Thesis (MScConEcol (Conservation Ecology and Entomology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Two populations of Acacia mellifera were noted in Pniel, which is a semi-arid savanna, near Kimberley in the Northern Cape province of South Africa. One population appeared on a rocky, andesitic laval ridges (soil pHKCL 6.5-7.0) along the Vaal river. The other appeared in a sandveld area (soil pHKCL 4). Bush encroachment by A. mellifera was found to be more extensive on the rocky areas than in the sandveld and the two habitats differed extensively on soil pH, clay and silt contents and also on water holding capacities. The rocky habitat was thus deduced to have a higher CEC. Seeds were sampled on a logarithmic scale for allozyme analysis and also randomly in each of the two habitats for local adaptation tests, in which case lime (CaCO3) and organic matter (cow-dung) were used in a completely-crossed design. Detected interaction effects (between population source and pH; population source and organic matter and between pH and organic matter) and significant differences could not separate the two populations as the differences occurred across populations. Random genetic differences leading to phenotypic plasticity in the two observed populations, might be responsible for the observed phenotypic differences. Allozymic data showed no significant differences between the two populations and the genetic distance between and within the populations also confirmed that the two populations had not genetically differentiated. The Mantel Test on the two populations, showed nonsignificant results. Nei‟s UPGMA dendrogram revealed that the game farm subpopulations were more primitive and genetically related to each other. Despite differences in allozyme frequencies, between the sampled sites, genetic differentiation was found to be low (FST = 0.337). Nei‟s (1972) original measures of genetic distance ranged between 0.871 and 1.000 with a mean of 0.949 ± 0.053. The study concluded that the two observed populations had not genetically differentiated and no local adaptation could be established rather phenotypic plasticity was evident and resulted in the observed divergent growth forms. Nonetheless, the overall direction of spread of encroachment appeared to be the eastward. / AFRIKAANSE OPSOMMING: Twee bevolkings van Acacia mellifera is gevind in Pniel, wat „n semi-ariede savanna is naby Kimberley in die Noord-Kaap provinsie van Suid-Afrika. Een bevolking het voorgekom op klipperige andesitiese lava riwwe (grond pHKCL 6.5-7.0) al langs die Vaalrivier. Die ander het voorgekom in „n sandveld area (soil pHKCL 4). Bos-oorskryding deur A. mellifera was meer uitgebreid op die klipperige areas as in die sandveld en die twee habitats het noemenswaardig verskil ten opsigte van grond pH, klei en silt inhoud asook waterhoukapasiteit. Dit kan was dus afgelei word dat die klipperige habitat „n hoër CEC het. Die sade was versamel op „n logaritmiese skaal vir allosiem-analise en ook ewekansig in die twee habitats vir lokale aanpassings toetse. In dié gevalle was kalk (CaCO3) en organiese material (koeimis) gebruik in „n totaal-gekruisde ontwerp. Bespeurde interaksie effekte (tussen bevolkings bron en pH; bevolkings bron en organiese material en tussen pH en organiese material) en noemenswaardige verskille kon nie die twee bevolkings skei nie, aangesien die verskille voorgekom het regdeur die twee bevolkings. Ewekansige genetiese verskille wat lei tot fenotipiese plastisiteit tussen die twee waargeneemde bevolkings mag dalk verantwoordelik wees vir die waargeneemde fenotipiese verskille. Allosiem-data het geen beduidende verskille gelewer tussen die twee bevolkings nie en genetiese afstand binne en tussen die bevolkings het ook bevestig dat die twee bevolkings nie geneties gedifferensiëer is nie. Die Mantel toets op die twee bevolkings het geen beduidende resultate gelewer nie. Nei se UPGMA dendogram get gewys dat die wildsplaas bevolkings was meer primitief en geneties verwant aan mekaar. Ten spyte van die allosiem frekwensies tussen die gemonsterde gebiede, was die genetiese differensiasie laag (FST = 0.337). Nei (1972) se oorspronlike meeting van genetiese afstand het tussen 0.871 en 1.000 beloop met „n gemiddeld van 0.949 ± 0.053. Die studie het bepaal dat die twee waargeneemde bevolkings nie geneties gedifferensiëer het nie en dat geen lokale aanpassing teenwoordig was nie. Fenotipiese plastisiteit was duidelik waarneembaar en het gelei tot die divergerende groeivorme. Nieteenstaande, was die algehele rigting van oorskryding ooswaarts.

