Periods of anchovy and sardine abundance alternate in many upwelling areas. In the southern Benguela ecosystem, anchovy were dominant in the 1980s whereas sardine abundance increased in the 1990s. Mass-balanced models were constructed of the trophic flows in the southern Benguela ecosystem for 1980-1989 and 1990-1997 and in the northern Benguela ecosystem for the 1980s, based on the best available data and estimates. Comparing biomass per trophic level, transfer efficiencies, mixed trophic impacts and several other ecosystem-level attributes suggests that trophic functioning of the southern Benguela ecosystem was similar in the 1980s and 1990s. However, because stocks and catches of small pelagic fish and model zooplankton biomass were larger in the 1990s, the ecosystem was less tightly constrained by predators and food availability than in the 1980s. An extension ofOdum's development theory also suggests that the ecosystem was more mature in the 1990s. Using the trophic models, indices quantifying interactions between species and trophic groups were developed to provide useful measures for the comparison of marine ecosystem structure and function. A new trophic similarity index for anchovy and sardine explains the strong similarities in trophic functioning of the southern Benguela ecosystem in the 1980s and 1990s. Modelling experiments using the dynamic ecosystem simulation tool Ecosim, suggest that observed changes in pelagic fish catches between the 1980s and 1990s are unlikely to have played a large role in driving changes in abundance of anchovy and sardine in the southern Benguela ecosystem. It is hypothesized that changed environmental conditions may have influenced the size composition of planktonic food of anchovy and sardine, thus changing their relative abundance, with some signs of a "regime shift' from anchovy to sardine dominance. Steady-state models show that there are structural and functional differences between the northern and southern Benguela sub-systems. Dynamic simulations of altered fishing strategies show that in the south, heavy fishing on model hake and small pelagic fish has larger negative effects on horse mackerel and large pelagic fish respectively than in the north. There are large differences between the effects of altered fishing simulated under different assumptions oftop-down and bottom-up flow control. A new way of approaching fisheries management is proposed according to a 4-step plan using information from ecosystem modelling studies to address the call for "responsible fishing" and the need to take ecosystem effects into account in managing fisheries.

Includes bibliographical references. / The study investigated changes in populations of Protea caffra at five sites in the central and northern regions of the uKhlahlamba Drakensberg Park, a UNESCO world heritage site. Based on an archaeological study in 1994 that used charcoal remains to compare the size of Protea species populations in the Drakensberg to a much earlier era (between 1260 to 1880 BP), it was hypothesized that there would be a further decline in the number of individuals. A total of 76 historical photographs (dated from 1950-1995) were re-photographed in 2014 and the number of individual P. caffra plants in the two sets of photographs counted to assess the extent and rate of population change. The landform units were demarcated on each photograph according to their catenal position, aspect, elevation and the extent of rocky cover. Geological parameters for each landform unit were obtained from GoogleEarth, climatic data from the South African Atlas of Climatology and Agrohydrology and fire data from MODIS. In 76% of the landform units there was an increase in the number of individuals over time, in 17% a decrease and in 7% there was no change over time. Several hypotheses were generated from a conceptual model based on ecological insight into the study area to explain change in the abundance and distribution of P. caffra. Using an Akaike test, the input models were ranked according to how representative the explanatory variables were of the observed change. The model with aspect and elevation as explanatory variables was ranked the best predictor of change. A greater proportion of increase in the size of the population was found on lower slopes. With increasing atmospheric CO2, P. caffra on the warmer lower slopes are likely to have increased photosynthetic rates and increased productivity. A greater proportion of landform units showing a decrease in P. caffra was shown at higher elevations. The reason could be higher fire intensity at higher elevations. The variation in change influenced by fire suggests it is an important regulator of P. caffra numbers. The fact that there is no relationship between fire frequency and landform units showing an increase in P. caffra implies that the majority increase in the species is more likely to be driven by climatic changes, i.e. increases in atmospheric CO2 rather than a change in the fire regime. Increasing atmospheric CO2 levels lead to enhanced growth rates, postburn recovery and resprouting of tree species in grasslands and savannas, which could account for the majority increase in P. caffra populations in the grassland of the Drakensberg. This has important conservation management implications for the reserve, in that the current fire regimes do not appear to be having a negative impact on the abundance in P. caffra. Further, fire will continue to be an important management tool in maintaining the vegetation structure and grasstree codominance in the reserve.

