A thesis submitted to the Faculty of Science, University of the Witwatersrand, in fulfilment of the academic requirements for the degree of Doctor of Philosophy. May 2016 Johannesburg / This thesis reveals previously unknown facts concerning the invasion, ecology and management of the perennial alien forb Campuloclinium macrocephalum (Less.) DC. (Asteraceae, pompom weed) in the grassland biome of South Africa. All these areas of research are of critical importance to identify the causes of invasion and prescribe best management practises aimed at reducing the density and spread of the weed and restoring these ancient grasslands. Grassland biomes throughout the world are receiving international attention because of their vulnerability to transformation, a history of ignorance regarding their evolution and prejudice as evidenced by their exploitation. There are many theories as to why alien plants become invasive outside of their native range but most are controversial, except those that support the absence of natural enemies as the primary reason for invasiveness. Few studies have attempted to empirically measure environmental and ecological factors that facilitate invasion, not to dispute the Absence of Predators Hypothesis (APH); APH regulates invasiveness but the external factors affecting habitat vulnerability to invasion remain unchanged. Based on the assessments of 80 invaded grasslands in Gauteng Province prior to the release of any host-specific biocontrol agents, it was concluded that C. macrocephalum favours disturbed grasslands. Numerous agencies of disturbance were identified; the most important being heavy grazing, abandonment (e.g. old lands) and modification (e.g. draining of wetlands). Herbivory by generalist insects was insignificant. The main drivers of native species composition in the invaded study sites were rainfall, topography and soil texture. The weed was most problematic in grasslands with a basal cover of <19% and in poor condition from a pastoral perspective. Other alien and native invasive species were also found in grasslands with C. macrocephalum. High fire frequency also appeared to exacerbate weed density. The Novel Weapons Hypothesis postulates that some invasive species transform vegetation for establishment, densification and expansion because they are allelopathic. Stems and leaves of C. macrocephalum have both rigid multicellular hairs and glandular trichomes that exude an unidentified substance. It has been speculated that allelopathy may be an important trait aiding its rapid expansion in invaded grasslands. The importance of allelopathy and competition was investigated under controlled conditions using Eragrostis curvula (perennial grass), E. tef, (annual grass) and Lactuca sativa (lettuce) as test species. Petri-dish studies proved that root and shoot extracts of adult C. macrocephalum plants had zero inhibitory effect on the seed germination in all three test species. Stunting of radicles was evident in treatments comprising leaf extracts at 10 and 25% w/v; with E. tef displaying a higher tolerance than E. curvula. Eragrostis curvula, because it was the most sensitive of the test species, was used in a pot study together with C. macrocephalum to evaluate allelopathy and interference. The biomass and growth of E. curvula was not affected by C. macrocephalum at densities of one or five plants per pot. The weed on the other hand incurred density-dependant trade-offs in size, biomass and mortality. In a separate pot study, the incorporation of weed residues into the potting medium had no impact on the growth of E. curvula. The process went one step further by analysing the association between E. curvula and C. macrocephalum from the 80 grassland assessments. Eragrostis curvula had a narrower ecological niche and was only found in disturbed grasslands on well drained soils. Campuloclinium macrocephalum invaded a broad gradient of soil types including poorly drained wetland soils not amenable for E. curvula. Competitive exclusion between the two species was not apparent. Pot studies and field observations support a degree of tolerance between C. macrocephalum and E. curvula that lends support to coexistence at a range of weed densities. The conclusions from this study were (a) C. macrocephalum is not allelopathic and allelo-chemistry cannot be inferred as a causal mechanism for the weed’s invasiveness, and (b) C. macrocephalum and E. curvula have different limiting resource requirements that enables coexistence in areas where the latter can grow. In 2006 C. macrocephalum infestations in Gauteng Province were severely damaged by Puccinia eupatorii Dietel (Pucciniaceae), a biotrophic rust identical to the P. eupatorii strain in quarantine that was imported into South Africa from Argentina as a potential biocontrol agent. An investigation of the rust’s impact on C. macrocephalum was carried out in the 80 rangeland infestations previously assessed and how pathogen pressure affected the weed’s realised niche. The rust caused premature senescence of the stems in late summer with compensatory regrowth in autumn. In contrast disease-free plants senesced