Thesis (MScFor)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: Increases in woody plant density ('bush encroachment') reduce livestock production and biodiversity. By convention, soil moisture, soil nutrients, fire and herbivory are regarded as the principal factors governing the tree-grass ratio of savannas. An experiment with a completely-crossed design was employed to investigate woody seedling (Acacia me/lifera) recruitment near Kimberley, Northern Cape, South Africa, after fire and under conditions of maximum-recorded rainfall, nitrogen addition and grazing. The field experiment was repeated as a garden experiment to determine if the two experiments yield comparable results. Tree germination in the field was extremely low, probably due to below-average natural rainfall in plots that only received natural rain, and insufficient watering frequency in irrigated plots. As a result of low germination, none of the treatments (rain/nitrogen/fire/grazing) had a significant effect on tree recruitment in the field experiment. The duration of the experiment (2000/2001 growing season) was insufficient for the treatments to affect grass composition, although the high rainfall treatment and grazing exclusion significantly improved grass cover and height. The garden experiment showed that frequent watering, no nitrogen addition and grass clipping significantly enhanced tree germination and survival (termed 'recruitment'). There were also significant interactions among rain, nitrogen and grazing in their effects on tree recruitment. The effects of rain on tree recruitment were more pronounced under nitrogen supplementation and vice versa. Similarly, high rain and high nitrogen enhanced the effect of grazing on tree recruitment. It is inferred that above-average rainfall years with frequent rainfall events are required for mass tree recruitment. Tree seedlings can further benefit from space and resources which are made available through grass defoliation. Conversely, nitrogen enrichment improves the competitive ability of the fast-growing grasses relatively more than that of the N2-fixing tree component, thereby suppressing tree recruitment. In contrast to conventional wisdom that grazing alone causes encroachment, it is suggested that there are complex interactions between the abovementioned factors and 'triggering' events such as unusually high rainfall. Contrary to many claims that equilibrium models are inappropriate for explaining savanna dynamics, it was shown that consumer-resource theory has explanatory power for bush-grass dynamics of the savanna studied. The state-space approach that was used facilitated the understanding of savanna dynamics and enabled predictions about the system's response to perturbations. The applicability of consumer-resource theory to semi-arid nutrient-poor savannas confirmed the importance of resource competition in structuring natural systems. / AFRIKAANSE OPSOMMING: Toenames in die digtheid van houtagtige plante ('bosverdigting') verlaag veeproduksie en biodiversiteit. Volgens konvensie word grondvog, grondvoedingstowwe, vuur en beweiding beskou as die belangrikste faktore wat die boom-gras verhouding van savannas bepaal. 'n Volledig-gekruisde ("completely crossed") eksperiment is ontwerp om boomsaad-ontkieming (Acacia mellifera) naby Kimberley, Noord-Kaap, Suid- Afrika, te bestudeer na 'n brand en onder toestande van maksimum-aangetekende reënval, stikstof toevoeging en beweiding. Die veldeskperiment is herhaal as 'n tuineksperiment om vas te stel hoe resultate van die twee eksperimente vergelyk. Boomsaad-ontkieming was uiters laag in die veld, waarskynlik weens ondergemiddelde reënval in persele wat slegs natuurlike reënvalontvang het, en 'n te lae benattingsfrekwensie in die besproeide persele. As gevolg van lae ontkieming in die veldeksperiment, het geen behandeling (reënval/stikstof/brand/beweiding) boomsaad-ontkieming beduidend geaffekteer nie. Die duur van die eksperiment (2000/2001-groeiseisoen) was te kort vir die behandelings om grassamestelling te beïnvloed, alhoewel besproeiing en geen beweiding die grasbedekking en -hoogte betekenisvol verhoog het. Die tuineksperiment het getoon dat boomsaadontkieming en vroeë oorlewing (genoem 'vestiging') betekenisvol verhoog is deur gereëlde benatting, geen stikstof toevoeging en die sny van gras. Daar was ook beduidende interaksies tussen reën, stikstof en beweiding in hul invloed op boomvestiging. Die reënbehandeling het 'n groter uitwerking op boomvestiging gehad onder stikstoftoevoeging en vice versa. Hoë reënval en stikstoftoevoeging het ook die invloed van beweiding op boomvestiging versterk. Die afleiding is dat bogemiddelde reënvaljare met gereëlde reënbuie 'n vereiste is vir grootskaalse boomvestiging. Boomsaailinge kan verder voordeel trek uit die spasie en hulpbronne wat beskikbaar raak wanneer gras ontblaar word. Daarteenoor verhoog stikstofverryking die mededingendheid van die vinniggroeiende