming mostly grass. 

When a dense stand of A. karroo was felled and sheep and 

goats allowed to browse on regrowth, sheep spent 6% and 

goats 50% of their foraging time feeding on the A. karroo 

coppice shoots (Plate 6C). Cattle also browse A. karroo, 

particularly when it is the only green forage in woodland at 

Products and uses 27 

the end of the dry season, but they do not browse it 

preferentially as do goats. In the Transvaal, South Africa, A. 

karroo is particularly susceptible to heavy losses of soft 

green shoots to browsing wild animals in spring (Milton, 

1987). 

The nutrient and mineral content of Acacia karroo browse 

is known to vary with the population, individual tree, soil, 

climate, season, age and browsing pressure. A proper 

understanding of the influence of these factors will not be 

achieved until experiments are established to control them. 

The material that will become available from the Oxford 

Forestry Institute's acacia trials network will provide an 

opportunity to study their effects. The results of one 

comprehensive proximate nutritional and mineral analysis of 

the leaves and pods are given in Table 4. 

The green foliage and pods of Acacia karroo are proteinrich 

(14-15% dry weight), well supplied with phosphorus 

(0.11-0.20% dry weight) (Steenkamp and Hayward, 1979). 

Nitrogen levels in A. karroo foliage are high (23.8 mg g-1 

dry matter) in comparison with levels in the foliage of 

associated plant species growing in river beds in the arid 

southern Karoo region of South Africa (Dean et al., 1994). 

In an investigation into the occurrence of cyanogenic 

glycosides (Steyn and Rimington, 1935), fresh leaves, 

flowers and immature pods of Acacia karroo and four other 

Acacia species from the northern Transvaal, South Africa, 

were submitted to the prussic acid test on fresh and wilted 

material. For A. karroo all tests yielded negative results. By 

comparison, fresh leaves and green pods of A. erioloba gave 

>70 mg ofHCN per 100 g dry weight of plant material, i.e. 

they contained dangerously high levels of cyanogenic 

glycoside. A. karroo is therefore more suitable as a stock 

feed than some other species in this genus. Fresh foliage, 

flowers and green pods of A. korroo sampled at 

Onderstepoort in the Transvaal, South Africa, were found to 

contain no cyanogenic glycoside (Steyn, 1943). 

In a study ofthe leaves of the main tree and grass species of 

a semi-arid savanna in Botswana (Tolsma et al., 1987), it 

was found that seasonal variation in concentrations of foliar 

nutrients followed similar trends in all species. 

Concentrations ofN and P were greater in young leaves than 

in mature leaves, while Ca and Fe accumulated until leaf 

abscission. Concentrations of Ca and Mg in Acacia karroo 

foliage peaked during the dry winter, whereas N, P and K 

levels were greatest in new foliage in early summer. It was 

concluded that P is the most limiting nutrient in this savanna 

because of the strong translocation from leaves to twigs 

before leaf abscission. A. karroo was the exception among 

the eight acacias and two other species included in the study 

in that it was the only tree that was not leafless at the end of 

the dry season. 

There is further evidence of seasonal nutritional variation in 

the foliage ofAcacia karroo in a study of the population 


dynamics ofthe psyllid Acizzia russella-e (Webb and Moran, 

1978). Population levels of the psyllid were ten times 

greater on regenerative foliage of pruned A. karroo than on 

normal trees and, during late summer and winter, 

populations of the psyllid declined more slowly on pruned 

than on normal trees. It is suggested that the availability of 

quantities ofhigh quality nutrients in the leaves of pruned A. 

karroo trees may explain the epidemic population levels 

achieved by the psyllid on pruned plants. 

Patterns of browse selection of goats in Acacia karroo 

woodland were studied in the Cape Province, South Africa 

(Teague, 1989a). The rate of intake of browse was 

positively related to the leaf mass/unit length of the shoot. 

Generally, tannin levels and in vitro digestibility decreased 

following browsing. Leaf and shoot intake was negatively 

related to tannin content and positively related to 

digestibility, thus influencing patterns of selection for 

different plant parts and size classes of A. karroo. 

Viscum and Loranthus spp., of the family Loranthaceae are 

common parasites ofAcacia karroo throughout the range of 

A. karroo. These are browsed by livestock and, in times of 

drought, have been lopped from the trees to help sustain the 

animals. The mistletoes Moquinella rubra, Viscum 

obscurum and V. rotundifolium on A. karroo in the Addo 

Elephant Park of the Eastern Cape, South Africa, are 

selectively browsed by elephant (Midgeley and Joubert, 

1991). A. karroo in the southern limit of its range supports 

four mistletoe species (Dean et al., 1994). 

Bees, Apis mellifera,. collect pollen and nectar from the 

flowers of Acacia karroo in summer (Timberlake, 1980) 

and the honey is used by the rural population throughout the 

species' natural range (see e.g. Archer, 1982). The long 

flowering period of the species makes it a particularly useful 

bee tree (see e.g. Carr, 1976; Timberlake, 1980). 

[References:-13, 17, 18, 19,20,45,52,64,68,117,118,130, 

133,138,145,156,195,197,198,221,224,233,235,247,249] 

Medicine and food 

Acacia karroo roots are prescribed as an aphrodisiac in 

Zimbabwe (infusion taken by mouth) and for pain in the 

alimentary canal, rheumatism (infusion taken by mouth and 

ash from burnt root rubbed onto incisions made on painful 

parts), convulsions (infusion taken by mouth and face 

washed with infusion), gonorrhoea (infusion taken by 

mouth), generalized pains (body wash with infusion), 

syphilis (powder applied on penile sores), and vertigo 

(infusion or powder taken by mouth) (Gelfand et al., 1993). 

A decoction of the bark, which contains 19.7% tannin, has 

been used as an emetic and to treat diarrhoea in humans and 

"tulp" poisoning in cattle. 

The roots are also placed in the fowl run to kill external 

parasites (Gelfand et al., 1993). 

Products and useslEstablishment, yield and management 29 

The gum of Acacia karroo is widely eaten as confection in 

southern Africa (Archer, 1982 & 1988; Wild et al., 1972). 

It is also eaten by animals, particularly vervet monkeys 

(Cercopithecus aethiops) and bushbabies (Galago spp.). 

Children chew the sweet thorns of A. karroo in kwaZulu 

(Milton and Bond, 1986). Seeds have been used as a 

substitute for coffee (Watt and Breyer-Brandwijk, 1962). 

[References:- 13, 14, 24, 86, 133, 146, 155, 244] 

Soil amelioration 

Once its "skirt" of thorny branches has died and fallen off or 

been pruned, Acacia karroo has only a moderately dense 

crown that allows enough light through for the development 

of a grass and shrub understorey. It flushes early in the 

spring when the temperatures are at their highest and before 

the rains have come which is when shade is most needed to 

reduce soil temperatures (Plate 6B). 

Acacia karroo is known to nodulate (Bames et al., 1994) 

(Plate 6D). Increases in dryland crop yields following 

clearance of A. karroo are well known in the communal 

areas of Zimbabwe. The benefits are not as marked where 

crops are planted in mixture with the trees but this is said to 

be due to shading effects rather than to a reduction of 

fertility or competition for water. 

Cattle farmers recognize the beneficial effects that Acacia 

karroo has on the range through its influence on the species 

composition of the associated grasses. There is typically 

development of an understorey of perennial, palatable and 

nutritious grasses, such as Panicum maximum and 

Cenchrus ciliaris, which thrive on the environmental 

benefits that stem from the species' ability to provide shade, 

utilize water and nutrients from depth, fix nitrogen, improve 

soil structure and aid infiltration of rainfall (Roberts, 1963; 

Felker, 1981; Acocks, 1988). Grasses such as Panicum 

maximum are, in fact, dependent for their existence on the 

presence of bush (Acocks, 1988). If the trees are cleared 

away, this grass survives for only one or two years and is 

then replaced by less valuable species. Results obtained 

from grazing trials in Zimbabwe leave no doubt that, where 

the rainfall is sufficient to support perennial grasses, the 

ideal stage in the succession to maintain is where perennial 

grasses predominate (West, 1955). 

[References:- 2, 25, 27, 80, 169,254] 

ESTABLISHMENT, YIELD AND 

MANAGEMENT 

There is no published record of Acacia karroo having been 

planted and managed on an operational scale. Populations 



that have been used for studies of establishment, yield and 

management have all been naturally regenerated stands (see 

under life cycle) in the species' indigenous range. 

Nevertheless, research conducted to establish introduction 

plots and trials for genetic evaluation have resulted in some 

knowledge being gained on the technology for the artificial 

establishment of the species. 

In its natural range Acacia karroo is reported as being easy 

to raise from seed (Carr, 1965) and it has been planted 

widely in experimental plots in South Africa (Browne, 

1981) and also in Botswana in test plots for fuelwood 

production (Tietema and Merkesdal, 1986). It has been 

reported as one of the fastest growing species planted in the 

Botanical Gardens in Harare, Zimbabwe (Muller, 1979). It 

has also been recommended for special sites such as mine 

dumps (Aylen, 1961) and the central strip in dual 

carriageways (Carr, 1977). 

As an exotic, Acacia karroo has been reported as doing well 

in desert conditions (100-200 mm annual rainfall) in Israel 

(Gindel, 1946; Kaplan, 1957) and in the Rajasthan Desert, 

India (1980). It is threatening to become naturalized in 

Western Australia (Scott, 1991). It has even been suggested 

as a suitable subject for bonsai (Ormond, 1968). 

[References:- 41,44,46, 114, 140, 142, 150, 184, 232] 

Establishment 

Seed collection 

The pods ofAcacia karroo dehisce on the tree. If they are 

collected before they open, the viability of the seed is 

severely prejudiced. Therefore collection must be during 

the period when the sound seed is still suspended from the 

pod on the thread-like funicle (Plate IF). The funicle is 

brittle at this stage and any shaking of the pods will result in 

the seed falling to the ground where it is unrecoverable 

unless a ground sheet is laid beneath the canopy. The seed 

is therefore most effectively collected by breaking off the 

whole bunch ofpods direct into a cloth or polythene bag and 

separating seed from pods later by crushing and winnowing. 

A high proportion of the seed is often already damaged by 

bruchids when the pods open and, as this seed is light, it 

remains suspended by the funicle for a much longer period 

than the heavier sound seed. It is therefore critical to make 

sure that the seed is collected before the sound seed has 

fallen otherwise viability in the seed collected can be so low 

that it is virtually useless. 


Seed storage 

Provided the seed is sound, ripe and hard when collected, it 

is robust and can remain viable for 50 years or more in dry 


conditions in ambient temperatures (Story, 1952). It is 

thought that if the seed is subjected to freezing down to 

15°C for 48 hours, remaining bruchid eggs and larvae are 

killed (Nixons pers. comm.)8 


Seed pretreatment 

As with most Acacia species, the seeds of Acacia karroo 

have water impermeable dormancy (Du Toit, 1966) and this 

must be broken before the seed can germinate. In nature 

this is either accomplished through the erosion of time in 

moist soil or, more rapidly, by passage through the digestive 

tract ofa browsing animal. Artificially any of the techniques 

used to break or soften the seed coat can be used. These 

include boiling in water (Story, 1952), hot wire 

scarification, abrasion of the seed coat (Carr, 1976) and 

nicking the coat with a pair of nail cutters. The most 

effective way of ensuring rapid and uniform germination is 

to nick the seed coat at the micropylar end, soak in water for 

12 hours, pre-germinate in a controlled temperature cabinet 

at a constant temperature of 35°C and sow the seed in the 

nurserywhen the radicle appears which is usually in two to 

three days. 

[References:- 26, 40, 45, 60, 62, 70, 164, 199] 

Nursery 

The seed ofAcacia karroo must be sown directly into pots, 

tubes or "speedling" polystyrene trays. Pretreated seed 

germinates within three or four days of sowing. If nicking is 

used, damaged seed can be recognized during the nicking 

process and discarded; this can ensure 90-100% 

germination (Barnes et al., 1995). 

It is amenable to being raised in a container with a medium 

volume of as little as 100 cm 3 and will tolerate repeated 

pruning ofthe taproot by shearing or by desiccation through 

placing the container off the ground or on an impervious 

substrate (Nixon, pers. comm.)8. 

Sterilization of nursery soil kills the rhizobia and probably 

delays the development of nodules on the roots until after 

planting out in the field. Inoculation with rhizobia of plants 

growing in soil that has been sterilized does not appear to 

bring about as good a response as inoculation of plants 

growing in unsterilized soil; this has been tentatively 

attributed to the mycorrhizae also being killed by the 

sterilization (Sutherland et al., 1994). Low soil fertility and 

small container size in which the nutrient reserves are 

rapidly depleted stimulates the development of nodules on 

the roots. Although there is some indication that 

performance can be enhanced through inoculation in the 

% K. NixOIl, ICFR, p.a. Box 375, Pietermaritzburg, 3200 South Africa


No. of specimens 

120---------------,------------, 

-4- Buds and flowers 

100 . 

80 . 

60 . 

40 . 

20 . 

00--.-::=:Q::==-----------------------.---1t' 

jul aug sep oct nov dec jan teb mar apr may jun 

Month 

Figure 5 Flowering and fruiting phenology ofAcacia karroo. This chart was constructed using the flowering and fruiting 

status entered for the herbarium specimen held in the BRAHMS database. The total numbers in the "buds and flowers" and the 

"mature fruit" categories are plotted against month ofcollection. 

1.0-----------------------r-I 

0.9 

0.8 

0.7 

0.6 

1Q) 0.5 

E ::J 

(5 > 

0.4 

0.3 

0.2 

0.1 

volume =-0.042 + 0.000668·basal area bh 

r 2 =0.963 

o 200 400 600 800 1000 1200 1400 1600 

basal area at breast height (cm2) 

Figure 6 Relationship between basal area at breast 

height (1.3 m) and total over-bark volume to 5 cm minimum 

branch diameter for a stand of Acacia karroo on Umguza 

Valley Estates in Zimbabwe. (From Gourlay et al., in press). 

Bames, R.D., Filer, D.L. & Milton, SJ. 

1.0 

0.9 

0.8 

0.7 

0.6 

1 Q) 0.5 

E ::J 

(5 > 

0.4 

0.3 

0.2 

0.1 

0.0 

volume = -0.089 + 0.000634·basal area ah 

l =0.933 

.:- 

: . 

. 

200 400 600 800 1000 1200 1400 1600 

basal area at ankle height (cm2) 

Figure 7 Relationship between basal area at ankle height 

(0.1 m) and total over-bark volume to 5 cm minimum 

branch diameter for a stand of Acacia karroo on Umguza 

ValleyEstates in Zimbabwe. (From Gourlay et al., in press).

Plate 5 Acacia kan-oo (left to right sequence) 

A In scrub near the coast in the eastern Cape Province of South Africa 

B On the beach on Bazaruto Island in Mozambique 

C In the coastal dune forest of Zululand, South Africa 

D On black vertisols in the Umguza Valley, Matabeleland, Zimbabwe 

E On a salt-encrusted (sodium carbonate) island in the inland Okavango Delta in 

Botswana 

F In the Bokaap district of Cape Town 

G In the Kalahari Gemsbok National Park in South Africa

Plate 6 Acaci mIToo (left to right sequence) 

A Lush perennial Panicum maximum pasture beneath the trees 

B The trees follow A. erioloba in being among the first to flush at the end of the dry 

season 

C Foliage and flowers in reach are heavily browsed by domestic and wild animals 

D The species nodulates early and prolifically 

E Intensive root system on a tree uprooted in the coastal sand dunes 

F The parasitic mistletoe, Viscum sp., is conspicuous after it has been killed by a 

heavy frost while the tree has survived 

G Extensive root system exposed of a tree growing near a river in a black vertisol

Plate 7 Acacia katToo (left to right sequence) 

RUN 147089 25-APR-91 (250um) 

OPS39: Acacia Kr 

A Gum exudation from the inner bark associated with wood-boring insect activity 

probably a cossid moth in this case 

B The larvae of a number ofCerambycid beetles bore in the stems 

C The thin continuous line of marginal parenchyma in the wood can be distinguished in 

transverse section from the aliform parenchyma associated with the vessels (photo I.D. 

Gourlay) 

D The chambered cells of the marginal parenchyma are crystalliferous (Photo I.D. 

Gourlay) 

E Drought and wood borers stimulate gum production at the end of the dry season 

F The marginal parenchyma has been shown, by wounding experiments, to be laid down 

annually during the dry season (photo I.D. Gourlay) 

G The crystals in the marginal parenchyma have been found to be calcium oxalate by 

scanning proton microprobe (Photo I.D. Gourlay) 

H The fungus Ravenelia macowaniana on pods: the galls are inhabited by an assemblage 

of microlepidoptera


Browse 

In southern Africa, livestock is produced mainly in the 

Karoo, grassland and savanna biomes (Bosch and Tainton, 

1988). The grasslands lie on a gradient from the more arid 

south-west area where the vegetation retains its nutritional 

value throughout the year, to sour grasslands and savannas 

in the more eastern parts of the region where the rainfall is 

higher, the soils more leached and acid, and the herbage less 

acceptable to livestock in winter. In grassland and 

grassland/savanna that receives a mean annual rainfall of 

500-800 mm, unsound livestock management practices and 

abandonment of worked-out arable lands have led to 

encroachment by shrubs and trees that prejudice the 

production of grass. Foremost among these bush 

encroaching trees are a number of the Acacia species, the 

natural pioneers on disturbed and degraded land. A. karroo 

is prominent in this role over large parts of the Karoo and 

grassland biomes of South Mrica as it is on the heavier 

soils, particularly in vleis and along rivers, in the open 

savanna woodlands that fall into this environmental category 

in other parts of southern Africa. Often, both grazing 

(cattle, sheep) and browsing (goats) animals are farmed in 

these areas where they compete for forage and further 

influence the competitive balance between herbaceous and 

woody plants (Stuart-Hill, 1985). 

A great deal of attention and research has been focused on 

devising methods to eradicate encroaching Acacia karroo. 

In the Eastern Cape, removal of thickets has been attempted 

by using goats to browse the bush, by ringbarking and by 

poisoning with arsenite of soda, dieseline and oil waste. 

When there is continuous, heavy grazing by cattle, sheep 

and goats, the ground can become colonized by Cynodon 

dacty[on, a rhizomatous grass, and under such conditions, 

seedlings ofA. karroo are grazed down and cannot establish 

themselves (Comins, 1962). Continuous grazing by goats 

causes higher mortality of trees than does rotational grazing 

(du Toit, 1972b). However, there has been little success in 

eradicating the tree from rangeland and recently there has 

been much more effort directed towards conducting research 

to understand its ecology and quantify its potential with a 

view to managing it to increase productivity of non-arable 

land, particularly in the farming systems of the Eastern Cape 

Province ofSouth Africa where the species occurs in almost 

pure stands over very large areas. 

Most studies in rangeland dominated by Acacia karroo have 

been directed towards identifying and understanding the 

influence of factors affecting the relative amounts of grass 

and browse produced off the veld and being able to quantify 

these. In the course ofthis work there has been considerable 

development of the methodology to evaluate browse 

management systems and strategies. 

In a model to simulate browse production and response of 

Acacia karroo to defoliation (Teague et al., 1990), 

sensitivity analyses indicated that five parameters had a very 

strong influence on the output of the model. These were 


moisture, soil depth, the magnitude and duration of growth 

stimulation following defoliation, how soon growth was 

initialized and how favourable growing conditions were in 

spring; plant size and the carry-over of growth stimulation 

from one year to the next had a moderate influence. 

Indices of potential competition with grass and browse 

productivity of single-stemmed Acacia karroo trees can be 

predicted within c. 25% error using maximum tree height, 

maximum canopy radius and height of the canopy bottom as 

basic measurements (Hobson and de Ridder, 1991). 

Various quantitative descriptive units for woody plant 

communities have been proposed (Smit, 1989). These are 

the Evapotranspiration Tree Equivalent (ETTE), Browse 

Tree Equivalent (BTE) and Canopied Subhabitat Index 

(CSI), which describe the status of a woody community in 

terms ofpotential moisture use, value of the trees as food for 

browsers and subhabitat suitability for grass-tree 

associations, respectively. A Quantitative Description Index 

(QDI) for woody plant communities, containing descriptive 

unit-values, is proposed. Regression equations were 

developed from harvested Acacia karroo trees. 

In a study to compare the response of Acacia karroo plants 

to defoliation by hand compared to defoliation by goats 

(Teague, 1988a), leaf growth on plants 50% defoliated by 

goats was approximately three-fold that on plants 50% 

defoliated by hand but, at the same time, leaf growth on 

hand-defoliated plants was approximately twice that of 

undefoliated plants. This suggests that the browsing animals 

themselves should be used in any defoliation studies. 

In a study in semi-arid savanna in South Africa (Stuart-Hill 

and Tainton, 1989b), experimentally isolated Acacia karroo 

showed that trees suppressed grass growth up to 9 m away, 

depending upon their height, but that tree removal also 

reduced grass growth. Grass growth was reduced when 

trees were frequently defoliated, probably because of the 

stimulatory effect ofdefoliation on the competitiveness ofA. 

karroo. Tree production increased in response to sward 

removal but was unaffected by sward harvesting, except if 

trees were defoliated frequently when production of browse 

increased in response to frequent grass harvesting. It is 

argued that residual soil moisture levels remain relatively 

high when grass growth is poor, so that water penetrates to 

greater depths after rain than when grass growth is vigorous 

and this favours the deep rooted trees (Stuart-Hill and 

Tainton, 1988). 

In the same region, research to investigate the competition 

between Acacia karroo and grass for water (Stuart-Hill, 

1985), showed that the trees thrived only where water 

penetrated regularly to some depth. Stemflow did not 

appear to be important in supplying water to the deeper soil 

la)efs. Most of the water penetrating to deep soil did so by 

moving through the uninterrupted soil profile. The process 

was enhanced where boulders were embedded in the soil. 

Dense grass rapidly depleted soil water to a depth of 60 cm.

In the absence of dense grass, evaporative losses were low 

and water was retained in the profile. Rainfall on an area 

with low grass biomass resulted in penetration of the wetting 

front to a depth that permitted vigorous tree growth. 

Generally, trees can have both a beneficial and a detrimental 

influence on the herbaceous layer. Grass benefits from the 

shade and leaf litter supplied by the trees but suffers from 

the reduced amount ofmoisture available (Stuart-Hill, 1985) 

(Plates 6A and 8G). 

A study was conducted in the Eastern Cape Province of 

South Africa to explore the response of Acacia karroo 

plants to defoliation by goats in a farming situation (Teague, 

1987). Growth in A. karroo was dominated by current 

growing conditions. Plants were able to make opportunistic 

growth at any time to take advantage of favourable 

environmental conditions. By growing in flushes and 

consolidating after each flush, these plants are able to cope 

with a variable climate and damage from herbivory. 

Moisture stress merely slows growth, with the pattern of 

growth being unaffected. 

In a study on the effect of intensity and phenophase of 

defoliation and water stress on the rate of photosynthesis and 

the recovery of carbohydrate reserves in Acacia karroo 

(Teague,1988b and 1988c), the rate of photosynthesis of 

fully expanded leaves increased markedly following 

defoliation. Light defoliation increased photosynthetic rate 

the most. Total non-structural carbohydrate levels dropped 

significantly after defoliation. The magnitude of decrease 

was directly related to the intensity of defoliation. Recovery 

ofcarbohydrate levels was much faster after heavy than after 

light defoliation. Rates of recovery were also faster 

following defoliation in the second half of the growing 

season than in the first half, but the plants that had been 

heavily defoliated in the second half of the growing season 

had not fully recovered carbohydrate levels before leaf fall 

in late autumn. Moisture stress has very little effect on 

carbohydrate levels in comparison with the defoliation 

treatments. 

Another study to determine the effect of browsing (Teague, 

1986), showed that leaf production in Acacia karroo was 

increased two- to three-fold at an optimum browsing 

intensity that varied with the phenophase of the tree. Trees 

were most sensitive to defoliation at the early flush, when 

carbohydrate levels are at their lowest, and at the 

reproductive phase and it is recommended that, for 

maximum production, they be defoliated by 25-50%, 

followed by a rest period of 3-6 months, depending on the 

phenophase. (See also Teague and Walker, 1988a and 

1988b; Aucamp, 1976.). The more frequently plants are 

defoliated, the more carbohydrate reserves drop but plants 

do adjust to cope with very frequent defoliations (Teague, 

1989b). Trees are more sensitive to defoliation in the upper 

than in the lower canopy (Teague, 1989c). 

Acacia karroo occurs in the semi-arid Eastern Cape 

Establishment, yield and management 35 

Province ofSouth Africa in almost pure stands in an open to 

dense tree savanna. It has a deleterious effect on grass 

production and its increase cannot be prevented by burning, 

resting or judicious grazing management with cattle. 

