Bibliography: Land Degradation in South Africa project

Drought conditions, which comprised a major system disturbance, led to stability

at State 3, dominated by U mosambicensis. Post-drought recovery was influenced

by pre-drought composition and stocking levels where tuft numbers, basal cover

and seedbank size were significantly reduced by increases stocking within a

sward dominated by species of low stature such as Aristida congesta subsp.

congesta, Urochloa mosambicensis, Sporobolus nitens, Sporobolus iocladus and

Tragus racemosa. It was suggested that extensive soil loss may lead to

stabilisation across an irreversible threshold at a forth state characterised by

shallow rooted species such as Tragus racemosa and Aristida congesta subsp.

congesta. Sensitivity of optimum economic stocking rate and net return to price

and interest rate fluctuations, and wage and feed cost increases were examined

for various rainfall and range condition scenarios. Net return and optimum

economic stocking rate increased as fainfall and range condition increased

through the effect of increased residual herbage mass at the end of summer,

decreased forage deficit periods and reduced supplementary feed costs. Net

return was highly responsive to changes in beef price where an increase in beef

price led to an increase in optimum economic stocking rate and net return. The

effect of reduced prices may be compounded by dry seasons, where supply-driven

decreases in price may occur. This suggested that for dry seasons the optimum

stocking rate was the lightest within the range of economic stocking rates.

Although an increase in interest rates would increase variable costs and lead to

reduced returns, the influence of interest rates on enterprises will vary in

relation to farm debt loads. Increased labour costs would result in a

corresponding decline in net return although optimum economic stocking rate

would remain unaffected. Increased supplementary feed cost had little influence

on net return relative to the effect of demand-driven increases in feed costs as

rainfall decreased. The distribution of net returns for stocking strategies of

0.20, 0.30 and 0.40 LSU ha-1 and climate-dependent stocking (where stocking

levels were varied in relation to rainfall and hence forage availability) and

range condition scores of 10, 50, 80 and a dynamic range model were examined for

60 year rainfall sequence (1931 - 1991). While a range score of 10 would see

residual herbage mass decline to below grazing cut-off of 1695 kg ha-1 before

the end of summer, a range score of 80 suggested that, irrespective of stocking

strategy within the range invstigated, herbage would not become limiting. This

suggested that irrespective of stocking strategy a range score of 10, estabished

across an irreversible soil loss threshold, would reflect accumulated losses

over the 60 year period. In contrast, a range score of 80 would lead to

positive accumulated returns. A dynamic range model (where range composition

was related to previous seasons rainfall) and a climate-dependent stocking

strategy, suggested that herbage would not become limiting by the end of summer

and forage deficit periods would be restricted to an average of 88 days per

year. Such an approach would yield a higher accumulated cash surplus than fixed

stocking strategies. Incorporation of stochastic rainfall effects allowed the

development of cumulative probability distributions based on 800-year

simulations to evaluate the risk associated with various stocking strategies.

Range condition played a major role in determining the risk of financial loss

where decreased range condition was associated with enhanced risk. An increase

in stocking rate resulted in increased variability in returns. Although the

risk of forage deficits and financial losses may be reduced with lighter

stocking, this may be at the cost of reduced returns during wetter seasons.

Increased stocking may increase the probability of higher returns during wetter

seasons although this may be at the cost of increased risk of forage deficits

and highly negative returns during dry seasons. Importantly, ecological risk

may increase as stocking is increased. A flexible or climate-dependent

strategy, where stock numbers are adjusted according to previous seasons

rainfall, may combine the financial benefits of each approach and reduce

financial risk. Although errors may carry high ecological costs where, for

example, the effect of an above-average rainfall seasons would be to increase

stock numbers into a subsequent dry season, the probability of incurring such

error was low. Current livestock production systems in the semi-arid savanna of

Natal based on breeding stock may not be appropriate in a highly variable

environment where low rainfall may require extended periods of supplementary

feeding or force the sale of breeding stock. A change in emphasis from current

systems to a mixed breeding system, where the level of breeding stock would be

set at the optimum economic stocking rate for drier seasons, may decrease both

financial and ecological risk. Growing stock may either be retained or

purchased during wetter seasons to reach the optimum economic stocking rate for

such seasons. Although growing stock may display a greater tolerance to

restricted forage intake (during drier seasons) than would breeding stock,

additional growing stock may be rapidly sold in response to declining rainfall

with no influence on the breeding system. Integration of woldlife into current

cattle systems may be an important means of reducing financial risk associated

with variable rainfall and profitability and ecological risk associated with

woody plant encroachment.Doctor of Philosophy.

