The Hantam-Tanqua-Roggeveld subregion is located within the Succulent Karoo and Fynbos Biomes, in the predominately winter rainfall area of the Northern and Western Cape Provinces. A phytosociological analysis identified and mapped eight plant associations and 25 subassociations. Forty Whittaker plots were surveyed to quantify the botanical wealth in the area. Each plant association produced its own species-area curves, with the curves of the Mountain Renosterveld and Winter Rainfall Karoo more similar to one another than to the Tanqua Karoo. Species richness was highest for Mountain Renosterveld, intermediate for Winter Rainfall Karoo and lowest for Tanqua Karoo vegetation. The Mountain Renosterveld and Winter Rainfall Karoo values for evenness, Shannon and Simpson indices were not significantly different, but these values were significantly higher than for the Tanqua Karoo. An ordination of diversity data confirmed a clear Tanqua Karoo cluster, but the Mountain Renosterveld could only be partially separated from the Winter Rainfall Karoo. Chamaephyte, cryptophyte and therophyte species dominated the study area. Comparisons of life form spectra among associations showed clear differences at a species and vegetation cover level. The percentage contribution of succulent species was low in Mountain Renosterveld, intermediate in Winter Rainfall Karoo and highest in the Tanqua Karoo. Results confirmed the Tanqua Karoo and Winter Rainfall Karoo inclusion into the Succulent Karoo Biome and the strong karroid affinities of the Mountain Renosterveld. Abandoned croplands of various ages surveyed in the Roggeveld revealed that species richness increased with age yet no similar increase in evenness, Shannon or Simpson indices was found. An abandoned cropland of approximately 33-years should be as species rich as the natural vegetation but was floristically still very different. Recovery rates of the different life forms varied across the different ages of the abandoned croplands. A ten-year post-fire study in the Mountain Renosterveld indicated that species richness and Shannon index values usually reached a maximum within three years and then declined. A Principal Co-ordinate Analysis of species compositional data separated the first two years from the following eight years. Succession seemed to follow the ‘initial floristic composition’ model of Egler (1954). / Thesis (PhD)--University of Pretoria, 2010. / Plant Science / unrestricted

Thesis (MScConsEcol(Conservation Ecology and Entomology)--Stellenbosch University, 2008. / The Succulent Karoo biodiversity hotspot is threatened by pressure caused by increasing human populations and its associated land use types. Land use is primarily focussed on agriculture, with livestock grazing as a dominant land use in the region. Cultivation is also practiced along the major perennial rivers, and in drier areas, where this largely depends on rainfall. Only about seven percent of the biome is formally protected, and this area substantially under-represents the biodiversity of the Succulent Karoo and does not incorporate key ecological processes and biodiversity drivers. Therefore, there is urgent need for outside reserve conservation initiatives, whose success depend on understanding the ecosystem function of the Succulent Karoo. This study aimed to determine the impacts of heavy grazing, light grazing and cultivation (in a 30-year old fallow field) on assemblages of ground-dwelling and flying invertebrates. Seasonal assemblage changes were also determined. Vegetation structure and composition were determined using the line-intercept method to determine if vegetation patterns explain patterns in invertebrate assemblages. Abandoned fields harbour the lowest number of plant species, and these together with the heavily grazed sizes are dominated by a high cover of Galenia africana (Aizoaceae). Lightly grazed sites have the highest structural complexity, with a high cover of succulents and non-succulent perennials. After the winter rains, annual plants occupy most of the bare ground in heavily grazed and previously cultivated sites. Seasonal changes in assemblages of ground-dwelling and flying invertebrates were determined by sampling during the four seasons at the same localities. Results of pitfall traps sampling for ground-dwelling invertebrates and coloured pan traps for flying invertebrates showed that overall species richness and diversity peaked in spring for flying invertebrates while peaks in richness for ground-dwelling invertebrates were in summer, with no difference in overall diversity. Overall abundance for ground-dwelling invertebrates was highest in summer and lowest in winter. Ground-dwelling invertebrate fauna was dominated by Formicidae and Araneae. Grazing and cultivation lead to skewed community composition of ground-dwelling invertebrates which favours disturbance tolerant and generalist species such as Anoplolepis steingroeveri (Forel).