However, it has been found to be possible to control the 

species with browsing goats and, at the same time, to 

increase meat production per unit area without adversely 

affecting grass production (Teague, 1986). 

A model was developed to simulate the response of Acacia 

karroo to a wide range of different climatic patterns and 

defoliation regimes (Teague et al., 1990). Increases in A. 

ka"OO harvests can be achieved with different management 

strategies such as increasing the number of camps, varying 

the length of stay in each and varying the rest period before 

the next occupation at different stocking rates. But the most 

important predictions of the model were that large increases 

in productivity could be expected by sparing use early in the 

growing season and that even if it were possible to reduce 

stock in times of drought, it would be of very little benefit. 

It has been recommended that Acacia karroo should be 

utilized by browsers and converted into saleable animals 

rather than removed to keep grazing animals (Aucamp and 

Barnard, 1980). This recommendation has been supported 

by a study (Aucamp and Danckwerts, 1986) which showed 

that grass production did not decrease linearly with 

increasing tree density and that maximum red meat 

production and profitability occurred when A. karroo 

density approached 1600 tree equivalent/ha and goats and 

cattle were stocked together. In another study (Hobson and 

de Ridder, 1993), A. karroo browse production was found 

to be negatively related to tree density at the beginning

Acacia karroo is a species full of contradictions. 

CONCLUSIONS AND FUTURE RESEARCH 

1. Morphologically, it is so variable at its extremes that 

taxonomists repeatedly propose that it should be 

divided into as many as six different taxa; yet none of 

these proposals has ever matured because the variants 

are generally linked to the central type by so many 

intermediate forms. 

2. Ecologically, it is essentially a pioneer; yet there are 

environments, both man-made and natural, in which it 

perpetuates itself as the dominant, and often virtually 

the only tree species in the plant community. 

3. Economically, it is described as a species with an 

almost unlimited number of uses but, at the same time, 

most of the research done is on its eradication. It is 

accused of invading grassland and reducing 

productivity; yet it has been shown that it should be 

maintained at a very high stocking in the range for 

maximum red meat production. 

4. Nutritionally, it is a preferred browse for livestock; yet 

it has a high tannin content that appears to prejudice the 

retention ofproteins. The gum has for many years been 

widely used in the food and pharmaceutical industries 

locally; yet it is not accepted in international trade as it 

has not been proven to be non-toxic. 

A. karroo is, however, accepted universally as a 

rehabilitator of degraded sites and dunes, as providing the 

environment for sustained production of nutritious perennial 

grasses and as a very high quality fuelwood. 

The research and review on Acacia karroo reported in this 

monograph highlight five areas of recent findings. 

1. The molecular studies and the fITst field trials have 

indicated that there is significant genetic variation in A. 

karroo across environments, particularly between the 

coastal and the inland provenances, and the species' 

tolerance of a wide range of climates and soils may be 

due to genetic diversity rather than to a versatility of 

genotype. 

2. The discovery of an anatomical feature in the wood of 

A. karroo that corresponds with annual growth now 

means that the productivity and dynamics of natural 

stands can be quantified and modelled. Further, the 

strongly linear correlation that has been found between 

basal area and volume suggests that the simple and 

economic mean tree method of stand volume estimation 

can legitimately be used. 

Conclusions and future research 37 

3. The application of the dendrochronological techniques 

has shown A. karroo to be short-lived but much more 

highly productive than was previously thought. 

4. Review ofthe literature from the eastern Cape Province 

of South Africa on browse production has drawn 

attention to the large amount of information that is now 

available on the inter-relationship of A. karroo and 

grass production and the value of the species for goats. 

5. It has been found that A. karroo crosses naturally with 

other acacias, which reveals that there is the potential to 

complement its desirable attributes in hybrid 

combination with those of other Acacia species. 

In the light of these findings, where do we go from here? 

What more do we need to know about Acacia karroo before 

we can start managing the natural stands, planting degraded 

land and bringing in the goats? The following are put 

forward as the most important areas for research. 

1. A rangewide ecological assessment of the vegetation 

types that include A. karroo is required to determine the 

common factors that govern its occurrence. How 

important is it ecologically? What determines whether 

it is secondary with disturbance or whether it is it part 

ofthe climax? Does karroo modify its environment to 

suit itself? To what extent is its expansion in abundance 

and range primarily attributable to the increase and 

enclosure of domestic livestock? What are the precise 

conditions that are required for episodic invasion? 

2. Field evaluation trials are needed over a wide range of 

sites to establish the degree and mode of genetic control 

of the adaptational, morphological, physiological and 

chemical traits of interest in A. karroo. The extremes 

of environment over which the species is indigenous 

will in itself have a profound effect on the morphology 

of the tree but these environments will certainly have 

induced significant genetic responses, an understanding 

ofwhich is essential for effective domestication and use 

of the species. These trials should also provide the 

opportunity to resolve some of the species' intractable 

taxonomic problems. 

3. The isozyme studies of A. karroo are unusual in that 

they suggest that there may be some link between a 

chemical product at the level of the gene and an 

adaptive trait. Further research is needed to establish 

this; and if it is found to be so, there may be a unique 

opportunity to use early molecular screening in 

selection for economically important traits. 



4. The potential benefits from species hybrids are such 

that controlled pollinations should be made between A. 

karroo and a number of other species selected for the 

complementarity of their attributes. Quite apart from 

the heterosis that could emerge from testing these 

crosses, the hybrids might also be sterile which would 

eliminate the invasive problems in the range. 

5. There is an urgent need to quantify the benefits that 

stem from A. karroo in terms of both soil fertility and 

the species composition, mass and nutritional value of 

the grasses that are dependent upon it to counter the 

traditional denigration of the species as an unwelcome 

invader. 

6. The new dendrochronological techniques should be 

used in studies of stand dynamics and productivity in 

representative stands of A. karroo to quantify its 

economic worth throughout its range. 

7. The acceptability of the gum of A. karroo for 

international trade in the food and pharmaceutical 

industries needs to be investigated with a view to the 


development of exports from the countries where it is 

indigenous. 

8. Research is needed to determine the precise nature of 

the tannins in the foliage ofA. karroo and their effect on 

the accessibility ofproteins in livestock rumens. 

9. Management systems must be devised to exploit the 

potential of natural stands of A. karroo, to introduce it 

into agricultural systems and to integrate genetically 

superior material into agroforestry situations where an 

indigenous variant already exists. 

The diversity and ubiquity ofAcacia karroo evokes this rich 

response of research to exploit its undoubted potential to 

increase productivity from non-arable land in semi-arid 

lands in some ofthe most problematical and poorest regions 

of the world. Although the work recommended is selected 

for its immediate downstream developmental value, there is 

little doubt that it will also lead to the understanding of much 

more basic issues that have an application far beyond the 

domestication of A. karroo itself.

ANNOTATED BIBLIOGRAPHY 

Annotated bibliography 39 

This bibliography is arranged in alphabetical order of authorship. Subject groupings can be accessed by reference to the 

publication numbers at the end of each section in the main text of the monograph. There is also an author index at the end of 

the bibliography in which the publication numbers are given for each author. 

Both the published and the grey literature on Acacia karroo have been searched for this bibliography. Many references were 

found in which the species has been noted to occur in particular vegetation types or in certain areas during visits and travels by 

various individuals and groups; these have not been included in the bibliography unless there is information in them that is 

additional to a note of their occurrence. In some abstracts, information is given on other species where this serves to place A. 

karroo in context in the subject being discussed. 

Not all the publications cited were available to the authors and CAB International abstracts have been used in a number of 

instances and acknowledged. Where a publication was judged to be of significance from its title but neither the paper nor an 

abstract was available, it has, nevertheless, been included without annotation. 

In the monographic section, reference has been made to a number of works that do not specifically mention A. karroo but which 

are pertinent to the discussion of the particular topic. For ease of reference, these are included, without annotation, in this 

bibliography rather than in a separate section. 

1 ACOCKS, I.P.H. Riverine vegetation of the semi and 

arid regions ofSouth Africa. Journal ofthe South African 

Biological Society (1976) 17, 21-35 [En] 

Acacia karroo occurs along rivers in 26 of 30 

vegetation types sampled in arid and semi arid parts of 

South Africa. 

2 ACOCKS, l.P.H. Veld Types of South Africa. 3rd 

edition Botanical Survey ofSouth Africa Memoirs (1988) 

No. 40, 128 pp. [En, 20 ref.] 

South African vegetation types are comprehensively 

examined with vegetation maps and separate veld type map 

given. Acacia karroo is an important constituent of the 

following south African vegetation types: savanna, karoo 

(semi-desert) along river courses, coastal dune forest. It 

occurs in regions receiving between 170 and 900 mm p.a. 

in winter, and summer rainfall regions. Associated plant 

species are listed and reports given on the western 

movement of A. karroo which is already a very widespread 

species throughout the region. A map is included to show 

this movement. 

3 ACOCKS, lP.H. Acock's notes: key grasses ofSouth 

Africa. Zacharias, PJ.K. (compiler) Grassland Society of 

southemAfrica, P.O. Box 750, Howick 3290, South Africa. 

(1990) 82pp. [En] 

4 ADAMSON, R.S. Notes on the vegetation of the 

Kamiesberg. Botanical Survey of South Africa Memoirs 

(1938) No. 18,24 pp. [En] 

Acacia karroo is restricted to water courses on the 

plains surrounding the Kamiesberg mountain in 

Namaqualand, Cape, South Africa. This region receives an 

annual rainfall of 200-300 mm. 

5 ALLISON, G.E. Gum arabic: an ancient trade in 

decline? M.Sc. Thesis, Oxford Forestry Institute, 

Department of Plant Sciences, University of Oxford (1993) 

165 pp [En] 

The approach in this work is basically historical. 

Sources of gum arabic are fIrst described together '·with 

production techniques. The development of the gum arabic 

trade is traced from the earliest times to the present. Factors 

affecting supply to the world market are identified and there 

is discussion on how demand has changed over the years. 

The future of the trade is discussed in the context of current 

developments and the findings of the study. Although there 

is only brief mention of Acacia karroo being used in 

Zimbabwe and South Africa, this work constitutes a 

comprehensive account of the subject that is highly relevant 

to the acceptance ofthe species as a source of gum arabic on 

the world market. 

6 ANDERSON, D.M.W.; Chemotaxonomic aspects of 

the chemistry of Acacia gum exudates. Kew bulletin 

(1978) 32 529-536 [En] 

7 ANDERSON, D.M.W.; CREE, G.M. Studies on 

uronic acid materials Part XXVI. The aldobiouronic 

acids in gums from Acacia species. Carbohydrate 

Research (1968a) 6 214-219 [En, 15 ref.] 

Reports on a number of studies, the results of which 

indicate that the methoxyl content in an Acacia gum 

polysaccharide is associated with the uronic acid residues, 



but is not present as methyl ester. Of the species studied to 

date, those having positive specific rotations contain the four 

aldobiouronic acids (A-D); the exceptions were A. karroo 

andA. nubica gums which have low methoxyl contents and 

consequently small proportions (if any) of the 4-0-methyl 

acids C and D. [CABI abstract] 

8 ANDERSON, D.M.W.; CREE, G.M. Studies on 

uronic acid materials Part XXVII* The structure ofthe 

gum from Acacia nubica Benth. Carbohydrate Research 

(1968b) 6 385-403 [En, 17 ref.] 

A study ofthe polysaccharide exuded by Acacia nubica 

trees was made. The disaccharide, 

3-0-a-D-galactopyranosyl-L-aravinose, found in A. senegal, 

A. cyanophylla and A. karroo, was not detected. [CABI 

abstract] 

9 ANDERSON, D.M.W.; DEA, LC.M. Review Article 

Chemotaxonomic aspects of the chemistry of Acacia 

gum exudates. Phytochemistry (1969) 8 167-176 [En, 89 

ref.] 

The results of chemical studies of the gum exudates 

from thirty Acacia species are reviewed, and their 

taxonomic significance is discussed with respect to 

Bentham's divisions of the genus. According to Benthamls 

classification of gum exudates A. karroo belongs to the 

Gumifferae series sub-series Medibracteatae. [CABI 

abstract] 

10 ANDERSON, D.M.W.; KARAMALLA, K.A. Studies 

on uronic acid materials Part XVI!. Inter-nodule 

variation and the acidic components in Acacia nilotica 

gum. Carbohydrate Research (1966) 2 403-410 [En, 11 

ref.] 

A study of the inter-nodule variation and acidic 

components in Acacia nilotica gum was made. Prior to this 

investigation only A. karroo and A. senegal were reported 

to contain two aldobiouronic acids; on reexamination, those 

species previously reported to contain only 6-0 

(B-D-glucopyranosyluronic acid)-D-galactose may be found 

to be more complex. [Author's summary] 

11 ANDERSON, D.M.W.; PINTO, G. Variations in the 

composition and properties of the gum exuded by 

Acacia ka"oo Hayne in different African locations. 

Botanical Journal of the Linnean Society (1980) 80 (1) 

85-89 [En, 13 ref.] 

The variation in chemical composition of 15 specimens 

of the gum exudate from Acacia karroo Hayne, obtained 

from four different African locations, was investigated. The 

range of analytical values found (e.g., specific rotation +36° 

to +67°; uronic acid 10.3 to 18.1 %; rhamnose 4 to 10%) 

reflect the well known variability of this species. The major 

analytical difference concerns the unusually wide range of 

molecular weights observed, Le., 1.5 x lOS to 48 x 10 3 • The 

Barnes, R.D., Filer, D.L. & Mihon, S.J. 

material of highest molecular weight, from trees infested 

with Cerambycid beetle, is consumed by bush-babies 

(Galagidae). [CABI abstract] 

12 ANDERSON, D.M.W.; BRIDGEMAN, M.M.E.; DE 

PINTO, G. Acacia gum exudates from species of the 

series Gummiferae. Phytochemistry (1984) 23 (3) 575-57 

[En, 19 ref.] 

Data are reported from gum polysaccharide analyses of 

specimens from the African species Acacia ehrenbergiana, 

A. xanthophloea, A. hockii andA. sieberana [A. sieberiana] 

var. villosa, and the Australian species A. calcigera. 

Comparisons are made with published data for A. sieberana 

var. sieberana and A. karroo and taxonomic implications 

discussed. [CABI abstract] 

13 ARCHER, F.M. [A preliminary study on edible 

plants of the Kamiesberg] In Voorstudie in verband met 

die eetbare plante van die Kamiesberge. Journal ofSouth 

African Botany (1982) 48 (4) 433-449 [Af] 

The Nama herders of the Kamiesberg area of the 

northwestern Cape, South Africa (29°S 1SOE) eat Acacia 

karroo gum as a confection. Bees (Apis mellifera) collect 

nectar from the flowers of A. karroo in summer and the 

honey is used by the herders. The people also eat the fruits 

ofthe mistletoes Moquinella rubra that grows on A. karroo. 

Pods and foliage are browsed by livestock and green 

branches are used to build the framework of traditional 

Nama dwellings. 

14 ARCHER, F.M. Customary plant use in 

Namaqualand: Acacia lean-oo Hayne - A tree with many 

uses. Veld & Flora (1988) 74 (3) 111-112 [En] 

Gum exuding from injuries to the bark of Acacia karroo 

is eaten or mixed with cattle dung for sealing the floors of 

dwellings. Extracts from the bark are used as a colic remedy 

and as a dye for leather. Bark from the roots is used to make 

twine and rope. Tall, young branches are used to make the 

framework of dwellings and are also bent to make crooks 

and hooks used in hunting and livestock management. The 

rotten heartwood is used as tinder and the most important 

use ofsound wood is as fuel. A bracket fungus that grows on 

green and dead wood is pounded and used as talcum 

powder. 

15 ARCHER, F.M. [Construction of a typical Nama 

mat house] Die konstruksie van 'n tradisionele Nama 

matjieshuis. Saggitarius (1989a) 4, 20-22 [Af] 

Use ofAcacia kllrroo poles and bark in construction of 

traditional Nama dwellings in Leliesfontein, Namaqualand, 

Cape, South Africa. 

16 ARCHER, F.M. [Plant 

Nama-speaking KhoiKhoi 

utilization by the 

of Namaqualand]

Plantegebruik in die tradisionele vel verwerking van die 

Nama-sprekende KhoiKhoi van Namaqualand. Saggitarius 

(1989b) 4, 23-24 [Af] 

Use ofdye and fibre from Acacia karroo bark and roots 

by Nama people in Leliesfontein, Namaqualand, Cape, 

South Africa. 

17 AUCAMP, A.1. The role of the browser in the 

bushveld of the eastern Cape. Proceedings of the 

Grassland Society ofsouthern Africa (1976) 11135-138 

[En] 

Goats reduce Acacia karroo cover as well as providing 

meat from farmland with high densities of scrubby A. karroo 

trees. 

18 AUCAMP, AJ.; BARNARD, H.H. [An investigation 

ofthe stock production potential of the dry grass-bush 

community of the eastern Cape] Die ontplooing van die 

veekuddepotensiaal van die droe gras-bosgemeenskappe in 

die Oos-Kaap. Proceedings of the Grassland Society of 

southern Africa (1980) 15 137-140 [M] 

In semi-arid rangeland a plant should not be removed 

unless it can be replaced by something better and plants 

(such as Acacia karroo) that can be converted into saleable 

animals should be utilized by browsers rather than being 

removed so as to keep grazing animals. 

19 AUCAMP, A.1.; DANCKWERTS, J.E. Browse as a 

forage source in semi-arid south savannah rangelands: 

a resource under siege. Proceedings of the 2nd 

International Rangeland Congress, Adelaide, Australia, 

13-18 May 1984. Canberra, Australia; Australian Academy 

of Science (1986) 403-404 [En] 

Five treatments were replicated twice:- 1) complete 

removal of woody plants; 2) partial clearing to a density of 

five hundred Acacia karroo plants/ha; 3) partial clearing to 

one hundred A. karroo/ha; 4) partial clearing to 1500 A. 

karroo/ha; 5) no removal ofwoody plants. Grass production 

did not decrease linearly with increasing tree density. 

Maximum red meat production and maximum profitability 

occurred when A. karroo density approached 1600 tree 

equivalents/ha and goats are run in conjunction with cattle. 

20 AUCAMP, A.1.; DANCKWERTS, lE.; TEAGUE, 

W.R.; VENTER, 1.1. The role of Acacia karroo in the 

False Thomveld ofthe Eastern Cape. Proceedings ofthe 

Grassland Society ofSouthern Africa (1983) 18, 151-154 

[En] 

Grass production did not decrease linearly with 

increasing densities ofAcacia karroo. Grass production was 

not affected up to a density of 297 tree equivalents per 

hectare but decreased rapidly when tree density exceeded 

1000 units/ha. Maximum feed production (grass plus bush) 

was achieved at 847 tree equivalents per ha. Maximum 


profit would be obtained by using cattle and goats together 

(112 cattle and 500 goats/1000 ha) where A. karroo was at 

a density of 1600 trees/ha. Total clearing of bush cannot be 

justified in terms of meat production. 

21 AUCAMP, AJ.; DANCKWERTS, J.E.; VENTER, J.1. 

The production potential of an Acacia ka"oo 

community utilized by cattle and goats. Journal ofthe 

Grassland Society ofSouthern Africa (1984) 1 (1) 29-32 

[En, af, 15 ref.] 

In studies on the relationships between bush density and 

animal production and profitability/ha, Boer goat farming 

was more profitable in the short term than beef ranching. 

The best long-term strategy was a combination of goats and 

cattle in an integrated animal production system. Such an 

integrated system was approximately three times as 

profitable as a pure beef production system. A prerequisite 

for implementing such a system is that stocking rates of 

cattle must be set according to the condition of the 

herbaceous vegetation and stocking rates of goats must be 

set according to the condition of the woody vegetation. 

22 AYLEN, D. Vegetation growing in unlikely 

conditions: Rhodesia Trees in South Africa (1961) 13 (3) 

58-61 [En] 

Observations are made on natural or planted vegetation 

succeeding under unlikely conditions; trees as yet form only 

a minor part ofthat vegetation. On mine dumps a number of 

species have been found including Acacia karroo. 

23 BALA, B.B. A comparative study of sporogenesis 

and embryogeny in Acacia ka"oo and Acacia caffra. 

M.Sc. Thesis (1978) Faculty of Science, Fort Hare, South 

Africa. 73 pp. [En, 61 ref.] 

In Acacia karroo, four microspore mother cells are 

formed in each lobe of the anther and each of these gives 

rise to 16 microspores. The young ovule is orthotropous at 

first gradually becoming anatropous. The archesporium 

appears as a single cell and is hypodermal in origin; it cuts 

off parietal tissue on the upper side and forms the megaspore 

mother cell which_ divides into two dyad cells which give 

rise to a linear tetrad of megaspores. The chalazal 

megaspore forms an embryo sac while the micropylar 

megaspores degenerate. The primordia of integuments 

appear at the megaspore mother cell stage; the micropyle is 

formed by the outer integument alone. Two polar nuclei are 

suspended in the centre of the embryo sac by means of 

cytoplasm and the three antipodal cells. The first division of 

the embryo is transverse, the second vertical and later 

divisions irregular. The cotyledons are differentiated when 

the proembryo is of a massive type. The endosperm follows 

the nuclear type of development. It is not completely 

reabsorbed by the developing embryo and a little endosperm 

remains in the mature seed. 



24 BARNARD, A. The Cape Journals of Lady Anne 

Barnard. Eds. Robinson, Lenta, M., and Driver, D. van 

Riebeck Society, Cape Town (1994) p 345 [En] 

On Acacia karroo:- "I pluck'd from the great thorn trees 

some of their prickles of which I send you a few...they 

exactly resemble the horns of the Cattle, I hear the plant has 

found its way to Kew Gardens and is there called the 

"Cuckold Tree" it is certainly no scandal to give it that name, 

for richIy does it deserve it from the quantity of horns it 

bears, and all being white, at a distance looks as if the Tree 

was covered with snow. They are excellent toothpicks and 

in case of necessity might do very well for pins the points 

are so sharp and the wood so tough." 

25 BARNES, R.D.; FAGG, C.W. The potential of 

African acacias in agricultural systems in the dryland 

tropics. Paper at Inter-Divisional Session 4, Tropical and 

sub-tropical dry forests, IUFRO xx World Congress 

(1995), Tampere, Finland, 6-12 August, 1995. 12 pp. [En] 

Acaciaipecies dominate the dry zones of Africa. They 

provide the rural people of the continent with multiple 

products including fuelwood, fodder, food, fibre and gums. 

Their role is becoming more prominent because of their 

ability to use deep sources of water and nutrients, fix 

nitrogen and colonize and rehabilitate the increasing amount 

of degraded land. Genetic variation and their range of 

ecologies give them the potential of being more formally 

used to ameliorate soils and climate and to increase 

productivity throughout dryland Africa. Their most likely 

use is in improving animal production by enriching the 

range in silvopastoral systems, in restoring fertility in bushfallows, 

in inter-cropping with grain crops and in woodlots 

dedicated to fuelwood or gum production. Research into 

genetic variation of six important species including A. 

karroo, is providing the information and materials necessary 

for breeding. Research is also needed into their ecology to 

help integrate this superior material into operational 

agricultural systems. A knowledge of the environmental 

conditions that are required for the periodic mass 

regeneration events and an understanding of the 

competitional and allelopathic relationships must be 

acquired to provide a basis for the development of 

management techniques to establish and control the 

improved germplasm in the new environments. 

26 BARNES, R.D.; CHIMBALANGA, J.; MARUNDA, 

C. Project RS6S3: genetic evaluation ofAfrican Acacia 

species: phase I. First }ear report, Oxford Forestry Institute 

(1995) 38 pp. [En. 10 figs.] 

This report describes the work of a project to establish 

genetic evaluation trials of 70 provenances of six species of 

African acacias, including 10 provenances of Acacia 

karroo, over a number of sites near Bulawayo, Zimbabwe. 

Differences between seedlings from various provenances of 

A. karroo are illustrated. The eight sites selected for 

screening trials cover a range of climatic and edaphic 

conditions with mean annual rainfall varying of 300-650 


mm and soils derived from granitic, basaltic and metavolcanic 

parent materials and wind-blown sands. 

27 BARNES, R.D.; FILER, D.L.; LOCKHART, L.A.; 

GOURLAY, I.D. Acacia karroo: evaluation and 

assembly ofgenetic resources. Unpublished Final Report 

ofODA Forestry Research Scheme R.4526. Oxford Forestry 

Institute (1994) 157 pp [En, 17 tables, 30 figs, 275 ref.] 

This final report describes the work completed under a 

three-)ear (plus one-year extension) Research Scheme (No. 

R.4526, 1 January 1989 to 31 December, 1993) conducted 

by the Oxford Forestry Institute and funded by the Overseas 

Development Administration of the United Kingdom 

Government. It also describes uncompleted studies, started 

with non-project scientists and agencies, which also 

constituted important accomplishments of project. The 

development ofthe database BRAHMS (Botanical Research 

And Herbarium Management System) and the production of 

a systems manual was a major output from the project. 

