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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

The roles of competition, disturbance and nutrients on species composition, light interception and biomass production in a South African semi-arid savanna.

Mopipi, Keletso. 14 November 2013 (has links)
Plants are the major source of food or energy required to sustain life on the planet, but humans are grappling with the deteriorating conditions of natural ecosystems such as compositional change, desertification, invasive plants and soil erosion. In the face of global climate change and growing demands for agricultural productivity, future pressures on grassland ecosystems will intensify, therefore sustainable utilization of all plant resources is of vital importance to enhance food security within the limits of good conservation. The semi-arid grasslands of southern Africa represent major grassland resources for grazing. Herbage production in these areas is determined not only by water and nutrient availability, but also by controlled and uncontrolled fires. Since fire is regarded as a natural factor in savannas, it is essential to develop a deeper understanding of the role of fire in community structure and function for the development of appropriate burning regimes. A study was conducted in the Eastern Cape of South Africa where the rural communities are faced with the challenges of rangeland degradation in the form of encroachment by unacceptable bush, karroid, macchia and less desirable grass species, as well as soil erosion. The main objective of this thesis was to investigate the roles of competition and disturbance regimes (fire and simulated non-selective grazing) on species composition, habitat productivity and the performances of selected species from this semi-arid savanna. Long-term effects of burning frequency on herbaceous species composition, Leaf Area Index (LAI), Photosynthetically Active Radiation (PAR) within the herbaceous canopy, biomass production and soil chemical properties were investigated. These studies were conducted on a fire trial set up in 1980 at the University of Fort Hare research farm in the Eastern Cape, South Africa. The treatments comprise an annual, biennial, triennial, quadrennial, sexennial and no burn control, all replicated twice in a Complete Randomized Design. The data from the trial collected between 1980 and 2008 were used to determine compositional variation for herbaceous species using the Non-metric Multidimensional Scaling and Bray-Curtis Dissimilarity tests. The PAR ceptometer was used to determine LAI and intercepted PAR, while random samples were harvested from 1m² quadrats from each plot. Soil samples were taken at four depths (0-2 cm; 2-4 cm; 4-6 cm and 6-8 cm) from each plot and analyzed for pH, Ca, K, P, total C and total N. The Resin-Bag technique was used to determine nitrogen mineralization. Burning frequency caused significant variation in herbaceous species composition over time. The species were distributed along gradients of increasing burning frequency, and these responses were in three categories: Those that increased with burning frequency such as Themeda triandra; those that decreased with burning frequency such as Melica decumbens, and those that showed little response such as Panicum maximum. The three-year burn resulted in the highest compositional variation, light interception, Leaf Area Index, aboveground biomass production, while the annual, biennial and no burn treatments resulted in the lowest. The fact that infrequent burning resulted in higher species variation, improved habitat productivity due to increased leaf area for light interception shows that appropriate use of fire can maintain a more diverse and productive savanna system. Burning frequency had significant effects on the soil properties, while soil depth did not show any significance. Frequent burning increased soil pH, K, Ca, and Na, but reduced C, N, P and N mineralization. There was a negative correlation between burning frequency and N mineralization, but no correlation existed between N mineralization and total N, total C or the C:N ratio. These results imply that frequent burning can cause nutrient losses and a greater nutrient limitation to plants in the long-term, especially soil C and N loss from combustion of organic material in the soil top layer. The ability of shade-tolerant plants to persist under shade and regular defoliation such as in burnt and grazed systems may be of greater importance for long-term productivity and sustainability of forage crops. It is therefore imperative to explore the mechanisms by which some species were favoured by frequent burning which created low shade conditions, while others were favoured by high shade conditions where burning is infrequent or absent. A pot experiment was conducted to investigate the shade tolerances of seven grass species that were abundant in the long-term fire trial. The test species were