grasse meer as dié van die N2-bindende boomkomponent, met die gevolg dat boomvestiging onderdruk word. In kontras met die konvensionele veronderstelling dat beweiding opsigself bosverdigting veroorsaak, word voorgestel dat ingewikkelde interaksies plaasvind tussen die bogenoemde faktore en ander 'sneller-gebeurtenisse', soos buitengewoon hoë reënval. In teenstelling met baie aansprake dat ekwilibrium modelle ontoepaslik is om savanna-dinamika te verklaar, is getoon dat die verbruikers-hulpbron teorie ("consumer-resource theory") oor verklaringsvermoë beskik vir boom-gras dinamika van die savanna wat bestudeer is. Die staat-spasie ("state-space") benadering gebruik, het begrip van savanna-dinamika bevorder en voorspellings moontlik gemaak aangaande die sisteem se reaksie op versteurings. Die toepaslikheid van verbruikers-hulpbron teorie vir semi-ariede, nutriënt-arm savannas bevestig dat kompetisie vir hulpbronne 'n sentrale rol speel in die strukturering van ekologiese sisteme.

This document consists of three sections, and they are the academic paper (section 1), literature review (section 2) and research methodology (section 3). The academic paper consists of the purpose of the research, the summarised literature review, summarised research methodology and the research findings. The literature review section is a detailed review of literature used in this study. The research methodology section explains the research methodology and design which was employed in this study and it gives more details than the summarised version of the academic paper section. This summary integrated all the elements of section 1, section 2 and section 3. The purpose of this research is to identify the main problems that the Department of Environment and Nature Conservation (DENC) could encounter during the implementation and use of a performance management system, based on employee perspectives. The objectives of this research are therefore: to establish how often a particular problem has been encountered during the implementation and use of a performance management system in DENC; to identify the impact of various problems on the implementation of a performance management system, to establish whether these problems can be easily solved or not, and to analyse the problems associated with the implementation of a performance management system, as well as making recommendations for the successful implementation of a performance management system in the future. In this study, the researcher employed both quantitative and qualitative research approaches, informed by post-positivism as research orientation. The data collection techniques employed in this research include survey questionnaires and individual interviews. The survey questionnaire was answered by fifty respondents, and interview questions were answered by four respondents. The ethical issues were addressed by writing a letter to the Head of Department and getting authorisation to complete the research and informing respondents of their right to withdraw and to participate voluntarily. The findings indicate that the problems are either sometimes encountered or rarely encountered, and the division is about fifty percent of those sometimes encountered to those rarely encountered. This research indicates that most of the problems have a moderate impact on the use and implementation of a performance management system. The lack of management has a high impact, and a lack of positive attitude to performance management system (PMS) certainly has an impact on the use and implementation of the performance management system. Items such as the problem of information and communication technology (ICT) which does not support PMS adequately, and defining too many key performance indicators (KPI), have a small impact on the use and implementation of the performance management system. There are three problems which are difficult to solve and they are: lack of management commitment, organisational members‟ lack of positive attitude to the PMS and an insufficient period of commitment from management to PMS. This research indicates that most of the problems associated with PMS are moderately easy to solve. Two other problems that are easy to solve include the problem where there are too many KPIs defined and the problem where there is no organisational member appointed to take ownership of the PMS. According to this research, the top ten ranking problems have high ranking scores and this indicates that they can create major difficulties for the DENC in implementing the performance management system, and the chance of encountering these problems is high in the DENC in comparison to other problems. Almost all the problems ranked in the top ten seem to score highly in terms of the severity of their impact, and therefore this means that these are the problems which have an impact and, when they are not easily solved, they can become a tenacious issue for the organisation.

