I describe the spider biodiversity for a savanna ecosystem, assess sampling techniques, investigate surrogate measures of species richness and measure the biotic and abiotic processes affecting spider diversity. Spiders were sampled at Makalali Game Reserve, Northern Province, South Africa from February to December 1999 using pitfall traps, sweep netting, beating and active searching. A total of 4832 individuals from 268 species (14 potentially new), 147 genera (8 endemic and 2 new records for South Africa) and 37 families (1 new record for South Africa) were recorded. There was no overall significant difference in spider diversity among different physiognomic habitat types. However, analysing the results at a functional group level revealed that the web builders were significantly affected by the habitat type. Mopane woodland habitat type had the greatest number of web builders and general bushveld the least. Sweeping and active searching sampled the greatest number of individuals and species respectively. I recommend a combination of at least beating and active searching, which together sampled the highest number of unique species, for efficient and cost effective surveys. There was a significant relationship between the spider species richness and other invertebrate richness. However, the relationship is not significant when functional groups are considered separately. There was also a significant relationship between the number of species and families and species and genera. However, species level identifications remain ideal for conservation purposes. Inexperienced participants significantly overestimate the number of species. The use of surrogates is not supported by the work conducted in this study. It is still unclear what biotic and abiotic processes or combination of processes influence spider diversity patterns at the local scale. Different spider functional groups are significantly influenced by different factors. However, habitat diversity (branches and vegetation density) was the most common factor influencing spider diversity . Predicted diversity (modelled using GIS and beta-coefficients from multiple regression analyses) was higher than measured diversity values. While further research into the role of other environmental variables is clearly required, current reserve management should aim to maximise microhabitat structural diversity. / Thesis (M.Sc.)-University of Natal, Durban, 2000.

The growth and recovery of trees from disturbances such as fire and browsing is driven by the intensity of the disturbances and the availability of resources. In savannas, resprouting has become recognized as a key functional trait in plant ecology over the past decade. Although this may indeed be the case, there is still limited information about the physiology and growth strategies of resprouting trees. Available information about the influence of disturbance comes from ecosystems that are in many ways different from tropical and sub-tropical savannas. Therefore it is important to know and understand post-disturbance tree responses and limitations so as to establish sustainable use and management practices. This thesis reports the findings of a study, conducted in the Mpumalanga province of South Africa, aimed at achieving a better understanding of the influences of resource availability (water and nutrients) and disturbances (herbivory and repeated cutting) on the coppicing of a widely distributed savanna tree species that is both ecologically and economically important; Terminalia sericea. To investigate the effects of resource availability, cut trees were exposed to different levels of water and nutrient (nitrogen and phosphorus) supplementation over a period of two years in a factorial experimental design. A number of coppice regrowth variables (e.g. shoot production, resprout shoot diameter and shoot length) were measured monthly, while the phenological responses (e.g. timing of leaf discolouration and fruit presence) were monitored every two weeks. The effects of disturbances were investigated in two separate experiments, in which cut trees were exposed to a five month browsing period and different cutting frequencies, respectively. Coppice regrowth variables were monitored for 12 months in trees exposed to browsing and for five months in trees exposed to different cutting frequencies. The effect of multiple cutting cycles on total non-structural carbohydrates and leaf chemistry (carbon, nitrogen and phosphorus) was measured. There was evidence of self-thinning of coppice shoots within cut trees in all experiments in the second year of growth, with supplemented trees also recording lower shoot numbers. With shoot production higher in trees that received no resource addition, water and nutrients interacted