Magister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv & Cons Biol) / Fire as a form of disturbance is unique in the way it impacts upon the environment, acting like a herbivore with a ubiquitous appetite. Consuming both dead and living material, converting complex organic molecules into organic and mineral products, which return to the soil. The role of disturbance has long been considered a driver of diversity within Mediterranean type ecosystems. Recently the interest in soil microbes has been piqued, as the importance thereof has been emphasised, particularly their role in nutrient cycling and the chelation of essential plant nutrients. The occurrence of fire results in several environmental and ecological impacts on soil, as well as the dynamics of the microbial populations present. This study explores the impact of fire as a disturbance on the plant and bulk soil microbial communities of the Succulent Karoo. This was achieved through two sub-studies, in which three different states were studied: unburnt, 7-year and 2-year post-fire. Today microbial profiles are also used as indicators of disturbance, thus many techniques exploring microbial community composition are available.

Philosophiae Doctor - PhD / Gethyllis multifolia L. Bolus and G. villosa Thunb. are winter-growing, summerblooming,deciduous and bulbous geophytes that grow naturally in the semi-arid succulent Karoo biome of South Africa. Both species grow under full sun conditions and have four distinctive growth phases: a winter (cold and wet) growing phase, leaf senescence phase towards spring, flowering phase during the hot and dry summer months, and fruit and leaf formation phase in autumn. The medicinal uses of this genus (including G. multifolia “Kukumakranka” and G.villosa “hairy kukumakranka”) range from cures for colic, digestive disturbances,teething problems, fatigue, boils, bruises and insect bites, to being used as an aphrodisiac. Gethyllis multifolia is threatened in its natural habitat and is listed in the ‘Vulnerable’ category of the ‘Red Data List of Southern African Plants’ and the ‘IUCN-World Conservation Union List of Plants’. The literature indicate that the habitats of both species are being exposed to drier conditions and is further threatened by the encroachment of invasive indigenous plant species. It is not known to which extent these factors may pose a threat to the existence of both species. The first objective of this investigation was to determine the costs of vegetative and reproductive growth during the seasonal life cycle of the plant, using carbon(C) and nitrogen (N) as a physiological currency. The second objective was to elucidate a functional basis to explain the difference in the conservation status of both species in their natural habitat. Both species were subjected to drought and shading as environmental stresses and the plant physiological performance was investigated via photosynthetic gas exchange. The third objective of the study was to evaluate the antioxidant content (total polyphenol, flavonol/flavone and flavanone content) and antioxidant capacity [ferric reducing antioxidant power (FRAP), oxygen radical absorbance capacity (ORAC) and 2,2'-azino-di-3-ethylbenzthiazoline sulphonate (ABTS) radical cation scavenging ability] of natural populations and plant samples that were exposed to photo-and-drought environmental stresses. This study was done to elucidate the antioxidant profile of plant parts of natural populations as well as providing farmers, traditional healers and pharmaceutical companies with cultivation environmental conditions to enhance the antioxidant properties of the species. This investigation also attempted to isolate and characterize, by means of thin-layer chromatography (TLC) and column chromatography (CC), natural compounds from both species to lend support to the purported antioxidant benefit of both species and to further lend support to claims made by traditional healers of the medicinal potential of the genus. This study, however, did not engage in any in vivo studies or human trials to support published literature of the medicinal benefits of the genus.

Thesis (MScConsEcol (Conservation Ecology and Entomology))--Stellenbosch University, 2008. / The widespread ecological impacts of overgrazing by livestock within the Succulent Karoo have received considerable attention. Literature shows communal and commercial rangelands have been thoroughly studied, and vegetation responses have been investigated in an attempt to understand the effects of overgrazing. Regarding animal species, literature is in short supply. In a one-year study of small mammal assemblages, the effect of the rangelands, and subsequently vegetation, on small mammal assemblages was examined, as well as the effects on number of occupied, unoccupied and collapsed burrows. This study shows that vegetation composition differs between rangelands, with a greater perennial shrub cover on the communal rangelands and a greater perennial succulent cover on commercial rangelands, consequently creating different habitats for animal assemblages. This study supports the notion of small mammal composition relating to vegetation structure, with certain species being impacted by heavy grazing. Four small mammal species were found in greater abundances on commercial rangelands, with one being exclusive, while communal rangelands were exclusively occupied by three nocturnal species. Diet and habitat requirements are the most important factors regarding species occurrence. With small mammal species composition differing between rangelands, and species richness not being affected by rangeland type, this study illustrates that the disappearance of certain species may arise without these different rangelands. This could result in reduced species richness, and thus diversity being lost. Regarding species present on both rangelands, no differences were observed in body mass, body size or body condition. Despite no differences found in body condition, calculating a body condition index is a good method for investigating how a species is coping within an environment. The proportion and number of occupied and collapsed burrows can be seen as a measure of trampling effect. It was expected for grazing intensity, as well as vegetation changes, to affect the occurrence of such burrows. This study showed differences between the communal and commercial rangelands as negligible. As expected, numbers of burrowing small mammal species were negatively correlated with numbers of collapsed burrows. However, a lack of consistency deemed this result unimportant. Results show that the effects of overgrazing on small mammal populations are complex and require more attention if to be fully explained. This study provides insights into the effects of land use on small mammals and burrow numbers, which have implications for the conservation of these species within arid regions.