The Paleoproterozoic Transvaal Supergroup in the Northern Cape Province of South Africa is host to high-grade BIF-hosted hematite iron-ore deposits and is the country’s most important source of iron to date. Previous work has failed to provide a robust and all-inclusive genetic model for such deposits in the Transvaal Supergroup; in particular, the role of hydrothermal processes in ore-genesis has not been adequately clarified. Recent studies by the author have produced evidence for hydrothermal alteration in shales (Olifantshoek Supergroup) stratigraphically overlying the iron-ore intervals; this has highlighted the need to reassess current ore-forming models which place residual supergene processes at the core of oregenesis. This thesis focuses on providing new insights into the processes responsible for the genesis of hematite iron ores in the Maremane anticline through the use of newly available exploration drill-core material from the centre of the anticline. The study involved standard mineralogical investigations using transmitted/reflected light microscopy as well as instrumental techniques (XRD, EPMA); and the employment of traditional whole-rock geochemical analysis on samples collected from two boreholes drilled in the centre of the Maremane anticline, Northern Cape Province. Rare earth element analysis (via ICP-MS) and oxygen isotope data from hematite separates complement the whole-rock data. Iron-ore mineralisation examined in this thesis is typified by the dominance of Fe-oxide (as hematite), which reaches whole-rock abundances of up to 98 wt. % Fe₂O₃. Textural and whole-rock geochemical variations in the ores likely reflect a variable protolith, from BIF to Fe-bearing shale. A standard supergene model invoking immobility and residual enrichment of iron is called into question on the basis of the relative degrees of enrichment recorded in the ores with respect to other, traditionally immobile elements during chemical weathering, such as Al₂O₃ and TiO₂. Furthermore, the apparently conservative behaviour of REE in the Fe ore (i.e. low-grade and high-grade iron ore) further emphasises the variable protolith theory. Hydrothermally-induced ferruginisation is suggested to post-date the deposition of the post-Transvaal Olifantshoek shales, and is likely to be linked to a sub-surface transgressive hydrothermal event which indiscriminately transforms both shale and BIF into Fe-ore. A revised, hydrothermal model for the formation of BIF-hosted high-grade hematite iron ore deposits in the central part of the Maremane anticline is proposed, and some ideas of the author for further follow-up research are presented.

Background and purpose. The purpose of the study was to determine the costs incurred on the average length of stay (ALOS) on patients with Human Immunodeficiency Virus (HIV) and Acquired Immune Deficiency Syndrome (AIDS) related illnesses admitted in hospital and whether there are any other significant costs involved. Method. A quantitative approach was used to collect data; analysed; interpretation and report writing. Purposive sampling and data collection was done using data collection sheet. This was a retrospective cost analysis data from in-patients records (record review) of ages from 15 years to 49 years both gender. Data analysis and presentation of information was presented by the use of tables; different types of graphs and the interpretation thereof. Results. The study found that males (63%) with HIV Human Immunodeficiency Virus (HIV) and Acquired Immune Deficiency Syndrome (AIDS) related illnesses had longer average length of stay in a hospital compared to females. However, females illustrated higher in-patient costs but majority of patients had costs of between R0–R17 500. Patients with longer hospital stay (>3 days of hospitalisation) had higher in-patient costs. Conclusion. The findings also showed that in-patient care costs were directly proportional to length of stay with higher costs for HIV and AIDS patient management care. Our findings are consistent with other studies regarding higher economic implications of care for HIV infected persons being almost as twice as people who are HIV negative due to longer periods of hospitalisation. / Health Studies / M.A. (Public Health)

Thesis (MPhil) -- University of Stellenbosch, 2004. / ENGLISH ABSTRACT: This study describes and analyses the water services education and training needs of councillors in local authorities in the Northern Cape to enable them to implement their legislative framework in the new dispensation in South Africa. It is the proposition of this study that during the transitional period from 1994 to 2003 and thereafter, there is a likelihood of lack of capacity in most local authorities in the Northern Cape to execute their legislative requirements. This invariably imposes leadership responsibilities upon a range of stakeholders and councillors in Local Authorities (LAs), and creates the need for a redefined model of representation on the part of councillors "from resemblance to responsibility and responsiveness" (Sartori 1968: 465). Using literature review to analyse leadership responsibilities of councillors, four priority education and training (E&T) needs of councillors have been identified: • the need to understand water services policy and business cycle within the context of decentralisation and devolution of powers and functions • to local government; • the need for water services business programme management and planning skills; • the need to understand community participation in water services development plans and development processes; and • the need for