synergistically, doubling shoot diameter and shoot length for supplemented trees after 12-months of addition. The majority of the phenophases monitored peaked in the wet growing season. Supplemented trees changed colour from the typical green to senescent yellow later in the growing season than unsupplemented trees. Fruit presence occurred in the second year after cutting for supplemented trees. Shoot length and shoot diameter for unbrowsed trees were twice those for browsed trees, with leaf nitrogen and phosphorus content significantly higher for browsed trees compared to unbrowsed trees. Trees subjected to multiple cutting cycles recorded half the TNC levels, and half the resprout shoot diameter and shoot length of trees cut only once. Results from this study demonstrate that self-thinning (i.e., negative change in shoot number) is not primarily under resource control. By contrast, the findings suggest that shoot growth characteristics, the timing and duration of phenological stages in coppicing trees are resource-limited in savannas. Browsing induces an initial compensatory response through higher shoot production in browsed trees and should be kept minimal because, in the long run, browsed cut trees would take longer to recover lost biomass compared to unbrowsed cut trees. Repeated cutting significantly depleted non-structural carbohydrate reserves in stems, implying that repeatedly cut trees rely heavily on non-structural carbohydrate reserves for regrowth. The significantly lower shoot diameter and shoot length in repeatedly cut trees imply that the coppicing ability of a tree reduces as the cutting frequencies increase. Such information can be vital in establishing the competitive growth ability of T. sericea in a multiple-species ecosystem affected by changes in resource availability as well as natural disturbances. With reference to multiple cut trees, a form of cutting or harvesting strategy should be in place that allows for sustainable regeneration of the study species. A threshold in terms of number of cutting cycles a tree can tolerate based on either maximum or minimum levels of reserve carbohydrates should also be established, as this has a direct effect on the coppice growth and survival.

Ph.D., Faculty of Science, University of the Witwatersrand, 1987

A thesis submitted to the Faculty of Science University of the Witwatersrand, Johannesburg for the Degree or Doctor or Philosophy October 1987 / A t h r e e - y e a r study was un dertaken in the semi-arid (500mm p a . ) n o rth -eastern lowland area of South Afric a. All the woody plants were removed from one -hectare savanna plots on three d i f f e r e n t soil types , and key hydrological and biological changes were monitored relative to adjacent controls. Runoff increased initially, but decreased once the grass cover increased. Deep drainage and lateral subsurface flow increased on the sandiest site. Evaporation from the soil surface increased on the heavier t e x t u r e d soils. The duration of plant - available water in the soil increased on all cleared p l o t s . & The p re - c l e a r in g woody plant abo veground biomass was in the range of of which 0 . 6 6 to 0 . 8 0 t ha was 5.6 to 11.2 t ha -1 leaf biomass. The annual herbaceous production was stron gly rainfal' dep endent, averaging 1 to 1.5 t ha -1 , and increased by 0 . 4 - 0 6 t .ha -1 except on the most f erti le site ( 0 . 6 - 2 0 t ha ) . Total available forage increased with c l e a ring, but so did its variability The observed changes in herbaceous layer palatability could not be a t trib u t e d to clearing. Woody plants and grasses wore shown to have w a te r- u s e niche separation in both rooting depth and time of water use. Simulation over forty years of wetting patterns indicated 75 to 85 % niche overlap, w t h separation on the depth axis more important in sandy sites, and on the time axis in clayey sites. Competition between woody plants and grasses was strongly asymmetrical in favour of woody plants. w >

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, 2014. / Landscapes are highly organised, with recurring patterns of co-varying and interacting biotic and abiotic ecosystem components. Although there is a rising demand for landscape classifications and maps that describe these patterns, emerging conceptualisations of ecosystems as complex, open and inherently uncertain question the existence of geographically definable ecological regions. It is now well recognised that perceptions of ecological patterns are highly subjective, changing with the scale of observation and the particular combination of environmental attributes that are emphasised. Hence many different valid descriptions (and hence maps) of the same ecosystem are possible, each relating to different perspectives and