No abstract available. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1983.

Patch grazing may be an important factor providing the focus from which wide-scale veld degradation has occurred in the humid grasslands of KwaZulu-Natal. A number of discrete studies were therefore initiated to examine the patch grazing patterns and selected factors which may influence patch grazing at two sites in the humid grasslands of KwaZulu-Natal. The sites were located at Ukulinga Research Farm, situated in the Southern Tall Grassveld, and Kokstad Research Station in the Highland Sourveld. An investigation into the frequency and intensity of gazing patches and non-patches at Ukulinga Research Farm indicated that patch grazing was most evident and most extensive during summer and autumn. As forage in the patches became limiting during winter animals were forced to forage in areas not frequently grazed during the season. The patch grazing pattern was further modified by the time of grazing commencement after a burn in early spring. Early grazing significantly reduced the extent of patch grazing. With early stocking animals were forced to graze less selectively while with increased delay in the commencement of grazing, animals became increasingly patch-selective. Early grazing in conjunction with an autumn rest and heavy grazing during winter could significantly reduce patch grazing. Urine and dung significantly influenced the patch grazing pattern. The sward surrounding a urine deposit was preferentially grazed by both cattle and sheep for a period of at least six months after deposition. Cattle rejected the sward surrounding cattle and sheep dung immediately after deposition and for a period of up to six months. Sheep also rejected cattle and sheep dung patches immediately after deposition. As dung deposits aged, sheep tended to increase their grazing around both cattle and sheep dung pats, and after six months dung did not seem to influence sheep grazing. Urine may be an important factor influencing patch initiation and consequent patch development. A study to examine the characteristics of patches and non-patches in the Highland Sourveld revealed that patches were characterised by lower soil moisture, soil depth and hydraulic conductivity, but by a higher soil nutrient status. Patches and non-patches could also be distinguished in terms of species composition and basal cover. Patches were characterised by Increaser II species, especially Microchloa caffra and, non-patches by Increaser I species such as Trachypogon spicatus, Alioteropsis semialata and Eulalia villosa. Three seasons of patch grazing at Kokstad Research Station negatively influenced the vigour of Themeda triandra in patches relative to the non-patches. The vigour of T. triandra in patches was consistently low throughout a full season's rest. The vigour of T. triandra in non-patches was initially significantly higher than the vigour in the patches and remained so for c. 24 weeks. Vigour measurements at the start of the following season showed that photosynthate accumulation had taken place and a full seasons rest proved to be sufficient in restoring the vigour of T. triandra in patches to the same level as that in non-patches. A full seasons rest did, however, not prevent animals from regrazing the same previously grazed patches the following season. Growth in patches also started c. six weeks later than in nonpatches and above-ground herbage production in patches was significantly lower than nonpatches for at least 20 weeks after a bum. At the end of a full season's rest above-ground herbage production in patches was still slightly lower than that in non-patches possibly due to a difference in species composition between patches and non-patches. Some implications of patch grazing are discussed together with an evaluation of some management recommendations for the humid grasslands with the aim of reducing the potential for patch degradation. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1995.

The overall objective was to develop stocking rate models for three veld types. namely the Lowveld. the Southern Tall Grassveld and the Natal Sour Sandveld. in Natal. Sub-objectives were to determine the 1) residual herbage mass at the end of the summer, 2) residual herbage mass at the end of winter and 3) individual animal performance under grazing conditions, and the effect of stocking rate on these three variables. Multiple linear regression component models were successfully developed to meet all three of the sub-objectives for each of the three veld types. Results show that veld condition is an extremely important factor determining animal production from veld, and that stocking rate on veld in good condition could possibly be double that on veld in poor condition. Stocking rate did not have the expected impact on individual animal performance in the summer. although it did have an important moderating influence under any particular set of environmental conditions. Stocking rate did. however. have a marked effect on herbage production and therefore on herbage availability in winter and so also on the ability to overwinter cattle without having to supply additional supplementary feed. Stocking rate in summer therefore had a major indirect effect on animal production in the winter. Carryover of residual herbage from one year to the next is probably not as important in these veld types as in some other parts of the country. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1990.