conflict-resolution skills. Based upon inferences drawn from literature evidence, it is concluded that Local Government (LG) patterns of responses involving the application of managerial and analytical principles grounded firmly in the twentieth century Organisational Development (00) and public service management experience and thoughts, can neither explain nor remedy the complex variables of Local Government Developmental Agenda (LGDA) and/or the complex array of water crises that are unfolding in Northern Cape. Thus, for water services to remain a viable "instrument of humanity" especially at a municipal level, it is concluded that more effective E&T strategies are required to equip current and future councillors with intellectual water business tools to address the complex challenges that lie before them. Furthermore, an Outcomes Based Education (OBE) action-based strategy is offered as an alternative to the current traditional training approaches in Northern Cape. It is also clear from the researcher's interpretations and analysis of LGDA variables that the water services E&T needs and the relevant "gaps" identified are not simply questions of "how to do things". Rather an OBE action-based strategy under LGDA processes involves a fundamental reorientation of all participants in E&T programme for councillors that should be relevant to the special demands of the Northern Cape LAs and councillors. The researcher makes recommendations for enriching the sociology of LG studies, to match the skills requirements, given the complexity of LGDA and numerous challenges for competent and innovative councillors in LAs. Finally, this study is not intended to be exhaustive but rather to complement a number of education and training initiatives commissioned or under preparation by water sector stakeholders in line with Skill Development Act of 1998 and SAQA of 1995 (South African Qualifications Act) processes. KEYWORDS: Best Value Regime, Local Government Developmental Agenda, Spheres of government; local government; socio-economic & political dynamics in transition; decentralisation; constitutional powers and functions of local government; education and training (E&T) needs of councillors in water services; Northern Cape Province. / AFRIKAANSE OPSOMMING: Hierdie studie beskryf en ontleed die behoefte aan onderwys en opleiding (E&T) by raadslede in plaaslike owerhede in die Noordkaap, om hul moeilike taak te kan verrig in In veranderende beleidsomgewing in Suid Afrika. Die studie besin daaroor dat daar waarskynlik gedurende die oorgangstydperk vanaf 1994 tot 2003 en ook daarna, In tekort aan bevoedgheid om hul funksies te vervul, by heelwat plaaslike owerhede in die Noordkaap bestaan. Dit is deels In gevolg daarvan dat nuwe verantwoordelikhede op die skouers van die rolspelers en raadslede in plaaslike owerhede geplaas word. Die nuwe rol van raadslede word herdefinieer vanaf verteenwoordiging na verantwoording en optrede; "from resemblance to responsibility and responsiveness" (Sartori 1968: 465). Vier belangrike areas waar onderwys- en opleidingsbehoeftes ten opsigte van die leierskapsprofiel van Raadslede bestaan, is op grond van In literatuuroorsig ge'identifiseer: • die belangrikheid daarvan om beleid- en besigheidsaspekte van die lewering van waterdienste te verstaan teen die agtergrond van desentralisering en stelselmatige afwenteling van magte en funksies na die plaaslike owerheidsvlak; • die behoefte wat bestaan aan bestuurs- en beplanningsvaardighede met betrekking tot waterdienste en water-ekonomiese aspekte; • In begrip van die rol van die plaaslike gemeenskap in beplanning en uitvoer van ontwikkelingsprojekte vir die lewering van waterdienste; • konflikhanteringsvaardighede. Na aanleiding van die getuienis uit hierdie literatuurstudie word dit duidelik dat die heersende reaksie- en besluitnemingstyle van Plaaslike Owerheid (LG) wat spruit uit beginsels van organisasie ontwerp (00) wat dateer uit die vorige eeu en die staatsdienservaring en -denke van daardie era, nie die komplekse veranderlikes van die nuwe Plaaslike Owerheid Ontwikkelingsagenda (LGDA) kan verduidelik of aanspreek nie, en dus nie geskik is om In dreigende krisis in die Noordkaap te af te weer nie. am waterdienste in die toekoms as 'n voertuig vir die opheffing van agtergeblewe gemeenskappe te kan gebruik, veral op plaaslike owerheidsvlak, is dit belangrik dat huidige en toekomstige raadslede deur middel van effektiewe onderwys - en opleidingstrategiee toegerus word met water-ekonomie kennis en vaardighede. Sodoende sal hulle die komplekse uitdagings wat aan hulle gestel word, die hoof kan bied. 'n Aksie-gerigte strategie gefundeer op 'n uitkomsgebaseerde (aBE) kurrikulum, word voorgestel as plaasvervanger vir die huidige tradisionele onderwysbenadering in die Noordkaap. Dit is duidelik uit die outeur se interpretasie en ontleding van LGDA veranderlikes, dat die ge"identifiseerde onderwys- en opleidings behoeftes en gapings 'n heeltemal nuwe benadering vereis. Die benadering behels 'n deurdagte herorienterinq tot opleidingsprogramme vir raadslede in plaaslike owerhede (LG) in die Noordkaap. Die studie dra by tot die sosiologie van plaaslike owerheidstudie, en wys op die vaardighede, vermoens en innovasie-eienskappe van raadslede wat benodig word om die kompleksiteit van LGDA en die uitdagings in plaaslike owerhede aan te spreek. Ten slotte is die studie nie bedoel om volledig te wees nie maar om wei 'n bydrae te lewer tot die onderwys- en opleidingsinisiatiewe wat voortspruit uit die aksies van belanghebbendes in die water sektor in ooreenstemming met die Wet op Vaardigheidsontwikkeling (1998) en SAKWA (1995).

