<p>A study of the microbial diversity in sediments of the Great Berg River estuary is carried out using modern molecular phylogenetic methods. The aim of this study was to determine the effect of (pollution by) the effluents of the fish industry on the composition of the microbial community in the sediments. The diversity in microbial groups of sediment samples that received wastewater from the local fishing industry was investigated by a PCR-DGGE (polymerase chain reaction-denaturing gradient gel electrophoresis) approach and compared to an unaffected site.</p>

The main aim of this study was to test rehabilitation interventions in a system altered by heavy grazing, and to develop methods of monitoring these interventions.

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

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy Faculty of Science University of Witwatersrand Johannesburg SOUTH AFRICA / A three-year study was undertaken In the province of Mpumalanga, South Africa to Investigate the competitive effects of the grass Setaria megaphylla on the growth of the tree species Pinus patula. A replacement series field trial, where six different competition regimes were Implemented, clearly demonstrated the suppressive effects of S. ( Abbreviation abstract ) / AC2017

A thesis submitted in the Faculty of Science, University of Witwatersrand, Johannesburg for the degree of Doctor of Philosophy. Johannesburg, 1996. / Litter accumulates on the forest floor in Pinus patula plantations in Mpumalanga, South Africa and as a result nutrients become immobilized and site productivity is reduced. Studies have correlated litteraccumulation with abiotic factors, such as high altitude sites, high rainfall soils derived from the timeball series (shale) have thick litter layers. This study focuses on the biotic factors involved in litter accumulation. [Abbreviated Abstract. Open document to view full version] / GR 2017

Investigations were carried out on aspects of the biology of the vetigastropod Turbo sarmaticus. Studies included: 1) the distribution and standing stock of this animal at four sites along the coast of the Eastern Cape Province of South Africa; 2) the growth rate of animals on a wave-cut platform; 3) the reproductive cycle of an intertidal population; and 4) aspects of the feeding biology examining the ability of this mollusc to consume and digest six macroalgae, the influence of algal diet on growth rate and reproductive fitness and the polysaccharolytic activity of the digestive enzymes. On eastern Cape shores, T. sarmaticus had a size related distribution, with smaller animals being found towards the upper mid-shore and larger animals being found in a downshore direction. The mean shore densities of T. sarmaticus at three sites where exploitation of animals was minimal, were very similar (1.2 - 1.7 individuals/m²). The largest animals (up to 110 mm shell length) were found on an offshore island. This may have been a result of animals not being exploited, as well as a possible increase in primary productivity and food availability. The lowest density (0.2 individuals/m²) and animal size (<70 mm shell length) was recorded at a site (Kelly's beach - Port Alfred) where exploitation was more intense. It is probable that intense overexploitation was threatening the populations at this site. The growth rate of T. sarmaticus was determined by means of the von Bertalanffy growth model and expressed by the equation L[subscript]t = 81.07(l-e⁻°·⁵⁴⁴[superscript](t)). The initial growth rate of T. sarmaticus (up to ≈ 80 mm shell length) was similar on shores with different geomorphologies (i.e. boulder shores and wave-cut platforms). Growth rates of individuals were variable, which means that individuals within a population reached exploitable size (3 - 6 years old) and sexual maturity (1.5 - 2 years old) at different ages. Seasonality of reproduction of T. sarmaticus was determined using gonad index, egg diameters and spermatozoa content within the gonad. Turbo sarmaticus was dioecious and had a sex ratio in favour of males (1.2: 1). Animals attained sexual maturity at a size of about 52.5 mm shell length. There was little variation in the reproductive cycle over time with gametogenesis occurring from March/April until August/September, whilst maturity (Gonad Index = 15%) was maintained until the spawning event from December to March. After spawning the gonad regressed. Field and laboratory observations of the feeding biology of T. sarmaticus confirmed that this mollusc was a generalist grazer capable of consuming and digesting algae from the Rhodophyta, Chlorophyta and Phaeophyta. The consumption rates (juveniles: 1.45 - 9.50% body weight/day, adults: 1.06 - 6.08%) and digestibility (9 - 75% apparent dry matter) of six macroalgae was found to vary. For most algae, juvenile T. sarmaticus had higher consumption rates (1.6 - 2.8 times higher) and digestibility values (12 - 24% higher) than adults. It is suggested that consumption rates were dependent on the digestibility of the algae. In addition, it is suggested that the consumption rates of the different algae were not related to the nutritional content, but rather the energetic content of the algae. In both juvenile and adult animals, temperature had a positive influence on consumption rates, resulting in an increase at higher temperatures. However, in both juvenile and adult T. sarmaticus, algal digestibility was not affected by temperature. Finally, it was proposed that Viva rigida, Codium extricatum, Ecklonia radiata and Gelidium pristoides would provide the best nutritional value for growth and reproductive fitness in T. sarmaticus, whilst Jyengaria stellata and Corallina spp. would provide the poorest. Experiments on the effects of four algal diets on the biology of T. sarmaticus showed that the best growth rate (up to 13.8 mm shell length increase per annum), reproductive fitness (Gonad Index up to 33%) and energy levels (up to 4.76% glycogen in the foot) were achieved when T. sarmaticus was fed G. pristoides, U. rigid a or a mixed diet. Turbo sarmaticus fed Corallina spp. showed reduced growth (2.4 mm shell length increase), reproductive fitness (Gonad Index up to 4.4%) and energy levels (up to 3.42% glycogen in the foot). A study of the polysaccharolytic enzyme activity of T. sarmaticus indicated that this mollusc possesses enzymes that can, at least partially, digest most of the storage and structural polysaccharides found in the Chlorophyta, Rhodophyta and Phaeophyta. This further supported the findings that T. sarmaticus was a generalist grazer. Two levels of activity were detected: 1) high levels of enzyme activity (up to 328.2 Ilglmglmllhr)occurred on the storage polysaccharides that occur in the Rhodophyta and Chlorophyta, and 2) lower levels of activity were detected on the storage polysaccharides (up to 44.8 μg/mg/ml/hr) of the Phaeophyta and on all the structural polysaccharides tested (<45.5 μg/mg/ml/hr). It was suggested that T. sarmaticus did not rely heavily on structural carbohydrates as a source of carbon. Finally, the results of this study were discussed in relation to the future management of T. sarmaticus stocks, the possible role of this macro algal grazer in the intertidal zone and the effects of over-exploitation of this animal. The potential aquaculture of this mollusc was also addressed briefly.