BRAHMS is an information system for storing and 

processing botanical data. It is a tool that has been 

developed to assist with botanical research, both 

monographic and floristic, and to provide curatorial support 

in the herbarium. It was an invaluable asset in the study of 

the taxonomy, natural distribution and phenology of Acacia 

karroo and details of 800 specimens from all the main 

herbaria for the species were logged into the system. 

BRAHMS is also now being used by a broad range of ODA 

and other projects in Europe, Africa, Latin America and 

Asia. The second major achievement of the project was 

the seed collections that were made to represent the full 

geographic, climatic, edaphic, ecological and morphological 

range of the species as indicated by the data accumulated in 

BRAHMS and by observations made on field trips. These 

26 seed collections are being used in evaluation of genetic 

variation both in the laboratory and in the field. The third 

achievement concerned two isozyme studies of A. karroo, 

one an extension of Brain's (1989) leaf peroxidase study to 

cover the species' whole range and the other a study of 12 

isozyme systems over 12 populations selected to cover the 

species natural distribution. The results indicated that, 

although the majority of genetic variation is within 

populations, there are important regional groupings. This 

information was used to improve the precision of the 

sampling strategy for seed collection. One of the most 

significant findings was that a particular allele in one of the 

leaf peroxidase loci becomes fixed in the east coast dune 

populations. Another significant finding was that the 

populations of A. karroo on the islands of the Bazaruto 

archipelago in Mozambique are genetically distinct from all 

other populations studied for these allozyme systems. The 

fourth achievement was the development of an ageing 

technique for A. karroo through counting the crystalliferous 

terminal parenchyma bands from stem discs or cores, and 

the use of this technique to make the fust assessment of 

growth rate and productivity of a natural stand of the 

species. The fifth major achievement was the production of 

plans for the field trials, including selection of sites and

cooperators and deciding on the composition and design. 

These trials ofA. karroo will provide the structured material 

needed for future research not only into genetic variation, 

but also into its silviculture and use in agricultural systems. 

The objectives of the trials include studies to clarify the 

taxonomy and reproductive biology of the species as well as 

studies of variation and its control in adaptability, 

productivity, phenology and ability to ameliorate site. A 

crucial area for future research will be an investigation into 

the conditions that cause the species to adopt its invasive 

mode and whether sterility can be induced into the species 

either directly or through species hybrids so that its 

multifarious attributes can be used without the risk of 

invasion. 

28 BAXTER, B.; YEATON, R.I. Partitioning of an 

environmental resource between the sexes ofa dioecious 

hemiparasiJe. South African Association ofBotanists 17th 

Annual Congress Abstracts, University of Natal, 

Pietermaritzburg (1991) 152 pp. [En] 

In the Weenen Nature Reserve the major host of Viscum 

verrucosum (lIarv.), a dioecious hemiparasite, is Acacia 

karroo. The broad pattern of distribution of A. karroo 

follows water courses. Over an environmental gradient at 

right angles to the water course, A. karroo experiences 

increasing water stress. The distribution of V. verrucosum 

on A. karroo is governed by water stress and not host 

availability. The distribution of the hemiparasite is far 

narrower than that of its host. At the dry extremes of the 

gradient both the hemiparasite and its host are more stressed 

than at the wet extreme. The V. verrucosum exhibits sexual 

segregation along the moisture gradient, the sex ratio being 

female biased in the wet sites and male biased in the dry 

sites. Fruit diameters were significantly greater in wet sites. 

29 BAYER, A.W. The Thornveld tree: a note on plant 

adaptation. South African Journal ofScience (1943) 39, 

44-55 [En] 

An ecological study of the vegetation of the Natal 

thornveld, with particular reference to modes of plant 

adaptation to the extreme conditions of drought, evaporation 

and temperature which occur in this habitat at certain 

seasons ofthe year. The dominant trees which have invaded 

these former grasslands seldom exceed 12-15 ft. in height 

and are usually rather widely spaced (20-60 or more yards 

apart). The most common dominants are certain Acacia 

species (e.g. A. karroo, A. arabica, A. caffra and A. 

robusta) and a few leafless succulent species of Euphorbia. 

Species of Gymnosporia, Cassine, Dovyalis and Zizyphus 

are also common. The author discusses different types of 

plant adaptation as exemplified in succulent and 

non-succulent species. Attention is drawn to the extensive 

root system of most thornveld trees, to the production by 

many species ofthorns and axillary leaf fascicles, and to the 

water relations (specific conductivity, osmotic pressure, 

transpiration rate, etc.) of woody plants growing in this 


environment. The transpiration rate of thornveld trees is 

normally high but is subject to sharp fluctuations. As 

compared with forest trees, the trees of the thornveld show 

a much greater latitude of functional response to 

environmental changes. [CABI abstract] 

30 BEMBRIDGE, TJ. Eradication of thorn trees. 

Rhodesian Agricultural Journal (1966) 63 (4), 86-88 [En, 

2 ref.] 

Control of thornveld dominated by Acacia karroo and 

A. nilotica on a cattle ranch in Rhodesia was achieved in 

trials (at a cost of 25 S.ll000 trees) by frill-cutting all trees 

> 2 in. d.b.h. and brushing with 2,4,5-T at 1: 200 dilution in 

diesel oil. A burn twelve months later controlled all new 

regeneration. Use of old motor oil was cheaper than and 

almost as effective as diesel oil for the dilutent. Treatment 

resulted in twice as much dry-matter production of grass as 

on control plots two years later. 

31 BEMBRIDGE, TJ.; TARLTON, J.E. Woodfuel in 

Ciskei: a headload study. South African Forestry Journal 

(1990) 154 88-93 [En, 29 ref.] 

The results are presented of a study of the use of 

fuelwood in one region in the Ciskei, South Africa. Data 

were provided by respondents on the number ofheadloads 

per week and the time taken in collecting wood. The 

amount, sizes and types of wood collected were recorded. 

On average, rural women spend over two hours per day 

collecting fuelwood headloads of 24 kg air-dry mass, 

comprising approximately twenty eight pieces of 2.40 m 

length with a diameter of 44 mm and a mass of 862 g. The 

number of headloads averaged over five per week and 

average per capita consumption of fuelwood was 1.14 t. 

Women have a good local knowledge of tree species 

collected for fuelwood. Acacia karroo was the most 

favoured species. The open fire is used for cooking two to 

three meals per day. Paraffin was the most favoured 

alternative fuel but was used mainly for lighting. Patterns of 

fuelwood usage are location specific and vary widely. 

Research is needed into the multiple use of woody 

vegetation, as well as appropriate means of conserving 

fuelwood. [CABI abstract] 

32 BENTIIAM, G. Revision ofthe sub-order Mimoseae. 

Trans. Linn Soc. Looo. (1875) 30 335-664 

33 BEWS, lW. Plant succession in the thorn veld. 

South African Journal ofScience (1917) 14 (4) 153-172 

[En] 

Acacia horrida (A. karroo) andA. arabica (A. nilotica) 

are the chief pioneer species establishing on bare ground in 

the Pietermaritzburg area, Natal, South Mrica. They are 

well adapted to establishing with no shade, shelter or 

protection from grass frres. Many other woody plants 

germinate beneath the these thorn trees and may 



subsequently kill the pioneer. 

34 BOSCH, OJ.H.; TAINTON, N.M. Ecological 

principles and their application to rangeland 

management in South Africa. In Vegetation science 

applications for rangeland analysis and management 

[edited by Tueller, P.T.]. Dordrecht, Netherlands; Kluwer 

Academic Publishers ISBN 90-6193-195-9 (1988) 363-397 

[En, 87 ref.] 

In South Africa, livestock is produced mainly in the 

Karoo, Grassland and Savanna biomes. The grasslands, 

strongly dominated by hemicryptophytes of the Poaceae, 

follow a soil gradient from the more arid area in the west 

whose vegetation retains its nutritional value throughout the 

year to sour grasslands in the more eastern fringe whose 

herbage is acceptable to livestock only in the summer 

growing season and in whose structure fITe has played a 

large part. In grasslands receiving rainfall of 500-800 mm 

per annum, overgrazing leads to encroachment by shrubs 

and trees, particularly Acacia karroo. The savannas have 

shrub components, includingA. karroo, whose management 

includes the use of goats to browse shrubs not consumed by 

cattle and sheep. Ecological studies over the last six decades 

have provided useful principles with regard to limitations 

inherent in rangeland production and are being used to 

define sound management practices. 

35 BRAIN, P. Leafperoxidase types in Acacia kaTToo. 

Geographical distribution and influence of the 

environment. South African Journal ofBotany (1986) 52 

(1) 48-52 [En] 

Leaf peroxidase types were examined by starch gel 

electrophoresis in 1 662 individuals ofAcacia karroo Hayne 

from twenty localities in southern Mrica. The patterns show 

a zone of slow anodic migration with relatively little 

variation, and a fast zone under independent genetic control 

which is highly polymorphic. Most individuals have either 

one or two fast bands, but a proportion (5% overall; 0-20% 

at individual localities) has three or four. Multiple banding 

is more frequent in colder localities. Fast zone phenotypes 

vary both geographically and with climate, and phenotypic 

diversity is strongly correlated with low temperature and low 

rainfall. 

36 BRAIN, P. Immunology and phylogeny: a 

preliminary study of Acacia. South African Journal of 

Science (1987) 83 (7) 422-427 [En, 16 ref.] 

The seed proteins of thirty seven species of the 

cosmopolitan genus Acacia were investigated serologically 

by double diffusion and immunoelectrophoresis, using rabbit 

antisera to separate A. karroo, A. ataxacantha, and A. 

meamsii. Identity and absorption tests showed remarkable 

homogeneity in the series Gummiferae; all the Mrican 

species, except A. albida, reacted identically, as did the 

Australian A. bidwillii. The two American species (A. caven 

and A. farnesiana) were identical to them in three of the 

four bands observed on immunoelectrophoresis. A. albida 


reacted atypically with all the antisera, and is probably not 

an Acacia. The four African species with spicate 

inflorescences, classified in the series Vulgares, also form a 

tight group, but the series Phyllodineae originating from 

Australia is very variable, only one of the 17 species 

examined absorbing all activity from the anti-mearnsii 

serum. The Australian Phyllodineae and Botryocephalae 

appear serologically closer to the African Vulgares than to 

the Gummiferae, confirming hypothesis of a separate origin 

for the latter group. These findings are considered in the 

light of phylogeny and plate tectonics. 

37a BRAIN, P. Genetic races in a ring species, Acacia 

kaTroo. South African Journal of Science (1989) 85 (3) 

181-185 [En, 9 ref.] 

In a study of 3080 Acacia karroo trees from forty two 

sites in South Africa and Namibia, electrophoresis of leaf 

extracts and staining for peroxidase revealed a 

polymorphism. Cluster analysis differentiated three genetic 

races: a western or Karoo race with highest frequencies of 

the slower K and L bands; an intermediate or Eastern Cape 

race with highest frequency of the central M band; and an 

eastern or Natal-Lowveld race lacking K and with highest 

frequencies of the fastest N and 0 bands. The species 

encircles the Drakensberg massif, with no latitudinal gene 

flow. The Natal-Lowveld race meets a race of higher K 

frequency at two places: near the Natal-Transkei border on 

the east coast, where there is a gradual reduction in K going 

north; and at the northern end of the ring west of 

Pietersburg, where there is a very sudden west to east fall in 

K frequency, from 29% to 3%, in the course of a few 

kilometres. [CABI abstract] 

37b BRAIN, P.; HARRIS, S.A.; BARNES, R.D. Leaf 

perioxidase types in Acacia ka"oo Hayne (Acacieae, 

Leguminosae): a range-wide study. (in prep.) 

Peroxidase variation has been assessed in 63 

populations (4322 individuals) of Acacia karroo Hayne 

(Acacieae: Mimosoideae) from across its entire southern 

Africa range. Twenty-seven different phenotypes were 

identified with between two and 22 phenotypes found per 

population. Shannon's measure of phenotypic diversity 

varied from 0.15 to 4.11 (mean 2.71), whilst apportionment 

of the diversity showed that 74% of the diversity occurred 

within populations. Six coastal dune populations of A. 

karroo from Zululand and Mozambique clustered together 

and had a low phenotypic diversity. Band M is common 

throughout the range ofthe species but it is virtually fixed to 

the exclusion ofother bands in the coastal dune populations. 

Band K, on the other hand, is restricted to the Karoo region 

ofthe Cape Province ofSouth Mrica with lower frequencies 

in the adjacent Highveld region of the central and western 

Transvaal province to the north. It is completely absent to 

the east of the Drakensburg Mountains and very rare in the 

west and north of its range. The implications of these data 

for seed sampling strategies in A. karroo are considered. 

[Authors'summary]

38 BREDENKAMP, G.1.; BEZUIDENHOUT, H. The 

phytosociology ofthe Faan Meintjies Nature Reserve in 

the western Transvaal grassland, South Africa. South 

African Journal ofBotany (1990) 56 (1) 54-64 [En, 1 map, 

23 ref.] 

Near Klerksdorp, Transvaal, South Africa, Acacia 

karroo woodland occurs on the lower slopes of lava and 

quartzite hills. A. karroo was the dominant tree, 5-6 m in 

height with a canopy cover of 22%. Understorey has a 

canopy cover of about 9% and is made up of low shrubs, 

particularly Grewiaflava, Protasparagus suaveolens, and 

Zizyphus zeyheriana. 

39 BROOKE, R.K. The bird community of 

Tamarix-clad drainages, northwestern karoo, Cape 

Province. Ostrich (1992) 62 (1) 42-43 [En] 

Lists twenty eight species of birds found in Acacia 

karroo dominated drainage lines in arid parts of the Cape 

Province, South Africa, and compares them with the twenty 

species of birds found in Tamarix usneoides dominated 

drainage lines in the same region. 

40 BROWN, N.A.C. A study of seed-coat 

impermeability, seed germination and seedling growth 

in certain Acacia species. M.Sc thesis in Department of 

Pasture Science, Faculty of Agriculture, University of Natal, 

Pietermaritzburg, South Africa (1965) [En] 

In this investigation, a detailed study was made of the 

morphology of the seed and the anatomy of the seed coat of 

Acacia nilotica ssp. kraussiana and A. torti/is ssp. 

heteracantha and some observations were made on A. 

karroo. 

41 BROWNE, C.W. Sowing tree seeds in situ. Trees in 

South Africa (1981) 32 (4) 95-98 [En] 

Reports on experimental planting at fifty sites with the 

seeds of various indigenous and exotic trees. The seeds of 

Acacia karroo were among those that germinated 

successfully.] 

42 BRYANT, 1.P.; KUROPAT, P.1.; COOPER, S.M.; 

FRISBY, K.; OWEN-SMITII, N. Resource availability 

hypothesis of plant antiherbivore defence tested in a 

South African savanna ecosystem. Nature (1989) 340 

227-229 [En] 

Acacia karroo seedlings grow faster during their first 

three months than three other sympatric acacia species 

grown in green house experiments. 

43 BURLEY, 1.; HUGHES, C.E.; AND STYLES, B.T. 

Genetic systems of tree species for arid and semi-arid 

lands. Forest Ecology and Management (1986) 16 317 

344 [En] 


44 CARR, 1.D. The propagation of indigenous trees. 

Trees in South Africa (1965) 17 (2) 30-40 [En] 

It is suggested that one positive step to preserving 

native flora would be to engage actively in the propagation 

of those species that will enhance a garden. Amongst the 

highveld species Acacia karroo is suggested as a species 

that could be raised from seed. 

45 CARR, 1.D. The South African acacias. 

Johannesburg, South Africa; Conservation Press (Pty.) Ltd. 

(1976) 68-77 [En] 

Detailed descriptions are given of all the forms of 

Acacia karroo that occur in South Africa. For cultivation 

from seed, seeds should be sanded on one edge, scalded with 

boiling water and left to soak for 24 hours. Seedlings take 

from 5-13 days to emerge. Saplings can reach 2 m within 

their fIrst year on good soils with adequate water. Early 

pruning may be necessary to produce a straight stem. 

Vigorously-growing plants should be staked. Young plants 

are frost sensitive. 

46 CARR, 1.D. Indigenous trees as street subjects in 

Sandton. Trees in South Africa (1977) 28 (4) 110-112 [En, 

1pt] 

Trees planted in the central strip of a dual carriageway 

in a Johannesburg suburb in the highveld region of South 

Africa proved to be much more frost-resistant than in 

adjacent gardens. Promising species (including Acacia 

karroo, Dombeya rotundifolia) and unpromising species 

are listed. The protective effect of being in the central strip 

could not be completely explained. 

47 CARR, J.D. Indigenous Trees on the Median Strip. 

Trees in South Africa (1981) 33 (2) 48-52 [En] 

Reports on the success of planting various species on 

the median strip ofdual carriageways in detail; other species 

involved in the experiment are listed, including Acacia 

karroo [both "Typical" and "Lydenburg" forms]. 

48 CHAPPILL, 1.A.; MASLIN, B.R. A phylogenetic 

assessment oftribe Acacieae. In: Crisp, M., and Doyle, 1.1. 

(editors) Advances in legume systematics 7: Phylogeny 

(1995) Royal Botanic Gardens, Kew, p. 77-99 [En] 

49 CHARLSON, AJ.; NUNN, J.R.; S1EPHEN, A.M. The 

composition of Acacia ka"oo gum. Journal of the 

Chemistry Society, University of Cape Town (1955) 

1428-1431 [En] 

Acid hydrolysis of Acacia karroo gum furnishes Lrhamnose 

(2%), L-Arabopyranosyl-L-arabopyranose, 4-0alpha-D-glucuronosyl-D-galactose, 

and 6-0-beta-Dglucuronosyl-D-galactose 

have been isolated from the 

products of partial hydrolysis. The gum differs markedly in 



structure from other Acacia gums so far examined. 

50 CHOWN, S. Moths for monitoring. Our Living World 

(1993) South African Nature Foundation [En] 

A community of small moths is closely associated with 

the fungus galls growing on the widespread tree species 

Acacia karroo in southern Africa They will be used to 

monitor climatic changes due to global warming, and 

changes in environmental quality caused by pollution and 

habitat loss. Significant differences have already been 

observed in highly disturbed as opposed to undisturbed 

natural areas in the Pretoria region. 

51 CHURMS, S.C.; STEPHEN, A.M.; STEYN, C.B. 

Analytical comparison of gums from Acacia hebeclada 

and other Gummiferae species. Phytochemistry (1986) 25 

(12) 2807-2809 [En, 25 ref.] 

Analyses are reported of arabinogalactan-proteins from 

Acacia hebeclada and comparisons made with analyses and 

published data on A. tortilis ssp. heteracantha, A. karroo, 

A. erioloba and A. robusta var. clavigera. [CABI abstract] 

52 CLARKE, 1. Building on indigenous natural 

resource management: Forestry practices in 

Zimbabwe's communal lands. Forestry Commission, 

Harare, Zimbabwe (1994) 55 pp. [En] 

This book marks a step in the search for a new 

approach to development forestry in Zimbabwe. It builds on 

the experience of the Forestry Commission in promoting a 

new approach to working with rural communities. Attitudes 

of foresters have had to be changed from one of being 

"gurus" of development forestry to one of being catalytic 

agents. To do this they have had to build on indigenous 

knowledge, promote participation, develop local-level 

capacity, demonstrate tangible benefits of sound resource 

management and devolve control. Descriptions of 14 diverse 

case studies by local farmers are contained in a matrix of 

two chapters, one on recognition of existing forestry 

practices and one on building on these practices. Acacia 

karroo figures significantly in the study of village-based 

woodland management in Ntabazinduna. This communal 

area was deforested as a result of fuelwood cutting for the 

nearby city ofBulawayo. One resident started protecting the 

A. karroo near his home and the practice of pruning and 

thinning rather than cutting is now spreading on its own. 

The pruned branches are spread on the ground to reduce 

run-off and to promote grass establishment. None of the area 

is fenced and stock graze and browse beneath the pruned 

trees. The trees provide poles, fuelwood, fodder and 

protection from wind. 

53 Q.ARKE, J.M.; CROCKFORD, KJ. An evaluation of 

eucalypt woodlots and acacia woodland management 

practices in Ntabazinduna Communal Land, Zimbabwe 

(in press.) Comnwnwealth Forestry Review [En, 31 ref.] 


The promotion of eucalypt woodlots and management 

of Acacia woodlands in Ntabazinduna, a low rainfall 

communal land in Zimbabwe, are evaluated. With the 

exception of the council plantation which has shown good 

yields, many ofthe small community woodlots of Eucalyptus 

camaldulensis have completely failed and the very best 

showed an MAl of only 2.09 m 3 ha-1 yr-1. Innovative self 

help initiatives in woodland management have been 

concentrated on protecting and managing the Acacia 

regrowth near homes. Six woodland groves, predominantly 

A. karroo, aged between 4 and 30 years were examined and 

productivity was found to range between 0.7 and 3.2 t ha-1 

yr-l. The local communities list a wide range of products 

and values being derived from the Acacia woodland 

including fuelwood, poles, gum, shade for livestock, 

windbreaks, improved grazing, browse and fodder. 

54 CLEGHORN, W.B.; McKAY, A.D.; CRONIN, C.H. 

Results of preliminary arboricide and herbicide trails 

on a number of species limiting livestock carrying 

capacity of veld in Southern Rhodesia. Proceedings of 

the 1st African Weed Control Conference, Victoria Falls 

(1958) 39 pp. From abstract in Weed Abstract 7 (12), 

(1958) 2215 [En, 10 ref.] 

Reports on the effectiveness of various arboricides on 

Brachystegia spicijormis, Isoberlinia globiflora, 

Terminalia sericea, A. heteracantha, Combretum 

apiculatum and Dichopetalum cynwsum and a number of 

Acacia species. Monuron and diuron up to 120 lb/acre had 

little effect on Acacia species generalIy. Na arsenite (50%) 

at 1.5 oz/stump killed 93% of Acacia subalata; paraffin as 

a basal bark treatment was less effective. A. karroo was 

much less susceptible, the best kill being only 15%. 

Preliminary observations showed that ring barking, blazing 

or applying NH4 sulphamate or 2,4,5-T in water to blazes 

had little effect on A. karroo, A. subalata, A. gerrardii, A. 

nigrescens or A. rehmanniana; 2,4,5-T in dieselene, or 

diesel oil alone, applied to blazes, were promising. A. 

rehmanniana reacted similarly. 

55 COATES-PALGRAVE, K.E. Trees of Southern 

Africa. Cape Town; Struik (1977) 240 pp. [En] 

The book describes and illustrates all the indigenous 

and many ofthe naturalised non-indigenous species of trees 

at present known to occur in South Africa, Zimbabwe, South 

West Africa, Botswana, Lesotho, Swaziland and 

Mozambique. The distribution map for Acacia karroo 

shows it to be the most widespread acacia if not one of the 

most widespread trees in the region. It describes the species 

as a tree to 15 m occurring over a wide range of altitudes 

from coastal scrub to woodland, wooded grassland, often 

along rivers and streams. Its presence is considered to be an 

indication of sweet veld and its uses described as almost 

unlimited making it an asset on any farm. It is a good be tree, 

a good fodder and the gum can be used for confectionary and 

adhesive purposes. The bark can be used to make rope and 

the timber, although susceptible to borers, is suitable for

making furniture. It is a very adaptable tree, frost- and 

drought-resistant and fast-growing. It provides shade, fuel 

and very effective fences made from the thorny branches. It 

is a protected tree in the northern Cape Province and the 

lacobsdal district of the Orange Free State in South Africa. 

56 COE, M.; COE, C.E. Large herbivores, acacia trees 

and bruchid beetles. South African Journal of Science 

(1987) 83 (10) 624-635 [En, 85 ref.] 

The African acacias comprise 128 of the 1200 species 

throughout the world. These are variously defended by 

spines or hooks. Eleven per cent of the African species 

develop "pseudo-galls" which are occupied by predatory 

Crematogaster ant species. Acacia pods may be classified 

into dehiscent and indehiscent forms, the latter being 

favoured by large browsing herbivores which disperse the 

seeds. Seeds from indehiscent pods are thick and robust, and 

resist the shearing forces of the molar teeth of large 

herbivores much better than dehiscent seeds. Acacia pods 

reach their full size before the seeds swell, thus conserving 

their nutrients. The activities of ants and the rapid 

mobilization of chemical defences may explain why 

specialist browsers feed only in short bursts. The larvae of 

bruchid beetles are important predators of acacia seeds. The 

larger bruchids are more likely to attack indehiscent than 

dehiscent seeds. Virtually all seeds may be colonized by 

these beetles on occasion, though 10% is more common. 

X-ray studies show that up to 16% of acacia seeds are 

digested in their passage through the gut of large herbivores. 