Includes bibliographical references. / Fire is a major driver of vegetation patterns in the savanna biome of southern Africa and is hypothesized to allow for the tree-grass co-existence. However, to better understand the drivers of the savanna vegetation structure, more research is required. Furthermore, fire management can benefit greatly from the knowledge of fire history and vegetation change. Palaeo-ecological studies endeavour to fill this knowledge gap by investigating past ecological changes throught the use of paleao-proxies. Charcoal - burned pieces of vegetation - is a proxy for fire and vegetation history. However, little is known about the relationship between charcoal found in sediment and environmental features in the savanna biome. This study aims to fill the knowledge gap by investigating the links between macro-charcoal ( > 150 ìm) from surface samples and fire history and physical characteristics of the landscape, vegetation composition and settlement density. Sediment surface samples (top 2cm) were taken from six sample sites in Bwabwata National Park (BNP), Namibia and analysed for macro-charcoal pieces using the swirling method. Here we show that there is a strong relationship between charcoal abundance and burned area, as well as charcoal abundance and grassy vegetation density. Thus broad inference can be made about the past vegetation composition and burned area by looking at long-term charcoal data. This information is useful for fire management, as past burn history can act as a reference point for current burn policy. This calibration work will inform long-term palaeo-data from sediment cores.

Identifying the primary determinants of forest distribution has been a considerable challenge for ecologists. Although focus was traditionally directed towards climatological variables, predictive models showed that suitable forest conditions were far more extensive than the actual forest distribution. This study investigated the primary constraints of forests in the Cape Floristic Region (CFR), in South Africa. Based on a study by Lehmann et al. (2011) on savanna ecosystems, it was hypothesised that seasonal drought and moisture balance were more likely to limit forest distribution than broader rainfall patterns. The biomes of the CFR were mapped using Mucina & Rutherford’s (2006) vegetation map. Environmental data was extracted from Schulze (2007) and analysed using various statistical methods and the effective rainfall during the wet and dry seasons was examined in relation to vegetation patterns. As a complementary analysis, high resolution spatial data was extracted from the Worldclim database (www.worldclim.org) and run in the program Maximum Entropy. The presence of forest was shown to be constrained by soil moisture deficits in the driest half of the year. However there was considerable overlap of climactic and edaphic conditions across the different biomes. It was suggested that seasonal drought may play an indirect rather than direct role in shaping vegetation type. As the length of the dry season correlated with the length of the dry season, it was determined that seasonal drought may effect vegetation by promoting landscape-shaping fires. These findings have implications for predicting and understanding historical and future ecosystem shifts and their relationship with global and local climate change.

Repeat photography photosets were used to analyse 20th century changes in populations of Widdringtonia cedarbergensis from four sites in the Cederberg Mountains, South Africa. Systematic evaluation of 115 photosets was combined with field observation and environmental data to determine the age class and degree of foliage cover, as well as fire frequency, rockiness of habitat, altitude, aspect of slope, annual mean temperature and annual precipitation for each tree viewed in photosets. Mortality and recruitment events were documented in each of the photosets. A total of 1315 trees were recorded in historical photographs (1931- 1982), with 968 of these shown to have died in the repeat photographs (2007-2013), indicating 74% mortality. With only 45 (3.4%) recruits being recorded, the total current living population of W. cedarbergensis in the repeat photographs was 392. There was no significant difference found in mortality or recruitment across the sampled sites. From the historical to repeat photosets there was an 8% increase in the proportion of mature adults and a 13% increase in the proportion of W. cedarbergensis individuals with sparse foliage cover. A generalized linear model was used to determine the effects of environmental factors on W. cedarbergensis mortality in natural populations.