Gethyllis multifolia L. Bolus and G. villosa Thunb. are winter-growing, summerblooming, deciduous and bulbous geophytes that grow naturally in the semi-arid succulent Karoo biome of South Africa. Both species grow under full sun conditions and have four distinctive growth phases: a winter (cold and wet) growing phase, leaf senescence phase towards spring, flowering phase during the hot and dry summer months, and fruit and leaf formation phase in autumn. The medicinal uses of this genus (including G. multifolia “Kukumakranka” and G. villosa “hairy kukumakranka”) range from cures for colic, digestive disturbances, teething problems, fatigue, boils, bruises and insect bites, to being used as an aphrodisiac. Gethyllis multifolia is threatened in its natural habitat and is listed in the ‘Vulnerable’ category of the ‘Red Data List of Southern African Plants’ and the ‘IUCN-World Conservation Union List of Plants’. The literature indicate that the habitats of both species are being exposed to drier conditions and is further threatened by the encroachment of invasive indigenous plant species. It is not known to which extent these factors may pose a threat to the existence of both species. The first objective of this investigation was to determine the costs of vegetative and reproductive growth during the seasonal life cycle of the plant, using carbon (C) and nitrogen (N) as a physiological currency. The second objective was to elucidate a functional basis to explain the difference in the conservation status of both species in their natural habitat. Both species were subjected to drought and shading as environmental stresses and the plant physiological performance was investigated via photosynthetic gas exchange. The third objective of the study was to evaluate the antioxidant content (total polyphenol, flavonol/flavone and flavanone content) and antioxidant capacity [ferric reducing antioxidant power (FRAP), oxygen radical absorbance capacity (ORAC) and 2,2'-azino-di-3- ethylbenzthiazoline sulphonate (ABTS) radical cation scavenging ability] of natural populations and plant samples that were exposed to photo- and -drought environmental stresses. This study was done to elucidate the antioxidant profile of plant parts of natural populations as well as providing farmers, traditional healers and pharmaceutical companies with cultivation environmental conditions to enhance the antioxidant properties of the species. This investigation also attempted to isolate and characterize, by means of thin-layer chromatography (TLC) and column chromatography (CC), natural compounds from both species to lend support to the purported antioxidant benefit of both species and to further lend support to claims made by traditional healers of the medicinal potential of the genus. This study, however, did not engage in any in vivo studies or human trials to support published literature of the medicinal benefits of the genus. The photosynthetic adaptation studies indicated that G. villosa had a better photosynthetic performance than G. multifolia during both drought and low light conditions because of the inability of G. multifolia to adapt to a wider range of environmental extremes. The C and N cost of growth and reproduction studies revealed that G. villosa had a more efficient resource utilisation strategy for both growth and reproduction. These physiological responses suggest that G. villosa, in general, has a more efficient survival strategy and that G. multifolia will struggle to adapt to drier environmental conditions, as well as growing in the shade of encroaching invasive plant species. To conclude, this could be a contributing factor as to why G. multifolia is threatened in its natural habitat and G. villosa not. The antioxidant content-and -capacity study on natural populations of both species revealed the highest total polyphenol content, FRAP and ORAC values for the flowers and fruits of G. multifolia and G. villosa compared to other plant parts. These values were found to be in line with and in some cases higher than most commercial fruits and vegetables. The antioxidant activity during drought and photo-stress of the leaves, bulbs and roots was found to be highest in the roots of both species during drought stress. Gethyllis multifolia, in general, exhibited higher total polyphenol content than G. villosa, with the highest content measured during drought stress in the roots of G. multifolia. Phytochemical investigation of the leaves, bulbs and roots of G. multifolia and G. villosa revealed the presence of tannins, flavonoids, phenolics, saponins, glycosides