Consumption by these mammals not only aids in the 

dispersal of seeds but also reduces bruchid attack. It has 

been demonstrated that in the bright yellow flowers of A. 

karroo and some other species, small sterile involucellate 

flowers develop as a small secondary capitulum before the 

main fertile flowers open. It has been suggested that these 

may serve to attract insects, to ensure that they are already 

present in large numbers before the fertile flowers open. A. 

karroo has dehiscent seeds. [CABI abstract] 

57 COE, M.; BEENTlE, H.E. A Field guide to the 

Acacias of Kenya. Oxford University Press (1991) 3 [En] 

This work describes 43 Acacia species in Kenya. Notes 

the increased commercial use of gum from A. karroo in the 

confectionery industry. 

58 COETZEE, l.A.E. The morphology ofAcacia pollen. 

South African Journal ofScience (1955) 52 23-27 [En, 1 

ill., 14 ref.] 

A study was made of 28 South African and 31 

Australian species ofAcacia. In this insect-pollinated genus, 

only eight large pollen grains are produced per anther. On 

vaselined slides exposed for twenty four hours on a warm, 

windy day in a flowering A. horrida (A. karroo community, 

no more than 8 pollen grains were found per 7 cm 2 • An 

illustration show the germination ofA. karroo pollen grains. 


59 COETZEE, B.1.; VAN DER MEULEN, F.; 

ZWANZIGER, S; GONSALVES, P.; WEISSER, P.1.E. A 

phytosociological classification of the Nylsvley Nature 

Reserve. Bothalia (1976) 12 (1) 137-160 [En, fr, af,27 

ref., 1 map, 3 tab.] 

This work classifies the vegetation in the Nylsvley 

Nature Reserve in the Transvaal mixed bushland 

hierarchically by the Braun-Blanquet method. There are four 

major groups ofplant communities in the seasonal grassland 

and deciduous savannas of which the third, grassland and 

thorn savanna on calcareous self-mulching vertisols, is 

dominated by A. karroo. 

60 COHEN, C.E. Stoebe vulgaris. A study of an 

ecological problem. Journal of South African Botany 

(1940) 6 (2) [En] 

Seeds ofAcacia karroo were kept on the soil surface at 

air temperature and watered daily, but no germination 

occurred in sixty two days. 

61 COMINS, D.M.E. The vegetation ofthe districts of 

East London and King William's Town, Cape Province. 

Botanical Survey ofSouth Africa Memoirs (1962) No. 33, 

1-32 [En, 1 detailed vegetation map, photos, 38 ref.] 

A parklike Acacia karroo woodland with large trees 

scattered in grassland occurs in some areas of the eastern 

Cape and is ideal for grazing. Scattered A. karroo trees 

serve as foci for development of clumps of fruiting shrubs. 

Thickets ofsmall A. karroo trees with little grazing beneath 

them develop on parkland overgrazed by cattle and on 

abandoned ploughed fields. Removal of thickets was 

attempted using goats to browse the thickets, ringbarking 

and poisoning with arsenite of soda, dieseline and oil waste. 

When there is continuous, heavy grazing by cattle, sheep and 

goats, the ground is covered by a rhizomatous grass 

(Cynodon dactylon). Under such conditions, seedlings of 

A. karroo are grazed down and cannot establish. 

62 CUNLIFF, K.M.E. Trees for tomorrow (Acacia 

kan-oo). Trees in South Africa (1975) 27 (2) 50-51 [En, 3 

photos of flowers, thorns, pods] 

Acacia karroo is the most widespread Acacia in 

southern Africa. This hardy, deciduous tree is armed with 

paired, white stipular spines varying in length from 2-10 cm. 

Flowers are bright yellow, sweet scented and are usually 

produced in early to mid summer (November-December). 

The pods, which are 50-120 mm long and 6-10 mm wide, 

split when ripe to release several seeds measuring about 6 

by4 mm. The hard-coated seeds should be soaked in water, 

initially hot, for a day or two before sowing. It does not grow 

well in acid soil. Transplanting should be done early so as 

not to damage the long tap root that develops soon after 

germination. Once established the trees are frost and drought 

resistant. 



63 DAMIANO, A.E. Casama innotata, a Iymantriid 

injurious to Acacia ka"oo in Tripolitania. Riv. Agric. 

subtrop. trop., Firenze (1965) 59 (4/6) 143-148 [It. it. eJ. 

span, 5 ph.] 

Describes the morphology, life history, distribution and 

natural enemies of this insect, apparently a newcomer to 

Tripolitania, where it can completely defoliate and 

sometimes kill Acacia karroo, which is a species of vital 

importance for soil conservation. [CABI abstract] 

64 DEAN, W.R.J.;MIDGELEY, J.1.; STOCK, W.D. The 

distribution of mistletoes in South Africa: patterns of 

species richness and host choice. Journal of 

Biogeography (1994) 21 503-510 [En] 

The distribution records of mistletoes (Loranthaceae 

and Viscaceae) in South Mrica were analyzed in terms of 

host taxa and geographic patterns. Few species were found 

in the nutrient-poor Cape shrublands or in the southern 

evergreen forests on nutrient-poor sands. The most speciesrich 

areas are the nutrient-rich mesic savannas. Mistletoe 

species richness is significantly correlated with the average 

nitrogen levels of the woody plants in any biome. The 

analysis of host-choice of mistletoes also indicates a nonrandom 

distribution; 33 genera in 22 plant families host 

from 3 to 24 different mistletoe species suggesting that 

parasitism is not related to phytogenetic position. The most 

important host genera are Acacia (hosting 24 mistletoe 

species) followed by Combretum (14), Maytenus (13) and 

Rhus (12). The species richness and number of mistletoes 

are significantly correlated with mean host N. In this study, 

A. karroo had the highest number of mistletoes and the 

highest number of mistletoe species associated with it of any 

of the host plants studied. 

65 DEAN, W.R.1.; MILTON, S.1.; SIEGFRIED, W.R. 

Dispersal ofseeds as nest material by birds in semi-arid 

Karooshrubland. Ecology (1990) 71 (4) 1299-1306 [En] 

Acacia karroo trees are common along dry water 

courses and rivers in the southern Karoo near Prince Albert, 

South Africa, but are absent from the intervening plains and 

hillsides. The spiny trees are favoured by birds as nest sites. 

66 DICKSON, C.G.C.; KROON, D.M. Pennington's 

butterflies of southern Africa. Johannesburg, South 

Africa; A.D. Donker (Pty) Ltd. (1978) 670 pp. [En] 

Acacia karroo is listed as a food plant for larvae of the 

following butterfly species: Lycaenidae: Anthene amarah, 

A. definita, A. otacilia, A. talboti (flowers and leaves), 

Azanus moriqua (flowers and buds), A. natalensis (flowers 

and buds),A. ubaldus, Cruderia leroma (young shoots and 

thorns), Charaxidae: Charaxes zoolina. 

67 DRUMMOND, R.B. Common trees of the central 

watershed woodlands of Zimbabwe. Causeway, 

Zimbabwe; Natural Resources Board (1981) 46-47 [En, 1 

Barnes, R.D., Filer, D.L. & SJ. 

map] 

Common names in Zimbabwe are sweet thorn; muunga, 

mubayamhondoro (Shangaan); isinga (Ndebele). Acacia 

karroo is normally found in wooded grassland and on vlei 

margins. 

68 DUBE, J.S. Nutritive value of four species ofbrowse 

preferred by indigenous goats in a redsoil thornveld in 

southern Zimbabwe. M.Phil. thesis, Department of Animal 

Science, Faculty of Agriculture, University of Zimbabwe 

(1993). [En 93 ref. 93 pp.] 

The nutritional value of Acacia karroo, A. nilotica, 

Securinega virosa and Ziziphus mucronata were 

investigated by laboratory analysis, the nylon bag technique 

and feeding trials. All species contained high nitrogen (19, 

25, 34 and 26 g kg- l of DM respectively), low fibre ( 337, 

314, 305 and 336 g NDF kg- l of DM respectively and 

variable condensed tannin (243, 67, 15 and 46 g kg-} of DM 

respectively). The four species were allocated to four 

rumen-fistulated goats in a 4x4 latin square design. Ten 

nylon bags containing samples of each species were placed 

in the rumen and withdrawn in pairs after 3, 6, 12, 24 and 

48 hours in each period. S. virosum degraded fastest 

(degradation constant c when p=a+b(l-e- ct ) = 0.1528), 

followed by A. nilotica (c=0.0922), Z. mucronata 

(c=0.0679) and A. karroo (c=0.0266). Hand-clipped 

browse was offered with hay to 16 Matabele goats in 

metabolism crates. The goats were randomly allocated to 

diets. The intake of browse (g kg- l WO. 75 d- l ) was highest for 

S. virosa (34), followed by Z. mucronata (32), A. nilotica, 

(27) and A. karroo (26). Browse intake was unrelated to 

tannin content or hay intake. Digestibility of the browselhay 

mix was significantly (p=

Acacia ka"OO seedlings. Delayed germination is caused by 

hard-seededness and a water soluble inhibitor in the seed 

coat. When moisture conditions are favourable the seeds can 

germinate at temperatures ranging from 10-400c. 

Temperatures that fluctuated between 10 and 200C were 

optimum for germination. Optimum temperatures for growth 

were higher than for germination, and lay between 25 and 

33°C. The species has a deep taproot and is independent of 

surface moisture where underground water is available. The 

species is drought resistant but cannot withstand desiccation 

and loss of water from the protoplasm. Light intensities are 

seldom limiting for A. karroo in grassland, but the tree is 

light-demanding. The seedlings are very sensitive to 

desiccation because they are fairly slow growing and have 

a high temperature and moisture requirement for growth. 

Any factor that causes rapid drying of topsoil or delays root 

development will be deleterious to A. karroo seedlings. The 

latter may include low diurnal temperatures. 

71 DU TOIT, P.F. Bush encroachment with specific 

reference to Acacia ka"oo encroachment. Proceedings 

of the Grassland Society of Southern Africa (1967) 2 

119-126 [En] 

Acacia karroo seedlings are sensitive to desiccation and 

temperature changes. A. karroo is the African acacia most 

susceptible to attack by psychid moths Kotachalia junodi 

(bagworm). 

72 DU TOIT, P.F. A preliminary report on the effect of 

Acacia kan-oo competition on the composition and yield 

ofsweet grassveld. Proceedings ofthe Grassland Society 

ofSouthern Africa (1968) 3, 147-149 [En] 

A dense stand of Acacia karroo was killed by basal 

bark application of 2,4,5-T in paraffin. Cleared paddocks 

yielded more grass. Encroachment of A. karroo into grassy 

areas is a symptom rather than the cause of rangeland 

deterioration. 

73 DU TOIT, P.F. Acacia ka"oo intrusion: the effect of 

burning and sparing. Proceedings of the Grassland 

Society ofsouthern Africa (1972a) 7 23-27 [En] 

There is evidence that buried Acacia karroo seed 

remains viable for up to seven years. Burning and grazing 

treatments do not prevent A. karroo seedling establishment. 

At high densities A. karroo reduces grass production. 

74 DU TOIT, P.F. The goat in a bush-grass community. 

Proceedings ofthe Grassland Society ofsouthern Africa 

(1972b) 744-50 [En] 

A dense stand ofAcacia karroo was cleared by felling 

all the trees. Sheep and goats were permitted to browse on 

regrowth rotationally or continuously. Sheep spent 6%, and 

goats 50% of their foraging time feeding on A. karroo 

coppice shoots. Continuous grazing by goats caused higher 

mortality of trees than did rotational grazing. 


75 DU TOIT, P.F.; NEL, L.O. Chemical control of 

Acacia ka"oo. Proceedings of the Grassland Society of 

Southern Africa (1973) 8 29-34 [Af, en, 6 ref.] 

Reports trials in 1967-72 in eastern Cape Province, 

where large areas ofproductive grassland have been invaded 

by Acacia karroo and other species. 

76 EARLE, R.A. Factors governing avian breeding in 

Acacia savanna, Pietermaritzburg, Parts 1, 2, 3. Ostrich 

(1981) 5265-73,74-83,235-243 [En] 

Factors governing breeding of birds in savanna 

dominated by Acacia karroo, Erhetia rigida, Grewia 

occidentalis and Maytenus sp. were studied near 

Pietermaritzburg, Natal, South Africa. Over two breeding 

seasons, 421 nests of 49 birds species were found in an 

areas of 1.4 km 2 • Peak breeding coincided with the rapid 

spring increase in insect biomass. 

77 EBERHARD, A.A. Fuelwood calorific values in 

South Africa. South African Forestry Journal (1990) 152 

17-22 [En, 5 ref.] 

The gross calorific value ofAcacia karroo sapwood is 

18.69 MJ kg-I and of heartwood is 18.85 MJ -kg. The 

density of the wood is 890 kg m 3 - 1 at 10% moisture content 

and 862 kg m 3 - 1 dry mass. The calorific value per cubic 

metre is 16 185 MJ. 

78 EDWARDS, D. A Plant Ecology Survey of the 

Tugela River Basin, Natal. Botanical Survey of South 

Africa Memoirs (1967) No. 36, 285 pp. [En, many ref.] 

The catchment system ofthe Tugela River is considered 

to be an area with considerable economic and industrial 

potential. The Natal Town and Regional Planning 

Commission has undertaken a comprehensive study of the 

region. In order to provide information for agricultural 

development and other aspects. One project was a study of 

the plant ecology. Acacia-karroo is included in a species list 

collected and recorded during the survey of the Tugela 

Basin. The list may be regarded as comprehensive for trees 

and shrubs. [CABI abstract] 

79 ERNST, W.H.O.; DECELLE, lE.; TOLSMA, DJ. 

Predispersal seed predation in native leguminous 

shrubs and trees in savannas of Southern Botswana. 

African Journal ofEcology (1990) 28 (1) 45-54 [En] 

Seed predation by insects in the seed crop of nine 

Acacia species including A. karroo was examined in various 

tree savannas in Botswana. The degree of infestation varied 

strongly between and within species from 0% to more than 

80%. Whereas in all Acacia species only one phytophagous 

hymenopteran (Oedaule sp.) was present, the number of 



bruchid species varied between one and eight species. The 

life history of B. sahlbergi was studied in detail and lasted 

at least 100 days from egg to adult beetle. The life-span of 

adult beetles may extend to a further 57 seven days. [author's 

summary] 

80 FELKER, P. Uses of tree legumes in semi-arid 

regions. Economic Botany (1981) 3S 174-186. 

81 FOURIE, C. Small camps really pay. Farmers 

Weekly, April 15th (1981) 62-65 [En] 

In the eastern Cape, dense stands of Acacia karroo 

were felled at 30 cm above ground level then controlled by 

running goats with cattle at high densities in small camps on 

a rotational basis. 

82 FOURIE, O. Beat bush with boer goats. Farmers 

Weekly, June 18th 1982, 35-37 [En] 

In the eastern Cape, South Africa, Acacia karroo has 

increased greatly in density over the past 50 years on 

rangeland. Some ranchers fell the trees then use goats to 

reduce regrowth. 

83 FREEMAN, B.H.; STEPHEN, A.M.; WOOLARD, 

G.R. The G.L.C. (gas-liquid chromatographic) analysis 

of methylated polysaccharides using derivatives of 

alditol methyl ethers. Journal Of South African Chemistry 

Institute (1973) 26 (3) 106-110 [En] 

Mixtures of methylated sugars, obtained by hydrolysis 

ofcomplex methylated polysaccharides, have been reduced 

and converted to their acetates and to their trimethylsilyl 

ethers. The relative proportions of these derivatives have 

been estimated by g.l.c., and the relative merits of the two 

methods of analysis are compared. Analytical results for 

eight methylated Acacia gums are presented, including the 

African species A. giraffae and A. karroo, and 6 Australian 

species alien to South Africa. Major components of A. 

karroo gum were 2,3,5-Ara, 2,3-Ara and 2,4-Gal. The 

relationship obtained between end groups and branch points 

was poor in this species. [CABI abstract] 

84 FRIEDEL, M.H. A preliminary investigation of 

woody plant increases in the western Transvaal and 

implications for veld assessment. Journal of the 


[En] 

The relationships between tree density and indices of 

pasture and soil condition were examined in western 

Transvaal grasslands where Acacia karroo had increased 

following disturbance. The correlation between tree density 

and pasture condition was not linear, indicating a threshold 

in condition below which dramatic increase in trees is likely. 

Some evidence is presented for a second threshold where 

soil compaction inhibits seedling establishment and tree 


density declines. The necessity for assessing tree and soil 

status in addition to pasture condition is discussed and a 

variety of possible indicators of pasture, woody plant and 

soil status is considered. 

85 GALPIN, E.E. Native timber trees of the Springbok 

Flats, Transvaal. Botanical Survey of Africa Memoirs 

(1925) No. 7, 26 pp. [En] 

Acacia karroo wood is hard, tough and pale and the 

grain is often twisted. It is used to make fence poles but is 

subject to attack by borers. 

86 GELFAND, M.; MAVI, S.; DRUMMOND, R.B.; 

NDEMERA, E.B. The traditional medical practitioner in 

Zimbabwe. Mambo Press, Gweru, Zimbabwe. (1993) 411 

pp. [En, 49 re£., 23 tables, 62 plates] 

This book consists of two parts, the first a general 

survey of the practice of the n'anga (traditional medical 

practitioner) and the second a survey of the plants used in 

the remedies of the n'anga. Acacia karroo (roots) is among 

the plants prescribed as an aphrodisiac (infusion taken by 

mouth) and for pain in the alimentary canal, rheumatism 

(infusion taken by mouth and ash from burnt root rubbed 

onto incisions made on painful parts), convulsions (infusion 

taken by mouth and face washed with infusion), gonorrhoea 

(infusion taken by mouth), generalized pains (body wash 

with infusion), syphilis (powder applied on penile sores), 

and vertigo (infusion or powder taken by mouth). The roots 

are also placed in the fowl run to kill external parasites. 

87 GERSlNER, 1. Three closely related Acacias of 

southern Africa. Journal ofSouth African Botany (1948) 

14 19-27 [En, 1 ill.] 

This author proposed that Acacia karroo Hayne (Zulu 

"umuNga"), A. natalita E. Mey (Zulu "umSama") and 

A. conflagrabilis Gerstner (Zulu "isiKhombe") were three 

distinct species. All have stipules modified to form paired 

white spines which are sometimes enlarge and inflated. An 

ant Cataulacus rugosus nests in these hollow spines. All 

three species are insect pollinated and isolated plants often 

bear no fruits. Cattle and other herbivores disperse the seed. 

A table summarises differences in bark colour and texture, 

inflorescence development and pinnule size and shape for 

the three forms. 

88 GHIMPU, V. Contribution a L'etude 

chromosomique des Acacia. Comptes-Rendus Acad. 

Sciences Paris (1929) 188 1429-1431 [Fr] 

Reports Acacia karroo as being a polyploid with a 

chromosome number of 2n=4x=52. 

89 GmSON, I.A.S. (COMPIlER) Diseases offorest trees 

widely planted as exotics in the tropics and Southern 

Hemisphere. Part I. Important members of the


seldom clearly and unambiguously defined. This study 

investigates whether any anatomical feature in the wood 

delimits annual periods of growth in Acacia karroo Hayne, 

one of the most widely distributed tree species in southern 

Africa. Samples from 36 trees from four Mrican countries, 

covering over 14 degrees of latitude were included in the 

study. Complete stem cross sections were examined from 

these trees, the majority of which were selected for their 

supporting data on planting dates. In addition a sub-set was 

wounded at documented time intervals to produce a callus 

which could be located and related to anatomical variation 

and phenological events. Seasonal growth rings in the 

anatomy were apparent as narrow bands of marginal 

parenchyma filled with long crystal chains of calcium 

oxalate. The number of bands was shown to correspond 

closely to the known ages of the trees. There was further 

confmnation that they were annual in that the width of the 

growth rings was correlated with annual rainfall. The bands 

were laid down during the dry winter season when stem 

diameter growth ceased. 

97 GOURLAY, I.D.; GRIME, G.W. Calcium oxalate 

crystals in African Acacia species and their analysis by 

scanning proton microprobe (SPM). lA WA Journal 

(1994) 15 (2) 137-148 [En] 

The radial and cross-sections of wood samples from 

individual trees ofknown age ofa number of Mrican Acacia 

species including A. karroo were examined for growth 

rings. These were apparent in most species as narrow bands 

ofmarginal parenchyma filled with long crystal chains. The 

crystals were subsequently identified as calcium oxalate 

through the use of a scanning proton microprobe. Several 

other chemical elements were concentrated around this 

zone. The number of bands formed annually corresponded 

to the number of peaks in the annual rainfall distribution. 

These results suggest that the presence of marginal 

parenchyma bands and crystalliferous chains define growth 

phases in African Acacia species, and can be used for age 

determination. 

98 GOURLAY, I.D.; KANOWSKI, P.I. Marginal 

parenchyma bands and crystaUiferous chains as 

indicators of age in African Acacia species. lAWA 

Bulletin n.s. (1991) 12 (2) 187-194 [En, 28 ref.] 

The radial cross sections of wood samples from 

individuals ofknown age in six African Acacia species were 

examined for growth rings, which were apparent in most 

species as narrow bands of marginal parenchyma filled with 

long crystal chains. The number of bands formed annually 

corresponded to the number of peaks in rainfall distribution. 

The results suggested that marginal parenchyma bands and 

crystalliferous chains define growth phases in African 

Acacia species, and may therefore be useful for age 

determination. Two samples of A. karroo (Hayne) trees 

self-sown in 1975n6 on abandoned hay fields (black cotton 

soil ) in a region of Zimbabwe with unimodal summer 

rainfall and felled in 1989 had mean diameter of 15.5 cm 


and 12.0 cm, and mean ring widths of 8.61 mm and 7.50 

mm. One sample had 9 rings and the other had 8 rings. Both 

had very clear, fine, marginal parenchyma bands, and crystal 

chains were present in the marginal bands. 

99 GOURLAY, I.D.; SMIlH, I.P.; BARNES, R.D. 

Estimation of wood production in a natural stand of 

Acacia ka"oo using growth ring analysis. Forest 

Ecology and Management (in press) [En] 

Trees are important components of agricultural systems 

in the dry tropics of Africa. The assumption that exotic 

species are more productive than the indigenous woodland 

in these situations is not supported by quantitative data 

because ofthe difficulty of assessing yield in natural stands. 

In this study a new technique of recognizing annual growth 

rings from the bands of marginal parenchyma has been used 

to model growth in a natural population ofAcacia karroo 

Hayne, one of the most widespread and useful trees in the 

savanna woodlands of southern Africa. The study showed 

both basal area at breast height and basal area at ankle 

height to be good predictors oftotal tree volume. Stands may 

yield from about 1 to about 4 m 3 ha- 1 yr-l depending upon the 

regularity of spacing and uniformity of site; individual trees 

produced up to 1m 3 of wood in 26 years. Maximum current 

annual increment was reached about 14 years after the trees 

were established and then they declined until they became 

moribund at about 26 )ears. The economic rotation for wood 

production was close to the lifespan of the tree. 

100 GROBIER, PJ.; MARAIS, 1. Die plantegroei van 

die Nasionale Bontebok Park, Swellendam. Koedoe 

(1967) 10, 132-146 [Af, 1 map] 

The park lies on the southern Coast of the Cape 

Province, South Africa and receives year round rainfall (725 

mm). Acacia karroo is restricted to deep, sandy soils on the 

banks of the Bree River. The understorey is trampled by 

antelope seeking shade beneath the trees and is therefore 

dominated by the grass Cynodon dactylon. 

101 GUIU.OTEAU,1. The problem ofbush fires and 

burns in land development and soil conservation in 

Africa south of the Sahara. Sols Africains (1958) 4 

64-102 [En, fr] 

Southern African Acacia species including A. karroo 

and A. stolonifera withstand fITe and coppice after being 

burned. 

102 GUINET, P.; VASSAL, 1. Hypotheses on the 

differentiation of the major groups in the genus Acacia 

(Leguminosae). Kew Bulletin (1978) 32 509-527 

103 HALL, P.E. Notes on the analyses of certain 

South African woods with special reference to their use 

as a producer gas generator fuels. Journal of the

Chemical, Metallurgical and Mining Society of South 

Africa (1939-1940) 40, 350-2 [En] 

This investigation was carried out jointly by the Forest 

Products Institute and the Fuel Research Institute. Three 

groups ofspecies were tested, pines, eucalypts and acacias; 

the latter included Acacia karroo. The analytical tests made 

on each sample included: (1) specific gravity, (2) proximate 

analysis, and (3) low temperature carbonization assay. 

Among the Acacia woods, specific gravity varied from 0.68 

to 0.86. The ash contents of the acacias were high (0.9%) in 

the proximate analysis. The moisture figures were 

reasonably constant (8.5% to 10.0%); the acacias were drier 

than the others. The calorific values lay between 7,410 and 

7,820 B.T.U'sllb. In the low temperature carbonization 

assay, the acacias gave approximately 24% of charcoal, 

13.5-17% tar, 40% of liquor and 10% of CO 2 , While from 

these analyses there did not appear to be any marked 

difference between the woods tested, the acacias proved 

reasonably satisfactory, the charcoal yield being fair, the 

specific gravity being medium and the tar yield being fairly 

low. 

