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).

The patch structure of the grass sward at Kroomie (26°25'38"E 33°48'30"S) in a semi-arid savanna in the Eastern Cape, South Africa, was investigated. The study was conducted on long term grazing trials on five treatments varying in stocking rate (SR; recommended (low) and 1.5 x recommended (high), grazing system (continuous and rotational), and animal type (cattle and sheep). The treatments studied were CR (cattle, rotational stocking, low SR), CC (cattle, continuous stocking, low SR), CH (cattle, rotational stocking, high SR), SC (sheep, continuous stocking, low SR), and SR (sheep, rotational stocking, low SR). Rainfall during the two years of the study (1997/98 and 1998/99) was slightly below the mean average rainfall of the area (66 and 84% of the mean of 519 mm, respectively). Analysis of sward height data using Maximum Likelihood Estimation reflected a bimodal height structure in all treatments. Due to a high overlap of the two distributions in some cases, however, the height at which to separate patches (short grass) from non-patches (tall grass) could not be determined. Canonical Correspondence Analysis (CCA) was used to relate species composition to sward height. It emerged that there are two distinct grass communities at Kroomie, and these are associated with sward height (i.e. patches and non-patches). The interface (in cm) between these two communities, as determined using Two Way Indicator Species Analysis (TWINS PAN) was 6 cm, and this value was subsequently used to discriminate between patches and non-patches. Sward structure was affected by treatments. Animals (cattle and sheep) stocked rotationally at low SR's grazed less than a third of the total area, and this grazing was concentrated primarily in small patches (< 6 m; length is used as a linear indicator of patch size). Animals stocked continuously at low SR's grazed approximately half the area, in small and large (up to 40 m) patches. Animals in the CH treatment grazed approximately two-thirds of the area, in both small and large patches. There was an inverse relation between the size of patches and the size of non-patches, as expected. Nine common grass species were related to sward height. Digiteria eriantha, Eragrostis racemosa, Eustachys paspaloides, and Microchloa caffra were associated with short swards, while Cymbopogon pluronodis, Eragrostis chloromelas, and Sporobolus fimbriatus were associated with tall swards. Themeda triandra (themeda), the most abundant grass at Kroomie, was principally associated with tall swards, but was present at all sward heights. Applying CCA demonstrated a considerable difference between the species composition of patches and of non-patches. There was also a difference in composition between treatments, although these were not as pronounced. Patches reflected a higher species diversity than non-patches. There was a significant (P<0.05) effect of treatment, and of an interaction of treatment by sward structure (i.e. patches and non-patches), on the density of themeda plants. The density of themeda plants was positively correlated with patch size, which suggested that themeda plants that have been grazed may suffer fatal competition from ungrazed neighbours. Anecdotal evidence suggested that patches are stable over the medium term, and that non-patches that are grazed during a drought return to a non-patch structure after rainfall. There was no evidence to support the contention that rotational stocking reduced patch-selective grazing, nor that the species composition of rotationally stocked treatments was better than continuously stocked treatments. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2003.

This study is an effort to provide new information on the effects of isolated tree canopies on understory vegetation composition and soil characteristics of northern Indiana black oak savannas. Temperate savannas in the United States have been greatly altered by human activities. Management of these areas is an important consideration for Midwest natural resource agencies. It is hypothesized that isolated trees within a savanna may alter the soil and plants around them, much in the same way that gaps in a forest canopy alter the plant composition and soil characteristics on the forest floor. In this study, isolated trees were selected in three northern Indiana black oak (Quercus velutina) savannas. Plots were located under the tree canopies and in adjacent open areas, in four directions from the tree stem. Populations of herbaceous plants were inventoried and the soil characteristics analyzed for both inside-canopy and outside-canopy plots. The environmental variables measured accounted for only about 20 percent of the variation in plant community between plots according to a Canonical Correspondence Analysis. Most of the variation in plant composition between plots was explained by pH, the amount of rain throughfall, and the thickness of the A horizon. It is clear that these black oak trees do alter the soil and plant composition around them. This information has implications for the long-term management of northern Indiana savannas. / Department of Natural Resources and Environmental Management