This thesis explores how interactions and feedbacks between environmental and socio-historical factors influenced fire management dynamics in north-east Namibia. Fires are mostly human ignited, but precipitation patterns influence when and where fires can occur, and there are feedbacks between fire, climate and vegetation cover. Yet, knowledge of historical and contemporary use of fire by societies is fragmented in southern Africa, and is therefore disputed. As a result, the complex interaction between climate, vegetation and human factors that influence fire dynamics remains poorly understood. This thesis explores how the political history, livelihoods, land-use practices, policy changes, vegetation and climatic variation are relevant to present-day fire regimes and management. The study is located in Bwabwata National Park (BNP), north-eastern Namibia, which is managed for both conservation objectives and people’s livelihoods. The park is inhabited by the Khwe (San), former hunter-gatherers, who have been using fire for millennia, and the Bantu-speaking Mbukushu people, who are agriculturalists and pastoralists. The area has been subject to colonial regimes, war, inter-ethnic conflict, social-political resettlement, conservation and associated changing fire management approaches since the 19th century. The vegetation includes omiramba grasslands, savanna-woodlands, Burkea shrublands and riparian types. For this study, qualitative semi-structured interviews with Namibian stakeholders, in combination with multi-year (2000 – 2015) remote sensing products, were used to understand the past and present fire regime characteristics. Interviews with community stakeholders revealed that the Khwe and Mbukushu communities use fire for a diverse range of livelihood activities. Specifically, early season burning is used to assist in hunting, tracking and gathering of veld foods, and for improving forage for livestock. The traditional practice of early season burning is not only culturally and ecologically significant, but has positive consequences for Bwabwata National Park’s conservation objectives, and fire policies, in terms of suppressing late season fires. However, explicit marginalisation of the Khwe since the C19th due to colonial regimes and cross-border wars has disrupted traditional fire management. Interviews with government and conservation stakeholders revealed recognition of the benefits of early season burning for biodiversity. Furthermore, despite the complex social-ecological history of the area, recent policy changes reveal an emerging willingness to incorporate traditional fire management into fire management policy. Moderate Resolution Imaging Spectrometer (MODIS) data was used to analyse the fire regime (burned area, fire frequency, fire number and size, intensity, and seasonality), together with climate (El Niño Southern-Oscillation [ENSO] events; local rainfall patterns) and vegetation data in multiple use (inhabited) and core conservation areas, over a time period that covered a shift in policy from fire suppression (2000-2005) to early season burning (2006-2015). Results from the analysis of the MODIS data revealed that a high frequency of early season burning in the inhabited areas of the park reduced the late season fires and dampened the local rainfall and burned area relationship. Nonetheless, grass growth (i.e. available biomass) during ENSO wet season events (La Niña) resulted in greater area burned and fire sizes in above average rainfall years in the early dry season in the community inhabited areas. In contrast, higher fire intensity and larger fire sizes were evident in the conservation core areas where people were not actively burning. Fire frequencies and burned areas were highest in the omiramba grasslands and savanna-woodlands, in the early dry season under the early burning policy in the east of the park, which reduced fire intensities in these vegetation types. In contrast, burning in the Burkea shrublands was frequent in the late dry season, at higher intensities in the Western conservation area under both policy phases. This study indicates that burned area depends on rainfall, ignitions and fire sizes in inhabited landscapes, where people practice early burning, which has consequences for decreasing the intensity and therefore spread and impact of fires on vegetation. This study highlights the complex interactions between people, rainfall seasonality and fuel availability, as well as the need to incorporate historical factors. The study uses a pyrogeographic framework to integrate the social-cultural, climatic-biological, and topographic-environmental factors with fire. The synthesis reveals that the park communities are currently socially and ecologically vulnerable to global environmental change, given their dependence on fire for ecosystem services. However, the study also highlights how traditional fire management, and specifically early season burning, improves food security and contributes to livelihood subsistence and biodiversity conservation in the park. BNP is characterised by complex historical and present-day social-ecological fire dynamics. The study highlights the importance of understanding the historical and political context of fire for determining and managing current spatial-temporal fire patterns. Respect for diverse fire knowledge and culture, communication and shared governance are central to improving community livelihoods and fire management strategies in BNP. Specifically, the shared interest in early season burning provides a point of confluence between diverse stakeholders in BNP and a basis for fire management policies that benefit biodiversity as well as livelihoods.

Includes bibliographical references. / Species turnover is a measure of a diversity that attempts to quantify the change in species composition along a spatial, temporal or environmental gradient. One such environmental gradient that has been shown to affect species turnover is local edaphic variation. This is seen in the Western Cape Province of South Africa, where the unique edaphic character of large earth mounds, known as heuweltjies, support distinct plant communities. The aim of this study is to assess whether these mounds, and the termite Microhodotermes viator commonly associated with them, also support distinct invertebrate communities, thereby contributing to invertebrate species turnover in the region. Pitfall and emergence traps were set on heuweltjies and in the surrounding matrix in the Karoo Desert National Botanical Gardens, Worcester, Western Cape Province. On- and off-mound community contrasts were assessed by means of a cluster analysis, and species turnover was measured using the Jaccard distance. Invertebrates were more abundant on the heuweltjies, which also had distinct communities when compared to the matrix. Spiders (Aranaea) were more abundant on the heuweltjies, as were in the invertebrates emerging from the frass, suggesting a trophic cascade. Invertebrates commonly associated with M. viator were found more commonly on the heuweltjies. The Jaccard distances indicated that environmental homogenisation of the heuweltjies resulted in homogenisation of the on-mound invertebrate communities. Heuweltjie soil enrichment was most similar to that of termite frass when compared to the matrix, supporting a termite origin for the heuweltjies.