This thesis describes the behavioural ecology of South African fiscal shrikes through detailed field observations and experimental manipulations, and discusses these in the context of reproductive ecology, life history strategies, territoriality, and foraging theory. A population of fiscal shrikes was observed during the period October 1995-0ctober 1997 in a 336 Ha area of grazed bushveld near Pietermaritzburg, South Africa. Fiscal shrike reproduction coincided with the onset of the rainy season. Nests were placed in the centre or north-west regions of tree canopies and contained three or four eggs. Incubation and brooding were performed by females, and shading behaviour was observed in hot weather. Hatching and fledging success averaged 48%. High, exposed nests were less successful than other nests as they were prone to damage during inclement weather. There was a trend in life history strategies between equatorial and South African fiscal shrikes (an increase in clutch size, incubation and brooding durations, and territory size and a decrease in breeding season length), and between northern hemisphere Laniinae (increased intensity in the northern hemisphere), that could be explained by variability in precipitation and temperature, and clutch survival. Fiscal shrikes maintained individual or pair-held territories throughout the year using visual and vocal signalling. Territories averaged 2.2 Ha in area and almost all contained man-made structures. Territory size was inversely proportional to tall tree density, as trees were used for foraging. Fiscal shrikes resided in areas with few natural perch sites by utilising fence lines and overhead cables. When perch density was manipulated fiscal shrikes decreased and increased territory size accordingly. Fiscal shrikes were sit-and-wait foragers and primarily used perch-to-ground forays. The diet of breeding birds consisted of large invertebrates. Small items were consumed and larger items were cached or fed to offspring or females. Fiscal shrikes were central place foragers. Prey size increased in patches over 35 m from the nest. Perch height affected search area, which in turn affected foraging methods, search duration and subsequent movements. Perches may be the limiting resource for other sit-and-wait foragers and the manipulation of perch density could act as a conservation strategy for declining populations. / Thesis (M.Sc.)-University of Natal, Durban, 1998.