D. Tech. Engineering: Civil. / Aims to map and model the salinity trends in Vaal Harts irrigation schemes in Jan Kempdorp, Northern Cape Province of South Africa using Landsat SRS, GIS computational tools (IDRIS and ERDAS). The resulted maps and models will aid the effective management of salinity problem and thereby minimizing its occurrence in the future through planning and policy formulation, on the irrigation scheme within the context of environmental sustainability.

M. Tech. Architecture (Professional) / Over the last decade, South Africa (RSA) has experienced a substantial growth in the field of astronomy and astrophysics. Post 2005, the largest optical telescope in the Southern hemisphere, known by its acronym, SALT, was constructed in RSA. It is expected that by 2024, this country will host the largest array of radio telescopes in the world, the Square Kilometre Array (SKA). It could be argued that RSA is at the forefront of modern cosmological research. This exponential growth in the field of astronomy has resulted in local astronomical bodies and universities falling behind in astronomy education. This provides a unique opportunity to strengthen the latter. The aim of this dissertation is to design an International School of Astronomy and Astro-Tourism Centre. The proposed building aims to introduce a unique facility in the Northern Cape that would benefit the field of astronomy worldwide. The proposed facility is situated at the South African Astronomical Observatory (SAAO) in Sutherland. It is nested within the South-west-embankment of the mountain, currently hosting the Southern Africa Large Telescope (SALT). The resultant design takes on a linear building typology with radial aspects to document astronomical events. The project investigates the semi-arid Karoo climate and how the resultant architecture reacts to harsh environmental conditions.

The long-term economic viability and ecological integrity of savanna rangelands is being undermined by increasingly dense woody thickets at the expense of palatable herbaceous cover. This process is known as shrub- or bush-encroachment. Bush encroachment is a subset of a broader ecological riddle underlying the coexistence of woody and herbaceous vegetation that has been the subject of many ecological models. The ecophysiological mechanisms and interactions between trees and grasses on which most assumptions of ecological models are premised have seldom been tested empirically. This document synthesises the results of greenhouse and field-based investigations of the underlying ecological mechanisms and ecophysiological interactions between encroaching Acacia mellifera trees and grasses in a semi-arid environment. In a greenhouse study, I determined the contribution of N2 fixation to the N-budget of Acacia mellifera under conditions of both varying N availability and competition from grass. Tree seedlings had longer shoots and greater total dry mass in the absence of grass. The leaf δ15N values were lower with grass than without grasses. Thus, trees were more reliant on N2 fixation in the presence of grasses. N2 fixation may enable the tree seedlings to survive competition with grass at critical and vulnerable developmental stages of germination and establishment. In a field removal experiment, I monitored the growth rates, water relations and mortalities of shrubs around which neighbouring woody plants were removed (target) and control shrubs over three years. Results showed target trees to have benefitted from removal of neighbours, which was manifested in significantly faster growth rates, less negative predawn water potential and a relatively small degree of canopy die-back. Nonetheless, neighbouring trees appeared to prevent the whole plant mortalities resulting from severe environmental stress. Growing in close proximity with neighbours could therefore yield positive and negative ecophysiological effects. In another greenhouse experiment, I tested the effects of the separation of moisture uptake with depth between tree seedlings and grasses on two common substrate types. I also examined the influence of repeated grass clipping on the persistence of soil moisture. Results indicated a three-tier rooting pattern with a top layer exclusively exploited by grasses, an intermediate layer occupied by both grass and tree roots and deeper layers exclusively tapped by trees. Tree seedling biomass was negatively affected by