104 HARDY, M.B.; HOBSON, F.O. Evaluation of 

belt transect sampling to determine tree density in a 

semiaridAcacia kan-oo savanna. Proceedings ofthe First 

Natal Bushveld Symposium. Scottsville, South Africa; 

Grassland Society of Southern Mrica (1992) 33-35 [En] 

Belt transects 2 m wide are frequently used to sample 

the densities oftrees Acacia karroo savanna with 400-2000 

trees/ha. A minimum of 20-60 transects 2 m x 30 m would 

be required in order to reduce the coefficient of variation to 


Bulletin ofthe Grassland Society ofsouthem Africa (1993) 

4 (1) 19 [En] 

Acacia karroo browse production was negatively 

related to tree density at the beginning of the growing season 

but stabilized by the middle of the summer resulting in a 

positive relationship between browse production and tree 

density. Grass production varied more between seasons than 

A. karroo production and was inversely related to tree 

density. Maximum forage production (grass and browse) 

occurred at moderate densities of A. karroo. 

109 HOCKING, B. Insect associations with swollen 

thorn acacias. Transactions ofthe Royal Entomological 

Society ofLondon (1970) 122 (7) 211-255 [En, many ref.] 

Gives dimensions of the gall-like swellings in some of 

the stipulate thorns of acacia species including Acacia 

karroo. 

110 HOFFMANN, J.H.; MORAN, V.C; WEBB, J.W. 

The influence ofthe host plant and saturation deficit on 

the temperature tolerance of a psyllid (Homoptera). 

Entomologia Experimentalis et Applicata (1975) 18 55-67 

[En] 

In the laboratory, Acizzia russelae survived higher 

temperatures when sitting on its host plant, Acacia karroo, 

than when isolated from it. When the moisture saturation 

deficit was very low (and hence leaf transpiration also low) 

and when it was very high (causing rapid desiccation despite 

high plant transpiration) mortality of the psyllid was higher 

than at moderate moisture saturation deficits. In the field, 

high temperatures cause a reduction of populations. 

III HOWES, F.N. Vegetable gums and resins. 

Chronica Botanica Co., Waltham, Massetucets [En] 

Historical export ofAcacia karroo gum from the Cape, 

South African and Namibia to Europe. 

112 mPGR (International Board for Plant Genetic 

Resources). Forage and browse plants for arid and 

semi-arid Africa. Food and Agricultural Organization of 

the United Nations, Rome (1984) [En, 5 ref.] 

Acacia karroo occurs naturally in MozaInbique, 

Malawi, Zambia, Zimbabwe, Angola, Namibia, Botswana, 

South Africa; but is introduced in North Africa and India. It 

can easily be grown froIn seed or root suckers and is 

reportedly nodulated. 

113 JURACEK, P.; KOSlK, M.; PHll....LIPS, G.O. A 

chemometric study of the Acacia (gum-arabic) and 

related natural gums. Food hydrocolloids (1993) 7 (1) 

73-85 [En] 

114 KAPlAN, J. The arboretum at Gilat [N. Negev]. 

La-Yaaran (1957) 7 (3/4) 9-12, 40-39 [Hebrew, En, 1 


photo] 

More than 150 species were established to determine 

suitable species for planting on a large area of loess with 

200 mm annual rainfall. Plantings have been made since 

1951 in groups of 15, spaced 2 x 4 m, with 5-6 irrigations 

in the first two seasons. Acacia karroo was among those that 

showed promise. 

115 KARSlEN, M.C. Carl Peter Thunberg: an early 

investigator of Cape Botany. Journal of South African 

Botany (1939) 5,87-155 [En] 

Extracts from Thunberg's notes on his travels into the 

Karoo, Cape South Africa. In the Robertson Karoo he found 

that livestock were enclosed in circular kraals made of the 

thorny branches of Mimosa nilotica (Acacia karroo) and 

Carissa sp. 

116 KENRICK, J.; KNOX, R.B. Quantitative analysis 

ofself-incompatibility in trees ofseven species ofAcacUl. 

Journal ofHeredity (1989) 80 240-245 [En] 

117 KERLEY, G.I.H.; ERASMUS, T. Chemical 

attributes of seeds of some economically important 

Karoo plants. South African Journal ofWildlife Research 

(1991) 21 (1) 19-22 [En] 

The chemical composition of Acacia karroo seeds 

collected in the eastern Karoo (33°S 24°E) are given. Free 

water was 5.6%. Other components expressed as a 

proportion of oven-dry mass were cell walls 53.5%, cell 

contents, crude protein 24.20/0, ether extract 4.8%, ash 

4.7%, silica 0.47%, soluble carbohydrates 13.3% and 

polyphenols 0.41 %. 

118 KERLEY, G.I.H.; ERASMUS, T. What do mice 

select for in seeds? Oecologia (1992) 86, 261-267 [En] 

Acacia karroo seeds are eaten by the rodents 

Gerbillurus paeba, Mastomys natalensis and Mus 

minutoides. However the rodents took >3 minutes to 

consume one 0.052 ± 0.012 g seed. Although A. karroo 

seeds contained more energy (20.47 kJ g-l intact seed) than 

10 other Karoo plant species investigated, they were among 

the seed species least preferred by mice. Low preference for 

A. karroo seed was thought to be related to handling time. 

119 KOOIJ, M.S.; BREDENKAMP, G.J.; TIIERON, 

G.K. The plant communities ofthe hills and ridges in the 

north western Orange Free State, South Africa. 

Botanical Bulletin of Academia Sinica (1990) 31 (4) 

295-304 [En, Ch, 28 ref.] 

A phytosociological analysis of the vegetation of the 

hills and ridges in the northwest Orange Free State is 

presented. Releves were compiled in only 15 sample plots 

due to the restricted area occupied by hills and ridges. A 

TWINSPAN-classification refined by Braun-Blanquet

procedures revealed the following major communities: 

Maytenus heterophylla- Celtis africana shrubby thorn veld; 

Ehretia rigida-Rhus magalismontanum shrub veld; 

Heteropogon contortus - Eragrostis racemosa; Panicum 

coloratum - Eragrostis curvula bottomland grassland; and 

Acacia karroo - Protasparagus suaveolens river thorn veld. 

All communities are related to specific environmental 

conditions. Descriptions of the communities are given. 

[CABI abstract] 

120 KOOll, M.S.; SCHEEPERS, J.C.; 

BREDENKAMP, GJ.; lHERON, G.K. The vegetation of 

the Kroonstad area, Orange Free State I: vlei and 

bottomland communities. South African Journal of 

Botany (1991) 57 (4) 213-219 [En, 1 map, 17 ref.] 

At 27°S 2]OE, South Africa, Acacia karroo occurs in 

valley bottoms, on riverbanks and in steep ravines. Soils 

tend to be saline. The A. karroo dominated woodland has an 

understorey of shrubs and grasses. On uplands, A. karroo 

occurs on black vertisols associated with rock outcrops, and 

the understorey is grassy. 

121 KOTZE, D.C.; ZACHARIAS, P.J.K. Browsing of 

woody plants by black rhino in the western Itala game 

reserve. Proceedings of the First Natal Bushveld 

Symposium, Scottsville, South Africa; Grassland Society of 

Southern Africa (1992) 9-11 [En] 

Acacia nilotica contributed 18% and A. karroo 11 % to 

the diets of black rhino (Diceros bicornis) foraging in 

woodlands of the Itala Nature Reserve in northern Natal. 

Rhino preferred open acacia woodland with small trees to 

tall and closed woodland. 

122 KRESS, WJ.; Sibling competition and evolution 

of pollen unit, ovule number and pollen vector in 

Angiosperms. Systematic Botany (1981) 6 101-112 [En] 

123 KROMHOUT, C.P. 'n Sleutel vir die 

mikroskopiese uitkenning van die vernaamste inheemse 

houtsoorte van Suid-Afrika. Pretoria, South Africa; 

Department of Forestry (1975) Bulletin No. 50, 1-140 [Af, 

many ref., microphotographs] 

Describes the microscopic structure of the wood of 12 

species ofAcacia including A. karroo. lllustrated with black 

and white photographs of cross sections of wood. 

124 LEISTNER, O.A. The Plant Ecology of the 

Southern Kalahari. Botanical Survey of South Africa 

Memoirs (1967) No. 38,172 pp. [En, many ref., photos] 

Reports on the plant ecology of the Southern Kalahari. 

The research project had four main aims: 1. the compilation 

of a vegetation map of the region; 2. the description of the 

vegetation of the main habitats; 3. the study of plants in 


relation to climate, soil and animals; 4. the compilation of a 

check list. In the section on Physiography it was noted that 

the occurrence of large specimens ofAcacia karroo indicate 

the presence ofunderground water in the Aranos area. It was 

also noted that A. karroo was one of the few shrubs and 

trees that only flowers in the hottest months of the year 

December to February. A. karroo is largely restricted to the 

upper reaches of the river. [CABI abstract] 

125 LILLY, M.A. An assessment of the 

dendrochronological potential of indigenous tree species 

in South Africa. Occasional Paper, University of the 

Witwatersrand, Johannesburg, South Africa; Department of 

Geography (1977) No. 18,80 pp. [En, many ref.] 

Acacia karroo woods showed discontinuous rings and 

indistinct boundary parenchyma. Photographs show 

A. karroo wood cross-sections. 

126 MARCHANT, N.G.; WHEELER, J.R.; RYE, B.L.; 

BENNETT, E.M.; LANDER, N.S.; MACFARLANE, D.T. 

Flora of the Perth region, Part 1. Western Australian 

Herbarium (1987) [En] 

Acacia karroo was first collected in Australia in 1963 

from the banks of the Swan River, Midland. Specimens are 

housed in the Western Australian Herbarium. 

127 MCGEOCH, M.A. The microlepidoptera 

associated with a fungus gall on Acacia karroo Hayne in 

South Africa. African Entomology (1993) 1 (1) 49-56 [En] 

The rust fungus Ravenelia macowaniana is specific to 

Acacia karroo. Larvae ofseven species of Lepidoptera were 

associated with R. macowaniana near Pretoria, Transvaal 

and near Bloemfontein, OFS. The three most frequent 

species were Getulina nr. semifuscella (Pyralidae), 

Pardasena nr. virgulana (Noctuidae) and Ascalenia 

pulverata (Cosmopterigidae). Less common species were 

Anarsia nimbosa (Gelechiidae) and three Tortricidae: 

Cryptophlebia peltastica and Cydia (2 spp). An additional 

7 species (2 Cospopterigidae, 1 Tortricidae, 1 Gelechiidae, 

1 Tineidae, 1 Oecophoridae, 1 Gracillariidae) were collected 

at Ashton Bay in the eastern Cape. Galls from Pretoria 

contained a mean of 3.3 individuals/gall compared with a 

mean of 9.6 microlepidoptera from galls of the fungus 

Uromycladium tepperianum on Acacia decurrens near 

Melbourne, Australia. 

128 MCGEOCH, M.A.; KRUGER, M. Identification 

and diagnosis of Lepidoptera larvae inhabiting galls 

induced by Ravenelia macowaniana Pazschke on Acacia 

karroo Hayne in South Africa. African Entomology 

(1994) 2 (1) 37-43 [En, 4 ref.] 

Diagnoses, illustrations and head capsule widths are 

given of the five dominant Lepidoptera species that inhabit 

galls induced by Ravenelia macowaniana Pazschke 



(Uredinales:Pucciniaceae) on Acacia karroo Hayne in South 

Africa are presented. These five species constitute 

approximately 90% ofall the individuals. A key to the larvae 

inhabiting the galls is provided. This larval assemblage is a 

potential indicator of climate and habitat quality. 

129 MENTIS, M.T.; ELLERY, W.N. Post-mining 

rehabilitation of dunes on the north-east coast ofSouth 

Africa. South African Journal of Science (1994) 90 (2) 

69-74 [En, 19 ref.] 

The article examines a claim by environmentalists that 

miners revegetate but do not restore natural communities on 

coastal dunes subject to opencast mining. A test of the claim 

was conducted under the paradigm of ecological succession. 

It was supposed that restoring natural communities required 

reinstatement of community process, and succession in 

particular. Thirty sample plots were located on unmined 

areas and thirty seven on mined areas. Time-associated 

changes in community composition occurred on both 

unnlined but disturbed, and mined areas. Euclidean distance 

ofdisturbed stands from an average mature or climax stand 

decreased over time. There was no significant difference in 

this convergence on the climax state between mined and 

unmined areas. Plant species richness increased with time 

since disturbance, again with no significant difference 

between mined and unmined areas. Acacia karroo was the 

dOlninant woody pioneer in both natural disturbances and 

post-mining succession. It was concluded that succession 

was occurring on mined areas, and that this succession did 

not differ materially from that on unmined areas. 

130 MIDGEIEY, JJ.; JOUBERT, D. Mistletoes, their 

host plants and the effects of browsing by large 

mammals in Addo Elephant National Park. Koedoe 

(1991) 34 (2) 149-152 [En, 11 ref.] 

Moquinella rubra (Loranthaceae) was common and 

Viscum obscurum and V. rotundifolium (Viscaceae) were 

rare on Acacia karroo in the Addo Elephant Park, eastern 

Cape, South Mrica. These species were more common on 

A. karroo outside the park, and it was concluded that they 

were selectively browsed by elephant in the park. 

131 MILLER, O.B. The Woody Plants of the 

Bechuanaland Protectorate. Journal of South African 

Botany (1952) 18,22 [En] 

This paper describes the area, the species and their 

occurrence. Forty-four acacias are included. Acacia karroo 

grows to 10 m on deep black turf soils. It flowers in 

December-February but is also seen flowering in March 

near Lake Ngami, central Botswana. Local names are 

"mooka", "mookana", "mokha". 


132 MILTON, SJ. Phenology ofseven Acacia species 

in South Africa. South African Journal of Wildlife 

Research (1987) 17 (1) 1-6 [En, af, 25 ref.] 

Shoot growth, shoot mortality and the abundance of 

flowers, fruit and leaves on marked shoots of Acacia burkei, 

A. caffra and A. mellifera (hook-thorn), A. karroo and A. 

nilotica (straight-thorn) and A. leuderitzii and A. tortilis 

(mixed-thorn) were recorded for 13 months at Nylsvley, 

Transvaal, South Africa. All seven species began to grow or 

flower before the end of the dry season, but other aspects of 

the phenology and seasonal use of the plants by browsers 

differed at the species and superspecies level. Although the 

reproductive phenology of every species was unique, there 

were sinlilarities between members of a superspecies group. 

Phenology ofthe vegetative organs, at least in the case of A. 

tortilis, appears to be more flexible than reproductive 

phenology, and the timing and extent of leaf fall and shoot 

growth can be modified by environmental factors. A. karroo 

bears flowers only on green extending shoots and flowers 

throughout the growing season as the new shoots are 

produced. Flowers are most abundant between December 

and February. Pods ripen in winter; they are thin-walled and 

split open while still on the tree when the seeds dangle from 

the pod on their funicles. Elongating shoots bear only one 

leaf per node; more leaves appear in whorls as the shoot 

lignifies. Rapid extension of the shoots starts early in 

September about six weeks before the rain. Despite the 

irregular elongation of shoots, peaks were observed in 

October and December. A. karroo was the first to sprout in 

spring and therefore sustained heavy losses of soft green 

shoots to browsers in spring. A. caffra saplings were 

browsed towards the end of the growing season and giraffes 

took much new growth from the crowns of taller trees. A. 

torti/is was heavily browsed in June and July. [CABI 

abstract] 

133 MILTON, SJ. The effects of pruning on shoot 

production and basal increment ofAcacia tortilis. South 

African Journal ofBotany (1988) 54 (2) 109-117 [En, 36 

ref.] 

The shoot production of pruned, felled and undamaged 

Acacia tortilis trees on an old land site in the northern 

Transvaal was compared over two growing seasons. Trees 

were tolerant of damage and continued to increase in size 

when all current season's shoots were removed. Basal 

increment of treated pruned trees was less than controls. 

Shoot production, relative to basal area, increased after 

winter pruning and decreased after summer pruning. Shoot 

production and basal increment were positively correlated 

with rainfall and were indicators of soil moisture. 

Replacement shoots of pruned trees had a higher moisture 

content and leaf mass in the dry season and were more 

thorny than shoots ofundamaged trees. Repeated harvesting, 

continuous browsing or felling followed by browsing reduce 

shoot production in A. karroo and water stress inhibits its 

growth.

134 MILTON, SJ. Plant spinescence in arid southern 

Africa: does moisture mediate selection by mammals? 

Oecologia (1991) 87, 279-287 [En, 73 ref.] 

The prediction that spinescence in plants increases with 

aridity, soil fertility and mammalian herbivory was examined 

at regional and local scales in southern Africa. Spinescence 

tended to increase with aridity. Within arid areas, vegetation 

of moist, nutrient-rich habitats was more spinescent than 

that of the surrounding dry plains. Spinescence in plants of 

drainage lines and pans in arid southern Africa occurs in a 

wide range of genera and appears to have been selected by 

the effect of large mammals which concentrate on these 

moist patches. It is concluded that spinescence may be 

selected by breakage as well as herbivory, and that in arid 

areas moisture may be important in mediating mammalian 

selection of spinescence. Acacia karroo was recorded as a 

deciduous, phanaerophyte species of drainage line and pan 

habitat. 

135 MILTON, S.1.; BOND, C. Thorn trees and the 

quality of life in Msinga. Social Dynamics (1986) 12 (2) 

64-76 [En] 

Acacia species and Dichrostachys provide the people 

of Msinga, a dry and rugged district of kwazulu, with 

browse, fuel, building and fencing materials These products 

are currently worth about R425 per year to a rural family. 

Employment of rural people in agroforestry projects aimed 

at the rational management of existing plant resources could 

improve the quality of life for the people of Msinga. A. 

karroo was found to used for fencing, and children chew the 

sweet thorns of A. karroo. 

136 MILTON, 5.1.; MACDONALD, LA.W. Tree 

deaths near tar roads in the northern Transvaal. South 

African Journal ofScience (1988) 84 (3) 164-165 [En, 4 

ref.] 

This is a study of the mortality of large and small trees 

ofa number ofindigenous species, including Acacia karroo, 

recorded on verges of tar and gravel roads. 

137 MILTON, S.1.; SIEGFRIED, W.R.; DEAN, RJ. 

The distribution of epizoochoric plant species: a clue to 

the prehistoric use of arid Karoo rangelands by large 

herbivores. Journal of Biogeography (1990) 17 25-34 

[En, 53 ref.] 

Adhesive dispersal mechanisms are rare in the flora of 

the plains ofthe arid south western Karoo, South Africa, and 

most plants lack the long or hooked thorns normally 

associated with defence against browsing mammals on 

nutrient rich soils. The flora of drainage lines (often 

dominated by Acacia karroo), differs from that of the 

surrounding flats in that many of its species are thorny, bear 

pods or succulent fruits palatable to mammals, and more 

species have adhesive propagules. Before the advent of 

livestock ranching, large browsing mammals were probably 

restricted to the taller vegetation of drainage lines. The 


grassier northern and eastern Karoo, with its thorny trees 

and shrubs and barb-fruited grasses, probably provided 

permanent forage for herds of large ungulates which 

occasionally extended their ranges southwestwards, after 

relatively high rainfall periods had promoted improved 

forage in the arid Karoo. [Author's summary] 

138 MITGIEILWATT, 1. An ABC of trees in South 

Africa. Trees in South Africa (1957) 9 (3) 50-61 [En, 29 

ref.] 

Acacia karroo failed to give any indication of the 

presence of hydrocyanic acid and so is not thought to cause 

poisoning and death in stock. 

139 MOGG, A.O.D. Fruits ofthe woody plants ofthe 

Witwatersrand region. Trees ofSouth Africa (1963) 15 

(3) 56-60 [En] 

Listing of fruits arranged according to succulence and 

colour at maturity and in accordance with Ridley's colour 

attractiveness to birds. Acacia karroo is classified as having 

an inert mechanism of distribution. 

140 MULLER, T.H.Acacia species cultivated in the 

National Botanic Garden, Salisbury, Rhodesia. 

International Group for the Study ofMimosoideae Bulletin 

No. 7 (1979) 36-39 [En] 

Acacia karroo was found to be one of the fastest 

growing species in the systematic section that has been 

devoted to the genus. 

141 MUNTING, J. New and little known armoured 

scales (Homoptera: Diaspididae) from South Africa - 2. 

Journal of the Entomological Society of South Africa 

(1965) 28 (2) 179-216 [En] 

The scale Andaspis bulba (Munting) was collected on 

Acacia karroo at Hammanskraal, Transvaal. 

142 MUTHANA, K.D.; GYAN CHAND; ARORA, 

G.D. Silvicultural studies on indigenous and exotic tree 

species in Rajasthan Desert. Arid Zone Research and 

Development. Edited by Mann, H.S., Jodhpur, India; 

Scientific Publishers (1980) 339-343 [En, 3 ref.] 

Between 1958 and 1976,112 species of Eucalyptus, 65 

species ofAcacia and 82 miscellaneous species from both 

indigenous and exotic sources were investigated in trials at 

Jodhpur and Pali, India. The most promising species are 

listed and some oftheir characteristics briefly described. The 

Acacia species that gave the most favourable results were, 

in order ofperformance: A. tortilis [A. tortilis ssp. torti/is, A. 

tortilis ssp. raddiana, A. senegal, A. planijrons, A. ciliata, 

A. aneura, A. karroo, A. leucophloia [leucophloea], A. 

saligna, A. nilotica and A. catechu. [CAB abstract] 



143 NAUDE, TJ. Research into the control ofinsect 

pests. Farming in South Africa (1949) 24 (275) 105-13 

[En, 25 ref.] 

Contains a short section on forest insect pests in South 

Africa. Extensive dying-out ofAcacia karroo is not directly 

traceable to insects, but large numbers of cerambycid 

beetles (Zographus oculato and Ceroplesis thunbergi) have 

been found ovipositing heavily on moribund trees and 

hastening defoliation by ringbarking the shoots in feeding. 

The ecological study of the wattle bagworm has enabled 

reliable predictions of outbreaks to be made. An oil-based 

aerial spray, which should be partially rain-proof, is being 

investigated. [CABI abstract] 

144 NAUDE, C.P. Eradication of Lantana and 

Thorn trees. Farming in South Africa (1956) 31 (360) 

209-210 [En, 4 ref., 2 photos] 

Acacia karroo was controlled with paraffin and 

dieseline solutions of 2,4,5-T (3 1/6 oz. amyl ester in 2 gal. 

solvent). 

145 NCUBE, S; DUBE, 1.S.; HOVE, L. Value of 

browse, wild fruits as livestock feed. The Farmer 

(Zimbabwe) (1992) 60 (18) 7-8 [En] 

Natural veld is the major source of feed for ruminant 

livestock ofZimbabwe. The seasonal fluctuation of both the 

quantity and the quality of the veld are countered with 

protein supplement. With increasing costs farmers are 

encouraged to use more economical sources such as pods 

from wild trees. Chemical composition of browse was 

assessed for Acacia karroo and three other preferred 

indigenous species. A. karroo had 12% crude protein, 14% 

crude fibre, and 24% tannin; all three other species had 

higher crude protein and lower tannin, Securinega virosa 

being best at 21 % and 2% respectively. The crude protein 

and seed:pod ratio were also assessed for A. karroo and 

compared with those offour other indigenous species. Crude 

protein was 16.1 % for the whole fruit, 24.3% for the seed 

and 4.1 % for the seed alone; the seed pod ratio was 45:55. 

The most significant difference from the pods of other 

species assessed was the low protein content of the pods of 

A. karroo. The authors conclude that trees in the range can 

be a critical resource as the trees are affected less than the 

grass in times of drought. 

146 NEW, T.R. A Biology of Acacias. Melbourne, 

Australia; Oxford University Press (1984), 153 pp. [En, 28 

pp. of ref.] 

Chapters of this book deal with classification and 

phylogeny, ecology, and utilization of acacias by man, 

arthropods and other organisms. Information on Acacia 

karroo includes references to its chemistry, phylogeny, 

invasiveness, factors influencing seedling survival, fIfe 

tolerance, medicinal use, insects (psyllids, bagworm), and 

animals feeding on the gum. 


147 NOEL, A.R.A. The Heart of the Matter. Trees in 

South Africa (1982) 33 (4) 92-96 [En] 

Acacia karroo has a distinct differentiation between the 

sapwood which is a pale yellow and the heartwood which is 

red-brown. 