Reprint : In File,

Keywords : ECONOMIC ASPECTS; STOCKING RATE; SAVANNA; KWAZULU NATAL; MODELS;

FORECASTING; RAINFALL; DROUGHT; LABOUR; LIVESTOCK PRODUCTION

Notes : Abstract in file.

Ref ID : 1870

1056. Hatch, G.P. and Stafford Smith, D.M. The bioeconomic implications of

various drought management strategies for a communal cattle heard in the semi-

arid savanna of KwaZulu-Natal. African Journal of Range and Forage Science

14(1):17-25, 1997.

Reprint : In File,

Keywords : DROUGHT; SAVANNA; KWAZULU NATAL

Abstract : The widespread drought of the early 1990s resulted in considerable

stock losses in the semi-arid savanna of KwaZulu-Natal. We compared the

influence of four drought response strategies on herd number, milk yield, cost

and net present value for a communal cattle heard over the period 1983 to 2001

using a simulation modelling approach. The strategies were (1) no reaction to

drought; (2) moving stock to areas not affected by drought; (3) purchasing

replacement stock after the drought; and (4) supplementing stock during the

drought with sugar-cane residues. Moving, buying or feeding stock generated

greater milk yields and net benefits relative to no drought response, but at

considerably greater cost. Cost:benefit was greatest where a small proprotion

of female stock (10 percent) were moved. By doing nothing in the face of

regional drought, communal graziers may be acting rationally, given the

constraints under which they operate. The study reveals that simulation

modelling may provide a useful basis from which to assess the outcome of various

management strategies for communal graziers, and for integrating the disparate

suite of influences which drive decision-making on communal lands.

Ref ID : 1840

1057. Hatch, G.P. and Tainton, N.M. The influence of stocking rate, range

condition and rainfall on residual herbage mass in the semiarid savanna of

KwaZulu/Natal. African Journal of Range and Forage Science 12(2):76-80, 1995.

Reprint : In File,

Keywords : STOCKING RATE; RAINFALL; SAVANNA; KWAZULU NATAL; MODELS

Abstract : Grazing trials at two sites in the semiarid savanna of KwaZulu-Natal

were stocked with cattle at light (0.17 LSU ha-1), intermediate (0.23 LSU ha-1)

and heavy (0.30 LSU ha-1) stocking. Pasture disc meter data collected over 116

three-week periods were used to develop a step-wise multiple linear model to

predict the amount of residual herbage at the end of the summer growing season

and the period (days) over which forage supplementation would be required to

maintain animal mass during the winter dormant season. Residual herbage mass at

the end of summer was significantly related to cumulative summer grazing days,

rainfall and range condition (indexed as the sum of proportions of Themeda

triandra, Panicum maximum and P. coloratum). The period of forage deficit

during which herbage mass declined below a grazing cut-off of 1 695 kg ha-1 was

significantly related to residual herbage mass at the end of summer.

Ref ID : 1852

1058. Hatch, G.P., Tainton, N.M., and Ortman, G.F. Towards the development of a

bioeconomic stocking model for the semi-arid savanna of KwaZulu-Natal. African

Journal of Range and Forage Science 13(2):67-71, 1996.

Reprint : In File,

Keywords : MODELS; SAVANNA; KWAZULU NATAL; RAINFALL

Abstract : Rainfall variability is a major determinant of system dynamics and

profitability of livestock enterprises in arid and semi-arid environments.

Range managers consequently require detailed information on the financial and

ecological implications of various stocking strategies in order to formulate

viable management systems. Data collected over seven seasons (1986 - 1993),

from a series of extensive grazing trials in the semi-arid savanna of KwaZulu-

Natal with cattle stocked at three rates (0.17, 0.23 and 0.30 LUS ha-1) were

used to develop a bioeconomic stocking model (LOWBEEF). The model comprised two

biological sub-models (BEEF and GRASS), and an integrated economic component.