Promotion of a predictive understanding of plant community response to various forms, frequencies and seasons of disturbance, either through the direct physical effect on biota and or indirect effect on plants, through modification of microclimate and soil attributes is currently a major goal in plant ecology. In particular, the effect of disturbance on altering the ratio between available light and nutrients and their resultant effect on growth, shoot/root allocation, and thus community composition has gained considerable recognition in connection with the mechanisms of plant succession under a popular heading "the resource ratio hypothesis of plant succession". Contemporary and long-term (>50 years) burning and mowing experiments in KwaZulu-Natal (KZN) provide important sites for investigation that in the mesic grasslands of KZN, community composition changes in response to the frequency, time and type of disturbances such as burning, mowing and veld fertilization. However, the relationship between disturbance-resource-plant traits and their interactive role in species change is virtually unknown. This study sought to improve understanding of mesic grassland dynamics in. KZN, using short-term pot and plot experiments. The principal objectives were: 1) by subjecting plants to different levels of resources viz. light, nutrients, water and cutting to determine the relative above and below-ground growth performances (biomass allocation) of species from contrasting habitat preference in KZN, which implies their relative competitive ability for limiting resources and tolerance to cutting, 2) by using a short-term (one-season period) burning and mowing experiment to determine the effect of different veld management practices on microclimate and availability of soil resources and their subsequent effect on plant growth performances, 3) testing the relative shade tolerance of representative species from contrasting habitat preferences, 4) by combining the outcomes from these experiments, to provide a general synthesis concerning species' response to disturbance/resource which further signifies species change. The hypothesis that competitive ability as a function of biomass allocation is fertility dependent was supported by a pot experiment. In low nutrient treatments short grass species that predominate infertile soils in KZN viz. Aristida funcifarmis and Themeda triandra attained double the shoot biomass, more than double root biomass, initiated more tillers and re-grew better (after cutting) than those inherently tall species that predominate fertile sites viz. Eragrostis curvula and Hyparrhenia hirta. In contrast, in high nutrient treatments, tall species attained far higher shoot biomass and grew taller in height. Interestingly, short species had a smaller shoot: root ratio than tall species, consistent with the prediction of the resource ratio hypothesis. However, no evidence was obtained suggesting that tall species were more shade tolerant than short species. A field-based shade experiment rather showed that, those species that initiate tillers below-ground viz. Aristida junciformis, Eragrostis curvula and Tristachya leucothrix were more shade tolerant than those species that initiate tillers above-ground viz. Hyparrhenia hirta and Themeda triandra. On the other hand, the effect of disturbance/resource relationship in influencing the growth (biomass production, growth rate, and basal circumference) of contrasting species was examined by conducting a short-term (one season) burning and mowing experiment. The effect of disturbance, its form and frequency through its effect on light and soil moisture was able to account for a substantial difference in species vigour, which can potentially impact community composition. Short species (Themeda triandra and Tristachya leucothrix) showed their highest biomass production and higher basal circumference enlargement in burnt summer mown sites, whereas medium to tall species (Aristida junciformis, Eragrostis curvula and Hyparrhenia hirta) were less tolerant to summer mowing. Aristidajunciformis and Eragrostis curvula appeared to be more vigorous (both in terms of above-ground biomass production and growth rate) in burnt but not mown and control treatment respectively. High biomass and litter accumulation on sites protected from disturbance appeared to have a large influence on species vigour. Species such as Aristida junciformis, Eragrostis curvula and Tristachya leucothrix had high tolerance to litter accumulation while in contrast Hyparrhenia hirta and Themeda triandra were more vulnerable. In total this study has revealed that the association of some short species e.g. Themeda triandra with the reccurrence of disturbance is mainly due to increases in light availability and lowered dominance from tall species in frequently disturbed sites rather than nutrient related. However, this study has revealed that there are some indications whereby the notion that the inverse relationship between available light and nitrogen are important driving variables in species change is an important working theory in the mesic grassveld of KZN. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2004.