People's level of development is a significant determinant in their relationship to wild nature. People today characterized by a high level of development value wild natural resources primarily for non-consumptive aesthetic and humanistic purposes. Modern nature conservation has been dominated by developed peoples' concerns with wild nature. Concerns of developed peoples with wild nature are described by a resourcism-preservationism paradigm. In contrast underdeveloped peoples rely upon wild nature to maintain the integrity of their cultures and increasingly for purposes of physical survival and promoting, development; this involves consumptive use of wild nature. As all people increasingly become part of a global development trajectory, resourcism-preservationism is articulating itself as the global people-environment dynamic. Emergent relations between nature conservation agency staff and reserve neighbours in South Africa offer a unique opportunity to study competing concerns around wild nature and assess the ability of approaches which link conservation and development to meet developed and underdeveloped peoples' concerns. Evaluation of reserve-neighbour interaction at Giant's Castle and Kosi Bay areas is achieved through determining whether it empowers reserve neighbours and conservation agency staff; fundamental to empowerment is people managing natural resources themselves. Natal Parks Board's and KwaZulu Department of Nature Conservation's frameworks for extension do not empower reserve staff or neighbours at Giant's Castle and Kosi Bay respectively. Trends in competition between developed and underdeveloped peoples for use of wild nature evidenced in field studies mirror global trends in people-environment relations. Recent attempts in South Africa and internationally to address the concerns of underdeveloped peoples, witnessed in efforts to link development to conservation such as reserve-neighbour interaction, are efforts by developed people to protect their particular concerns with wild nature. As a result these attempts have not been integrated into a larger conservation and development process. Instead they have been plagued by short term vision among nature conservation agencies and reserve neighbours. Linking conservation and development is a process fundamental to the future of conservation, benefitting people at all levels of development. A fundamental redefinition of conservation agency objectives and restructuring conservation agency operations is required such that people are empowered to manage their own natural resources. Principles to guide and an approach for structuring such an undertaking are proposed involving collaboration with relevant agents. / Thesis (M.Soc.)-University of Natal, Pietermartizburg, 1996.