in late autumn; the rootstocks remained dormant throughout winter and did not produce compensatory regrowth. No significant changes in weed density were detected and C. macrocephalum retained its realised niche. The weed remains adapted to the rust despite a 40-year separation from the pathogen. Registered herbicides should provide 80% control of the targeted plants, providing label directions concerning concentration, mixing, application and environmental considerations are adhered to. Herbicide trials were conducted at two contrasting sites in Gauteng, a wetland and a rocky grassland, to test the efficacy of picloram and metsulfuron-methyl on the control of C. macrocephalum. Both sites had dense infestations of C. macrocephalum at the beginning of the study in 2005. Herbicides were applied in either February (summer) or April (autumn) annually for three consecutive years. Monitoring continued for an additional three years after spraying was terminated. Puccinia eupatorii established at both study sites from the second year of study. Both sites also experienced wildfires and drought. As these uncontrolled factors were not anticipated in the design their individual effects could not be factored out. Mean mortality however was <80% expected of registered herbicides which can only be attributed to uncontrolled factors acting as natural constraints. The efficacy of picloram was not significantly different (P<0.05) to that of metsulfuron methyl within a season. Autumn applications are not recommended because rust damage on the leaves is too advanced to ensure adequate herbicide uptake and translocation. Herbicide persistence in the topsoil was not detected by gas chromatography. Three applications of herbicide were inadequate to bring C. macrocephalum under control in plots. It is estimated that five to seven years of herbicide application are needed to reduce the weed density to <1 plant per plot (25 m2). This effectively renders chemical control in medium to dense infestations uneconomic. Chemical control of C. macrocephalum will only be effective if there is a commitment to follow-ups and remedial vegetation management practices. The herbicide trials also looked at the impact of picloram, metsulfuron methyl and hoeing on native species and other alien species that occurred in plots. Three plant functional groups were analysed, namely native grasses, native forbs and alien broadleaf species. The herbicides were applied as broadcast sprays over three years and therefore their effect on all broadleaf species was non-selective. Hoeing twice a year for three years only targeted C. macrocephalum. High forb richness coupled with low abundance and patchy distribution meant there was a high turnover between replicate plots across the study sites. Herbicides had a significant impact on the native forb functional group compared to hoeing which had a superficial effect. Hoeing did not suppress C. macrocephalum. The parasitic forb Thesium utile was killed in all treatments except the untreated control. The target-specific hoe treatment also eliminated T. utile, suggesting a new association might exist between parasite and C. macrocephalum. Hoeing also facilitated the establishment of alien annual weeds. In South Africa the grassland biome is under considerable threat from mining, afforestation, agriculture and urban development. Although alien plants pose a minor threat in contrast to these land-transforming activities they remain the greatest threat to grasslands that are not threatened by exploitation. Campuloclinium macrocephalum is not a pioneer species, but rather a long-lived perennial herb with evolutionary adaptations to fire, herbivory and disease. These characteristics have enabled it to establish and spread in grasslands that have been maintained in a variety of disturbed states by a range of agencies that reduce grass basal cover and exacerbate soil erosion. Addressing poor land use practises that foster C. macrocephalum invasion and spread are as important as the remedial activities necessary to control the species. Grassland restoration/rehabilitation practises have not been investigated in the context of C. macrocephalum management and is of critical importance to the integrated control of the weed. Although comprehensive literature about C. macrocephalum have recently been published gaps in our understanding of its biology, ecology and control still exist that prevent the development of best management practices. These areas for new research make ideal projects for post-graduate students. Future research should focus on (a) rust–herbicide interactions, (b) fire and seedbank dynamics, (c) integrated weed management incorporating biological control, fire, selective herbicide application techniques (e.g. spot-spraying) and ecosystem restoration practises. Grazing strategies promoting grass species adapted to frequent non-selective defoliation restrict pompom weed better than degraded underutilised rangelands, as evidenced by low levels of C. macrocephalum in communal areas, and warrants further investigation, including fence-line contrasts in invaded and un-invaded road reserves.