Climatic and market uncertainty present major challenges to livestock producers in arid and semi-arid environments. Range managers require detailed information on biological and economic components of the system in order to formulate stocking strategies which maximise short-term financial risk and minimise long-term ecological risk. Computer-based simulation models may provide useful tools to assist in this decision process. This thesis outlines the development of a bioeconomic stocking model for the semi-arid savanna of Natal. Grazing trials were established at two sites (Llanwarne and Dordrecht) on Llanwarne Estates in the Magudu area of the semi-arid savanna or Lowveld of Natal. The Lowveld comprises a herbaceous layer dominated by Themeda triandra, Panicum maximum and P. coloratum and a woody layer characterised by Acacia species. The sites differed initially in range composition. Llanwarne was dominated by Themeda triandra, Panicum maximum and P. coloratum, while Dordrecht with a history of heavy stocking was dominated by Urochloa mosambicensis, Sporobolus nitens and S. iocladus. Three treatments were stocked with Brahman-cross cattle at each site to initially represent 'light'(0.17 LSU ha-'), 'intermediate' (0.23 LSU ha-') and 'heavy' (0.30 LSU ha-') stocking. Data collected at three-week intervals over seven seasons (November 1986 to June 1993 or 120 measuring periods) provided the basis for the development of a bioeconomic stocking model (LOWBEEF - LOWveid BioEconomic Efficiency Forecasting) which comprised two biological sub-models (GRASS and BEEF), based on step-wise multiple linear regression models, and an integrated economic component (ECON) . The GRASS model predicted the amount of residual herbage at the end of summer (kg ha-') and the forage deficit period (days) over which forage supplementation would be required to maintain animal mass. Residual herbage mass at the end of summer (kg ha-') was significantly related (P < 0.01) to cumulative summer grazing days (LSU gd ha-'), rainfall (mm) (measured 1 July to 30 June) and range condition (indexed as the sum of the proportions of T. triandra, P. maximum and P. coloratum). The forage deficit period (days) over which herbage mass declined below a grazing cut-off of 1695 kg ha-' was significantly related (P < 0.01) to residual herbage mass at the end of summer. The BEEF model predicted the livemass gain over summer (kg ha¯¹) which was significantly related (P< 0.01) to rainfall (mm) stocking rate (LSU ha¯¹) but interestingly not to condition. The economic component (ECON) reflected the difference between gross income (R ha¯¹) and total costs, which were based on fixed and variable cost structures (using 1993 Rands), including demand-related winter costs, to reflect net returns to land management (R ha¯¹). A conceptual model of range dynamics based on three discrete states, was to developed to summarise the effects of rainfall and stocking rate in semi-arid savanna. State 1, characterised by iocladus and S. nitens, was associated with heavy stocking. Movement towards State 2, characterised by T. triandra and P. maximum, was associated with periods of above-average rainfall. Drought conditions, which comprised a major system disturbance led to stability at State 3, dominated by U. mosambicensis. Post-drought recovery was influenced by predrought composition and stocking levels where tuft numbers, basal cover and seedbank were significantly reduced by increased stocking within a sward dominated by species of low stature such as Aristida congesta subsp 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 species such as Tragus racemosa Aristida congesta subsp. congesta. Sensitivity of optimum economic stocking rate 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 rainfall and range condition increased through the effect of increased residual herbage mass at the end summer, decreased forage deficit periods and reduced supplementary feed costs. Net return was highly responsive to changes 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 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 a 60 year rainfall sequence (1931- 1991). While a range score of 10 would see residual herbage mass decline to below a 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 investigated, herbage would not become limiting. This suggested that irrespective of stocking strategy a range score of 10, established 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 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, combine financial benefits of each approach and reduce financial risk. Although errors may carry hig h ecological costs where, for example, the effect of an above-average rainfall season 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 intake (during dry seasons) than would breeding stock, additional growing may be rapidly sold in response to declining rainfall with no influence on the breeding system. Integration of wildlife 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. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1994.