148 OBAILA, P.O. Genetic variation within Acacia 

kan-oo Hayne. D.Phil. thesis, University of Oxford (1993) 

224 pp. [En, 388 refs., 17 tables, 24 figs] 

This isozyme study was based on material sampled 

across the natural range ofAcacia karroo. Interpretation of 

allozyme data requires a knowledge of the ploidy level in a 

species. An understanding ofcytotype distribution within the 

population under study is crucial to interpret the complex 

electrophoretic patterns that arise with increasing ploidy 

level. The chromosome number ofA. karroo was reported 

as 2n = 52 under its original name A. horrida (Grimpu, 

1929) and confrrmed later under A. karroo (Vassal, 1974). 

However, there had been no survey to determine the 

distribution of cytotypes among the ecotypes of the species. 

A cytological investigation of A. karroo was therefore 

undertaken. The survey revealed that all the populations of 

A. karroo that were studied had only one cytotype with 2n = 

52 chromosomes. Despite its morphological variation, 

therefore, the species has retained a single genome. 

However, the possibility of isolated occurrences of other 

cytotypes cannot be excluded given that naturally sterile 

trees have been documented previously in A. karroo. The 

tetraploid status was further supported by evidence from the 

isozyme inheritance patterns which also indicated that the 

species is a segmental tetraploid. Twelve populations of A. 

karroo were surveyed for 12 allozyme systems (aspartic 

aminotransferase, alcohol deh}drogenase, diaphorase, alphaesterase, 

beta-esterase, glucose-6 phosphoglucose 

dehydrogenase, glutamate dehydrogenase, malate 

dehydrogenase (mdh), malate dehydrogenase (mdhp), 

menadione reductase, 6-phosphogluconate dehydrogenase 

and shikimate dehydrogenase). All expressed a high level of 

genetic diversity. Ninety-eight percent of the isozyme loci 

were polymorphic with an average of 3.7 alleles per locus. 

The total gene diversity was 88%, higher than that reported 

for most plant species. The mean genetic identity was 90% 

and the coefficient of gene differentiation was estimated at 

5%; this indicated a low divergence between populations. 

Cluster analysis grouped the populations into three 

phylogenetic groups, the northern, the southern and the 

south-central-eastern. The distribution of some common 

alleles at the shikimate dehydrogenase and alcohol 

deh}drogenase loci were significantly correlated with some 

geographical factors, viz., latitude, longitude and rainfall. 

Estimates of mating system parameters in one population 

indicated that the species has a mixed mating system. 

Multilocus outcrossing rate was estimated at 0.88; single 

locus outcrossing rates were heterogeneous, ranging from 

0.53 to z 1.00, confirming the variable characteristics of the 

loci. The mean outcrossing rate, estimated using fixation 

indices for all 12 populations, was 0.72; the gene flow rate 

(Nm) was estimated at 4.47, consistent with the

entomophilous pollination mechanism reported for other 

tree species. Gene distribution within the population studied 

showed no specific spacial pattern. 

149 OBALLA, P.O.; OLNG'Ol1E, P.A.S. 

Chromosome numbers in two African Acacia species. 

Kew Bulletin (1994) 49 (1) 107-113 [En, 28 ref.] 

Chromosome numbers were surveyed in populations of 

Acacia karroo Hayne and A. tortilis (Forssk.) Hayne 

sampled across their wide geographical range. Seeds used 

in this analysis were collected from plantations maintained 

by the Oxford Forestry Institute. A. karroo plantations were 

in South Africa, Malawi, Zambia and Zimbabwe, and A. 

tortilis plantations were in Botswana, Israel, Kenya, Niger, 

Senegal and Zimbabwe. Only one cytotype, with a 

chromosome number 2 n = 52, was found in populations of 

A. karroo and A. tortilis subspecies tortilis, spirocarpa and 

heteracantha. Both 2 n =52 and 2 n =104 were found in 

populations of A. torti/is ssp raddiana. It was concluded 

that most common varieties of A. karroo and A. tortilis 

subspecies tortilis, spirocarpa and heteracantha are 

tetraploids, but the possibility of isolated cases of other 

cytotypes cannot be excluded given that naturally sterile 

trees have been documented previously in A. karroo. The 

cytotypes of A. tortilis are more variable. Clarification will 

require more detailed analysis. 

150 ORMOND, B. Indigenous Bonsai - A Plea for 

Experiment. Trees in South Africa (1968) 20 (3) 71-74 

[En] 

Acacia karroo is suggested as a suitable indigenous 

species for bonsai culture. 

151 PAPENDORF, M.C. Two new genera of soil 

fungi from South Africa. Transactions of the British 

Mycological Society (1967) 50 (1) 69-75 [En, 8 ref. 1 

plate] 

The fungi, isolated from leaf-litter and soil of an Acacia 

karroo community, are Hyalotiella transvaalensis and 

Arxiella terrestris. 

152 PAPENDORF, M.C. New South African soil 

fungi. Transactions of the British Mycological Society 

(1969) 52 (3) 483-489 [En, 4 ref., 3 fig.] 

Three new fungi are described, isolated from soil and 

litter ofa mixed Acacia karroo community in the Transvaal: 

Arthrocladium caudatum gen. et sp. nov., Veronaea 

simplex sp. nov., and Exophiala brunnea sp. novo [CABI 

abstract] 

153 PAPENDORF, M.C. The soil mycoflora of an 

Acacia ka"oo community in the western Transvaal. 

Bothalia (1976) 12 (1) 123-127 [En, ft, af, 56 ref.] 


A total of 858 sporulating cultures representing 76 

genera and 144 species were recovered from the soil under 

a community of Acacia karroo. The majority were fungi 

imperfecti, with a limited number of zygomycetes and 

ascomycetes. No oomycetes or basidiomycetes were 

recorded. The most abundant genera were Penicillium and 

Aspergillus. The greatest concentration of individuals and 

species occurred in the surface layers; numbers decreased 

with increasing depth. The nature of this mycoflora suggests 

a close correlation with the existing plant cover. [CAB 

abstract] 

154 PAPENDORF, M.C.; DU TOIT, lW. 

Melanophoma: a new genus of the Sphaeropsidales. 

Transactions ofthe British Mycological Society (1967) 50 

(3) 503-506 [2 ref., 1 set of diagrams, 1 pt] 

Melanophoma karroo, the type species, is described. It 

was found associated with the litter and surface soil of a 

mixed Acacia karroo community in Potchefstroom, South 

Africa. [CABI abstract] 

155 PAPPE, L. Florae Capensis Medicae Prodromus. 

2nd ed., Cape Town (1857) [La] 

Historical medicinal use of Acacia karroo in the Cape 

Province, South Africa. 

156 PARDY, A.A. Notes on indigenous trees and 

shrubs ofSouthern Rhodesia. The Rhodesia Agricultural 

Journal (1952) 49 (6) 316-317 [En] 

This note includes descriptions of Ricinodendron 

rautanenii and Acacia karroo. The latter is decried 

morphologically and noted as a tree to 9 m with bright green 

foliage and frequent exudations of gum. It is a common and 

widely distributed tree on a variety of sites but particularly 

common on black turf soils. It is often regarded as an 

indicator of good soils for agricultural crops. The timber is 

said to be useful only for fuel but goats and other livestock 

relish its foliage in spring when grazing is poor. The 

branches are used for fencing, the bark for tanning and the 

gum can be used as an adhesive. 

157 PEDIEY, L. Derivation and dispersal ofAcacia 

(Leguminosae), with particular reference to Australia, 

and the recognition of Senegalia and Racosperma. Bot. 

J. Linn. Soc. (1986) 92219-254 

158 PHllLIPS, 1 Fire in vegetation: a bad master, a 

good servant, and a national problem. Journal ofSouth 

African Botany (1936) 2 35-45 [En, 4 ref.] 

Withholding fire, in combination with overstocking, has 

been responsible for the marked increase of acacias 

including Acacia karroo, A. caffra, A. robusta and A. 

tortilis in various parts of South Africa. Overstocking has 



eased or removed competition between grass and acacias 

and has reduced grass fuel loads and hence frre frequency. 

This has accelerated succession to a mixed thorn scrub 

climax. 

159 porrs, G.; TIDMARSH, C.E. An ecological 

study of'a piece of Karroo-like vegetation near 

Bloemfontein. Journal ofSouth African Botany (1937) 3 

51-92 [En] 

In the Orange Free State near Bloemfontein, South 

Africa, Acacia karroo occurred in the mouths of river 

valleys on soils up to 1.5 m deep. Soils were acid although 

A. karroo is normally found on alkaline soil. A. karroo 

saplings were scarce and old trees were apparently being 

replaced by dense stands of Celtis, Rhus, Ziziphus and 

Diospyros. The inflorescences and young pods ofA. karroo 

were heavily infested by the rust-fungus Ravenalia 

macowaniana which caused gall-like growths, inhibiting 

seed production. A large percentage of the older trees were 

severely attacked by a borer larva Macrotoma palmata. 

160 POYTON, R.J. Characteristics and uses of 

selected trees and shrubs cultivated in South Africa. 

South African Directorate of Forestry, Pretoria; 

Department ofEnvironment Af!airs Bulletin (1984) No. 39, 

pp. 22, 66, 93 [En] 

This bulletin includes tables on characteristics and uses 

of species and recommended silvicultural zones for each 

including Acacia karroo. 

161 PRIOR, 1.; CU1LER, D. Trees to fuel Africa's 

tires. New Scientist (1992) 29 August 35-39 [En] 

The paper emphasizes the need for trees to provide fuel 

for rural people to cook their staple foods. Exotic species 

cannot withstand the severe droughts or provide fuelwoods 

with the burning properties of the indigenous species. The 

potential lies in the species of the African savannas which 

occupy 65 % of the continent's land area but which are 

themselves under threat because their fragile ecologies are 

under pressure from human need. In 1989, a three-year 

international research programme was set up in Zimbabwe 

for a detailed study of the structure, functioning and 

productivity of four popular indigenous frrewood species 

one of which was Acacia karroo. In determining wood 

quality, a key factor is given as the presence in the wood of 

these species of large crystals ofcalcium oxalate which are 

deposited in the tree when the salts in the water taken up by 

the roots are combined with oxalic acid to maintain its 

overall water balance. Oxygen-bearing calcium oxalate 

affects the wood density and how quickly it burns. Wood 

tends to burn rapidly at frrst, producing carbon monoxide 

which is itself flammable and raises the flame temperature. 

As the temperature rises above 370°C, calcium oxalate 

breaks down and the released oxygen leads to fuller 

combustion ofthe carbon in the wood. This produces carbon 

dioxide which acts as a flame retardant and promotes a 


glowing combustion similar to that of banked down coal. 

Test results confrrmed the flame retarding properties of 

calcium oxalate. It is also stated that calcium oxalate makes 

tropical trees less palatable to termites. 

162 ROBBERTSE, P.J. [Nastic movements in leaves 

of South African Acacia species] Slaapbewegings by die 

blare van die Suid-afrikaanse Acacia spesies. Koedoe 

(1972) 15, 83-89 [Af] 

Leaves of all 39 Acacia species investigated, including 

A. karroo, underwent nocturnal movements. The mechanism 

and its application to taxonomy is discussed. 

163 ROBBERTSE, PJ. [The genus Acacia in South 

Africa ill with special reference to the morphology of 

the seed] Die genus Acacia in Suid-Afrika III met spesiale 

verwysing na die morphologie van die saad. Tydskrif vir 

Natuurwetenskap (1973) 13 (2) 72-95 [Af] 

Describes the ontogeny of the seeds of Acacia karroo 

and the morphology and anatomy of this and other southern 

African acacias. 

164 ROBBERTSE, PJ. [Germination of thorn tree 

seed] Ontkieming van doringboomsaad. Journal ofSouth 

African Botany (1974a) 40 (4) 269-273 [Af] 

Piercing the testa of Acacia karroo and A. robusta 

seeds increased germination on moist filter paper from 3% 

(6/200 control seeds) to 99% and 93% respectively. 

165 ROBBERTSE, P.l. A scanning electron 

microscope investigation of the pollen of South African 

Acacia species. Journal ofSouth African Botany (1974b) 

4091-99 [En] 

166 ROBBERTSE, PJ. The genus Acacia Miller in 

South Africa. I. Stipules and spines. Bothalia (1975a) 11 

(4) 473-479 [En] 

A large number of seedlings and young twigs of South 

African Acacia species was sectioned and the 

vascularization of the nodes and internodes studied. The 

nodes of all the species examined are trilacunate and the 

vascular tissue ofthe stipules originates from the lateral leaf 

traces. The Gummiferae species, including Acacia karroo, 

all have spinescent stipules, while the stipules of the 

Vulgares species are membranous. Prickles containing no 

vascular tissue are found on the nodes and in some species 

also on the internodes of the Vulgares species. These 

prickles always occur on the ridges formed on the stem by 

leaf traces. 

167 ROBBERTSE, P.J. The genus Acacia in South 

Africa. IV. The morphology of the mature pod. Bothalia 

(1975b) 11 (4) 481-489 [En]


anther dehiscence. Deposition of self pollen on the stigma 

prior to attainment of receptivity rendered hand pollination 

of this species unreliable. [Abstracted from summary in 

ACIAR Forestry Newsletter No. 17] 

188 SMIT, G.N. Quantitative description of woody 

plant communities: Part 1, an approach. Journal ofthe 

Grassland Society ofSouthem Africa (1989) 6 (4) 186-191 

[En, af, 11 ref.] 

Various descriptive units for woody plant communities 

are proposed. These are the Evapotranspiration Tree 

Equivalent (ETlE), Browse Tree Equivalent (BlE) and 

Canopied Subhabitat Index (CS!), which describe the status 

of a woody community in terms of potential moisture use, 

value of the trees as food for browsers and subhabitat 

suitability for grass-tree associations, respectively. A 

Quantitative Description Index (QDI) for woody plant 

communities, containing descriptive unit-values, is 

proposed. The calculation of the various unit values, 

excluding the CSI, rests upon the relationship between 

spatial volume of a tree crown and its true leaf volume and 

true leaf DM, taking into account differences in leaf 

densities. These relationships and the factors that influence 

the estimation of leaf densities are discussed. Regression 

equations were developed from harvested Acacia karroo 

trees. Their applicability to other woody species was 

confIrmed, as predicted values differed non significantly 

from true values for two other species. 

189 SMITI-I; T.M.; WALKER, B.H. The role of 

competition in the spacing ofsavanna trees. Proceedings 

of the Grassland Society of southern Africa (1983) 18 

159-164 [En, 27 ref.] 

Acacia karroo and A. torti/is trees at Pilansberg Game 

Reserve, Boputhatswana were found to be regularly 

dispersed. Distances between Acacia trees increased 

linearly with the combined canopy cover of pairs of trees. 

The regular spacing is believed to be brought about by 

competition between Acacia trees. The dispersion of all 

trees (Acacias and non-Acacias) in the site was random, 

possibly because some of the other tree species were shade 

tolerant, generally occurring beneath canopies of Acacia 

trees. 

190 SMITTER, Y.H. Plants as indicators of ground 

water in southern Africa. Trees in South Africa (1955) 7 

(3) 6-10 [En] 

Acacia ka"OO is among the phreatophytes that occur in 

the xerophytic vegetation on fracture lines over groundwater 

at 21 and 32 feet. 

191 SOUTI-lGATE, BJ. Variation in the 

susceptibility ofAfrican Acacia (Leguminosae) to seed 

beetle attack. Kew Bulletin (1978) 32 (3) 541-544 [En] 

Many species of the family Bruchidae parasitize seeds 

Barnes, R.D., Filer, D.L. & Milton, S.I. 

of members of the Leguminosae. The female beetle lays an 

egg on a ripening or, more rarely, a dehisced ripened pod. 

The larva bores through the pod wall and burrows into a 

ripening seed within which it creates a chamber. In its final 

stages the larva eats away the outer layers of the seed until 

only a thin circular 'window' of testa remains. After 

pupation, the beetle emerges through the 'window'. In a few 

species the larva leaves the seed and pod, drops to the 

ground on a silk thread, and pupates in the soil beneath the 

tree. Fourteen of the 61 Acacia species recorded in East 

Africa are known to be the hosts of one or more species of 

bruchid. Examples of the very high rates of seed infestation 

that can occur in markedly different habitats are given by 

data relating to A. tortilis: ssp. spirocarpa (Tanzania) 

90-95%; ssp. raddiana (Israel) 72%; and ssp. tortilis 

(Israel) 99%. Moreover, species with very different seed 

pods may be parasitized bythe same bruchid, e.g. that which 

parasitizes the A. tortilis complex also infests seed of A. 

malacocephala and probably A. abyssinica ssp. calophylla 

in Tanzania, A. erioloba in Botswana, A. karroo in Natal 

and A. hockii in Ethiopia. Early indications from 

phytochemical investigations indicate that the concentrations 

of certain amino acids (pipecolic acid and some 

heteropoly-saccharides) determine if a bruchid larva can 

survive in a seed. A method for collecting and storing seed 

pods to preserve beetles emerging from them is described, 

and attention is drawn to the importance of international 

cooperation to gain further knowledge of the bruchid/host 

relationship. [CABI abstract] 

192 SPRENT, J.I. Legume trees and shrubs in the 

tropics: N 2 fixation in perspective. Soil Bioi. Biochem. 

1995 27 (4/5) 401-407 [En] 

193 STAPLES, R.R.; HUDSON, W.K. An ecological 

survey of the mountain area of Basutoland. U.K.; 

Lechworth Garden City Press (1938) 1-68 [En] 

Overgrazing between 1910 and 1938 led to the 

replacement of much of the original grassland of the 

Drakensburg mountain catchment area by Acacia karroo 

scrub. Carrying capacity for cattle was reduced by 50%. 

194 STEADMAN, E.C. A description of some trees 

and shrubs and Hanes of Southern Rhodesia. The Argus 

Printing and Publishing Co. Ltd, Bulawayo (1933) 191 pp. 

[En] 

A brief taxonomic description and uses of Acacia 

karroo is included in this work. On good sites it grows into 

a handsome tree and its presence denotes good soil. The 

wood is good for fuel and polo mallets. Goats relish the 

young leaves, shoots and fruits, the thorns are used as 

needles and the bark for tanning. The gum is used in the 

manufacture of sweets and is exported for use as an 

adhesive.

195 STEENKAMP, C.W.P; HAYWARD, F.C. 

[Chemical composition of common plants in the 

south-central section of the Great Escarpment] 

Chemiese samestelling van die vernaamste plantspesies in 

die suid-sentrale sektor van die Groot Eskarpment. 

Department of Agriculture, Pretoria, South Africa; 

Technical Report No. 149 (1979) 1-20 [Af] 

Acacia karroo was one of 100 species collected for 

forage analysis in the districts of Craddock, Somerset East, 

Graaff-Reinet, Aberdeen and Middelburg of the Cape 

Province South Africa. Dry season (winter) foliage, wet 

season (summer) foliage and pods proximate and mineral 

analyses are given respectively for each element in the 

nutrient and mineral analysis below. The Weende system of 

proximate nutritional analysis results were, on a % dry mass 

basis, crude protein (13.7, 14.7, 15.0), crude fibre (13.0, 

14.0, 26.3), ether extract including resins and lipids (3.6, 

4.6, 2.5), ash (10.6, 9.8, 6.9) and N-free extract including 

carbohydrates (59.2, 56.9,49.3). Minerals, as % dry mass, 

were respectively Na (0.12, 0.10, 0.07), K (0.87, 0.81, 

1.31), Ca (2.90,2.58, 1.23), P (0.11,0.14,0.20), Mg (0.49, 

0.48, 0.32) and as parts per million Fe (517, 334, 115), Cu 

(3.4,3.8,6.1), Mo (1.39, 0.99, 2.90), Mn (34, 31, 17) and 

Co (0.14, 0.13, 0.13). 

196 STEPHEN, A.M.; VOGT, D.C. Application of 

gas-liquid chromatography to the structural 

investigation ofpolysaccharides. ID. The gum ofAcacia 

karroo Hayne. Tetrahedron, Oxford (1967) 23 (3) 

1473-1478 [En 16 ref. 1 table] 

197 STEYN, D.G. Camel-thorn pods as stockfeed. 

Farming in South Africa (1943) 18 313-318 [En] 

Fresh foliage, flowers and green pods ofAcacia karroo 

sampled at Onderstepoort in the Transvaal, South Africa 

were repeatedly tested but found to contain no cyanogenic 

glycoside (prussic acid). 

198 STEYN, D.G.; RIMINGTON, C. The occurrence 

of cyanogenic glycosides in South African species of 

Acacia. I. Onderstepoort Journal of Veterinary Science 

and Animal Industry, Pretoria (1935) 4 (1) 51- 63 [En, 5 

ref.] 

Fresh leaves, flowers and immature pods of Acacia 

karroo Hayne and four other southern African species of 

Acacia were collected in the northern Transvaal and 

submitted to the prussic acid test (sodium picrate paper). 

Tests were performed on plant material alone or with 

chloroform or in an acid environment (pH 6.0). Tests were 

also run on wilted foliage. For A. karroo all these tests for 

prussic acid yielded negative results. By comparison fresh 

leaves and green pods of A.erioloba gave positive results 

(>70 mg HCN/1OO g dry weight of plant material) 

containing dangerously high levels of cyanogenic glycoside. 

A. karroo is therefore more suitable as a stock feed than 

some other species in this genus. 


199 STORY, R. A botanical survey of the 

Keiskammahoek District. Botanical Survey of South 

Africa Memoirs (1952) No. 27, 184 pp. [En, 85 photos, 

many ref.] 

Describes the climate and vegetation of the eastern 

Cape Province, South Mrica. Aspects of the ecology, 

utilization and management of Acacia karroo are discussed 

in some detail. The density ofA. karroo increased when the 

grass cover was reduced by grazing cattle. The tree is a 

source ofgum, offirewood and of thorn branches for making 

anirnal enclosures. Distribution of A. karroo in the Cape 

appears to be, limited by excess moisture, dryness and low 

temperatures. A sketch map shows how distribution is 

related to altitude and temperature. Rower and seed crops 

vary between years: data are presented. Seeds appear to be 

dispersed by wind, water and in the dung of cattle and other 

mammals. In some years many seeds contain bruchid 

beetles. Germination varies from 8-95%. Seeds have water 

impermeable dormancy and can remain damp for 29 months 

without germinating or rotting. Piercing the seed coat results 

in germination within four days. Seeds from herbarium 

sheets were viable after 28 and 57 years. 6-11 % of untreated 

seeds germinated over 423 days in field trials, but 17% of 

seeds scalded with boiling water germinated within eight 

weeks. Seedlings in cultivated ground had >90% survival 

rate and reached 18 in. in 18 months, whereas only 5% of 

seedlings in grassland survived and were only 4 in. high 

after 18 months. Seedlings were resistant to browsing, but 

all seedlings


benefitted from shade and leaf litter supplied by the trees, 

but these reduced the amount of moisture available for the 

grass. The trees were stimulated by moderate to light 

defoliation, and this increased their competitiveness. Using 

the data generated from this programme, a previously 

developed production model for the community was revised. 

This model predicts that maximum forage production, 

livemass production and profit will be achieved at 1220, 

1320 and 1000 tree equivalents respectively per hectare. An 

algorithm is presented as a guide to the estimation of longterm 

stocking rates of grazers and browsers. It was 

recommended that where trees exceeded densities of 

1320/ha trees should be removed in order of decreasing 

height. 

201 STUART-HILL, G.C. Refinement of a model 

describing forage production, animal production and 

profitability as a function of bush density in the false 

thornveld ofthe eastern Cape. Journal of the Grassland 

Society ofsouthern Africa (1987) 4 (1) 18-24 [En] 

The model describing the influence of Acacia karroo 

density on forage production, animal production and 

profitability (Aucamp et al 1983) over-estimated the 

potential for livestock production by 51 % and presented an 

over-optimistic view of the potential of bush utilization. 

202 STIJART-HILL, G.C.; TAINTON, N.M. Browse 

and herbage production in the Eastern Cape thornveld 

in response to tree size and defoliation frequency. 

Journal ofthe Grassland Society ofSouthern Africa (1988) 

5 (1) 42-47 [En, af, 12 ref.] 

Grass yields in the semi-arid savanna declined as the 

size of Acacia karroo increased. Browse yields did not 

increase as trees grew taller than 1.8 m. Simulated browsing 

of A. karroo trees stimulated browse production, provided 

it was not too intense. As a consequence, the competitive 

ability ofthe trees increased and grass yields were adversely 

affected. Conversely, simulated grazing reduced the 

competitiveness of the grass and thereby resulted in an 

increase in browse production. It is argued that residual soil 

moisture levels remain relatively high when grass growth is 

poor, so that water penetrates to greater depths after rain 

than when grass growth is vigorous and this favours the 

deep rooted trees. 

203 STUART-HILL, G.C.; TAINTON, N.M. Water 

utilization patterns around isolated Acacia ka"oo trees 

in the False Thornveld of the eastern Cape. Journal of 

the Grassland Society of Southern Africa (1989a) 6 (4) 

195-204 [En, af, 21 ref.] 