The evaluation of the state of grass species composition was conducted as an attempt to confirm the survey conducted by the United Nations Convention to Combat Desertification (UNCCD), where the Zeerust District was identified as an area with serious degradation problems. Quantitative data was obtained through botanical surveys (April 2001-February 2002) and verified by household surveys (March 2001-April 2002). Study sites included Braklaagte, Dinokana, Doomlaagte, Serake and Supingstad, with benchmark sites in Madikwe Grune Reserve. Between 6-12 survey points per site were selected after consultation with local Agricultural Extension Officers and communities. Survey points included the range of veld condition between bush encroached and severely denuded and eroded areas. The results indicate 12.3 % to 45.1 % loss of vegetal cover. Resistance above 2 000 ohms, base saturation exceeding 100 % and pH values below 5.5 are evidence of soil degradation. The general profile of the fanning household is that of an aging adult community, with however, a relatively good knowledge of fanning practices. 52 % of the respondents depend on the government pension fund as a source of income. 60 % of the respondents use crop fanning products strictly for household purposes. Poor economic return from fanning activities has resulted in overutilization of the herbaceous layer with consequent changes of grass species composition towards retrogression and the establishment of woody species. This environmental degradation is a serious risk to long-term sustainable development. It is therefore, recommended that environmental education programmes and ecological restoration projects be started in degraded areas. The government should set up and enforce land-use policies. Community participation should be encouraged in all land care activities. Land degradation is a real social problem that must be tackled before many people's aspirations of a better life are met. / Thesis (M.Sc. (Biology) North-West University, Mafikeng Campus, 2003

Major transitions between vertebrate and insect pollination systems have occurred many times during the angiosperm radiation and are associated with evolutionary modifications in floral traits. In the large ancestrally bird-pollinated African genus Protea (Proteaceae), an evolutionary shift from bird to insect pollination in the genus is suggested by the fruity diurnal scent of flowers in a recently evolved clade of grassland species. In this study, I confirm that four of these grassland Protea species have mixed mating systems and are indeed insect pollinated, and furthermore demonstrate the functional significance of their floral presentation and scent chemistry for attraction of pollinators, specifically cetoniine beetles. The study species, Protea caffra, Protea dracomontana, Protea simplex and Protea welwitschii, have colourful bowl-shaped inflorescences that produce copious amounts of pollen and dilute, xylose-rich nectar. Cetoniine beetles were found to be the most suitable pollinators due to their abundance, size, relatively pure Protea pollen loads, and their preference for the fruity scent and low growth form of these scented Protea species, as demonstrated by choice experiments in which inflorescences were offered at either end of a y-maze or at various heights above the ground, respectively. Bagging and hand pollinations revealed that these Protea species are self-compatible and capable of autonomous selfing. Self progeny of P. caffra were as vigorous as cross progeny in terms of germinability and survivorship to two months. Vertebrate-excluded and open-pollinated inflorescences yielded similar seed numbers for all species. Supplemental hand-pollinations, however, failed to increase seed set substantially, an indication of resource limitation. Outcrossing rates estimated using polymorphisms at eight allozyme loci in progeny from vertebrate-excluded and open-pollinated treatments of P. caffra were no different (t=0.59), indicating outcrossing by insects and an equal or insubstantial contribution from bird pollinators. The fruity-sweet scents of these species were more complex, with higher whole flower and mass-specific emission rates, than those in eight bird-pollinated congenerics. The overall floral scent is shown to be a blend of emissions from various plant parts, especially nectar. Electroantennography (EAG) revealed that the generalist pollinator Atrichelaphinis tigrina responds to a variety of volatile compounds found in fruity Protea scents. Field trapping confirmed that this cetoniine beetle is strongly attracted to ß-linalool (up to 60% of scent profile) and methyl benzoate. In conclusion, this study demonstrates the evolution of beetle pollination and mixed mating systems in a grassland clade of Protea. Volatile compounds that make up the unique (within Protea) fruity scent of the study species are shown to attract beetles, and the emission of large amounts of these compounds was probably a key step in the transition from bird to insect pollination in Protea. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.