The South African grassland biome is disappearing rapidly through advancing development and change in agricultural land use. One of the most threatened grassland types, Midlands Mistbelt, in the KwaZulu-Natal Midlands is an extremely diverse and home to many endemic species across an array of taxa. Three taxa, namely, grasses, grasshoppers and butterflies represent various trophic levels, which are important to the functioning of the grasslands. Ten grasslands were sampled by walking ten fifty metre transects for a twelve-month period. The grasslands were selected as they represented a range of management practices and varying environmental conditions. Using Indicator Species Analysis (ISA) twenty-two species of grasshopper were identified as indicators of environmental variables and management practices. The abundances of the various species indicated the intensity of the management regimes or disturbances. Using the twenty-two grasshopper species abundances and a three hundred point sampling assessment of the grasses creates an assessment tool that can rapidly appraise the management of the grassland, but due to lack of data for other taxa, cannot assess whether management practices for the focal taxa create congruent results for non-focal taxa. Two of the three taxa proved to be good indicators of grassland health, whilst the third, butterflies were ineffectual, due to low abundance and richness. From the results it was concluded that burning was taking place to frequently, and required a reduction to every four years, as this would improve butterfly richness and abundance, and increase abundance of endemic and flightless grasshopper speCies. A rotational grazing system needs to be implemented at sites where continual grazing takes place, wildlife or livestock, impacts on the grassland condition and species diversity. Increasing habitat heterogeneity increases species diversity, and allows later successional species to be included in the grasshopper assemblage. Management of the grasslands in the KwaZulu-Natal Midlands needs to be more responsive and adaptive. In addition, small fragment management needs to be intensified to provide a range of habitats and refugia that will suit all species. This study advocates the use of grasshoppers and grasses as suitable biotic indicators of grasslands in the KwaZuluNatal Midlands. / Thesis (Ph.D.) - University of KwaZulu-Natal, Pietermaritzburg, 2005

Aristida junciformis subsp. junciformis Trin. et Rupr. is an indigenous, densely tufted, evergreen perennial grass associated with the degeneration of grasslands over large areas of South Africa. More than two hundred thousand square kilometres of veld, c. 17% of the total land area of South Africa, contains A. junciformis. The aim of this study was to improve our understanding of the mechanisms by which this species invades and dominates grassland, specifically in this study, Southern Tall Grassveld. Aristida junciformis also has a low nutritional value resulting in a very low grazing value. The unpalatability of the plant is due to the high tensile strength of the leaves, whose hard, fibrous laminas are very difficult for a grazing animal to crop once their length attains 30 cm or more. This species lack of response to conventional grazing practices has often resulted in a grassland in which the carrying capacity has diminished to such an extent as to be virtually useless for grazing in a relatively short time. The extent of encroachment of veld by A. junciformis appears dependant on the frequency of disturbance and rest afforded to the veld. Annual burning and mowing maintained the species composition of A. junciformis at levels <10% whilst protection from fire, burning or grazing allows this species to dominate the herbaceous layer at levels approaching 90%. Aristida junciformis does not become moribund and is unlikely to die if left undefoliated. As the abundance of A. junciformis increases, veld deterioration gradually accelerates through increased selective grazing on remaining palatable species. Competition from adult A. junciformis plants increases the mortality of seedlings and constrains growth of surviving seedlings. Tiller production of Aristida junciformis seedlings declined from an average of 5.2 tillers per seedling in a no competition situation to 2.2 tillers per seedling when subjected to full competition. Tiller production of T. triandra seedlings decreased from 9.6 tillers per seedling free from competition to 3.3 tillers per seedling subject to full competition for resources. Once these seedlings have become adult plants they are avoided by grazing animals and grazing pressure on the remaining palatable species consequently increases. This allows the A. junciformis plants to increase their size and density in the sward. Once this density is sufficiently