Cymbopogon plurinodis, Digitaria eriantha, Eragrostis curvula, Melica decumbens, Panicum maximum, Sporobolus fimbriatus and Themeda triandra. Individual grass tillers of each species were collected from the natural vegetation, propagated in separate seedling trays and transplanted into individual pots, and were grown under five shading treatments: full sun (0 % shading), 55 %; 70 %; 85 % and 93 % shading respectively. Shading significantly reduced the dry matter production of all the species. Biomass production of all the species decreased linearly to varying degrees with an increase in shade intensity. Digitaria eriantha and Eragrostis curvula were most adversely affected by shading, hence are classified as shade intolerant, while Melica decumbens was the least affected by shading, and is hence classified as shade tolerant. Cymbopogon plurinodis, Panicum maximum, Sporobolus fimbriatus and Themeda triandra are classified as moderately shade-tolerant. From the results it was apparent that some species could perform optimally in partial shade than in full sunlight, and these results lead to a conclusion that for satisfactory natural regeneration and seedling growth of this savanna vegetation would require a gap large enough to provide at least 30 % of ambient light. Investigating patterns in competitive effects and responses of species in these communities may not only explain the abundance of each species, but may also provide insight into the nature of forces that affect the structure and function of that community. Since fire, herbivory and soil nutrients are natural drivers of savanna community structure and function, their influence on competitive interactions of selected species were investigated. Two experiments were conducted to investigate the competitive effects and responses of eight selected common species in the area. The test species (phytometers) included one woody shrub, Acacia karroo and seven grass species namely: Cymbopogon plurinodis, Digitaria eriantha, Eragrostis curvula, Melica decumbens, Panicum maximum, Sporobolus fimbriatus and Themeda triandra. In an outdoor plot experiment the responses of the phytometers to competition from neighbours (0; 2 and eight neighbours respectively), fertility (fertilized, unfertilized) and clipping (clipping, no clipping) were investigated. The second comprised a pot experiment where the competitive effects of the species were investigated. Each species was grown under 3 levels of fertility (0 %; 50 % and 100 % Hoagland‘s solution) and clipping (clipping, no clipping) in pots filled with fine river sand and 4 neighbours. Competition intensity, soil fertility and clipping had significant effects on the biomass production of the phytometer species. Acacia karroo and Melica decumbens, exhibited the weakest competitive effects and responses, and incurred the highest mortalities after clipping and with 8 neighbours. Digitaria eriantha and Panicum maximum exhibited the strongest competitive effects and responses, especially in high fertility, and experienced the lowest mortalities. T.triandra exhibited stronger competitive effect after clipping in low fertility, while A. karroo and C. plurinodis exhibited stronger competitive effects in moderate (50 %) fertility. Cymbopogon plurinodis, Eragrostis curvula and Sporobolus fimbriatus ranked between these two extreme groups in terms of competitive effects and responses. Relative Competitive Interaction increased with soil fertility and number of neighbours in the absence of clipping. These results indicate that in general, taller or broad-leaved grass species outgrow the shorter ones, and this gives them a competitive advantage over light and soil resources. One of the range management objectives in the False Thornveld of the Eastern Cape is to promote the abundance of Themeda triandra, which is of high forage value and an indicator of rangeland that is in good condition. The general situation under livestock farming conditions in this area is that if the grass sward is optimally grazed and rested then there is a great potential for Themeda triandra to dominate.The results of the competition experiments indicated that the species exhibits strong competitive interaction, and also exhibited stronger competitive effect after clipping in low fertility. These results imply that it has a low response and a high effect, an attribute that would enhance its performance if it is moderately grazed or the area is burnt. The species is also moderately shade tolerant, and this may explain why it thrives in burnt and moderately grazed areas. These studies have demonstrated the important role that competition and disturbance in the form of fire and herbivory play in the maintenance of this savanna grassland. Through natural selection species are able to occupy different niches in the same area and coexist in a heterogeneous environment and minimize their chances of extinction. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.