issues. This thesis aims to develop a conceptualization of the biophysical interactions that fashion the character and behaviour of water-dependent ecosystems in savanna landscapes that can be used to underpin land classifications and maps for transdisciplinary enquiry and the management and allocation of natural resources. Recent analytical approaches in geomorphology, hydrology, soil science and biogeography are synthesised in a heuristic landscape hierarchy that frames hillslopes within the context of a stream network that varies between different geological and climatic settings. Savanna landscapes offer excellent opportunities to develop this new approach, since many hydrological, geomorphic and biotic processes are tightly coupled around the limited availability of water. Thus many biotic and abiotic variables are spatially clustered, forming a biophysical template that constrains the character and behaviour of a wide range of organisms and processes. Maps of these clusters can therefore provide a platform for integrating a similarly wide range of scientific and managerial perspectives. The credibility and relevance of the conceptualisation is assessed through its application to a land classification in Kruger National Park (KNP), South Africa. The approach is iterative and reflective, endeavouring to reconcile the impossibility of using traditional reductionist approaches to describe complex systems with the need for reductionist generalisations to describe and analyse complex systems. Assumptions and decisions form a narrative that expressly acknowledges the inclusion of normative values and subjective judgements in conceptualisations of complex systems. Implementation is based around the use of generalised archetypes to navigate between general principles and particular instances and also between conceptualisations and their representation in a map. Rather than using standardised, pre-determined scales and attributes, archetype development is based on the extensive research that exists for KNP, together with observation and analyses that give the landscape a ‘voice’, using concepts such as hillslope catenas and topographic grain. Analytical lenses are reframed to reveal differences as well as similarities, recognising that not all instances of a class are equally similar to the class archetype, so that some locations may conform more than others to the anticipated class character and behaviour. At regional scales, physiographic zones are characterised by particular geology, patterns of landscape dissection and catchments that contain certain repeating toposequences of catenal elements. Differences in topographic grain have substantial implications for the construction of ecological maps, since the optimum scales of observation for the same level of the landscape hierarchy differ between landscapes. The associated differences in catchment size, hillslope length and stream density also have profound impacts on the nature and scale of many ecological processes, such that differentiation between physiographic zones is vital for good science, modelling and management. Two study sites were mapped at catchment and hillslope scales, serving to contrast landscape structures in the finely dissected granites and the coarsely dissected basalts. At both catchment and hillslope scales, the basalt site conformed well to the a priori archetype that described a vegetation toposequence. However, only about half the area of the granite study corresponded to the archetype. Many of these mismatches did not show any difference in vegetation between midslopes and crests, suggesting they lack the contrasting clay/sandy soils that are typical of catenas in this area. It was therefore concluded that these subcatchments are likely to be generated and sustained by a different suite of processes to those described by the archetype and may therefore warrant the development of new archetypes. These findings illustrate how the explicit mapping of catenal elements allows the variability within an area to be assessed, identifying anomalous areas and hillslopes that are likely to behave differently to the hillslopes that conform more precisely to archetypal conceptual models. Understanding the nature and extent of such variations will improve the performance of broad-scale extrapolations and models based on the behaviour of idealised archetypes. Ultimately, end users will determine whether or not the conceptualisation of savanna landscapes developed in this thesis is capable of rising to the challenges posed by the complexity and heterogeneity of ecological systems in KNP (and elsewhere). Initial indications are positive, given the early uptake of the approach both by the South African Water Research Commission and South African National Parks (SANParks).