high, grass seedlings of either A. junciformis or more desirable grass species such as T. triandra are unable to establish, eventually resulting in a monospecific stand of A. junciformis if left undisturbed. Large amounts of caryopses are produced by A. junciformis - up to a 19 000 caryopses from a large mature plant (c. 38 000 caryopses/m²). Of these c. 40% is likely to be infertile but the remaining c. 60% viable caryopses are dispersed in a typically leptokurtic distribution, the number of caryopses dispersed rapidly declining within a 10 metre radius. A large proportion of the caryopses was trapped in surrounding foliage but in open swards caryopses had greater opportunity to be blown further distances than in a closed sward. The density of A. junciformis caryopses on the soil surface was positively correlated with the density of flowering adult plants in the area and varied from 400 caryopses/m² (density of parent plants c. 0.6 plants/m²) in less effected areas to 11000 caryopses/m² (density of adult plants c. 6 plants/m²) in severely encroached areas. The primary function of the three awns appears to be orientating the caryopsis correctly for in its descent from the parent plant to expedite germination. Caryopses orientated vertically with the awns uppermost exhibited the highest and most rapid germination (67%) compared to caryopses lying horizontally (35%) whilst only 1% of inverted caryopses germinated. Caryopses trapped in litter and effectively held off the soil surface failed to germinate. Removal of the glumes from A junciformis seed greatly enhanced the rate and overall germination of the seed except for inverted seed of which <1% germinated. The highest numbers of A. junciformis seedlings (32 seedlings/m²) were found in those areas with the highest density of caryopses on the soil surface. Despite the large amounts of caryopses produced, dispersed and landing in apparently suitable micro-sites for germination, comparatively few A. junciformis seedlings (n=992) were found and overall germination ranged between 1 % and 4% of the initial caryopses density on the soil surface. Seedling survival through winter was low with only 13% surviving to the following spring. The basal areas of A. junciformis increased overall by 66% whilst that of other grass species increased overall by only 3% in the time monitored. These results suggest that the primary method of encroachment of A. junciformis in the grass sward appears to be through vegetative expansion and not seedling recruitment. Frequent defoliation of the sward and avoidance of overgrazing to enhance the competitive abilities of palatable species and provide as high a fuel load as possible appear to be the most economically and logistically feasible ways to remove or at least inhibit A. junciformis veld encroachment at present. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1998.

The overall aim of the study was to investigate re-vegetation of disturbed sites, using nursery grown plugs (from seedling trays) of Themeda triandra, Heteropogon contortus and Hyparrhenia dregeana in order to reach practical management guidelines for re-vegetation using indigenous grass plugs. A number of field trials were set up at Kamberg Nature Reserve (29°24'S, 29°40'E) on a site that was clear felled of A. mearnsii in October 1997. The trials were established in January 1998 and January 1999. A total of approximately 52 ,000 nursery raised plugs of T. triandra, H. contortus and H. dregeana were planted into an area of approximately 7,000 m2 . In the planting density trial , plugs of H. dregeana only and a combination of T. triandra/H. contortus were planted at 15 cm and 30 cm spacings. The T. triandra/H. contortus combination at 30 spacing showed the greatest survival and lateral plant growth (tiller number and basal area) and this combination is thus recommended. In the over-sowing trials, the H. dregeana and T. triandra/H. contortus combination at both 15 cm and 30 cm spacing were over-sown with E. curvula. The survival and lateral growth of the T. triandra/ H. contortus combination at 30 cm was again greater than the other treatments. Over-sowing with E. curvula suppressed the survival and lateral growth of the planted plugs across all treatments compared to not over-sowing. The over-sown conditions showed a significant decrease in the diversity of the plots, both in the number of species present and the Shannon diversity index. An area that had been cleared of A. mearnsii and sown to E. curvula 25 years previously was shown to have a lower number of species than the neighbouring veld. Nursery raised plugs of T. triandra were planted into the mature E. curvula in an attempt to improve the biodiversity of these areas. To re-introduce T. triandra into these E. curvula swards the plugs must be planted into the