Throughput of UWC students who did at least one semester of third-year statistics.

Latief, Abduraghiem January 2005 (has links)
This study explored the completion rates (the number of years a student takes to complete a degree) of graduates at the University of the Western Cape. Differences between students who finished their studies in the prescribed time of three years and those who took longer than the prescribed time was highlighted.

Unlocking human agency through youth development programmes: An exploratory study of a selected NGO working in youth development on the Cape Flats

Schippers, Deidree Dianne January 2019 (has links)
Magister Artium (Development Studies) - MA(DVS) / This study explored how human agency could be unlocked through youth development programmes using a case study of a selected NGO working in youth development on the Cape Flats in the Western Cape Province in South Africa. The aim of the study was to explore whether the selected youth development organisation encourages and unlocks young people’s aspirations and agency in its program design. The objectives of the study were, firstly, to determine if the organisation provided the students with opportunities and spaces in which the young people could exercise their agency in the development process in order to pursue their goals and aspirations. Secondly, to identify challenges that could inhibit the students from exercising their agency; and lastly, to arrive at recommendations on how the challenges could be overcome or prevented. The argument in this study was that youth development organisations should empower and help to develop the youth in such a way that they could realise their full potential in order to make a positive and constructive contribution to their communities and the South African economy. Human development interventions, the kind that is instrumental to youth development, stresses the importance of helping people to expand on their existing capabilities and strengthening human values such as democracy and agency (Conradie & Robeyns, 2013). As such, the Capability Approach as pioneered by Amartya Sen (1988), was used as the theoretical framework because individuals, specifically young people’s well-being, is often dependent on the extent to which they have the aspirations, freedom and capabilities (in other words the opportunities) to live the lives which they value (Robeyns, 2005). Human agency is thus necessary to translate aspirations, freedom and capabilities into actions that could assist individuals to achieve their desired states of well-being. The six dimensions of agency that the study focused on were reflective judgement, motivation, goal pursuit, autonomy, relatedness and competence as conceptualised by Conradie (2013). The study was located in a qualitative research paradigm and used a case study design. The research participants consisted of two groups. The first group were the two programme managers of the selected organisation. The second group was 40 Grade 10 learners who participated in the youth development programme offered by the selected organisation at a high school on the Cape Flats. The research instruments used included a biographical information sheet, a self-reflective questionnaire and a focus group discussion for the student participants, and individual interviews conducted with the programme’s two staff members. The quantitative data consisted of the students’ biographical information and were analysed through Excel software. Content analysis was used to analyse the qualitative data through a three-stage open coding process. The importance of the findings of the study was that the youth development organisation added value to the students’ development by assisting them to identify their aspirations and unlock their agency role. The findings also showed that being part of a community characterised by poor households, alcohol and drug abuse, violence and crime, and disadvantaged public schooling; the students’ chances to succeed against those odds were slim. Based on the findings, recommendations were proposed for the Department of Social Development, youth development organisations, post-school institutions, families and communities, and young people, on how the different role players could engage collaboratively in order to empower and assist the youth to realise their full potential; and in so doing, enable them to make a constructive contribution to South Africa at large.

Goema’s Refrain: Sonic anticipation and the Musicking Cape

Layne, Valmont January 2019 (has links)
Philosophiae Doctor - PhD / This thesis traces the making of a social world of the musicking Cape through sound, which it calls sonic anticipation. Sonic anticipation is threaded through a Cape-based musicking milieu called goema in the Nineteenth century, and through the regional jazzing culture that emerged in Cape Town in the latter part of the Twentieth century. A key concern is to read the sonic archive of Cape music without folding into a representational discourse of (apartheid) group identity or of a Cape exceptionalism. First, the thesis explores goema's emergence as folk music. In a central example, sonic anticipation is discernible in the intensities of a song called Daar Kom die Alibama [translated as ‘There Comes the Alibama’]. This song enabled goema to secure a status as racialised folk memory. Later in the Twentieth century, the song set the scene for a rearticulation that laid claim to the city as a response to the 'anxious urbanity' of race formation. This shift from the Nineteenth to Twentieth century musicking tradition is at the heart of what we have come to know as Cape jazz. In its genealogical construction of Cape jazz, the thesis traces a prefigurative aesthetics and politics that proposes new ways of thinking about the political significance of jazz. It traces the pedagogic strategies that musicians – Tem Hawker, Winston Mankunku, Robbie Jansen and Alex van Heerden - used in pursuing ‘ethical individuation’ with this racialised folk memory. By the early 1960s, jazz had become a method ‘archive’ or formative canon for these musicians. The thesis outlines how musicians used ‘nomadic’ pedagogies; following the energies that moved through the city, inside the technological, and discursive formations by which the social world was made. This thesis on goema’s refrain and the musicking Cape offers a way to consider a ‘difference that is not apartheid’s difference’.

The reflections of young deaf adults regarding transition the from school to higher education and employment within the Western Cape

Mitchell, Leilani January 2016 (has links)
A dissertation submitted in fulfilment of the requirements for the degree of Master of Arts in Audiology in the Faculty of Humanities, University of the Witwatersrand, Johannesburg March 2016. / Only a small number of Deaf school-leavers in South Africa enter higher education institutions (DeafSA, 2009). There does not seem to be an incentive to encourage Deaf school-leavers to enter higher education which contributes to the 90% unemployment rate of Deaf adults in South Africa (DeafSA, 2009). Deaf learners do not always seem to have opportunities for further study due to poor literacy skills. Deaf school leavers appear inadequately prepared for further education and employment when they leave high school and experience difficulty with communication and socio-emotional adjustment in the hearing world. This study explored the preparedness of young deaf adults for further education and employment within the Western Cape by describing the reflections of Deaf school-leavers regarding their transition from school to higher education and vocation. Focus group interviews and in-depth individual interviews were conducted with 19 Deaf participants between the ages of 21 and 25 who use SASL as their primary mode of communication and have attended a signing school for the Deaf in the Western Cape. The services of two SASL interpreters were used and the data collected were analysed using a thematic analysis. The findings of this study point to possible strategies that may facilitate the transition of the Deaf school leaver to higher education and vocation in the Western Cape. The data obtained in this study indicated a need for improved academic preparation of Deaf learners; an increase in educators of the Deaf that are fluent in SASL; an increase in SASL interpreters at higher education institutions and stronger transition programs at schools for the Deaf in the Western Cape. Moreover, participants in this study indicated a need for financial assistance for Deaf students to further their education and expressed the need for Deaf awareness and sensitization training of employers, employees, lecturers and fellow students of the Deaf in the Western Cape. Furthermore, the findings of this study suggested assistance from job placement officers with regard to integration and socialization of deaf employees in the workplace. / GR 2017