The effect of various vegetation treatments on two soil 

moisture regimes (i.e. the proportion of the experimental 

period when the soil had sufficient water for growth and to 

keep the plants turgid in the vicinity of experimentally 

isolated Acacia karroo trees) was monitored over a 

two-year period. Removal of all vegetation had the greatest 


effect on soil moisture, increasing the moisture regime by 

around 200%. Grass removal had the next most significant 

effect, increasing moisture regimes within 9 m of the tree by 

around 100%. Removal of the tree had the smallest 

significant effect, increasing the moisture regime by < 20%. 

There was no difference in the moisture regime surrounding 

trees with heights ranging between 1.4 and 2.5 m, or where 

various combinations of tree and/or grass defoliations were 

implemented. It was concluded that water supply to the trees 

was enhanced when soil water extraction was reduced e.g. 

during winter or when the sward was harmed. It was 

suggested that this may be a mechanism of accelerating bush 

encroachment in semi-arid savannas. 

204 STIJART-HILL, G.C.; TAINTON, N.M. The 

competitive interaction between Acacia karroo and the 

herbaceous layer and how this is influenced by 

defoliation. Journal ofApplied Ecology (1989b) 26 (1) 

285-298 [En, 35 ref.] 

A study in semi-arid savanna in South Africa of 

experimentally isolated Acacia karroo trees (all other trees 

and shrubs had been cleared from the sites). Three 

treatments were given in plots of 9 m radius: with a central 

tree surrounded by grass; with all grass removed; with 

central tree removed. Grass/foliage was harvested 1, 2 or 3 

times a year for three years to simulate grazing and/or 

browsing. Trees suppressed grass growth up to 9 m away, 

tall trees more so than short trees, and tree removal also 

reduced grass growth. Grass growth was reduced when trees 

were frequently defoliated (attributed to the stimulatory 

effect of defoliation on competitiveness ofA. karroo). Tree 

production increased in response to sward removal but was 

unaffected by sward harvesting, except when trees were 

defoliated frequently, when production of browse increased 

in response to frequent grass harvesting. [CABI abstract] 

205 STIJART-HILL G.C.; TAINTON, N.M.; 

BARNARD, HJ. The influence of an Acacia karroo tree 

on grass production in its vicinity. Journal of the 


[En, af, 37 ref.] 

It was established that a consistent pattern of grass 

production (Digitaria eriantha, Sporobolus fimbriatus, 

Cymbopogon plurinodis) occurred around isolated Acacia 

karroo trees. This was characterized by high yields under 

and immediately south of the tree canopy, and low yields 

immediately to the north of the canopy. The former was 

attributed to favourable influences by the tree (e.g. shade 

and tree leaf litter), whereas the latter was probably a result 

of reduced water input associated with physical 

redistribution ofrainfall bythe tree and competition from the 

tree for soil water. It is argued that the net effect of the 

favourable or unfavourable influences of A. karroo on grass 

production was dependent on tree density. This explains why 

grass production was greater where there were a few A. karroo 

trees than where there were no trees and why grass production 

declined as tree density increased beyond a critical level.

206 SUTHERLAND, 1.; MCINROY, S.G.; ODEE, 

D.W.; STANFORTII, A. African acacia rhizobia) 

technology and ecology: ODA Project R. 4714. Final 

report (1994). Department of Biological Sciences, 

University of Dundee, United Kingdom. 88 pp. 

The principal conclusion of this research was that one 

mixed medium could be used in unsterilized soil for the 

successful inoculation of all seven Acacia species tested (A. 

arenaria, A. karroo, A. nilotica, A. senegal, A. tortilis ssp. 

heteracantha, A. torti/is ssp. spirocarpa, Faidherbia 

albida) resulting in increases in both nitrogen fixation and 

dry weight. Effective means of strain identification were 

achieved with capillary electrophoresis of whole cell 

proteins and methods were developed that use no volatile 

toxic chemicals, unlike the more commonly used gel 

electrophoresis. Successful conclusion of these identification 

investigations were prevented by loss of effectiveness of the 

inoculated rhizobium strains. The authors conclude that the 

future of acacia research must lie in designer trees selected 

and bred for particular purposes in consultation with local 

users and that rhizobia research would be most cost effective 

if linked to tree breeding programmes. 

207 SWART, H.J. Fungi and Trees Part ID: Some 

Fungi found on leaves and branches. Trees in South 

Africa (1963) 15 (2) 34-36 [En] 

Includes diagram of the distorted inflorescence of 

Acacia karroo caused by the fungus Ravenelia. 

208 SWAR1Z, P.P. [A numerical taxonomic 

evaluation of the taxon Acacia ka"oo Hayne in 

southern Africa] Numeries-taksonomiese evaluering van 

die takson Acacia karroo Hayne in suidelike Afrika. M.Sc. 

thesis, University of Pretoria, Pretoria, South Africa (1982) 

[Af](ex Webb) [En] 

Using numerical taxonomic methods and a combination 

of 38 characters for Acacia karroo from southern Mrican 

populations, six well defined intra-specific groups were 

distinguished. Seedlings of these groups cultivated under 

controlled conditions similarly showed phenotypic variation, 

indicating that the groupings are genetically fixed. The 

morphology, distribution and ecological characteristics of 

members of the six groups are described in detail in this 

thesis. The author suggests that the groups should have 

subspecies status, suggests new name combinations, and 

provides a key to the groups. 

209 TALBOT, P.H.B. New and interesting records of 

South African fungi. Bothalia (1957) 6, 183-204 [En, 1 

ill.] 

A specimen of the Discomycete fungus Patellaria 

atrata (Hedw.), found on dead wood in Pretoria, South 

Africa, is housed in the Mycological Herbarium, 

Department of Agriculture, Pretoria. A specimen from the 

living bark ofAcacia karroo is housed in the South Mrican 


Museum, Cape Town (SA Mus No. 33426, MacOwan 

1058). 

210 TAYLOR, J.D. Notes on Lepidoptera in the 

eastern Cape Province -I. Journal ofthe Entomological 

Society ofSouthern Africa (1949) 12, 78-95 [En, 6 ref.] 

Larvae of the following families and species of 

lepidoptera were reported feeding on Acacia karroo in the 

Districts of Albany and Fort Beaufort, South Africa: 

Noctuidae: Sphingomorpha chlorea, Polydesma 

quenavadi; Lymantriadae: Euproctis fasciata; Sphingidae: 

Chaerocampa celerio; Notodontidae: Braura truncata; 

Geometridae: Semiothisa brongusaria, S. observata, 

Traminda ocellata, Zamarada opposita, Z. metallica; 

Saturnidae: Gynanisa maia Lasiocampidae: Anadiasa 

punctijascia, Beralada prompta, B. fumosa, Gonometela 

postica. Text gives descriptions and notes on behaviour and 

seasonality. 


eastern Cape Province - 2. Journal ofthe Entomological 

Society of Southern Africa (1951) 14 (2) 94-125 [En, 9 

ref.] 



Districts of Albany, East London, Fort Beaufort and Kei 

Road, South Africa: Noctuidae: Earias biplaga, Pericyma 

scandulata, Sphingomorpha chlorea; Lymantriidae: 

Dasychira municipalis, Porthesis aethiopica; Geometridae: 

Chlorerythra rubiplaga, Omphalucha maturnaria, 

Semiothisa streniata, S. procidata, Zamarada pulverosa; 

Lasiocampidae, Pachypasa capensis; Limacodidae: 

Coenobasis amoena; Pyralidae: Myelois ceratoniae. Text 

gives descriptions and notes on behaviour and seasonality. 


eastern Cape Province - 3. Journal ofthe Entomological 

Society ofSouthern Africa (1953) 16 (2) 143-167 [En, 12 

ref.] 



Districts of Albany, East London, Fort Beaufort and Kei 

Road, South Africa: Noctuidae: Pericyma scandulata; 

Geometridae: Prasinocyma scissaria, Tephrina spissata, 

P. decraria, Semiothisa streniata, S. umbrata, S. procidata, 

Heterostegane indularia; Lasiocampidae: Anadiasa 

sweirstrae, Braura truncata, Odontocheilopterix myxa, 

Beralada prompta, B. perobliqua. Text gives descriptions 

and notes on behaviour and seasonality. 


eastern Cape Province - S. Journal ofthe Entomological 

Society ofSouthern Africa (1965) 28 (2) 137-154 [En] 




Lepidoptera were reported feeding on Acacia karroo near 

Port Elizabeth, South Africa: Lymantriidae: Laelia cf. clarki 

Geometridae: Tephrina spissata. The larva and pupa of 

L. cf. clarki is described in detail. 

214 lEAGUE, W.R. The expected response ofAcacia 

karroo Hayne to moisture stress and defoliation. 

Proceedings ofthe Grassland Society ofsouthern Africa 

(1983) 18 147-150 [En] 

The ontogeny and annual growth cycles of Acacia 

karroo are given and possible responses to water stress and 

defoliation are discussed. 

215 TEAGUE, W.R. Leaf growth ofAcacia ka"oo 

trees in response to frequency and intensity of 

defoliation. In Ecology and management of the world's 

savannas, International Savanna Symposium (edited by 

Tothill, lC.; Mott, J.C.). (1984) pp. 220-222. 

Depending on the frequency, Acacia karroo plants 

defoliated bygoats showed some activation of growth. This 

led to a similar amount of leaf accumulation of plants under 

a 75% defoliation regime when defoliated at two-weekly, 

four-weekly and twelve-weekly intervals. 

216 lEAGUE, W.R. Response ofAcacia karroo trees 

to intensity ofdefoliation at different phenophases in a 

South African savanna. In Rangelands, a resource under 

siege. Proceedings of the 2nd Intemational Rangeland 

Congress, Adelaide, Australia, 13-18 May 1984 (edited by 

Joss, Pl.) Canberra; Australian Academy of Science (1986) 

466-467 [En] 

In the semi-arid eastern Cape area of South Africa, 

Acaciil karoo occurs in almost pure stands over large areas 

as the woody component in an open to dense, dwarf tree 

savanna. It has a deleterious effect on grass production and 

its increase cannot be prevented by burning, resting and/or 

judicious grazing management with cattle. However, goats 

are simultaneously able to control A. karroo and increase 

total red meat production per unit area by browsing, without 

adversely affecting grass production. In order to define the 

potential of the species as a fodder source for goats, its 

response to defoliation was studied. Leaf growth was 

measured in trees in which the entire canopy had been 

defoliated bygoats at intensities of 25, 50, 75 and 95%. The 

defoliation was arranged at each of 5 phenophases: early 

flush, pre-reproductive, reproductive, post-reproductive and 

late season. In all phenophases leaf production at the opt. 

defoliation intensity was 2-3 X that in control trees; trees 

were most sensitive to defoliation at the early flush and 

reproductive phases. In order to achieve max. leaf growth, 

it is recommended that they be defoliated by 25-50%, 

followed by a rest period of 3-6 months, depending on the 

phenophase. [CABI abstract] 


217 TEAGUE, W.R. Defoliation and browse 

production ofAcacill ka"OO Hayne in the eastern Cape, 

South Africa. Ph.D. thesis, University of the 

Witwatersrand, Johannesburg, South Africa (1987) [En, 

many ref.] 

This thesis explores the response of Acacia karroo 

plants to defoliation by goats in a farming situation. Field 

experimentation at the individual plant level was conducted 

to examine the growth pattern and response of these plants 

to the abiotic environment and to defoliation by goats. At the 

plant community level the pattern and rates of consumption 

in a representative community were examined. A simulation 

model collates the data generated and considers the 

implications for management. Growth in A. karroo is 

dominated bycurrent growing conditions. Plants are able to 

make opportunistic growth at any time, to take advantage of 

favourable environmental conditions. By growing in flushes 

and consolidating after each flush, these plants are able to 

cope with a variable climate and damage by herbivory. 

Moisture stress merely slows growth, with the pattern of 

growth being unaffected. The model predicts that increasing 

the number ofcamps increases the total amount of A. karroo 

harvested that can be expected with different management 

strategies, particularly sparing or very light use during early 

in the growing season. Even if it is possible to reduce stock 

in times of drought, this was shown to be probably of very 

little benefit. 

218 TEAGUE, W.R. The response ofAcacia karroo 

plants to defoliation by hand compared to defoliation by 

goats. Journal ofthe Grassland Society Southern Africa 

(1988a) 5 (3) 122-124 [En, af, 19 ref.] 

Acacia karroo plants were 50% or 100% defoliated, 

with or without shoot-tip removal, by hand or by goats. Leaf 

and shoot production did not differ between plants where 

leaves only or leaves and shoot tips were removed. Leaf 

growth on plants 50% defoliated by goats was approx. 

3-fold ofthat on plants 50% hand-defoliated. Leaf growth on 

hand-defoliated plants was approximately twice that of 

undefoliated plants. Heavy defoliation by hand or goat gave 

approximately half the leaf growth of moderately defoliated 

plants. Shoot production was greatest under goat defoliation 

and least with no defoliation. 

219 TEAGUE, W.R. Growth patterns and annual 

growth cycle of Acacia ka"oo Hayne in relation to 

water stress. 11. The annual use and replenishment of 

non-structural carbohydrates in relation to 

phenological development Journal of the Grassland 

Society ofSouth Africa (1988b) 5 (3) 169-173 [En, af, 25 

ref.] 

In field studies at 3 sites in South Africa, Acacia karroo 

showed the seasonal fluctuation in total non-structural 

carbohydrate (lNC) content characteristic of deciduous 

species. lNC reserves declined rapidly and substantially at 

bud-burst in spring. lNC reserves also declined during

apid leaf, shoot or reproductive organ growth. lNC 

reserves were replenished while recently emerged leaves 

were still small. Water stress did not change the pattern of 

TNC use and replenishment but did slow down the 

replenishment process. It was suggested that this slowing 

down also slows down the beginning of the next annual 

growth event as well as the growth of previously initiated 

organs. It was also suggested that growth flushes followed 

by replenishment enable A. karroo to withstand harsh 

environmental conditions and damage by herbivory. 

220 TEAGUE, W.R. Effect of intensity and 

phenophase of defoliation and water stress on the rate 

of photosynthesis and the recovery of carbohydrate 

reserves in Acacia ka"oo Hayne. Journal of the 

Grassland Society of Southern Africa (1988c) 5 (4) 

223-226 [En] 

A field study was conducted with Acacia karroo plants 

to determine changes in relative photosynthetic rates, the 

extent of carbohydrate reserve depletion, and the rate 

reserves take to recover following defoliation by goats at 

different intensities and phenophases, at a wet and a dry site. 

The rate of photosynthesis of fully expanded leaves 

increased markedly following defoliation. Light defoliation 

increased photosynthetic rate the most. Total non-structural 

carbohydrate levels dropped significantly after defoliation. 

The magnitude of decrease was directly related to the 

intensity of defoliation. Following heavy defoliations, 

recovery of carbohydrate levels was much faster than after 

the light defoliations. Rates of recovery were also faster 

following defoliation in the second half of the growing 

season, than in the first half. However, the plants that had 

been heavily defoliated in the second half of the growing 

season had not fully recovered carbohydrate levels before 

leaf fall in late autumn. Moisture stress has very little effect 

on carbohydrate levels in comparison with the defoliation 

treatments. 

221 lEAGUE, W.R. The rate ofconsumption of bush 

and grass by goats in a representative Acacia karroo 

savanna community in the Eastern Cape. Journal ofthe 

Grassland Society ofSouthern Africa (1989a) 6 (1) 8-13 

[En, af, 30 ref.] 

Consumption of browse and grass by goats in a 

representative Acacia karroo savanna community was 

measured. A. karroo was preferred to grass. It was selected 

almost exclusively when available at high leaf densities. 

Grass was consumed in significant amounts only when 

approximately 50% ofthe available A. karroo leaf had been 

consumed. Maximum daily intake was 78 g kg- 1 W 0.75 per 

day and decreased with decreasing amount of browse on 

offer. When approximately 90% of the available A. karroo 

leaf had been removed, the goats had consumed only 30% 

ofthe available grass. Total intake of browse plus grass was 

lower during the period when the goats changed from 

consuming mostly A. karroo to consuming mostly grass. 

Goats did not appear to select a diet according to their 


nutritional needs, as judged by feeding tables, when this was 

possible. This may be due to protein indigestibility caused 

bytannin complexing by A. karroo, luxury consumption of 

A. karroo as a favoured food, an adaptation by goats to use 

browse more efficiently than grass, or differences in 

palatability between A. karroo and grass. 

222 TEAGUE, W.R. Effect of intensity and 

frequency of defoliation on aerial growth and 

carbohydrate reserve levels in Acacia ka"oo plants. 

Journal of the Grassland Society of Southern Africa 

(1989b) 6 (3) 132-138 [En, af, 24 ref.] 

Acacia karroo trees near Alice, Ciskei, were defoliated 

by goats at two intensities at 2, 4, 8 and 12-week intervals. 

Leaf accumulation and carbohydrate reserve levels were 

compared with a non-defoliated control, and to plants 

(defoliation control) which were defoliated for the first time 

that season each time a frequency treatment was defoliated. 

These plants are activated by defoliation in such a manner 

that successive defoliations can result in this activation being 

additive. There is clearly a defoliation level below which 

they are not activated. Activation appeared to be negated to 

a degree by defoliations at 2- and 4-week frequencies, 

relative to the 8-week defoliation frequency. The 12-week 

frequency at heavy defoliation produced less than the same 

defoliation at 8-week frequency. The 2-week frequency 

treatments produced as much leaf as the 4- and 12-week 

defoliations at the same defoliation intensity. The more 

frequently plants were defoliated, the more carbohydrate 

reserves dropped. Plants adjusted to cope with very frequent 

defoliations. There was no connection between leaf 

accumulation and carbohydrate reserve levels following the 

different frequencies and intensities of defoliation. 

223 TEAGUE, W.R. The response ofAcacia karroo 

plants to defoliation of the upper or lower canopy. 

Journal of the Grassland Society of Southern Africa 

(1989c) 6 (4) 225-229 [En, af, 17 ref.] 

In trials near Alice, Cape Province, the response of 

Acacia karroo trees to defoliation of either the upper or 

lower canopy only was compared with that of plants whose 

whole canopies had been defoliated at a range of defoliation 

levels. These plants were very sensitive to defoliation of the 

upper canopy; 100% defoliation of the upper canopy 

resulted in the same amount of growth as 100% defoliation 

of the whole canopy. This was considerably less than the 

growth of plants defoliated overall, at 25% and 50% leaf 

removal. In contrast, defoliating the bottom half of the 

canopy stimulated growth in the whole canopy to the same 

degree as defoliation of the whole canopy at 25-50%. The 

increases in growth were largely due to increased growth in 

the top half of the canopy. Plants were very sensitive to 

defoliation in the early-flush phenophase. This probably 

masked the positive effects ofthe partial defoliations applied 

at this phenophase. 



224 TEAGUE, W.R. Patterns ofselection ofAcacia 

karroo by goats and changes in tannin levels and in 

vitro digestibility following defoliation. Journal of the 

Grassland Society of Southern Africa (1989d) 6 (4) 

230-235 [En, af, 23 ref.] 

In trials near Alice, Cape Province, patterns of browse 

selection of Boer goats in a representative Acacia karroo 

community were studied. The rate of intake of browse was 

positively related to the leaf mass/unit length of the shoot. 

The ease of harvesting leaf material, as determined by the 

height above ground, modified the rate of intake. Generally, 

following browsing, tannin levels increased and in vitro 

digestibility decreased. These changes in tannin content and 

digestibility differed in magnitude according to plant size 

and age of the shoot and leaf. Generally, leaf and shoot 

intake was negatively related to tannin content and positively 

related to digestibility, thus influencing patterns of selection 

for different plant parts and size classes of A. karroo. 

However, some of the results were contradictory. 

225 TEAGUE, W.R.; KllLlllA, D.M. The application 

of various picloram formulations to cut stumps of 

Brachystegia spkijormis Benth., Julbernadia globulifera 

(Benth.) Troupin, Terminalia sericea Burch. ex DC. and 

Acacia ka"oo Hayne trees. Journal of the Grassland 

Society ofSouthern Africa (1990) 7 (2) 125-132 [En] 

The application rates of picloram/2,4-D amine or 

picloraml2,4,5-T amine (expressed as grams acid equivalent 

picloram per mm girth) required to kill 80% of Acacia 

karroo trees was 0.012-0.016 g/mm. 

226 TEAGUE, W.R.; WALKER, B.H. Growth 

patterns and annual growth cycle of Acacia ka"oo 

Hayne in relation to water stress. I. Leaf and shoot 

growth. Journal of the Grassland Society of Southern 

Africa (1988a) 5 (2) 85-95 [En, af, 26 ref.] 

The growth patterns ofAcacia karroo at different levels 

ofwater stress in different edaphic situations are described. 

Shoots are heterophyllous and are formed by free growth. 

The degree of development of a shoot, relative to others in 

the canopy, is governed by branch and position in the 

canopy. At least six phenological phases were identified in 

the annual growth cycle. The pattern of growth and the 

phenological cycle were not changed by water stress. 

Initiation, emergence and development of shoots and leaves 

were governed by environmental conditions. If there was 

little shoot growth early in the season, the plants could 

partially compensate by producing more leaf/unit of shoot if 

environmental conditions improved. Leaf and shoot growth 

at the beginning of the season took place only if there was 

sufficient moisture available, and if the minimum 

temperature rose above a threshold value. Where there was 

insufficient soil moisture, no growth was observed before 

rains had fallen. The growth strategy of A. karroo differed 

markedly from that of broad-leaved African savanna tree 

species. Growth in A. karroo was dominated by current 

growing conditions, rather than those of the previous season, 


and it was able to make opportunistic growth at any time. 

Soil depth had a marked influence on plant growth, 

presumably due to a larger available nutrient and moisture 

pool. 

227 TEAGUE, W.R.; WALKER, B.H. Effect of 

defoliation by goats at different phenophases on leaf 

and shoot growth ofAcacia kan-oo Hayne. Journal ofthe 

Grassland Society of Southern Africa (1988b) 5 (4) 

197-206 [En, af] 

Defoliation by goats (leaves plus shoots) during 

growing phases resulted in considerable stimulation of leaf 

and shoot growth relative to non-defoliated plants. The 

response differed depending on the intensity and phenophase 

of defoliation. Plants were most susceptible to defoliation 

and young shoot removal during the spring flush when 

carbohydrate levels were at their lowest. During the rest of 

the growing season, carbohydrate levels were high. At these 

times moderate to heavy (50%-75%) leaf removal) resulted 

in the greatest leaf and shoot growth. 

228 TEAGUE, W.R.; WALKER, B.H. Simulating 

browse production and response of Acacia ka"oo to 

defoliation ll. Evaluation of browse management 

systems and strategies. Journal ofthe Grassland Society 

ofSouthern Africa (1990) 7 (4) 243-248 [En, 13 ref.] 

To assess management implications, a model was used 

to simulate the response ofAcacia karroo to a wide range of 

different climatic patterns and defoliation regimes. The 

model predicts that if poor growing conditions initiate 

growth later in spring than normal, total season growth and 

harvest is significantly reduced. In comparison, cooler 

overall temperatures throughout the season reduce the 

season less markedly. Results indicate that increasing the 

number of camps in a pastoral system increases the total 

amount of A. karroo that can be harvested. The model 

illustrates, in general terms, the limits and constraints of 

increasing the number of camps, varying the length of stay 

in each and varying the length of the rest period before the 

next occupation at different stocking rates. It also indicates 

the increases in A. karroo harvests that can be expected with 

different management strategies. The most important 

prediction of the model was the large increase in 

prcxiuctivity that could be expected by sparing or very light 

use early in the growing season. Even if it is possible to 

reduce stock in times of drought, this was shown to be of 

very little benefit. [Author's summary] 

229 TEAGUE, W.R.; TEAGUE, R.e.; WALKER, B.H. 

Simulating browse production and response ofAcacia 

kan-oo to defoliation I. Model description and sensitivity 

analyses. Journal of the Grassland Society of Southern 

Africa (1990) 7 (1) 1-10 [En, 18 ref.] 

The model is aimed at synthesizing existing data to 

enhance the understanding of this data and explore the 

consequences of possible browse management strategies. It

gives a good reproduction of the shoot and leaf growth 

responses used to develop it and a reasonable prediction of 

leaf growth when tested against independent data. The 

prediction of shoot growth against independent data was 

poor. Sensitivity analyses indicate that five parameters have 

a very strong influence on the output of the model. These are 

moisture, soil depth, the magnitude and duration of growth 

stimulation following defoliation, how soon growth is 

initialized and how favourable growing conditions are in 

spring. Plant size and the carry-over of growth stimulation 

from one year to the next had a moderate influence. 