Connectivity is defined as the degree to which a landscape facilitates an organisms' movement. It is considered a vital element of landscape structure with key implications for metapopulation survival and ecological processes such as pollination. The connectivity of a landscape changes depending on an organisms' ability to move between patches of favourable habitat and this in turn is related to the dispersal ability of the organism. Connectivity thus changes with the scale at which the landscape is viewed; however the relationship between connectivity and dispersal ability is overlooked in many studies. This study looks at the connectivity of two types of fynbos: Highland fynbos (Thicket, Bushland, Bushclumps and High fynbos) which makes up 22.7%, and Lowland fynbos (Shrubland and Low Fynbos) which makes up 28% of the studied extent. These vegetation types are outlined by the National Land Cover Database (NLCD 2000) and analysed as a function of organism dispersal ability in the greater Cape Town area. It is shown that a relationship between dispersal ability and connectivity exists; however the relationship is not linear but sigmoidal with inflection points at 45% connectivity. This raises the question of a connectivity threshold in the Fynbos Biome. Characteristics of the landscape are assessed and it is shown that Fynbos vegetation in the greater Cape Town area is highly fragmented. Fragmentation and habitat loss decrease connectivity and are thus important factors in conservation. In order to simulate the effect of further fragmentation through habitat loss, patches of increasing size were removed and the results put into context for conservation of both the vegetation types and the dispersing organisms dependent on them. The importance of conserving patches of remnant vegetation in order to facilitate organism dispersal is highlighted by this study.

The dominant vegetation type on the Cape Peninsula, South Africa, is an oligotrophic shrub land that supports low numbers of medium-sized and large terrestrial mammals. Of these, only the adaptable and dextrous chacma baboon (Papio ursinus) has learnt to supplement its diet with protein-rich foods from the marine intertidal zone. There are qualitative descriptions of this behaviour in the literature, but the relative contribution of marine foods to baboon diet, the influence of lunar cycles on exploitation and the impacts of marine foraging on ranging behaviour and activity budgets through different seasons have yet to be quantified. Furthermore, all previous studies included data from troops that had access to nutrient-rich exotic foods, which may have reduced their reliance on marine organisms. For this thesis I collected behavioural data on ranging patterns, activity budgets and diet of a free-ranging, natural-foraging troop through full lunar tidal cycles over consecutive seasons. I supplemented the behavioural data with estimates of the troop's diet composition modelled from stable isotope ratios of foods, faeces and hair samples. The troop ranged over 45.262km2 and travelled an average of 6.044 km per day over the study period. The troop's activity budget was dominated by walking and feeding behaviour, both of which peaked during the hot, dry summer months. Both spatial and behavioural data suggest that the study troop is nutrient-stressed relative to other troops in this population, and hence it was surprising that they only consumed small amounts of marine foods during all four seasons. Models incorporating δ13C and δ15N values of baboon faeces and hair confirmed that marine foods were not major dietary items for these baboons, whilst generalized additive models revealed that a range of abiotic factors negatively affect the exploitation of marine foods. Both the probability and intensity of marine foraging within a given hour declined with increasing tide height and swell height, and fluctuated depending on wind speed and direction. Intensity of marine foraging varied through seasons (it was highest in autumn and lowest in spring), and was higher on the east coast than on the west. Together, these results suggest that exploitation of nutrient-rich foods in the intertidal zone is limited by rapid, unpredictable changes inaccessibility. The levels of deviance left unexplained by these models however imply that other as yet unknown factors (e.g. alkaloids in mussels and limpets) may also limit the troop's exploitation of marine foods. In conclusion, this thesis represents the first in-depth study of marine foraging, a behaviour which exemplifies baboons' remarkable behavioural and dietary flexibility. That said, the temporal unpredictability of ease of access, and potential dangers associated with harvesting this resource, appear to limit how much of this high nutrient food resource baboons are able utilise.

The South African Ophiuroidea were last reviewed by Clark and Courtman-Stock in 1976. In the current investigation, the systematics of the group is thus revised in its entirety for the first time in 40 years. The data used originated from a number of sources. Existing data were sourced from i) published literature, ii) large expeditions or survey data, iii) South African institutional collections and iv) international museums. The majority of new records and data were sourced from previously unidentified specimens deposited in the collections of various South African and international museums and/or institutions, as well as from photographic records and some new, project-specific collecting. A review is presented of the history of ophiuroid taxonomy in South Africa highlighting the progression of research and of species discovery in the region since 1783. All new records of Ophiuroidea from South Africa since (and including) 1977 are documented, with each species account detailing key references, distribution, ecology and additional remarks. As a result, an additional 28 species are added to the known fauna of the mainland Exclusive Economic Zone of continental South Africa, raising the total known number of ophiuroid species in the region to 136. The genus Ophiocoma Agassiz (Echinodermata: Ophiuroidea: Ophiurida: Ophiocomidae) is reviewed and the number of species in South Africa increased from four to eight. All species are briefly discussed in terms of taxonomy, geographic distribution and ecology. Furthermore, the juveniles of O. brevipes, which were found on the ventral side of some adult Ophiocoma brevipes specimens, are described in detail. The distribution of the type material of O. scolopendrina has led to some confusion, and it is considered appropriate to establish a neotype from the original type locality (Mauritius).