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

Bush encroachment is a major problem for the savannas supporting livestock in the Eastern Cape. Farmers employ chemical poisoning and mechanical clearing of woody vegetation to improve grass production. This thesis addressed the following questions. 1. Does soil fertility and hence, herbaceous production and/or quality increase beneath or between former bushclumps following woody clearing or poisoning? 2. Are chemical or mechanical control methods effective for all woody species? 3. Does bush density and height decline with increasing competition from the herbaceous layer? 4. Can fire and goats retard or revert woody re-establishment, thereby keeping these savannas open? A trial for assessing different methods of controlling bush was conducted near Kei Road. Initial treatments included chemical poisoning, mechanical clearing and a control, each replicated eight times in 0.36 hectare plots. Follow-up treatments were control, fire, goats, and the combination of fire and goats each replicated twice per primary treatment. Two additional mechanically cleared plots were oversown with Chloris gayana seeds. Herbaceous production, species composition, foliage quality and soil fertility, and mortality, recruitment, height increase and density of woody individuals were monitored for five seasons. Mechanical clearing of the woody vegetation increased soil fertility, except total nitrogen, and that explained the dramatic response in grass production that endured for the first four seasons since clearing. The periphery and ex-bushclump zones were characterised by increased colonization of Panicum maximum while there were no changes in frequencies of other key herbaceous species in all vegetation zones. Acacia karroo and woody "weeds" (Solanum incanum, Berkheya bipinnatifida) established from seed while all other woody species recruited mainly from coppicing. Seedling recruitment and resprouting resulted in high densities of woody stems and individuals by the second season after clearing when compared with the pre-clearing levels. Oversowing cleared areas with pasture grasses did not only increase grass production but also reduced the density of coppicing woody plants and "weeds". Chemical treatments mirrored the controls in terms of grass production, except during a very wet season, and species composition. Although encroaching woody species (e.g. Scutia myrtina, Maytenus heterophylla and Trimeria trinervus) were susceptible to poisoning, woody plant density was not reduced. Multi-stemmed woody individuals were resistant to poisoning. Fire and goats kept most coppicing woody plants short, less than half a metre, after three seasons of browsing and also improved grass production in the dense bushclumps suggesting that these clumps were being opened up. However, high browsing pressure forced goats to graze more hence this effect was masked. This study indicates that chemical and mechanical control of bush are economically unsustainable for beef and mutton production, at least in the medium term. Fire and goats are appropriate as a follow-up strategy for retarding woody regrowth, keeping bushclumps open, improving grass production and economic viability of mechanical clearing. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2000.

Thesis (doctoral)--Universität zu Göttingen, 2003. / Includes bibliographical references (p. 139-155).

Thesis (Ph. D. (Zoology and Entomology))--Rhodes University, 2005.

Thesis (Ph. D.)--University of Pretoria, 2005. / Title from PDF t.p. (viewed Mar. 27, 2006). Includes bibliographical references.