Common to the temperate floras throughout sub-Saharan Africa is a group of taxa with strong ties to the Cape Floristic Region (CFR) (≈ Cape elements). Their distribution is limited to the eastern escarpment of Africa (e.g. the Drakensberg Alpine Centre - DAC), on nutrient-rich humic soils, as well as on isolated sandstone outcrops of low elevation, on nutrient-poor soils (e.g. the Pondoland Centre - PC), suggesting that intrinsic soil fertility is not the primary determinant of their distribution. The principal aim of this study was to determine which aspect of the edaphic environment of the DAC is most influenced by temperature, that may indirectly render it nutrient-poor and therefore provide suitable niches for Cape elements, as in the PC. A multidisciplinary approach involving aspects of plant biogeography, plant ecology, plant ecophysiology and soil chemistry was therefore adopted. The study regions were the DAC, PC and the KwaZulu-Natal Midlands. The flora of the DAC was resurveyed for this study, and is richer than previously thought: 2818 native taxa, most of which (2520) are angiosperms. The phytogeography of the DAC and PC is discussed, and comparisons are made with the floras of KwaZulu-Natal and the CFR. Their climatic environments, as well as those for the CFR and Sneeuberge, were compared using rainfall and temperature data from a range of sources. These climatic regimes were correlated with the floristic patterns of Cape elements for the high-altitude regions of South Africa and Lesotho. Altitude and rainfall increased, and temperature decreased, as the number of Cape elements increased towards the DAC. This study provided a contemporary inventory of the Cape elements of the DAC and PC. A total of 89 genera are recognised as Cape elements, of which 60 (c. 67%) are shared between the two regions. The highest number of Cape elements recorded for the eastern escarpment was the DAC (72 genera), with the highest number from all sites analysed being the PC (77 genera). The most Cape elements are contributed by the Asteraceae, Scrophulariaceae, Iridaceae, Fabaceae, Orchidaceae and Restionaceae, partly due to the success of annual aerial parts and their geophytic growth forms, which are convergent in these families. Further compartmentalisation into life and growth forms shows that most Cape elements of the DAC and PC are either ericoid (and sclerophyllous) or mesic herbs and shrubs. The ecological and ecophysiological aspects of this study involved the use of reciprocal pot experiments established along a gradient of altitude from coastal hinterland to mountain, that investigated the interactions between altitude, temperature and substrate on plant productivity in sites known either to support or to exclude Cape elements. Three soils were used at each site, representative of the DAC, PC and KwaZulu-Natal Midlands. The interactions between 'soil' and 'site' (≈ the climatic environment) were quantified using a temperate test taxon (Diascia) that has a strong Cape-centred distribution. Plant characters relating to morphology and nutrient content, and soil characters relating to fertility, were used as the basis for comparing treatment effects (soil-site interactions). Soil nitrogen availability was assayed using pot experiments with Eragrostis curvula (Schrad.) Nees. Wheat pot experiments revealed no Al³⁺ toxicity in 'Drakensberg' soil. Non-metric multidimensional scaling (NMDS) and redundancy analysis (RDA) indicated that all soil-site interactions were significant contributors to biomass differences, and that the Cape taxon performed poorly in the nutrient-rich Drakensberg soil at low altitude. Soil samples indicated that Drakensberg soil was the most nutrient-rich, and Pondoland soil the most nutrient-poor. Although total nitrogen in Drakensberg soil was six times higher than Pondoland soil, both soils mineralised similar low levels of nitrogen at their respective spring temperatures. The result for Drakensberg soil (simulated so as to include the effect of altitude) meant that only 1.7% of its total nitrogen was mineralisable at 12°C (its mean spring temperature). These findings suggest that nitrogen mineralisation rate is a key growth-limiting factor in the DAC, exacerbated by a number of complex interactions with soil pH and organic matter. It is hypothesized that Cape elements are preadapted to high-altitude habitats. These habitats are nutrient-deprived due to low temperatures, which reduce metabolic rates and the movement of ions in cold soils. This constraint imposes nutrient-related stresses similar to those of the CFR and PC. Taxa that are adapted to the nutrient-poor soils of the CFR are preadapted to the temperature-induced 'nutrient-poor' soils of the DAC and vice versa. This 'compatibility' has allowed the reciprocal exchange of taxa between regions, as suggested by cladistic biogeographical analyses using Cliffortia, Disa, Moraea and Pterygodium. The strong overlap of Cape elements between the CFR and PC is a product of similar nutritional niches and ancient floristic continuity. The result therefore is a high number of Cape elements common to the DAC and PC. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2004.

Dominant understorey species, such as herbs, ferns, palms and shrubs may influence forest tree species diversity and dynamics. Their influence may be through shading the forest floor, thereby affecting regeneration of shade-intolerant species and reducing species diversity, or it may be through competition with seedlings for space and belowground resources, thus modifying or changing the structure of the forest. These effects may be compounded if the life cycle of the understorey species consists of synchronized reproductive and mortality events. This study examines the influence of a dominant understorey species, Isoglossa woodii (Acanthaceae), on regeneration of trees in Indian Ocean subtropical coastal dune forest in southern Africa. The species is a semiwoody herb and has population-wide synchronous reproduction at 4-7 year cycles after which it dies and regenerates from seed. In this thesis I examine three aspects of the ecology of this suppressive herb: (i) the ecological and environmental correlates of the distribution of I. woodii; (ii) the evolutionary advantages of synchronous monocarpy; and (iii) the ecological effects of the extensive cover and putative recruitment window caused by I. woodii on forest tree seedling dynamics and diversity. Isoglossa woodii covered 65–95 % of the understorey, while gaps in this understorey cover occupied the remaining 5–35 % of the area. The spatial distribution of I. woodii was strongly related to tree canopy structure, with the species excluded from sites with dense canopy cover. Woody seedling establishment was inhibited by low light availability ( / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.