[Author's summary} 

230 THODAY, D. Modes of union and interaction 

between parasite and host in the Loranthaceae. V. Some 

South African Loranthoideae. Proceedings ofthe Royal 

Society, London (1960) 152B, 143-62 [En, 17 ref.] 

Describes with illustrations the haustorial structure and 

behaviour of Loranthus elegans on Acacia karroo and 

Carissa arduina, L. prunifolius on Rhoicissus cuneifolia, 

L. glaucus on Lycium spp. and L. dregei on Zizyphus 

mucronata. 

231 llETEMA, T. Biomass determination of 

fuelwood trees and bushes of Botswana, Southern 

Africa. Forest Ecology and management (1993) 60257 

269 [En, 21 ref.] 

Samples of 14 tree species indigenous to Botswana, 

including Acacia karroo, were measured, cut and weighed 

to establish the relationship between tree fresh biomass and 

tree dimensions. The relationship best suited to the indirect 

estimation of total fresh weight was the regression between 

tree fresh weight and stem basal area at ankle height (5-10 

cm above ground level). The research showed that there was 

a sufficient similarity between the regression lines of a range 

of trees in Botswana to allow the determination of tree 

biomass in a normal diverse forest or woodland with the 

replacement of the regression lines of the individual tree 

species by one combi-line. The regression formulae for 

estimating individual tree fresh biomass (B) in kg from 

ankle height basal area (BA) in cm 2 for 36 trees of A. karroo 

growing at Dikeletsane in Botswana were 

B=0.2865xBA1. 2082 (R 2 =0.96), when BA was plotted on a 

logarithmic scale, and B=0.7558xBA (R 2 =0.93) when BA 

was plotted untransformed. The R 2 value for A. karroo fit to 

the combi-line was 0.89. The regression formula for the 

combi-line for 512 trees of 14 species was 

B=0.1936xBA 1 . 654 (R 2 =0.92). 

232 TIETEMA, T.; MERKESDAL, E. An 

establishment trial with Acacia tortilis, A. karroo, A. 

erubescens and A. erioloba at Morwa Forestry. The 

situation after one year. Journal of the Forestry 

Association ofBotswana (1986/87), 47-52 [En, 5 ref.] 

Eucalypt plantations in Botswana have failed to produce 

more wood than indigenous natural woodland. Therefore, 


seedlings offour indigenous Acacia species were planted in 

an establishment trial at Morwa Forestry, Kgatleng District, 

Botswana, in January 1986. About one year after planting, 

A. tortiUs had a survival of 85%; survival of the other three 

species ranged from 25.6% to 41 %; these low figures were 

caused mainly bya high incidence of death in early summer. 

Increased watering is recommended to increase survival 

rates of the three poorly performing species. 

233 TIMBERLAKE, 1. Handbook of Botswana 

acacias. Ministry of Agriculture (1980) Gaberone, 

Botswana. 120 pp. [En] 

This field guide to the 32 Acacia species of Botswana 

includes a dichotomous key for identification and some 

general notes about the taxonomy, ecology and uses of the 

genus. For each species, including A. karroo, a taxonomic 

description is given followed by notes on the distribution 

and habitat, uses and culture. The species is described as 

very variable in form and habitat; and it is useful, although 

it can encroach on badly-managed rangelands. The wood is 

hard and heavy and has many uses but is not durable. It 

makes good frrewood and charcoal, the bark is used for 

tanning, the flowers are valuable sources of pollen and 

nectar, the foliage, flowers and pods are valuable browse 

and the gum is edible. 

234 TIMBERLAKE, 1.R.; NOBANDA, N.; 

MAPAURE, I. Vegetation survey of the communal lands 

• north and west Zimbabwe. Kirkia (1993) 14 (2) 171 

270 [En, 93 ref. 1 Map] 

The survey was carried out using a phytosociological 

approach with initial stratification based on air photos 

followed by field sampling. The survey concentrated on the 

floristic composition of the various ecological units. Thirty 

seven vegetation types are described and these are grouped 

into eight vegetation classes. Acacia karroo is described as 

a tree of 4-10 m that forms stands on heavier-textured 

alluvium and is very common on red clay soils along 

watercourses and at the base of the Great Dyke. In high 

rainfall areas it occurs widely on clay-rich soils. Generally, 

it is an indicator of nutrient-rich soils. 

235 TOLSMA, DJ.; ERNST, W.H.O.; VERWEIJ, 

R.A.; VOOUS, R.T.I. Seasonal variation of nutrient 

concentrations in a semi-arid savanna ecosystem in 

Botswana. Journal ofEcology (1987) 75 (3) 755-770 [En, 

39 ref.] 

Presents data for seasonal changes of nutrient 

concentrations in the leaves of the main tree and grass 

species ofa semi-arid savanna in Botswana. Leaves, flowers 

and fruits (if present) were collected at 3-4 week intervals 

during September 1982 - December 1983 from the trees 

Acacia burlfei, A. erubescens, A. fleckii, A. karroo, A. 

mellifera ssp. detinens, A. nilotica ssp. kraussiana, A. 

robusta, A. tortilis ssp. heteracantha and Terminalia 

sericea, the shrub Dichrostachys cinerea and the grasses 



Eragrostis rigidior and Panicum maximum in the cattle-free 

zone of Gaborone. All plant material was analyzed to 

determine contents of N, P, K, Ca, Mg, Fe, Na, Zn and Mn 

and results for most elements are shown in graphs. With the 

exception ofA. kfl"oo, most tree species were leafless at the 

end of the dry season. Seasonal variation in concentrations 

of foHar nutrients followed similar trends in all species. 

Concentrations ofN and P were greater in young leaves than 

in mature leaves, while Ca and Fe accumulated until leaf 

abscission. Concentrations of Ca and Mg in A. karroo 

foliage peaked during the dry winter whereas N, P and K 

levels were greatest in new foliage in early summer. 

Variations in foliar nutrients in flowering and non-flowering 

trees and total nutrients in flowers and fruits of trees are also 

described. It is concluded that P is the most limiting nutrient 

in this savanna because of the strong translocation from 

leaves to twigs before leaf abscission. 

236 1ROILOPE, W.S.W.; TAINTON, N.M. Effect of 

fwe intensity on the grass and bush components of the 

Eastern Cape Thornveld. Journal of the Grassland 

Society ofSouthern Africa (1986) 3 (2) 37-42 [En, 8 ref.] 

Fire intensity is an important component of the fife 

regime and its effect on the grass sward and bush were 

investigated in the Eastern Cape thornveld. Research 

indicated that fife intensity had no effect on the recovery of 

grass after a burn. Conversely it had a marked effect on the 

topkill of bush to a height of 2 m. The results provide· 

valuable guidelines for the use of fife in controlling bush 

encroachment. The species studied included Acacia karroo, 

Rhus lucida, Ehretia rigida, and Grewia occidentalis. 

237 VAN DER WALT, P.T. A phytosociological 

reconnaissance of the Mountain Zebra National Park. 

Koedoe (1980) 23 (1) 1-32 [En, 38 ref., 4 maps] 

Acacia karroo is the dominant tree in xeric riparian 

bush in the Mountain Zebra Park, Cape, South Africa. 

Rainfall averages around 400 mm yr-t and 70% falls in 

summer months. The A. karroo trees are 6-9 m in height 

and are associated with shade-loving shrubs (Lycium, 

Diospyros), climbers (Protasparagus), forbs and grasses. 

The parasite Viscum capense is common on A. karroo at 

this site. 

238 VASSAL, J.; LESCANNE, N. [Cytology and 

taxonomy in the genus Acacia.] Cytologie et taxonomie 

dans le genre Acacia. Bulletin de la Societe d'Histoire 

Naturelle de Toulouse (1976) 112 (1-2) 101-110 [Fr, en, 

14 ref.] 

This work presents the main results of morphological 

investigations on chromosomes of the genus Acacia. 

Chromosome numbers and chromatin and chromosome 

lengths are given for the different sub-genus groups and the 

relationships between the different subgenera Aculeiferum 

Vas., Heterophyllum Vas. and Acacia Vas. are discussed. 


239 VENTER, HJ.T. [Ecology of the vegetation of 

Richards Bay] Ekologie van die plantegroei van 

Richardsbaai. South African Journal ofScience (1971) 67 

(2) 52-55 [Af] 

Rainfall at Richard's Bay (northern coast of Natal, South 

Africa) averages 1300 mm p.a., summer temperatures 

exceed 400C and relative humidity seldom falls below 50%. 

Winds and salt spray also influence and occasionally damage 

the coastal vegetation. Acacia karroo colonizes grassland in 

this area and is also found on bare drift sand. Large areas to 

the north and south of the Richards Bay lagoon are covered 

in A. karroo woodland which forms a zone between dune 

forest and grassland. The species grows exceptionally large 

here (15 m high, 1.4 m stem circumference). The mistletoe 

Loranthus dregei kills old A. ka"OO trees in the dune forest, 

often breaking their branches with its weight. 

240 VERDOORN, I.C. The nomenclature of the 

Cape Acacia. Bothalia (1954) 6 (2) 409-413 [En, several 

ref. in text, 2 photos] 

Acacia karroo is the correct name for the Cape Acacia 

which occurs within about c. 100 km of Cape Town. 

241 VERMEULEN, J.B; GROBLER, H. A guide to 

the use of herbicides, 9th ed. Department of Agriculture, 

Pretoria (1986) 112 pp. [En] 

1breeherbicides are registered for the chemical control 

of Acacia karroo in South African rangeland: bromacil, 

ethidimuron and tebuthiuron. 

242 VISSER, 1. South African parasitic flowering 

plants. Juta, Cape Town (1981) 177 pp. [En] 

Acacia karroo is listed as a host of the root parasite 

Sarcophyte sanguinea (Balanophoraceae). A colour 

photograph shows attachment of the parasite to the roots of 

an A. karroo sapling. The parasite, known from the eastern 

Cape, Natal and the eastern Transvaal, South Africa, has 

also been found on other species ofAcacia. 

243 VON BREfIENBAGI, F. The lost Natal Thorn: 

For a reinstatement ofAcacia natalitia E. Mey. Journal 

ofDendrology (1989) 12 1-10 [En, 23 ref.] 

The taxonomic history of Acacia natalitia E. Mey. is 

investigated from its description in the early 19th century to 

its recent amalgamation with A. karroo Hayne. The diffusion 

of the original A. karroo concept by the inclusion of A. 

natalitia and various other clearly differing forms is 

considered undesirable, but to isolate the true A. karroo by 

separating from it all definable divergent forms, is preferred. 

With its whitish bark, small thorns, more finely divided 

leaves, lemon-)ellow candle-like inflorescences and longer, 

more constricted pods, A. natalitia can be sufficiently well 

distinguished from A. karroo to justify its reinstatement as 

a separate taxon.

244 WAIT, I.M.; BREYER-BRANDWUK, M.G. The 

medicinal and poisonous plants of Southern and 

Eastern Africa. Edinburgh and London; E & S Livingstone 

Ltd. (1962) 543-544 [En, many ref., 1 ill.] 

A decoction of the bark of Acacia karroo which 

contains 19.7% tannin has been used as an emetic and to 

treat diarrhoea in humans and "tulp" poisoning in cattle. The 

bark is also used for tanning and for making twine. Pods and 

foliage give negative tests for hydrocyanic acid and are eaten 

by goats and other livestock. Seeds have been used as a 

coffee substitute. Branches are used in basket making and 

for supporting thatched roofs of traditional Mrican 

buildings. Wood is used as fuel. The gum (Cape gum) is of 

the arabinose-galactose type and has been analyzed. 

245 WEBB, lW. The population dynamics of an 

indigenous psyllid Acizzia russellae (Homoptera: 

Psyllidae) with special reference to the host plantAcacia 

ka"oo. Ph.D. thesis, Rhodes University, Grahamstown, 

South Africa (1974) [En] 

The study includes a taxonomic description of the 

psyllid, an account of its general biology, monitoring of the 

seasonal fluctuations in numbers of the psyllid and its 

hymenopterous parasites, a study of various aspects of the 

host plant (Acacia karroo) including nitrogen levels, water 

stress, leaf hardness, and the effect of cutting in relation to 

spatial and temporal differences in insect population 

numbers. Seasonal patterns in psyllid numbers followed 

fluctuations in nitrogen levels on individual trees. No effect 

of stress or leaf hardness was clearly discerned. Cutting of 

trees altered the characteristics of the subsequent 

regenerative growth so as to allow massive psyllid 

infestations to develop, thus showing the tremendous 

importance of the host plant in determining population 

levels in this insect. Preliminary investigations of the nature 

and mechanism of this effect were conducted, and its 

significance is discussed. The relevance of these findings to 

modern concepts of regulation in insect populations and to 

principles of pest management is discussed. 

246 WEBB, lW. The life history and population 

dynamics ofAcizzia russellae (Homoptera: Psyllidae). 

Journal ofthe Entomological Society ofSouthern Africa 

(1977) 40 (1) 37-46 [En, 27 ref.] 

The life cycle of the psyllid was studied under 

laboratory conditions and the population dynamics were 

studied in the eastern Cape, South Africa over three years. 

There was a single peak of high abundance each spring. 

Dispersal was important because psyllids were influenced 

by the physiological condition of their host plant Acacia 

karroo. 

247 WEBB, lW.; MORAN, V.C. New species of 

Acizzia (Homoptera: Psyllidae) from Acacia ka"oo in 

southern Africa. Journal ofthe Entomological Society of 

Southern Africa (1974) 37 (1) 118-124 [En] 


Describes Acizzia russellae collected on Acacia karroo 

near Grahamstown, Cape Province, South Mrica. 

248 WEBB, lW.; MORAN, V.C. The influence ofthe 

host plant on the population dynamics of Acizzia 

russelUze (Homoptera: Psyllidae). Ecological Entomology 

(1978) 3 313-321 [En, 26 ref.] 

Population levels of the psyllid were ten times greater 

on regenerative foliage of pruned Acacia karroo trees than 

on normal trees. During late summer and winter, 

populations declined more slowly on pruned than on normal 

trees. Laboratory measurements of several chemical and 

physical characteristics of the foliage of pruned and normal 

trees did not reveal any differences which could account for 

the observed effects. It is suggested that the availability of 

quantities of suitable high quality nutrients in the leaves of 

pruned A. karroo trees explains the epidemic population 

levels achieved by the psyllid on pruned plants. 

249 WEHMER, C. Die Ptlanzerstotfe, 2nd ed. Fischer, 

Jena (1935 supplement to 2nd ed. 1929) [Ge] 

Gives the tannin contents of bark and fruit, analysis of 

gum ofAcacia karroo. 

250 WEISSER, PJ.; MARQUES, F. Gross vegetation 

changes in the dune area between Richards Bay and the 

Mfolozi River, 1937-1974. Bothalia (1979) 12 (4) 

711-721 [En, fr, af, 11 ref., 7 pI.] 

Marked changes in dune vegetation in this region of 

Natal, as shown on air photos taken in 1937 and 1974, are 

described and quantified. About 55% of the study area had 

changed from one mapping unit to another during the 

period, the changes being mainly due to secondary 

successions resulting from protection by the Department of 

Forestry, which is also responsible for extensive 

afforestation. It is estimated that under the existing 

favourable climatic conditions it takes some dune grassland 

only 25-60 yr to develop to mature Acacia karroo woodland 

and a further 30-150 yr to proceed to secondary dune forest. 


251 WEISSER, PJ.; MULLER, R. Dune vegetation 

dynamics from 1937-1976 in Mlalazi - Richard's Bay of 

Natal, South Africa. Bothalia (1983) 14 (3/4) 661-667 

[En] 

Dune vegetation changes were studied qualitatively with 

the aid ofair photos taken in 1937, 1957 and 1976. Results 

were transferred to 1:10000 scale maps. In 1937 roughly 

80% of the dune forest habitat was occupied by planted 

fields and post cultivation seral stages such as Secondary 

Grasslands and Dwarf Shrubland, Secondary Scrub and 

Acacia karroo Woodland. In three areas, the vegetation 

cover had been completely destroyed and drift sands had 

formed. In the 1950's the trend of vegetation degradation 

was changed by the implementation of an afforestation 

programme by the Department of Forestry. The 1976 air 



photos indicate that the post cultivation seral stages of 1937 

had been largely replaced by forest plantations. In 

secondary, unafforested areas the vegetation is evolving 

rapidly towards a Secondary Dune Forest. [Author's 

summary] 

252 WElLS, MJ.; BALSINHAS, A.A.; JOFFEE, H; 

ENGELBREClIT, V.M.; HARDING, S.; STIRTON, C.H. 

A catalogue of problem plants in Southern Africa, 

incorporating the National Weed List of South Africa. 

Botanical Survey ofSouth Africa Memoirs (1986) No. 53, 

43 [En] 

Information listed on 1653 taxa, including 711 

naturalized exotics, which have been shown to be weedy in 

certain situations in southern Africa. Forty five Acacia t&Xa 

(mostly indigenous) are described, including A. karroo 

Hayne. It is included in the National Weed list having the 

undesirable characteristics of being competitive (for space, 

light, water, nutriment), replacing the preferred vegetation 

(grass), thorny (plant) and obstructive (access). It is 

cultivated as an ornamental or barrier crop. It is legislated as 

a declared invader and is subject to herbicide registration. 


253 WEST, O. The vegetation of Weenen county, 

Natal. Botanical Survey ofSouth Africa Memoirs (1951) 

No. 23, 183 pp. [En, many refs] 

254 WEST, O. Veld management in the dry, 

summer-rainfaU bushveld. In: The grasses and pastures of 

South Africa. (1955) (Meredith, D., Ed.). Cape Times 

Limited, Parow, C.P. 771 pp. [En] 

The Acacia arabica (A. nilotica) belt occurs in the 

driest parts of the valley, usually half way up the sides. 

Further down the valley with improving moisture conditions, 

are the A. caffra and A. karroo zones. Acacia karroo forms 

the lowest zone, also occurring along river valleys. A. caffra 

andA. karroo are more tolerant to frost and less tolerant to 

drought than A. nilotica. 


255 WHITE, F. Forest flora of Northern Rhodesia. 

London, Oxford University Press (1962) 76-85 [En] 

This comprehensive account of the woody plants of 

Northern Rhodesia gives a brief description of each tree 

species classified by family, including Acacia karroo. 

256 WHITE, F. The vegetation of Africa. Natural 

Resources Research, UNESCO (1983) 356 pp. [En] 

257 Wll..D, H. Arsenic tolerant plant species 

established on arsenical mine dumps in Rhodesia. 

Geobotanical anomalies in Rhodesia. 4. The vegetation 

ofarsenical soils. Kirkia (1974) 9 (2) 265-278 [En, 2 ref.] 

Describes the vegetation of 15 spoil mounds at gold 

mines, mainly deposits from slimes, and lists 77 indigenous 

and exotic plant species with their frequency and tolerated 

range of soil As contents (up to 30 000 p.p.m.). Some 

indigenous species were not recorded from natural As sites, 

notably Acacia karroo (up to 10 000 p.p.m. As); most of 

these species were associated with metalliferous sites. 

Plantations of Euphorbia tirucalli have succeeded in some 

instances at

ACOCKS, J.P.H. 1,2,3 

ADAMSON, R.S. 4 

ALLISON, G.E. 5 

ANDERSON, D.M.W. 6, 7, 8, 9, 10, 11, 12 

ARCHER, F.M. 13, 14, 15,16 

ARORA, G.D. 142 

AUCAMP, AJ. 17,18,19,20,21 

AYLEN,D.22 

BALA, B.B. 23 

BALSINHAS, A.A. 252 

BARNARD, A. 24 

BARNARD, H.H. 18 

BARNARD, HJ. 205 

BARNES, R.D. 25, 26, 27, 37b, 96, 99 

BAXTER, B. 28 

BAYER, A.W. 29 

BEENTJE, H.E. 57 

BEMBRIDGE, TJ. 30, 31 

BENNEIT, E.M. 126 

BENTIIAM, G. 32 

BEWS, J.W. 33 

BEZUIDENHOUT, H. 38 

BIEGEL, H.M. 258 

BOND, C. 135 

BOSCH, 0 J .H. 34 

BRAIN, P. 35, 36, 37a, 37b 

BREDENKAMP, GJ. 38,119,120 

BREYER-BRANDWIJK, M.G. 244 

BRIDGEMAN, M.M.E. 12 

BROOKE, R.K. 39 

BROWN, N.A.C. 40 

BROWNE, C.W. 41 

BRYANT, J.P. 42 

BURLEY, J. 43 

CARR, J.D. 44, 45, 46, 47 

CARTER, D.T. 92 

CHAPPILL, J.A. 48 

CHARLSON, AJ. 49 

CHIMBALANGA, 1. 26 

CHOWN,S.50 

CHURMS, S.C. 51 

CLARKE, J.M. 52, 53 

CLEGHORN, W.B. 54 

COAlES-PALGRAVE, K.E. 55 

COE,C.E.56 

COE, M. 56, 57 

COElZEE, BJ. 59 

COElZEE, J.A.E. 58 

COHEN, C.E. 60 

COMINS, D.M.E. 61 

COOPER, S.M. 42 

CREE, G.M. 7, 8 

CROCKFORD, KJ. 53 

CRONIN, C.R. 54 

AUTHOR INDEX 

CUNLIFF, K.M.E. 62 

CUTLER, D. 161 

DAMIANO, A.E. 63 

DANCKWERTS,J.E. 19,20,21 

DE PINTO, G. 12 

DE RIDDER, C.H. 107, 108 

DEA, LC.M. 9 

DEAN, R.J. 137 

DEAN, W.RJ. 64, 65 

DECELLE, J.E. 79 

DICKSON, C.G.C. 66 

DRUMMOND, R.B. 67, 86 

DUBE,1.S. 68, 145 

DU PREEZ, PJ. 69 

DU TOIT, J.W. 154 

DU TOIT, P.F. 70, 71, 72, 73, 74, 75 

EARLE, R.A. 76 

EBERHARD, A.A. 77 

EDWARDS, D. 78 

ELLERY, W.N. 129 

ENGELBRECHT, V.M. 252 

ERASMUS, T. 117,118 

ERNST, W.H.O. 79, 235 

FAGG, C.W. 25 

FELKER, P. 80 

FILER, D.L. 27 

FOURIE, C. 81 

FOURIE, O. 82 

FREEMAN, B.H. 83 

FRIEDEL, M.H. 84 

FRISBY, K. 42 

GALPIN, E.E. 85 

GELFAND, M. 86 

GERS1NER, J. 87 

GHIMPU, V. 88 

GIBSON, LA.S. 89 

GINDEL, G.F. 90 

GMELIN, R. 91 

GOLDSMITII, B. 92 

GONSALYES, P. 59 

GORDON-GRAY, K.D. 93, 94 

GOURLAY, LD. 27, 95, 96, 97, 98, 99 

GRIME, G.W. 97 

GROBLER, H. 241 

GROBLER, PJ. 100 

GUILLOTEAU, J. 101 

GUINET, P. 102 

GYANCHAND 142 

HALL, P.E. 103 

HARBARD, J. 187 

HARDING, S. 252 

HARDY, M.B. 104 

HARRIS, S.A. 3Th 

HAYWARD, F.C. 195 

Author index 75 


SWARTZ, P.P. 169, 208 

TAINTON, N.M. 34,202,203,204,205,236 

TALBOT, P.H.B. 209 

TARLTON, J.E. 31 

TAYLOR, J.D. 210, 211, 212,213 

TEAGUE, R.C. 229 

TEAGUE, W.R. 20,214,215,216,217,218,219,220, 

221,222,223,224,225,226,227,228,229 

THERON, G.K. 119,120 

llIODAY, D. 230 

TIDMARSH, C.E. 159 

TIETEMA, T. 231,232 

TIMBERLAKE, J. 233,234 

TOLSMA, D.1. 79,235 

TROLLOPE, W.S.W. 236 

VAN DER MEULEN, F. 59 

VANDER WALT,P.T. 237 

VAN RENSBURG, H.1. 170 

VASSAL, J. 102,238 

VENTER G. 170 

VENTER, H.1.T. 69, 239 

VENTER, J.1. 20, 21 

VERDOORN,I.C. 240 

VERMEULEN, J.B. 241 

VERWEU, R.A. 235 

VISSER, 1. 242 

VOGT, D.C. 196 

VON BREITENBACH, F. 243 

VOOUS, R.TJ. 235 

WAJLKER,B.H. 189,226,227,228,229 

WARD, C.1. 93,94 

WATT, J.M. 244 

WEBB, J.W. 110,245,246,247,248 

WEHMER, C. 249 

WEISSER, P.1.E 59,250,251 

WELLS, MJ. 252 

WEST, O. 253, 254 

WESTFALL, R.H. 180 

WHEELER, J.R. 126 

WHITE, F. 255, 256 

WILD, H. 257,258 

WOOLARD, G.R. 83 

YEATON, RJ. 28 

ZACHARIAS, P.1.K. 121 

ZWANZIGER, S. 59 

Author index 77

documented - University of Oxford

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