centre of a gap rather than around the base of an E. curvula plant. For improved survival of the plugs the E. curvula tufts must be clipped, while for best lateral growth the E. curvula tufts must be sprayed with a glyphosate herbicide three months prior to planting and clipping. However, the added expense of spraying and clipping is not warranted as the clipped treatments also showed good growth. Transplant shock is common when planting nursery raised plugs out into the field, as there is a relatively small root volume in the plug compared to the above ground leaf biomass. Alleviation of moisture stress at planting using a starch based polymer with high water holding capacity (Terrasorb®) and a white, needle punched geo-fabric (Agrilen®) to provide a seven day period of artificial shade after planting did not show significant improvements over the control with regards to survival or plant growth. Thus these methods of moisture amelioration are not recommended in revegetation through planting of plugs at this study site. A trial was established to investigate the biomass production of six different treatments to determine their potential to support a fire. The total biomass for the plots which were over-sown by E. tef and planted to only H. dregeana were on average sufficient for a fire, but there was a discontinuous fuel load across these plots, especially in the replications that had very low survival rates and thus these plots could not be burnt. The control and herbicide sprayed plots also showed sufficient fuel load for a fire, but this fuel load was made up of A. mearnsii saplings and bramble with very little grass cover and thus a fire would not have burnt through these plots either. The T. triandra/H. contortus combination did not produce sufficient fuel load, due to poor survival. Thus only the plots over-sown with E. curvula were able to burn in this trial and as a burning trial per se the trial was abandoned. Seed bearing hay (thatch) was collected in early summer (December 1997) and late summer (April 1998). Both times of year of harvesting proved to be successful in terms of grass cover, although the early harvested thatch had a greater number of species per plot. The Shannon diversity indexes of the two treatments were not significantly different. The multi-response permutation procedure technique confirmed that there was a compositional difference between the treatments. By the end of the trial Harpochloa falx and T. triandra and H. dregeana were indicators for the early and the late harvested thatch respectively. Comparing the thatching trial and the planting density trial indicated that the T. triandra/H. contortus combination at 30 cm spacing would be recommended to maximize biodiversity. The summer months have been shown to be the best time to plant the plugs, although the actual success will be dependant on the conditions within a particular year. The plugs should not be kept in the nursery for longer than three months and larger plugs (96 seedlings per tray) should be used. Nursery raised plugs of T. triandra and H. contortus were planted in an equal mix in an area that was cleared of A. mearnsii in 1996. By June 1998 661 H. contortus seedlings and 14 T. triandra seedlings had germinated naturally. The November 1998 population consisted of 418 H. contortus seedlings and 18 T. triandra seedlings. By May 2000 the June 1998 population showed a survival of 78.4% and the November 1998 population showed a survival of 91 .1 %. In the various trials, the ability of the nursery raised plugs used for re-vegetation to suppress the regrowth of A. mearnsii was investigated by determining the number of A. mearnsii seedlings per metre squared. The plant spacing and species of plugs used did not have a significant effect on the number of A. mearnsii seedlings per metre squared. Over-sowing with E. curvula did, however, significantly suppress the wattle re-growth. In the thatching trial the early harvested plots showed lower numbers of A. mearnsii per metre squared than the late harvest plots, as they were covered with a thick layer of thatch soon after the A. mearnsii was cleared which suppressed the A. mearnsii re-growth. Although E. curvula is able to produce a high biomass and suppress the A. meansii seedlings, it has a detrimental effect on the biodiversity of the area. Therefore, in conservation areas, where biodiversity is of great importance the planted plugs (at 30 cm spacing) or seed bearing hay must be used in preference to sowing E. curvula , although it must be remembered that greater follow up control is likely to be needed with planted plugs or seed bearing hay. The area must be planted or thatched as soon as possible after clear felling to provide competition for the A. mearnsii seedlings. / Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.