The grasslands of South Africa are the foundation of commercial and subsistence agriculture yet they are being degraded at an alanning rate. The coastal grasslands of the Eastern Cape are no exception and they suffer added pressure of coastal resort development because of their proximity to an attractive coastline. In order to determine the degree of conservation necessary for any area it is essential to know what species occur there in order to determine if protection from habitat destruction is required. Four aims were defined for this studv. The initial aim was a phytogeographical classification of the grasslands in the coastal region west of the Kei River. This was done by vegetation sampling followed by computer based analysis with TWINSPAN. This analysis defined ten grassland associations. five being located in the area west of the Keiskamma River and five occurring east of it. The associations in the eastern half are termed mesic while those in the western balf are xeric. The second aim was to determine the presence of any underlying ecological gradients affecting the distribution of tbe associations. Indirect gradient analysis was carried out where samples are analysed irrespective of environmental factors. Direct gradient analysis was then carried out using scores per sample of various environmental factors. Environmental factors whicb migbt produce such gradients are both naturally-ocurring and man-induced. Natural factors which were recorded in the field include depth of soil at sample site, soil family, aspect and distance from the shore. An important factor is the land / sea interface. Natural factors analysed in the laboratory include soil pH. conductivity. percent organic matter, calcium, magnesium, phosphate and potassium. Man-induced factors are land use history e.g. Ploughing and grazing. Both direct and indirect gradient analysis were carried out with the computer based programme CANOCO. The third aim of the study was to determine the presence of any successional trends between the ten defined associations. This was done using several characteristics of the associations. Alpha and beta diversity were the first factors compared between associations. The percentage contribution of the Cyperaceae, Fabaceae, Asteraceae and Poaceae to each association was assessed and compared. The presence of various life forms of the species occurring in each association was determined together with the cover abundance of different classes of grass species. These results were then combined and analysed in the light of the results from CANOCO analvsis. They show that the mesic Themeda Iriandra - Anthospermum herhoceum, association which occurs closest to the shore and with the least disturbance is a depauperate form of the mesic climax Themeda triandra association. The mesic Hyparrhenia hirta - Dtheteropogon amplectens association may be a secondary grassland on account of phosphate and potassiun poor soils and land-use. The mesic Hyparrhenia hirta - Themedo triandra association is a slightly degraded form of the climax association due to grazing. The severely disturbed Stenotaphrum secundatum - C'entella coriacea association, which is located close to the shore, is a secondary grassland. Analysis of the xeric associations indicates a clearly defined ordination of associations on the basis of land-use. The Cynodon daclylon - Helictolrichon hirtulum and Sporobolis africanus - Setaria sphacelata associations which occur where ploughed lands have been left to lie fallow are secondary in nature. The Themeda triandra - Ehrharta calycina association is thought to be the closest representati ve of a climax xeric association but the presence of E. calycina indicates that some disturbance has occurred. The vegetation is subject to moderate grazing. The Cynodon dactylon - Ehrharla calycina and Diheleropogon filifolius - Ehrharla calycina associations are subject to varying intensities of trampling and grazing and are degraded forms of the Themeda triandra - Ehrharla calycina association. Because of tbe overriding influence of the land-use gradient separation along gradients of the remaining eight factors was limited. The effect of fire and temporal change in the mesic Themeda triandra and Hyparrhenia hirta - Themeeia trianda associations was assessed via long-term studies at Potter's Pass outside East London. The results show a quick response to burning with a return to 100% cover within six months by both associations. During spring the two associations could not be separated by either TWINSPAN or DECORANA. indicating a temporal shift from the Hyparrhenia hirta - Themeda triandra association to the Themeda triandra association. The fourth and final aim was to identify plants requiring protection from habitat destruction and to make recommendations for further conservation areas and management of the coastal grasslands. Through the collection and identification of as many plants as possible a species checklist was prepared and the status of each was determined through reference to the Red Data Book of threatened and endangered species. Kniphofia rooperi is vulnerable in the Cape and Euphorbia hupleuroides is considered rare in kwazulu-Natal. Ten species are endemic to the Cape and / or South Africa. The richness of the vegetation lies in the presence of species representative of the four major floras which converge in the eastern Cape. i.e. The Cape, NamaKarroo, Tongoland-Pondolaod floras and the Kalahari Highveld Regional Transitional Zone. Suggestions are made for the conservation of the grassland associations at various sites within the study area based on the present area conserved. Less than 2% of the coastline in the study area is conserved and it is felt that the area under conservation should be increased. Management suggestions based on the available literature are given for both farmed and conserved areas. There is a great potential for further studies on grassland dmamics within the areas surveyed. In terms of management, the grasslands require careful examination to determine the most effective season in which to burn if at all. As with most agricultural systems in South Africa. grazing strategies will benefit from further research. Any additional research on the dynamics of these grasslands can only be of benefit to the sustained utilisation of this vital resource.