Acacia erioloba (synonym: Acacia giraffae) commonly known as Mpatsaka (Sotho), Mokala (Tswana), Kameeldoring (Afrikaans) and camel Thorn (English) is an indigenous leguminous tree that is adapted and commonly found in semi-arid savanna environments of South Africa. Being a leguminous plant, Acacia erioloba can fix atmospheric nitrogen into the soil. The objective of this study was to quantify the concentration of plant nutrients in soils beneath the canopies of Acacia erioloba trees in three land-use practices viz: fallow, grazing and bare land. Three trees were randomly selected in each land-use practice and soil samples were collected from beneath and beyond the tree canopies at depths of 0-10 and 10-20 cm. Consistently, soil analysis revealed that the concentration of nutrients (N, P, Ca, Mg, Zn and Mn) and soil biological properties (organic carbon, particulate organic matter, microbial biomass nitrogen and microbial biomass carbon) among the land-use practices were in the order: fallow > grazing > bare. Differences in the concentration of soil nutrients between the land-use practices seemed to be influenced by management within the land-use practices. Nitrogen, phosphorus, potassium and zinc were significantly higher (p<0.05) in land under grazing while calcium and magnesium, were significantly higher (p<0.05) under fallow land. As expected, bare land had the lowest concentration of all the nutrients studied. The presence of animals around Acacia erioloba trees contributed to higher concentration of nutrients in land under grazing. The differences in the values of biological properties were considered to be likely due to higher plant biomass on the topsoil compared to the subsoil that increased the microbial activity. The improved biological properties are thought to have improved the nutrient concentration through processes such as mineralisation of nutrients from organic matter. With the exception of phosphorus (P), potassium (K) and zinc (Zn), concentration of all other nutrients (N, Ca, Mg and Mn) was not significantly different (p<0.05) in soil from beneath the tree canopy and those from beyond the tree canopies in all land-use practices. Topsoil (0-1 0 cm) had, significantly higher (p<0.05) concentration of all nutrients and biological properties that were measured compared to the sub soil (10-20 cm). This was attributed to the fact that much of the decomposition of soil organic matter takes place on the surface layer of the soil where most of the organic materials are added. Nutrient uptake from deep soil layers by roots of the trees may be another important mechanism that could enrich surface soils beneath Acacia erioloba tree with nutrients. The availability to a wheat crop of the nutrients found beneath the canopies of Acacia erioloba was evaluated using a "Neubauer" seedling technique in a glasshouse. Wheat seedlings were grown into PVC pots filled with soils collected from beneath and beyond the tree canopies. The wheat that was grown in soils collected beneath Acacia erioloba trees had significantly higher (p<O.OS) growth ~d nutrient uptake than that grown in soils from beyond tree canopies. Plant height, dry matter yields and nutrient uptake by the wheat seedlings were in the order fallow>grazing>bare land. The plant height were 20.9, 16.4 and 14.2 cm for fallow, grazing and bare, respectively. This was attributed to the high accumulation of organic matter from different sources such as leaf litter, grass residues and animal wastes under fallow and grazing land. Fallow and grazing promotes large organic matter inputs and therefore create conditions that favour rapid decomposition of organic matter and mineralisation of nutrients. Correlation coefficients between soil nutrients and nutrients in the tissues of wheat show that there was a strong and significant relationship between the two. It was suggested from these results that Acacia erioloba trees has a potential to be used in agroforestry systems within the farming systems of the small-scale farmers in the semi-arid savanna ecosystem of the North-West Province. Such systems could include agrislviculture and sylvopastoral. If Acacia erioloba trees are to be included in agroforestry systems, the densities need to be increased. This would imply increasing their propagation. More techniques of propagating the tree need to be researched. The nitrogen fixing potential of Acacia erioloba needs to be thoroughly investigated. / Thesis (M.Sc (Agric.) North-West University, Mafikeng Campus, 2003