as well as essential oils, while alkaloids were absent. The chromatographic profiles of the leaves, bulbs and roots of both species further indicated that the roots of G. multifolia contained the highest concentration of natural products, compared to G. villosa and other plant parts. Further in-depth studies on the roots of G. multifolia led to the isolation and characterization of three known flavonoids, of which one was also isolated as its endogenously acetylated derivative. In contrast to the fact that both species had a high polyphenol content and exhibited high antioxidant activity, the isolated compounds in this study revealed very low antioxidant activity. However, the literature revealed that some of these isolated compounds exhibit antifungal, antibacterial, antiangiogenic and anticarcinogenic properties in vitro, which could be ascribed to the medicinal applications of plant parts of certain species belonging to this genus. Furthermore, this study suggests that further chemistry and pharmaceutical research on the genus, Gethyllis, in specific the flowers and fruit of these two species, be pursued. / Philosophiae Doctor - PhD

Magister Scientiae (Biodiversity and Conservation Biology) / Fog and dew interception and utilization by plant canopies remains one of the least considered aspects of vegetation studies at any scale yet the few studies that have been conducted point to their considerable influence on ecological processes and a critical role in modulating climate in southern African arid ecosystems. Their relevance to succulent plant hydrology was investigated in this study.The first study measured stable 18O and 2H isotope ratios in samples of rain, fog and dew water and compared these with those assayed monthly in stem xylem water of six succulent shrub species over a one year period. Negative 18O and 2H ratios were observed in the stem xylem water of all six species signifying a predominance of water derived from fog and dew precipitation which was most conspicuous during the wet winter. This implied that fog and dew are even more important sources of water than rain and corroborated by significant correspondence found between fog and dew frequencies, succulent foliar water contents and quantum yields of photochemistry.The second study monitored variations in stem diameter at 2-hourly intervals in 8 succulent shrub species of diverse growth form over a 9-month period. Two groups of species were distinguished based on whether their daily amplitudes in stem diameter were consistently positively correlated with daily fluxes in vapour pressure deficit, which were indicative of a persistent CAM photosynthetic mode, or intermittently correlated with daily fluxes in vapour pressure deficit, which were indicative of mixed CAM and C3 photosynthetic modes. Among species displaying a persistent CAM photosynthetic mode, high nocturnal fog and dew precipitation amounts corresponded with low daily amplitudes in stem diameter, and vice versa, which pointed to reduced nocturnal stomatal water loss. These patterns, which were indistinct among species displaying mixed CAM and C3 photosynthetic modes, were corroborated by small daily amplitudes in stem diameter also consistently observed in one species displaying a CAM photosynthetic mode in ambient than artificially fog and dew excluded environments.The third study monitored changes in water mass at hourly intervals of quartz gravel substrates with different dwarf succulent species assemblages over an 8-month period.Consistently greater net amounts of water were intercepted daily by quartz gravel substrates containing Agyroderma pearsonii than Cephalophylum spissum plants as well as those without plants. These attributed to a high water repellence of A. pearsonii leaves and less radiation absorbed by the paler silvery to grey-green leaves of A. pearsonii leaves than the dark green leaves of C. spissum resulting in lower leaf temperatures and less water loss by transpiration. Quartz gravel soils devoid of plants intercepted nearly 5-times greater amounts of precipitation contributed by fog and dew than that contributed by rain. These precipitation amounts exceeding the high percentages of total hydrological input contributed by fog and dew reported in other ecosystems.The study concludes that fog and dew are a vital source of water for succulent shrubs in arid South African ecosystems and imply that diminished fog and dew frequencies associated with elevated night time temperatures accompanying global warming could exacerbate plant drought stress.