The BEEF sub-model related to seasonal live mass gain to stocking rate and

rainfall. The GRASS sub-model related residual herbage at the end of summer to

summer stocking intensity, range condition (indexed as the sum of proportions of

three key forage species, Themeda triandra, Pancum maximum and P. coloratum) and

rainfall. The period over which supplementary feeding would be required to

maintain cattle mass was related to residual summer herbage mass. The

biological sub-models were linked to an economic component model (ECON) to

reflect the influence of various environmental and economic parameters on

profitability.

Ref ID : 455

1059. Haylett, D. Runoff and soil erosion studies at Pretoria. South African

Journal of Agricultural Science 3(3):379-394, 1960.

Reprint : Not in File,

Keywords : SOIL EROSION; RUNOFF

Ref ID : 302

1060. Haylett, D.G. Runoff and soil erosion studies at Pretoria. South African

Journal of Agricultural Science 3:379-394, 1960.

Reprint : Not in File,

Keywords : SOIL EROSION

Ref ID : 303

1061. Haylett, D.G. Studies in rainfall and crops at Pretoria. Outlook on

Agriculture 3(5):241-249, 1962.

Reprint : Not in File,

Keywords : CULTIVATION; DROUGHT; PRODUCTION POTENTIAL; HYDROMETEOROLOGY

Ref ID : 569

1062. Hazelton, D.G., Pearson, I., and Kariuki, A.W. Development of drought

response policy options for the cost effective provision of water supply to

rural communities subject to recurring droughts.Anonymous Pretoria:Water

Research Commission. 506/1/94, 1995.

Reprint : Not in File,

Keywords : DROUGHT; POLICY; HYDROLOGY; COMMUNAL AREA; SUBSIDIES

Ref ID : 817

1063. Hazelton, D.G., Pearson, I., and Karuiku, A.W. Development of drought

response policy options for the cost effective provision of water supply to

rural communities subject to recurring droughts.Anonymous Pretoria:Water

Research Commission. 506/1/94, 1994.

Reprint : Not in File,

Keywords : DROUGHT; POLICY; RURAL DEVELOPMENT

Ref ID : 1771

1064. Heard, C.A., Tainton, N.M., and Clayton, J. A comparison of five methods

for assessing veld condition in the Natal Midlands. Journal of the Grasslands

Society of Southern Africa 3(3):70-76, 1986.

Reprint : In File,

Keywords : VELD CONDITION; MONITORING; METHODOLOGIES; NORTHERN PROVINCE; VELD

MANAGEMENT

Abstract : Site rankings obtained from five methods of scoring veld condition in

the highland sourveld in the moist tall grassveld of the Natal Midlands were

correlated with rankings from methods of multivariate analysis. With few

exceptions, all methods gave rankings which were strongly correlated with

rankings from detrended correspondence analysis, thus indicating that they all

provide a practical means of indexing the relative veld condition of sites with

reasonable precision. The weighted quantitative climax and key species methods

were superior to the other three methods in this respect. The key species

method has the advantage of simplicity and speed, and should stimulate farmers

to undertake routine monitoring of their veld in these two regions.

Ref ID : 2148

1065. Heeg, J., Appleton, C.C., Davies, B.R., Joubert, S.C.J., and Walmsley,

R.D. Uses of, and human impact on rivers. The conservation of South African

rivers. O'Keeffe, J.H. Pretoria:Council for Scientific and Industrial Research.

131:24-35, 1986.

Reprint : Not in File,

Keywords : CONSERVATION

Notes : South African National Scientific Programmes Report no. 131.

Ref ID : 1330

1066. Heerden, J.M. and Langenhoven, J.D. Aangeplante graspeulgewasweidings in

die wintereengebied. Weiding: 'n stategie vir die toekoms.Anonymous Anonymous

Pretoria:Departement van Landbou en Watervoorsiening. :1-11, 1989. 0-621-12063-

4.

Reprint : In File,

Keywords : LIVESTOCK PRODUCTION; CLIMATE; GRASSLAND

Notes : See English translation in notes contained in ID no. 1289.