The structure and composition of savanna vegetation is influenced by resource availability and disturbance. Grasses, a major component of savannas, influence this resource availability by competing directly with trees for light, water and soil nutrient resources. The direct causes of bush encroachment are not always apparent, but are commonly ascribed to overgrazing and consequent decreased grass competition. The interaction, both above and belowground, between tree and grass seedlings and the surrounding grass sward is dependant on many factors, such as soil depth, seedling species and sward composition. These factors, as well as the presence or absence of defoliation, in the form of grazing or fire dictate whether the system will remain in a transition state as savanna or move towards a stable woodland state. The major competitive effects experienced by the tree seedlings were dependant on grass species and nutrient level. A. nilotica was affected by aboveground competition while A. karroo was affected by belowground competition. E. capensis caused the greatest decrease in A. karroo plant biomass. Both E. capensis and H. hirta had large competitive effects on the aboveground biomass of A. nilotica, while S. africanus had the greatest effect on belowground biomass. Increasing nutrient availability resulted in an increase in the competitive effect exerted on A. karroo, while little to no change was seen in the competitive effect exerted on A. nilotica. Soil depth constrained plant size in both tree species. The intensity of belowground interactions on tree biomass was unaffected by soil depth, while aboveground competition had a significant effect on shallow soils. Belowground competition was also of greater importance than aboveground competition in dictating tree seedling height. Grass seedlings growing on all three soil depths differed in mean mass, with E. racemosa having the least mass and T. triandra having the greatest. Simulated grazing by cutting the surrounding sward resulted in biomass increases in all three grass species. Changes in savanna composition and structure are thus likely to be influenced by initial species composition and soil depth and soil nutrient composition. While grazing creates niches for grass seedling establishment, heavy grazing has been observed to increase grass seedling mortality. Encroachment is thus more likely to occur on intensively grazed shallow and deep soils than on medium depth soils. This highlights the importance of ensuring the grass sward remains vigorous by resting and monitoring stocking rates to ensure veld is not over-utilized. It is then possible to maintain some form of tree-grass coexistence at a level where available grazing is not compromised. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.

A research journey involving people, cattle, and the landscape in rural Okhombe in the western part of the province of KwaZulu-Natal and lying at the foot of the uKhahlamba Drakensberg Mountain Range, South Africa, is the focus of this work. Using action research involving community members as co-researchers, it investigates why a rotational resting system for communal cattle grazing collapsed within six months of its launch. Despite having been designed in a participatory manner, the rotational resting system was not applied by cattle keepers. As a backdrop to the concern around the rotational resting system, it is necessary to understand how the current landscape of Okhombe was shaped. The history of the uKhahlamba Drakensberg Region over the past two hundred years was, therefore, explored. Four historical episodes were distinguished: economic expansion, nature conservation efforts, colonial and apartheid legislation, and encounters between people all left their imprint on the landscape. Digitized maps of aerial photographs of Okhombe, taken between 1945 and 2004, showed how Government intervention changed people’s multifunctional use of the landscape to concentrated settlements and cropping fields in the valley and cattle grazing on the mountain slopes. A survey in Enhlanokhombe, one of the sub-wards of Okhombe, further investigates how cattle keepers use the rangeland commons, and what determines these practices. People are keeping fewer cattle than in the past. A 24% decrease in cattle numbers was recorded between 2001 and 2008. Cattle keepers perceive stock theft as the most important threat. Yet, figures of stock losses showed that cattle disease resulting in death is an equally pressing problem. The decline in authority of traditional leaders and the view that herding is a family task have compounded the dominant management practice of continuous grazing by cattle. Rotational resting was found to be unsuited to the majority of cattle keepers who want to keep a close watch on their herds as they graze on the lower hill slopes. People in Okhombe disagreed about the condition of the range and what comprised appropriate grazing management. A community initiative has emerged to form cattle patrols to address stock theft. If successful, it may further enhance collective action. The concern with communal grazing management investigated in this research and in the Okhombe Landcare project, of which it was part, aimed to reverse land degradation and overgrazing. An analysis of digitized maps of Okhombe taken in the period between 1945 and 2004, however, showed that soil erosion did not increase rapidly as is commonly assumed by conventional rangeland scientists and extension staff. Rather, an increase in bare soil coincided with a period of drought. The focus of the Okhombe Landcare project on combatting soil erosion and rehabilitate degraded lands was underpinned by a particular interest in and need to conserve the uKhahlamba Drakensberg as a near-pristine wilderness landscape which provides marketable ecosystem goods and services. As such, cattle keeping in Okhombe can be described as being embedded in a social-ecological system comprising a series of nested, self-organizing subsystems which are interconnected. Sub-systems include the cattle production system, cattle grazing management practices, the wider ecosystem, and government policies and regulations. A spatial-temporal and systemic approach is proposed to make meaningful, policy-related decisions regarding communal rangeland management in the future. Such an approach would enable cattle keepers, other rangeland users, and outside stakeholders, such as extension workers and policy makers, to respond effectively to changes in the landscape by taking into consideration and balancing a complex set of biophysical, socio-political, and economic variables. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.