Philosophiae Doctor - PhD / Gethyllis multifolia L. Bolus and G. villosa Thunb. are winter-growing, summer blooming, deciduous and bulbous geophytes that grow naturally in the semi-arid succulent Karoo biome of South Africa. Both species grow under full sun conditions and have four distinctive growth phases: a winter (cold and wet) growing phase, leaf senescence phase towards spring, flowering phase during the hot and dry summer months, and fruit and leaf formation phase in autumn. The medicinal uses of this genus (including G. multifolia "Kukumakranka" and G. villosa "hairy kukumakranka") range from cures for colic, digestive disturbances, teething problems, fatigue, boils, bruises and insect bites, to being used as an aphrodisiac. Gethyllis multifolia is threatened in its natural habitat and is listed in the 'Vulnerable' category of the 'Red Data List of Southern African Plants' and the 'IUCN-World Conservation Union List of Plants'. The literature indicate that the habitats of both species are being exposed to drier conditions and is further threatened by the encroachment of invasive indigenous plant species. It is not known to which extent these factors may pose a threat to the existence of both species. The first objective of this investigation was to determine the costs of vegetative and reproductive growth during the seasonal life cycle of the plant, using carbon (C) and nitrogen (N) as a physiological currency. The second objective was to elucidate a functional basis to explain the difference in the conservation status of both species in their natural habitat. Both species were subjected to drought and shading as environmental stresses and the plant physiological performance was investigated via photosynthetic gas exchange. The third objective of the study was to evaluate the antioxidant content (total polyphenol, flavonol/flavone and flavanone content) and antioxidant capacity [ferric reducing antioxidant power (FRAP), oxygen radical absorbance capacity (ORAC) and 2,2'-azino-di-3- ethylbenzthiazoline sulphonate (ABTS) radical cation scavenging ability] of natural populations and plant samples that were exposed to photo- and -drought environmental stresses. This study was done to elucidate the antioxidant profile of plant parts of natural populations as well as providing farmers, traditional healers and pharmaceutical companies with cultivation environmental conditions to enhance the antioxidant properties of the species. This investigation also attempted to isolate and characterize, by means of thin-layer chromatography (TLC) and column chromatography (CC), natural compounds from both species to lend support to the purported antioxidant benefit of both species and to further lend support to claims made by traditional healers of the medicinal potential of the genus. This study, however, did not engage in any in viva studies or human trials to support published literature of the medicinal benefits of the genus. The photosynthetic adaptation studies indicated that G. villosa had a better photosynthetic performance than G. multifolia during both drought and low light conditions because of the inability of G. multifolia to adapt to a wider range of environmental extremes. The C and N cost of growth and reproduction studies revealed that G. villosa had a more efficient resource utilisation strategy for both growth and reproduction. These physiological responses suggest that G. villosa, in general, has a more efficient survival strategy and that G. multifolia will struggle to adapt to drier environmental conditions, as well as growing in the shade of encroaching invasive plant species. To conclude, this could be a contributing factor as to why G. multifolia is threatened in its natural habitat and G. villosa not. The antioxidant content-and -capacity study on natural populations of both species revealed the highest total polyphenol content, FRAP and ORAC values for the flowers and fruits of G. multifolia and G. villosa compared to other plant parts. These values were found to be in line with and in some cases higher than most commercial fruits and vegetables. The antioxidant activity during drought and photo-stress of the leaves, bulbs and roots was found to be highest in the roots of both species during drought stress. Gethyllis multifolia, in general, exhibited higher total polyphenol content than G. villosa, with the highest content measured during drought stress in the roots of G. multifolia. Phytochemical investigation of the leaves, bulbs and roots of G. multifolia and G. villosa revealed the presence of tannins, flavonoids, phenolics, saponins, glycosides as well as essential oils, while alkaloids were absent. The chromatographic profiles of the leaves, bulbs and roots of both species further indicated that the roots of G. multifolia contained the highest concentration of natural products, compared to G. villosa and other plant parts. Further in-depth studies on the roots of G. multifolia led to the isolation and characterization of three known flavonoids, of which one was also isolated as its endogenously acetylated derivative. In contrast to the fact that both species had a high polyphenol content and exhibited high antioxidant activity, the isolated compounds in this study revealed very low antioxidant activity. However, the literature revealed that some of these isolated compounds exhibit antifungal, antibacterial, anti angiogenic and anti carcinogenic properties in vitro, which could be ascribed to the medicinal applications of plant parts of certain species belonging to this genus. Furthermore, this study suggests that further chemistry and pharmaceutical research on the genus, Gethyllis, in specific the flowers and fruit of these two species, be pursued.