The aim of this study is to gain a predictive understanding of the patterns and determinants of plant biodiversity in temperate, mesic grasslands of South Africa with a primary focus on the geographical area of the Eastern Cape. From a review of the literature on hypotheses explaining diversity (Chapter 2) it was possible to formulate a number of hypotheses that could be tested to explain species richness patterns in Eastern Cape grasslands. This thesis is organised so that each main chapter deals with a specific body of theory concerning the explanation of diversity patterns. A detailed description of the study area is provided (Chapter 3), including environmental variation and a description of major vegetation patterns. A summary is provided of grassland plant community patterns, as determined by phytosociological studies in the study area. A multivariate analysis of environmental variables was undertaken to determine which variables contributed the most towards explaining environmental variation in the study area and to determine whether any variables co-vary, a possible problem for any multivariate analysis in later chapters. Altitude produced one of the strongest gradients in the study area. There were a number of variables that were correlated with altitude, most notably temperature. Rainfall co-varied partially with altitude, but there was also a strong rainfall gradient perpendicular to the altitude gradient. A description of species richness, diversity and evenness patterns at the plot scale within different grassland plant communities of the Eastern Cape is provided in Chapter 4. To determine whether the environment acts differently on different growth forms, the contribution to species richness by different major growth forms is analysed. Furthermore, since the majority of literature attempts to explain diversity in terms of environmental factors, it was necessary to analyse the relationship between species richness and various environmental variables. The results indicate that there is high variation in species richness both within and among grassland communities. Forbs make the most significant contribution to overall species richness per 100 m2, followed by grasses. Variance in richness of all species together is not significantly related to environmental variables in mesic grasslands, but is significantly related to environmental variables in semi-arid grasslands. The result of greatest interest from this chapter is the fact that richness amongst different life-forms in the same place is explained by different environmental factors, indicating that the environmental factors that affect coexistence of species have a different effect on different life-forms. A classification of all the species of the dataset into plant functional types using a multivariate approach based on functional traits was conducted (Chapter 5). The grass species were classified into 16 functional types and the forbs into 14 functional types. The functional type classification provided the opportunity for undertaking analyses to develop an understanding of 8 the contribution by niche differentiation towards promoting species richness (Chapter 6). The results provide evidence of niche differentiation in the grasslands of the study area and also that niche differentiation promotes species richness in the grasslands of the study area. It was found that higher rainfall grasslands are less structured by niche differentiation than semi-arid grasslands. A regional / historical analysis is undertaken (Chapter 7) to investigate the relationship between the regional species pool and local richness, and the relationship between local richness and phytochorological diversity. Regional richness appears to have little effect in promoting local richness in grassland plant communities of the study area except at sites where there is high local richness. This provides an indication that regional richness only promotes local richness in the absence of local limiting factors. Phytochorological diversity promotes local richness, but mostly through diversity amongst species with narrow distribution ranges. Some theories ascertain that seasonal uncertainty may provide opportunities to species that would otherwise be outcompeted and thereby promote local richness. The degree to which seasonal uncertainty and seasonality promote local richness in the Eastern Cape grasslands was therefore investigated (Chapter 8). A weak relationship exists between these variables and local species richness in grassland communities of the study area, indicating that they do not promote niche differentiation to a significant degree in the study area. It is clear that in the grasslands of the Eastern Cape, environmental limiting factors are more important in semi-arid grasslands and species interactions are more important in mesic grasslands for structuring plant communities (Chapter 9, Discussion). Regional processes do not appear to be important in structuring local communities, but the analysis undertaken in this study shows that they may be significant when factors operating at the other two levels are overcome (species interactions and environmental limiting factors.

In this study, I investigated the interaction between two megaherbivores, the African elephant and white rhinoceros, that has the potential to impact grazing lawns of which white rhino are the creators and maintainers and elephants are potentially the modifiers. I hypothesized that as elephants browse, they discard a variety of coarse woody debris onto the ground; should this woody debris (of varying amounts and sizes) fall onto grazing lawns, white rhino either move them, consume grass around the woody debris or abandon the lawn entirely. If high levels of woody debris are deposited here, grazing by white rhino is likely to be prevented, at which time I predicted that mesoherbivores would have a competitive advantage in accessing forage that white rhino cannot. I examined the mechanistic links between different levels of elephant-deposited woody debris and grass response at a point scale and feeding patch spatial scale of grazing lawns in an African savanna. In addition, I assessed the response of mesoherbivores in terms of vigilance behaviour with increasing levels of predation risk posed by increasing levels of woody debris. I present the first evidence of an indirect effect of elephant on white rhino foraging behaviour. I demonstrate how increasing levels of woody debris lead to a decreasing probability of foraging by white rhino. I also demonstrate how the probability of foraging by mesoherbivores increases as the amount of forage