Ref ID : 1289

1067. Heerden, J.M. and Langenhoven, J.D. Cultivated grass/legume pastures in

the winter rainfall area. Grazing management a strategy for the future.Anonymous

Anonymous Pretoria:Department of Agriculture and Water Supply. :1-10, 1989. 0-

621-12062-6.

Reprint : In File,

Keywords : RAINFALL; CLIMATE

Notes : It is important to bear in mind that pasture and animal production

systems are very complex. Factors such as locality, soil, climate and the

management skill of the farmer have a major influence on the ultimate result

achieved. Greater management skill is usually required for the successful

utilisation of grass/legume pasture than for pure grass pastures. As management

ability improves, and especially if certain basic principles are applied,

success will be achieved.

Ref ID : 1106

1068. Heine, K. Climate change over the past 135 000 years in the Namib Desert

(Namibia) derived from proxy data. Proceedings of the Nouakchott Symposium

"Desert Margin Changes of in Africa since 135 000 BP: Implications for Water,

Carbon and Man". Palaeoecology of Africa , 1997.

Reprint : Not in File,

Keywords : CLIMATE CHANGE; NAMIBIA

Ref ID : 2149

1069. Heinecken, T.J.E., Bickerton, I.B., and Morant, P.D. Estuaries of the

Cape. Part II: Synopses of available information on individual

systems.Anonymous Pretoria:CSIR. 411:72, 1982.

Reprint : Not in File,

Notes : Report no. 12: Buffels (Wes) (CSW1), Elsies (CSW2), Sir Lowry's Pass

(CSW8), Steenbras (CSW9), and Buffels (Oos) (CSW11).

Ref ID : 2150

1070. Hellawell, J.M. Biological indicators of freshwater pollution and

environment management, London:Elsevier Applied Science, 1986.

Reprint : Not in File,

Keywords : POLLUTION

Ref ID : 2019

1071. Henderson, L. Alien invasive Salix species in the grassland biome of South

Africa. South African Forestry Journal 157:91-95, 1991.

Reprint : Not in File,

Keywords : GRASSLAND

Ref ID : 1086

1072. Henderson, L. Invasive alien woody plants of the northern Cape. Bothalia

21(2):177-189, 1991.

Reprint : In File,

Keywords : ALIEN PLANTS; NORTHERN CAPE

Abstract : The frequency and abundance of invasive alien woody plants were

recorded along roadsides and at watercourse crossings in 31% (90/286) of the

quarter degree squares in the study area. The survey yielded 23 species of

which the most prominent invaders were Prosopis spp. The most prominent

remaining species were: Opuntia ficus-indica, Nicotiana glauca and Melia

azadarach. The greatest abundance and diversity of alien invader plants were

recorded near human settlements. More than half of the total recorded species

have invaded perennial riverbanks. The episodic Molopo and Kuruman Rivers have

been invaded almost exclusively by Prosopis spp. which in places have formed

extensive stands.

Ref ID : 934

1073. Henderson, L. Invasive alien woody plants of the eastern Cape. Bothalia

22(1):119-143, 1992.

Reprint : In File,

Keywords : ALIEN PLANTS; EASTERN CAPE

Abstract : The frequency and abundance of invasive alien woody plants were

recorded along roadsides and at watercourse crossings in 69.9% (151/216) of the

quarter degree squares in the study area. The survey yielded 101 species of

which the most prominent (in order of prominence) in roadside and veld habitats

were: Opuntia ficus-indica, Acacia mearnsii and A. cyclops. The most promenent

species (in order of prominence) in streambank habitats were: A. mearnsii,

Populus x canescens, Salix babylonica and S. fragilis (fide R.D. Meikle). The

greatest intensity of invasion was recorded in the wetter eastern parts and

particularly in the vicinity of Port Elizabeth, Uitenhage, East London,

Grahamstown, Hogsback and Stutterheim. There was relatively little invasion in

the central and western dry interior except along watercourses.

Ref ID : 2021

1074. Henderson, L. Plant invaders of southern Africa. Pretoria:Agricultural

Research Council. 5, 1995.

Reprint : Not in File,

Keywords : SOUTHERN AFRICA

Notes : Handbook no. 5 of the Plant Protection Research Institute.