Savannas are globally important ecosystems characterized by the coexistence of trees and grasses. Woody plants, which are slow-growing dominant life forms, influence the physiognomic structure and function of savanna ecosystems. Their density and distribution provides sustenance to a vast and unique savanna biodiversity, by forming a major source of food material to large mammalian herbivores, sheltering them and through their facilitation of diverse plant species. Savanna tree existence is strongly affected by factors that determine their sapling recruitment. We defined „sapling‟ as a young tree, in the first season of its growth, which does not depend on cotyledonary reserves (=seedling stage) and relies on external resources to grow further. Sapling recruitment may strictly be defined as the progression of a young plant from seedling to sapling stage. However, we believe that savanna tree saplings, present within the grass layer in the initial years of their growth, are equally vulnerable to environmental stresses. This study examines the factors affecting tree sapling establishment in a humid savanna (1250 mm mean annual precipitation). Additionally, the effects of fire were tested in a greenhouse experiment. Dominant species from humid savannas (> 1000 mm MAP), Acacia karroo, Acacia sieberiana, Schotia brachypetala and Strychnos spinosa, and mesic savannas (approx. 750 mm MAP), Acacia nigrescens, Acacia tortilis, Colophospermum mopane and Combretum apiculatum, were studied. In this thesis I examined the effects of resource availability (water, nutrients and light), disturbances (fire and herbivory) and competition (grass) on the sapling ecology of these species. Sapling recruitment and growth were assessed in terms of survival and aboveground growth responses, i.e. total biomass, stem growth rates (used as proxy measures for assessing persistence) and leaf biomass proportion (important for producing root reserves necessary to resprout). I studied the effects of fire and a nutrient gradient on survival and growth of four Acacia species in the presence of grass competition, in a controlled greenhouse experiment. Generally, Acacias invest in defenses after herbivory. I also determined their physical and chemical defense investments in this experiment. Sapling survival was not influenced by nutrients but highly varied among the species due to fire, indicating that fires may have a differential effect on species composition at a landscape scale. Intermediate levels of nutrients were found to be beneficial for sapling growth than high and low levels. This may be due to an increase in grass competition at higher levels of nutrients. Fires did not have a positive influence on sapling defence investment. To evaluate the relative importance of resource availability on sapling tree recruitment and its interactions with grass competition, I tested the effects of water (frequent irrigation vs. rainfall), shade (presence vs. absence), nutrients (addition vs. no addition) and grass competition (presence vs. absence) on sapling survival and growth under controlled field conditions in a humid South African savanna. Treatments did not have an effect on sapling survival, indicating that mortality is not defined by resource availability and grass competition in humid savannas. Shade had the greatest negative effect on sapling growth, suppressing the beneficial effects of nutrients and absence of grass competition. Nutrient limitation and grass competition had a relatively small influence on savanna sapling growth. Frequency of water availability had no effect on sapling growth, perhaps owing to high rainfall experienced over the experimental period. Therefore, canopy shade can be considered to be an important driver of tree dynamics in humid savannas with some degree of influence by nutrient availability and grass competition. The effects of clipping (i.e. simulated herbivory of grass and tree saplings) as influenced by nutrient availability and grass competition were examined on sapling survival and growth of all study species in a humid savanna. None of the treatments had an effect on sapling survival. This signifies that herbivory alone cannot significantly decrease plant density in humid savannas. However, tree saplings grew taller with a reduction in diameter and overall biomass, implying that saplings may become more susceptible to fires after herbivory. Nutrient addition and grass competition in general had a positive and negative effect, respectively, on sapling growth. This response was prominent in the stem length growth rates of defoliated saplings of one humid and two mesic species. These results imply that clipping (or herbivory) is the major factor reducing sapling vigour to establish, but is affected by both grass competition and nutrient availability. This study shows that fire has a differential effect on sapling survival of different species, particularly between humid savanna species. Light interception among all other resources limits the recruitment of saplings into adult size classes. Clipping, nutrient availability and grass competition had a relatively small direct effect, but may interact with other factors to alter sapling establishment dynamics. Wet-season droughts in humid savannas are not a hindrance to tree establishment because sapling survival was not dependent on frequency of rainfall. Thus, in humid savannas, fires can have a major impact on tree species density and composition while canopy shade has a very high potential to alter tree distribution. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.