increases. However, since this study took place during a severe drought where resources are extremely limited, I was unable to properly separate the effects of elephant-deposited woody debris from the severe lack of rainfall on grass response and subsequently herbivore foraging behaviour. Due possibly to the drought, mesoherbivores responded less or not at all to risk factors such as woody debris therefore woody debris was not a predictor of vigilance behaviour in my study. This study contributes to our understanding of how the impacts of elephants, as ecosystem engineers, have cascading effects on savanna ecosystems. My study showed that elephant impact mediates the foraging behaviour of white rhino during a drought. However, under average rainfall periods, my original hypothesized effect of the indirect impacts of elephants on white rhino foraging and grazing lawn dynamics could still hold. This key hypothesis that I was unable to test under ‘normal’ conditions due to the drought is still valid and functionally important for understanding the ecosystem processes driving grazing lawn formation, persistence and composition in African savannas where elephants and white rhinos coexist.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg 1992. / The aim of the study was to develop understanding of the relationships between vegetation types of the grassland biome of South Africa and the environment, with an emphasis on structural and functional characteristics. The grassland biome in South Africa has traditionally been divided into 'pure' grasslands, assumed to be climatically determined, and 'false' grasslands of recent anthropogenic origin. A review of literature from several disciplines including palaeobotany, archaeology, ecology and biogeography indicates that this is not a valid distinction. It is clear that the distribution of the grassland biome as a whole is poorly understood, but the general correlation between the distribution of biomes and climate elsewhere in the world suggests that this warrants more detailed investigation. A water balance approach was used to develop climatic incices that both predict the distribution of grasslands, and are easy to interpret biologically. The indices are the mean. number of days per annum when moisture is available for plant growth, tbe mean temperature on days when moisture is available for plant growth (wet season temperature),. and the mean temperature when moisture is not available for plant growth (dry season temperature). Based on these three.indices the grassland biome in South Africa call be distinguished from neighbouring biomes. The fynbos and succulent karoo biomes have rainfall in winter. The grassland, nama-karoo and savanna biomes have' rainfall in summer. The forest biome experiences rainfall throughout the year. Of the summer rainfall biomes, the quantity of water available in the grassland biome b greater than in the nama-woo, similar to savanna, but less than forest. Grasslands experience cooler dry season temperatures than savannas. The localised distribution of woody plants within the. grassland biome suggests that it is the effect of climate on the fire regime that may be of overriding importance h'l determining the distribution of the biome as a whole. Woody elements are restricted to sites that are either protected from fire, or experience fires of lower intensity than sites that support- grassland, The unifying feature of the grassland biome is its proneness to fire. The presence of a warm, moist season promotes plant production and leads to a high standing crop close to the ground. The prolonged dry season causes vegetation to dry out annually, rendering it flammable. More arid biomes have plants more widely spaced, making it difficult for fire to spread. In more mesic biomes where rainfall is less sea.sonal than in the grasslands or savannas, fuels do not dry out sufficiently to ignite, A number of additional climatic features may promote burning in the grassland biome, It has the highest lightning density of all South Africa's biomes. 'tVarm, dry 'berg' winds desiccate fuels and 1 omote burning in the more mesic grasslands, The 'curing' of the grass sward due to dry season frost and temperature drop is important in establishing early dry season flammability. Savanna trees are fire tolerant, but they appear sensitive to the cold temperatures prevaient in the grassland biome in. the dry season, The relationship between the distribution of functional characters of grassland plants and environmental conditions was investigated. The distincrion between sweetveld, mixed veld and sourveld was recognised as one of the most Important functional features of South Africa's grasslands, The distribution of these vegetation types was examined in detail. Sweetveld occurs In warm, dry areas; sourveld in cool, moist areas. There Is overlap between these tyP.Js that Is dependant on soil nutrient status. Sweetveld that occurs in climatic conditions that would be expected to support mixed veld and sourveld, is on soils derived from basic parent material, including basalt, dolerite, gabbro and norite. Similarly, sourveld that occurs in areas that climatically would be expected to support sweetveld, is on soils derived from acid parent material such as sandstone and quartzite .. Soil nutrients that are most highly correlated to the occurrence of these three veld types are phosphoms availability and an index of nitrogen mineralization potential. 'l'here is an increase in bot; available phosphorus and the index of readily mineralizable nitrogen from sourveld to mixed veld to sweetveld. These features am inc01).10111tedinto a conceptual model that relates the distribution of these grassland types to carbon and nitrogen metabolism, with the role of phosphorus either similar to nitrogen, or else it may act indirectly by affecting the. rate of nitrogen mineralization, Nitrogen mineralization OCcursat lower water availability than carbon assimilation, and its temperature optimum is higher than that of carbon assimilation. Where nitrogen mineralization is favoured ielative to carbon assimilation, sweetveld is likely to (}C(.1\Xr. Where carbon assimilation is. favoured relative to; nitrogen mineralization, sourveld is likely to occur ....Soil texture affects the balance between these two processes in the degree to wm.r;h it protects soil organic matter, and thereforv the size of the nitrogen and ph_QSPllO_rOll.S pools. Changes in the rlj,stribution of South Africa's b~\omesfor a scenario of climate change are predicted using the biome model developed in this study. This illustrates the value of developing predictive models. / MT2017