Orientadores: Paulo Sérgio Moreira Carvalho de Oliveira, André Victor Lucci Freitas / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-19T22:18:27Z (GMT). No. of bitstreams: 1 Silva_DaniloGermanoMunizda_M.pdf: 3019678 bytes, checksum: c1529979d45609cac62d29ee7dd332fe (MD5) Previous issue date: 2011 / Resumo: Em muitos ambientes tropicais, estações chuvosas se alternam com períodos de seca. A estação seca é um período de menor disponibilidade e qualidade nutricional de folhas, sendo, portanto, um período desfavorável para insetos herbívoros e gerando as oscilações sazonais em suas populações. O cerrado é um bioma neotropical sazonal, que inclui formações de savana (cerrado sensu stricto), e onde o clima se caracteriza por uma estação quente e chuvosa de outubro a abril e uma fria e seca de maio a setembro. A produção de folhas novas se concentra geralmente na estação chuvosa, tornando este um período favorável para muitos insetos herbívoros tais como as borboletas. Em seu estágio larval, as borboletas são herbívoros vorazes cujas populações comumente oscilam de acordo com a disponibilidade de folhas adequadas ao desenvolvimento dos imaturos. Borboletas podem ser divididas funcionalmente em duas guildas: as que se alimentam em sua forma adulta do néctar de flores, e aquelas que se alimentam dos líquidos oriundos de frutos em decomposição, seiva de árvores, carcaças de animais e excrementos. As espécies do segundo grupo são conhecidas como borboletas frugívoras. A guilda de borboletas frugívoras tem sido amplamente utilizada em estudos de ecologia de comunidades devido à facilidade de captura usando armadilhas com iscas de fruta fermentada, e a relativa facilidade de identificação. Entretanto, poucas vezes esta comunidade foi estudada em ambientes abertos, e raramente em trabalhos envolvendo sazonalidade. Nesta dissertação exploramos a sazonalidade das borboletas frugívoras do cerrado sensu stricto em dois capítulos. No primeiro abordamos a composição da comunidade, suas alterações ao longo do ano bem como suas oscilações de abundância. A maior abundância de borboletas ocorreu no meio da estação chuvosa, enquanto o pico de riqueza ocorreu ao final desta estação. Satyrini foi o grupo mais abundante na estação chuvosa (principalmente Yphthimoides manasses), enquanto na estação seca foi Biblidinae (principalmente Hamadryas februa). No segundo capítulo analisamos em detalhe a relação fenológica entre a borboleta Eunica bechina e sua planta hospedeira, o pequizeiro Caryocar brasiliense. Esta planta possui nectários extraflorais atrativos para formigas, que patrulham a planta e atacam as larvas de E. bechina. Observamos a maior ocorrência de larvas no início da estação seca, quando ocorreu a maior produção de folhas. Ovos e larvas estavam presentes em quase todos os meses de amostra, exceto no final da estação chuvosa. Propomos que este seja um período de inatividade reprodutiva na espécie, devido à baixa disponibilidade de folhas jovens / Abstract: In many tropical environments, rainy and dry seasons alternate. The dryer season has decreased leaf availability and the nutritional quality of leaves is also low - thus it is an unfavorable period for herbivorous insects and generates seasonal oscillations in their populations. The cerrado is a neotropical seasonal biome characterized by a hot/rainy and a cold/dry season. Leaf production is generally concentrated in the rainy season, which is the favorable period for herbivorous insects such as butterflies. In its larval stage, butterflies are voracious and specialized herbivores, and their populations commonly oscillate according to the availability of adequate leaves for immature feeding. Butterflies can be categorized in two functional guilds according to the food resources utilized by the adults: one group feeds on flower nectar, whereas another group of species feed on the liquids from rotting fruits, carcasses and excrements, and also plant sap. The latter group is known as fruit-feeding butterflies. Fruit-feeding butterfly guild has been widely used in studies of community ecology because they are easily captured using traps with fermented fruit, and also easily identified. Surprisingly, however, fruit-feeding butterflies have rarely been studied in seasonal, open environments. In this dissertation we investigated the seasonality of fruit-feeding butterflies in the cerrado sensu stricto. In the first chapter we decribe the composition of the community, changes through the year, and oscillations in its abundance. The greatest abundance occurred in the mid rainy season, while richness peaked at the late rainy season. Satyrini was the most abundant group in the rainy period (mainly Yphthimoides manasses), whereas Biblidinae (mainly Hamadryas februa) was more common in the dry season. In the second chapter we analyze in detail the phenological relationship between the butterfly Eunica bechina and its hostplant Caryocar brasiliense. The larvae feed only on the young leaves of C.brasiliense that bear extrafloral nectaries, which attract ants that patrol the plant and attack E. bechina larvae. We observed the larger occurrence of larvae in the early rainy season, when most young leaves are produced. Eggs and larvae where present at almost all sampling months, except in the late rainy season. We suggest that this is a period of reproductive inactivity in the species, due to the low availability of young leaves / Mestrado / Ecologia / Mestre em Ecologia

Sociality represents one of the major evolutionary transitions in life: a transition from individuality to societies as complex as our own. Animals exhibit a wide variety of societies, from temporary aggregations, such as schools of fish, to complex organizations where individuals maintain stable relationships, such as cooperative groups in birds, mammals, and eusocial ants. However, the diversity of social systems and the mechanisms driving the formation of complex societies remain unclear. In this dissertation, I aim to understand a less known complex social system, a colonial cooperatively breeding bird on the African savannah, grey-capped social weavers (Pseudonigrita arnaudi). I monitored daytime and nighttime relationships among more than 600 birds in over 100 colonies across three subpopulations for five breeding seasons using an auto-tracking system. In Chapter 1, I examine the social organization of this species and test the role of kinship in the organization of the society. In Chapter 2, I focus on the inter-annual variation in the fission-fusion process of colonies and test how social factors (i.e., group membership and colony membership) and ecological conditions (i.e., rainfall) may underlie individual and group decisions about settlement of colonies. In Chapter 3, I investigate the conflict in the form of infanticide behavior (i.e., egg tossing) in this social system and test nest predation as an alternative hypothesis against a presumed hypothesis that group conflict is the cause of the tossing behavior. In sum, my dissertation provides the first detailed study of a colonial and cooperatively breeding bird with high resolution of movement at the individual level. Understanding a new social system will not only expand our knowledge of the variety of animal societies, but will also give insight into how social complexity has evolved, including our own.