Of flowers and tears

Rodkin, Hayley Amanda January 2018 (has links)
Magister Artium - MA / The collection of ten short stories, Of Flowers and Tears, aims to capture the events that have shaped my life, impacted on my community. It hopefully gives a voice to topics such as mental trauma, sibling strife, abortion, drug use and abuse, suicide, as well as political and social activism. Whilst none of the topics are new, the collection could potentially add to a growing genre of short story fiction by local authors which examine issues relating to trauma, loss, violence and the acknowledgement of identities. As South Africans, we carry many metaphoric scars (including psychological, socio-economic, sexual) as well as literal ones, which act as testimonies to our violent and frequently traumatic past and present. Even though most of the material used in my collection forms part of my personal memory bank and will be interpreted in a wholly fictional way, I propose that such a collection speaks to pertinent, present and pervasive realities.

Studies of nitrogen fixation, nodule structure and nodule mineral distribution in the tribe Psoraleae

Kanu, Sheku Alfred. January 2011 (has links)
Thesis (DTech. degree in Crop Sciences) -- Tshwane University of Technology, 2011. / The genus Psoralea (tribe Psoraleae, family Leguminosae) is indigenous to the Cape Fynbos of South Africa and consists of 50 species that occupy different habitats, ranging from well-drained upland soils to creeks and permanent wetlands. However, little is known about their symbiosis, associated microsymbionts and or adaptation to the nutrient-poor, sandy, acidic soils of the Cape Fynbos. This study is the first to report the presence of calcium oxalate crystals in the outer cortex of P. pinnata and the occurrence of alkali and rare earth elements such as Sr, Rb, Zr and Y in tissue components of N2-fixing nodules (with unknown roles/functions).

Mineralogy and geochemistry of clay sediments in pans of the Northern Cape Province, South Africa.

Roelofse, Tiani. January 2010 (has links)
This thesis reports the results of a mineralogical and geochemical study of pans situated in the Northern Cape Province with special emphasis on the clay minerals. From east to west the depth and size of the pans increase and associated with this increased maturity the abundance of salt (halite and thenardite) and the quantity of green sediment are also enhanced. Chemically the sediments are dominated by SiO2 that also dilutes Fe2O3, K2O, Na2O, Al2O3 and MgO (when associated with dolomite) concentrations. Authigenic calcite, dolomite, analcime and loughlinite (Na-sepiolite) occur in some of the pans to the west and FTIR spectrometry indicates that all the pans host glauconite and/or celadonite. However, smectite, illite/smectite interstratification, kaolinite and/or chlorite and loughlinite only occur in some pans. The glauconite and/or celadonite does not occur as discrete mineral grains, but forms part of the fine-grained matrix common to all of the pans and no evidence of any precursor minerals were observed. The pan environment appears to present a closed, saline setting that is conducive for the direct precipitation of a mica with a chemical composition between that of glauconite and celadonite. The influence of the water-table on the formation of the glauconite and/or celadonite appears to be significant, as the highest abundance of salt is invariably associated with the position in the profile where the sediment appears to reach its most intense green colour. In the case of Koi Pan, the celadonite component of the solid solution seems to increase as the green colour intensifies. Loughlinite in Koi Pan and Brak Pan sediments also appear to be authigenic and it is suggested that it forms after precipitation of low Mg calcite that leads to Mg enrichment of the system and consequent sepiolite formation associated with minor dolomite. Thermoluminescence ages obtained from the Koi Pan sediment range between 37ka and 48ka before present at a depth of ~120cm below the surface, while for Brak Pan, at roughly the same depth, an age of between 110ka and older than 150ka before present was obtained. This may suggest different sedimentation rates in the pans or much younger ages and thus faster formation of glauconite and/or celadonite in Koi Pan since it is suggested that the mineral is authigenic. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2010.

Throughput of UWC students who did at least one semester of third-year statistics.

Latief, Abduraghiem January 2005 (has links)
This study explored the completion rates (the number of years a student takes to complete a degree) of graduates at the University of the Western Cape. Differences between students who finished their studies in the prescribed time of three years and those who took longer than the prescribed time was highlighted.

The epibenthic colonization of artificial subtidal habitats at the Cape d'Aguilar Marine Reserve, Hong Kong /

Hawkins, Susan Terry. January 1998 (has links)
Thesis (Ph. D.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 206-229).

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