Thesis (MSc)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: This study investigated the composition of Themeda triandra Renosterveld in part of the Grootvadersbosch Conservancy and the effects of selected environmental and management variables to provide guidelines for promoting the presence of Themeda triandra in the veld. The Zürich-Montpellier phytosociological method was used to determine the composition of the Renosterveld communities. The point quadrat method was used to determine the cover of Themeda triandra at three grass dominated sites and compare cover from one site with past cover measurements at the specific site. Ordination was used to examine the effects of the environmental and management variables on the plant communities. Two community groups, five communities and five subcommunities were identified and described. The Themeda triandra – Stoebe phyllostachys Grassland Community Group consists of two communities of which one has two subcommunities. The Themeda triandra – Elytropappus rhinocerotis Shrubland Community Group consists of three communities of which one has three subcommunities. The vegetation units described in this study have not been described previously in the literature. One community belongs to Silcrete Fynbos while another subcommunity is transitional between Renosterveld and thicket and gallery forest. The rest of the plant communities fit the definition for Renosterveld (the local Renosterveld type is Eastern Rûens Shale Renosterveld). Cover of Themeda triandra did not differ significantly either between sites or between years. The comparison of Themeda triandra cover between years was done at a site that had been burnt between the last two sampling times yet the cover was not significantly different. This indicates that fire and other management practices did not have a negative impact on Themeda triandra at the site. Unconstrained ordination of the dataset in which cover/abundance values were included, grouped the relevés by moisture and disturbance but the presence/absence dataset indicates that the two community groups have a slight transitional overlap. Constrained ordination of both datasets with a) soil variables and b) management variables, both showed a tendency to separate the relevés into community groups, that did not happen with topographic and vegetation variables. Ordination did not separate the community groups into their subdivisions. The soil variables (both nutrients and texture) influence the vegetation structure and the community distribution. Under the existing grazing management regime, fire at three to five year intervals promoted the dominance of Themeda triandra by affecting the structure of the plant communities, the abundance of species other than Themeda triandra, and influencing which plant community is present. The use of fire as a management tool was regulated by the importance of the natural veld pastures to the farmers. The natural veld pastures are not suitable for dairy cattle in milk. Thus dairy farmers are less likely to burn the natural veld (no planned burns only chance fires) than those who farm with mutton or beef (planned burns on a three to five year interval). / AFRIKAANSE OPSOMMING: Die studie het die samestelling van Themeda triandra Renosterveld in ’n deel van die Grootvadersbosch-Bewaria en die uitwerking van geselekteerde omgewings- en bestuursveranderlikes ondersoek om riglyne vir die bevordering van Themeda triandra in die veld daar te stel. Die Zürich-Montpellier fitososiologiese metode is gebruik om die samestelling van die Renosterveldgemeenskappe te bepaal. Die puntkwadraat-metode is gebruik om ’n skatting van die dekking van Themeda triandra by drie gras-gedomineerde persele te bepaal en om ’n vergelyking te maak tussen die huidige en vorige dekking van ’n enkele perseel. Ordinasie is gebruik om die invloed van omgewings- en bestuursveranderlikes op die plantgemeenskappe te bepaal. Twee gemeenskapsgroepe, vyf gemeenskappe en vyf subgemeenskappe is geïdentifiseer en gedefinieer. Die Themeda triandra – Stoebe phyllostachys Grasland-gemeenskapsgroep bestaan uit twee gemeenskappe waarvan een in twee subgemeenskappe onderverdeel is. Die Themeda triandra – Elytropappus rhinocerotis Struik-gemeenskapsgroep bestaan uit drie gemeenskappe waarvan een in drie subgemeenskappe onderverdeel is. Die plantegroei-eenhede wat in die studie beskryf is, is nie voorheen in die literatuur beskryf nie. Een gemeenskap behoort aan Silkreet-fynbos en ’n ander subgemeenskap is ’n oorgangsfase tussen Renosterveld en struikbosveld of woud, terwyl die res van die plantgemeenskappe binne die definisie van Renosterveld val (die plaaslike Renosterveld tipe staan bekend as Oostelike Rûens Skalierenosterveld). Die bedekking van Themeda triandra het nie betekenisvol gevarieer tussen óf die verskillende lokaliteite óf die verskillende jare nie. Die vergelyking van Themeda triandra-bedekking oor tyd is onderneem in ’n gebied wat tussen opnames gebrand is. Die bedekking het nie betekenisvol verskil nie. Dit dui aan dat vuur en ander bestuurspraktyke nie ’n negatiewe invloed op Themeda triandra in hierdie gebied het nie. Onbeperkte ordinasie van die datastel met die vergelyking van bedekking/volopheidwaardes, groepeer die relevés volgens vogtigheid en versteuring, terwyl die datastel ten opsigte van teenwoordigheid/ afwesigheid aandui dat die twee gemeenskapsgroepe ’n effense oorgangs-oorvleueling het. Beperkte ordinasie van beide datastelle met a) grondveranderlikes en b) bestuursveranderlikes, toon albei ’n neiging om die gemeenskapsgroepe te skei, wat nie gebeur het met die topografiese- en plantegroeiveranderlikes nie. Ordinasie het nie die gemeenskapsgroepe onderverdeel in gemeenskappe of subgemeenskappe nie. Die grondveranderlikes (beide voedingstowwe en tekstuur) beïnvloed die struktuur en die verspreiding van die plantegroei. Met die bestaande weidingsbestuur bevorder brande met ’n interval van tussen drie tot vyf jaar die oorheersing van Themeda triandra deur die struktuur van die teenwoordige plantgemeenskap te beïnvloed, deur die getal van die verskillende plantsoorte te beïnvloed en selfs deur die plantgemeenskap se voorkoms te beïnvloed. Die waarde wat die boer aan die natuurlike veld as weiveld heg bepaal die mate waartoe hulle veldbrand gebruik as ’n deel van bestuur. Die natuurlike veld is nie geskik vir melkkoeie wat in die melkproduksiestadium is nie. Die melkboere is dus minder geneig om die natuurlike veld te brand (geen beplande brande nie net kans brande) as die boere wat met vleisbeeste of skape boer (beplande brande elke drie tot vyf jaar).