Savanna degradation is an environmental problem occurring in most countries around the world and it poses threats to biodiversity conservation, the food industry, and other economic sectors. According to FAO, South Africa’s rangelands exhibit the highest rate of fragmentation in comparison to range ecosystems in neighbouring countries including Lesotho and Swaziland, and consensus among researchers is that communal rangelands are more degraded than commercial rangelands. Although researchers and communities have identified the occurrence of land degradation in communal savannas at a local scale, land degradation has been poorly estimated because little has been done to quantify the extent and dynamics of perceived and observed changes associated with land degradation. The main goal of this study is to provide empirical insights on the direction of changes in the communal savannas of Nkonkobe Local Municipality in order to inform policy formulation and implementation. Additional to the communal sites is a private farm included for comparative analysis of trends in communal and commercial savannas. Landsat imagery was used to map, assess, and quantify the extent of land degradation in Nkonkobe Local Municipality, over a period of 30 years between 1984 and 2014. Field investigations were undertaken in June 2015 to acquire reference data to guide supervised classification of Landsat images. Three algorithms (Mahalanobis-distance, Minimum-distance, and Maximum likelihood classification) were compared to identify a classifier that produced the best results. The maximum likelihood classifier produced the best results with classification accuracy levels of 95.24 percent, 89.66 percent, and 95.65 percent for Honeydale Farm, Thyume, and Sheshegu respectively. Regression analysis revealed that both communal and private lands have experienced statistically significant increases in bush encroachment and decreases in surface water. Communal savannas have been confronted more by expansion of built-up area, decrease in open grassland, abandonment of arable land, soil erosion, and a steady invasion by Acacia Karroo compared to the privately owned commercial farm. The land cover changes measured through this investigation suggest an environmental shift that threatens biodiversity and agricultural activity. The study provides empirically informed insights about the direction to which these savannas are changing with the hope that the findings will prompt formulation and implementation of effective policies.

This thesis explores techniques which ultimately strive to optimize production systems in rangeland areas of southern Africa. By linking spatially significant, satellite derived data to practical measurements of vegetation structure, valuable insight has been derived on processes of ecosystem function, in the Sabi Sand Game Reserve. A broad ecosystem response mechanism has been established from a conventional Normalized Differentiation Vegetation Index (NDVI). By responding to increases in production, which are driven by disturbance, this index has allowed quantitative systems theory in savanna to be tested and refined. Methods of biomass and production estimation which are specifically designed to reduce the cost and time involved with the more conventional method of destructive harvesting have been tested in the savanna at the Sabi Sand Game Reserve. Results from these estimates relate well with data derived through destructive harvesting in structurally similar savanna. Moreover, by relating the above-ground woody production estimates to remere sensing indices, it was possible to demonstrate that the problem of extrapolation, universal to most biomass and production studies can be overcome. Since remote sensing encompasses an array of tools fundamental to rangeland inventory, monitoring and management, valuable spatially significant information pertaining to ecosystem structure and function has been provided for managers in the Sabi Sand Game Reserve.

A thesis submi.tted to the Faculty of Science, University of the witwatersrand, Johannesburg I in the fulfillmen,,;"o:f' 't\ :he requirements of the Degree of Magister Scienta~. June 1992 / The present study was undertaken; withirl the South African " savannas, to provide "insight into a j;unctional classification of aavanna plants using ecophY$iologiLcal charact~:t's.THe pri.mary r.:>bjective of this study Was to investigate the vari.ation of these tt'aits throughout: the savanna, aridto relate this variation to plant avail.able moisture and nU~l'ie~~s• !t was conclu.ded that~ 1) no formal or specialized strategies have evolved within a number of the study sites, .2) unlike the woody component I neither divergellce nor convergence was demonstrated within the grass layer, c' 3) plant aVailable nutrients did not appear to be a major determinant of either component. Although plant available moistur~ proved to be unimportant in the woody layer, it did playa role as a determinant of the grass layer, and 4) constancy of the plant traits was not demonstrated to \": OCCllr over the gr~~ing season. A succeisf',\lclassification' would require the components to be separat~pl specific determinan.ts be identified for each component, and an element of time be included into both edaphic and biotic measurements.