grass competition although the biomass of grass was enhanced in the presence of tree seedlings on sandy substrates only. The repeated clipping of grass benefitted tree seedlings on rocky substrate more than it did on sandy substrate. The effects of heavy grazing on soil moisture availability to woody shrubs and thus bush encroachment may be contingent on substrate type, being more acute on rocky terrains. Grass competition suppresses tree seedlings but the removal of grass by grazing weakens this suppressive effect, particularly on rocky substrates. The insufficiency of space and soil resources on rocky substrates may necessitate increased investment in root biomass by plants. It is not known why grasses have lower densities on rocky substrates than on sandy substrates, but the obstruction by rocks disadvantages grasses against tree seedlings, leaving grasses vulnerable to grazing pressure. This may allow the woody plants on rocky substrates to benefit more from grass removal than on sandy substrates. Root restriction by rock barriers and, perhaps, sparse soil volume further lead to small tree sizes on the rocky substrate. Small shrubs are less likely to compete intensively for resources and cause density-dependent mortality. Intraspecific competition may maintain shrub sizes within the threshold that can be supported by available resource pools. I conclude from my results that the two-layer hypothesis of niche separation between savanna vegetation is valid although there is an overlap in the grass and tree rooting depth/moisture uptake. An additional factor that affects the success of A. mellifera is the substrate.Trees are more dense on rocky substrates but grow larger on sand. I have further shown that A. mellifera trees fix nitrogen when competing with grasses but do not do so when grasses are absent. A mechanistic model of savanna dynamics will need to integrate water use patterns, substrate and nutrients to make effective predictions about encroachment patterns. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

Thesis (MSc)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: The alarm calls of a colonial rodent, Brants' whistling rat (Parotomys brantsii), were investigated at Goegap Nature Reserve in the Northern Cape, South Africa. At this site P. brantsii occurs in sympatry with the congeneric P. littledalei, and the alarm calls in response to humans was compared between the two species. Parotomys brantsii's typical call in reaction to a human is a simple whistle, characterized by an initial upward frequency sweep and high frequency plateau, whereas the alarm whistle of P. littledalei has three overlapping components. Parotomys littledalei's calls are significantly shorter and lower in dominant frequency than those of P. brantsii, and have a significantly wider frequency bandwidth. These distinctions were attributed to species discrimination and habitat preferences. The acoustic adaptation hypothesis is supported in part, as P. littledalei, which inhabits a closed habitat in comparison with P. brantsii, has calls which are lower in frequency than P. brantsii calls, but contrary to the hypothesis, P. brantsii calls show less frequency modulation than those of P. littledalei. The high pitch of both species' vocalizations may be a convergent feature making the callers difficult for predators to locate. The alarm call repertoire of P. brantsii was investigated by presenting members of the P. brantsii colony with models of some typical predators, a raptor and puff adder, as well as a human observer. Virtually no variation was detected in the structure of alarm whistles elicited by different predators, indicating that P. brantsii did not identify different predator types by means of vocalizations, even though behavioural responses showed that P. brantsii do distinguish between different predators and non-predators. Note duration varied in conjunction with the physical reaction of the caller. When the caller bolted towards safety, the whistle was significantly shorter than when it remained aboveground. During an encounter with a snake or far-off human the caller would utter relatively long duration calls, signifying a low-risk situation, while highrisk situations such as a nearby human or raptor provoked short calls, emitted just before the whistling rat bolted underground. I regard P. brantsii's alarm call repertoire as a graded "urgency-based" system, indicating threat