Ref ID : 2022

1075. Henderson, L. South African Plant Invaders Atlas. Applied Plant Sciences

12:31-32, 1998.

Reprint : Not in File,

Ref ID : 2023

1076. Henderson, L. and Musil, K.J. Exotic woody plant invaders of the

Transvaal. Bothalia 15:297-313, 1984.

Reprint : Not in File,

Ref ID : 2024

1077. Henderson, L. and Wells, M.J. Alien plant invasions in the grassland and

savanna biome. Africa. In: The ecology and management of biological invasions in

southern Africa, edited by Macdonald, I.A.W., Kruger, F.J., and Ferrar,

A.A.South Africa:Oxford University Press, 1986,p. 109-131.

Reprint : Not in File,

Keywords : ALIEN PLANTS; GRASSLAND; SAVANNA; SOUTHERN AFRICA

Ref ID : 2026

1078. Hengelveld, R. Dynamics of biological invasions, London:Chapman & Hall,

1989.

Reprint : Not in File,

Ref ID : 304

1079. Henkel, J.J., Bayer, A.W., and Coutts, J.R.H. Subsurface erosion on a

Natal Midlands Farm. South African Journal of Science 35:236-243, 1938.

Reprint : In File,

Keywords : SOIL EROSION; KWAZULU NATAL; LAND USE; EROSION

Notes : The soil erosion studies described in this paper were carried out on

Major R. Thomlinshon's farm, near Rosetta RAilway Station, Natal. A new type of

sub-surface erosion due to the corrosive action of underground water is

described and analysed. The erosion is due to the production of an anastomosing

system of vertical cracks in the drying subsoil, thus permitting the formatio

nof underground water channels during heavy rain. The life history of the

underground channels is traced and several remedial measures are suggested.

Ref ID : 43

1080. Henning, J.A.G. and Kellner, K. Degradation of a soil (Aridosol) and

vegetation in the semi-arid grasslands of South Africa. Botanical Bulletin of

Academia Sinica 35:195-199, 1994.

Reprint : In File,

Keywords : DESERTIFICATION ASSESSMENT; SOIL NUTRIENTS; VELD CONDITION;

GRASSLAND; VEGETATION DYNAMICS; SOUTHERN AFRICA

Abstract : Degradation of the semi-arid grasslands of southern Africa involves

changes in the composition of vegetation and in the characteristics of the soil.

We have assigned the state of degradation to three classes, and we correlate

them to changes in the physical and chemical characteristics of the surface and

the subsurface soil. Decreased basal coverage by species of high ecological

status, and changes in the spatial distribution of the species resulted in

higher soil density, water run off loss, changes in the surface roughness, and

degradation of vesicular structures. Chemical changes included a considerable

decrease in the potassium, calcium and organic carbon content of the surface

soil, and an increase in the calcium and magnesium content of the subsurface

soils. We discuss possible explanations of the physical characteristics and

the changes in the nutritional state of the surface and subsurface soils.

Ref ID : 237

1081. Henrici, M. Grass or bush in the karroid area? South African Journal of

Science 28:266, 1931.

Reprint : In File,

Keywords : KAROO DESERTIFICATION; GRASSLAND; NAMA KAROO; PRODUCTION POTENTIAL;

STOCKING RATE; VEGETATION DYNAMICS; RAINFALL; DROUGHT; FREE STATE

Abstract : At the Veld Reserve, Fauresmith, different indigenous bushes and

grasses were tried out as to their suitability for feeding of sheep. Owing to

the low rainfall and the prolonged droughts, the area seems more fit for bushes,

although in summer sheep prefer grass. Analyses were done on grasses and bushes

to reveal their mineral content, the most important factor to characterise a

plant as a good or bad pasture plant. Phosphorus and calcium content are

discussed at full length. It appears that the mineral content of bushes like

Tripteris pachypteris, Phymaspermum parviflorum, Pentzia incana, Salsola aphylla

and glabrescens, Atriplex nummularia and A. halimus is high. But the grasses,

too are much richer in minerals than grasses (same species and others) of the

grassveld of Bechuanaland or Eastern Transvaal. In springtime, or in a bad

season after the first rain, the phosphorus content of grasses at Fauresmith is

as high or even higher than that of good bushes. Values over 1 per cent are not