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Master of Science. / This work describes the coastal grasslands of Mkambati Game Reserve and their suitability for the present large herbivore complement. The initial description makes use of both field survey and quantitative sampling and multivariate analysis which facilitated the production of soil and vegetation maps at tre scale of 1: 10 000. Suitability of these grasslands for herbivores is assessed in terms of both quantity and quality of food available and the present herbivore impact. Local variation in soil type was considerable. Eight standard soil forms were distinguished as well as severaI others previously undescribed. Most of the soils were dystrophic although nutrient 'hot-spots' were common. This determined floristic composition of the various communities to some extent. Three grassland communities and four subcommunities were recognized which contributed 81, 5% to the total area of the reserve. The remaining area comprised forest. wetlands. exposed rock and accommodation camps. Each grassland community was associated with particular ranges of the measured environmental variables. The standing crop of the three communities was high relative to other areas of Southern Africa. Absolute amounts varied seasonally being highest in summer and lowest in winter Partitioning between the phytomass, necromass and litter components also varied seasonally. Total standing crop increased with increasing interval since the last fire. Litter breakdown rates differed between communities and species. Forage quality was poor being lowest in autumn and winter and declining with age. This was probably a result of the dystrophic soils. Crude protein and phosphorus were limiting for several months of the year. Total forage quantity was in excess of the present herbivore needs although availability declined with age and during the non-growing season. However, the poor quality reduced the amount available such that present herbivore impact was low, at all times being less than 9%.. Removal by herbivores was highest several months after a fire when absolute amounts of various nutrients were at a maxinum per unit area. Thereafter it declined to less than 1% with aging of the sward. The implications of the results for management are discussed and future research needs identified. / AC 2018

Savannahs regulate an agro-ecosystem crucial for the production of domestic livestock, one of the main sources of income worldwide as well as in South African rural communities. Nevertheless, globally these ecosystem functions are threatened by intense human exploitation, inappropriate land use and environmental changes. Leaf area index (LAI) defined as one half the total green leaf area per unit ground surface area, is an inventory of the plant green leaves that defines the actual size of the interface between the vegetation and the atmosphere. Thus, LAI spatial data could serve as an indicator of rangeland productivity. Consequently, the accurate and rapid estimation of LAI is a key requirement for farmers and policy makers to devise sustainable management strategies for rangeland resources. In this study, the main focus was to assess the utility and the accuracy of the PROSAILH radiative transfer model (RTM) to estimate LAI in the South African rangeland on the recently launched Landsat 8 sensor data. The Landsat 8 sensor has been a promising sensor for estimating grassland LAI as compared to its predecessors Landsat 5 to 7 sensors because of its increased radiometric resolution. For this purpose, two PROSAIL inversion methods and semi- empirical methods such as Normalized difference vegetation index (NDVI) were utilized to estimate LAI. The results showed that physically based approaches surpassed empirical approach with highest accuracy yielded by artificial neural network (ANN) inversion approach (RMSE=0.138), in contrast to the Look-Up Table (LUT) approach (RMSE=0.265). In conclusion, the results of this study proved that PROSAIL RTM approach on Landsat 8 data could be utilized to accurately estimate LAI at regional scale which could aid in rapid assessment and monitoring of the rangeland resources. / Environmental Sciences / M. Sc. (Environmental Science)