level perceived rather than predator type. This system is widespread among ground squirrels and is usually associated with animals inhabiting a two-dimensional environment. Playback experiments were conducted to determine the meaning of alarm calls to conspecifics, focusing specifically on the effect of variation in single call duration and function of alarm-calling bouts. All alarm calls induced heightened vigilance in receivers, but the behavioural response did not differ between short and long single calls. Multiple calls lead to significantly longer periods of high vigilance than single calls even after calling bouts have ended, showing that one of the functions of multiple calls is to maintain high vigilance in conspecifics for relatively long periods. The non-iconic nature of their alarm calls and the undiscriminating response of receivers to different calls emphasizes the importance of contextual clues in the communication system of animals living in an open habitat like that of P. brantsii. / AFRIKAANSE OPSOMMING: Die alarm-roepgeluide van 'n koloniale knaagdier, Brants se fluitrot (Parotomys brantsii), is ondersoek by Goegap Natuurreservaat in the Noordkaap, Suid-Afrika, waar hulle simpatries voorkom met die naverwante P. littledalei. Die species se alarmroepe in reaksie op mense is met mekaar vergelyk. Die tipiese alarmroep van P. brantsii is 'n eenvoudige fluit, gekenmerk deur 'n aanvanklike skerp frekwensiestyging en hoë-frekwensie plato. Parotomys littledalei se fluitroep het drie komponente wat mekaar gedeeltelike oordek. Parotomys littledalei se roepgeluide is beduidend korter en laer in heersende toonhoogte as dié van P. brantsii, en hul frekwensie-wydte is ook beduidend wyer. Hierdie verskille word toegeskryf aan species-verskille en habitat-voorkeure. Die akoestiese aanpassingshipotese word gedeeltelik deur die studie ondersteun, aangesien P. littledalei, wat 'n geslote habitat verkies in vergelyking met P. brantsii, alarmroepe het met 'n laer dominante toonhoogte as P. brantsii. In teenstelling met die hipotese, toon P. brantsii se fluitgeluide minder frekwensie-modulasie as P. littledalei se geluide. Die hoë toonhoogte van beide species se alarmroepe kan 'n konvergente verskynsel wees wat dit vir roofdiere moeilik maak om fluitende individue te lokaliseer. Die alarm-repertoire van P. brantsii is ondersoek deur individue bloot te stel aan 'n menslike waarnemer en modelle van tipiese predatore, naamlik 'n jakkalsvoël en pofadder. Daar was omtrent geen variasie in die klank-struktuur van alarmroepe in reaksie op verskillende roofdiere nie. Dit wys daarop dat P. brantsii nie roofdiere deur middel van roepgeluide klassifiseer nie, hoewel gedragsresponse getoon het dat individue wel tussen roofdiere kan onderskei. Die duur van alarmroepe varieer na gelang van die gedrag van die fluitende individue - 'n fluitrot wat vlug, se roep is beduidend korter as die geluid van een wat bogronds bly. 'n Pofadder en 'n veraf mens ontlok lankdurende geluide, wat dui op 'n lae-risiko situasie, terwyl rotte op vlug slaan in reaksie op 'n hoë-risiko situasie, soos met 'n nabygeleë mens of jakkalsvoël, wanneer kort alarmroepe geuiter word. Ek beskou P. brantsii se alarmrepertoire as 'n gegradeerde "nood-gebaseerde" stelsel, wat die mate van bedreiging aandui, eerder as die identiteit van die spesifieke roofdier. Hierdie sisteem is tipies van grondeekhorings en word gewoonlik verbind met diere wat 'n twee-dimensionele omgewing bewoon. Parotomys brantsii se reaksie op die terugspeel van die species se geluide is hierna ondersoek. Ek het gefokus op die effek van 'n verandering in die duur van alleenstaande fluitnote, asook hulle reaksie op fluitreekse. Alle alarmroepe het gelei tot hoër vlakke van waaksaamheid in luisterende individue, maar reaksies op kort en lang enkelnote het nie van mekaar verskil nie. Fluitreekse het beduidend langer periodes van hoë waaksaamheid veroorsaak as enkele geluide, en waaksaamheid het hoog gebly selfs nadat reekse geëindig het. Dit beteken dat fluitreekse onder andere die funksie vervul om waaksaamheid in kolonielede vir relatief lang tye te onderhou. Parotomys brantsii se eenvoudige alarm-repertoire en nie-onderskeidende reaksie op verskillene roepgeluide, beklemtoon die belangrikheid van aanvullende inligting uit die omgewing vir diere in 'n twee-dimensionele habitat wanneer die akoestiese kommunikasiestelse slegs 'n algemene waarskuwingsfunksie vervul.