3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item The distribution and abundance of herpetofauna on a Quaternary aeolian dune deposit : Implications for strip mining(2008-11-04T11:31:54Z) Maritz, BryanExxaro KZN Sands is planning the development of a heavy minerals strip mine south of Mtunzini, KwaZulu-Natal, South Africa. The degree to which mining activities will affect local herpetofauna is poorly understood and baseline herpetofaunal diversity data are sparse. This study uses several methods to better understand the distribution and abundance of herpetofauna in the area. I reviewed the literature for the grid squares 2831DC and 2831 DD and surveyed for herpetofauna at the study site using several methods. I estimate that 41 amphibian and 51 reptile species occur in these grid squares. Of these species, 19 amphibian and 39 reptile species were confirmed for the study area. In all, 29 new unique, grid square records were collected. The paucity of ecological data for cryptic fauna such as herpetofauna is particularly evident for taxa that are difficult to sample. Because fossorial herpetofauna spend most of their time below the ground surface, their ecology and biology are poorly understood and warrant further investigation. I sampled fossorial herpetofauna using two excavation techniques. Sites were selected randomly from the study area which was expected to host high fossorial herpetofaunal diversity and abundance. A total of 218.6 m3 of soil from 311 m2 (approximately 360 metric tons) was excavated and screened for herpetofauna. Only seven specimens from three species were collected. All were within approximately 100 mm of the surface even though some samples removed soil 1 m below the surface. There was no detectable difference in fossorial herpetofaunal density (individuals.m-2) between methods or from areas under different land uses. Neither soil compaction nor land use nor soil texture predicted fossorial herpetofaunal density or abundance. The data suggest that fossorial herpetofauna occur at extremely low densities in the area. This finding has implications for population estimates and conservation measures for these species. In order to better understand the effects of land use on herpetofaunal diversity, I used sample-based rarefaction curves to compare the diversity of the herpetofaunal species assemblages occurring in each of the four main land uses on the study site. Forest areas hosted significantly higher diversity than grasslands and the two agricultural mono-cultures, Eucalyptus and sugarcane plantations. Additionally I demonstrated empirically that riparian woodlands host higher species richness and herpetofaunal abundance than non-riparian areas. Potential reasons for the apparently suppressed diversity of these areas include the use of pesticides and/or herbicides, harvesting regimes, and the reduction in habitat heterogeneity. The potential value of riparian woodlands as refugia and corridors that could facilitate recolonisation of revegetated areas post-mining is discussed. Negative influences of mining activities on local herpetofauna are of particular interest given the potential and verified presence of several threatened taxa in the area including Bitis gabonica, Python natalensis, Afrixalus spinifrons, Hemisus guttatus and Hyperolius pickersgilli. These, as well as the “conservation needy” species proposed in a specialist report on the impacts of the mine on local herpetofauna are discussed in the light of my fieldwork. Mitigatory measures are required to reduce the negative impacts likely to be experienced by certain threatened taxa. I discuss a proposal for the development of a wetland reserve targeting, among other amphibian species, H. pickersgilli.Item Diversity and Conservation of Ultramafic Flora in Swaziland(2007-02-21T12:18:22Z) McCallum, Donald AlexanderAs early as 1583 an ultramafic plant was described (Proctor & Woodell, 1975). Since the early 1900s a number of works documenting ultramafic vegetation in various parts of the world have been published (Proctor & Woodell, 1975). The vegetation of the Great Dyke, Zimbabwe was only described in 1965 (Wild, 1965). Much has been written since then, however. It was only as recently as 1989 that any work on ultramafic vegetation in South Africa was published (Morrey et al., 1989), possibly because ultramafic vegetation in the Barberton Greenstone Belt is not noticeably different from that of the surroundings and outcrops are much smaller than the Great Dyke. Studies since then have documented the flora of the ultramafic soils of the Barberton Greenstone Belt (BGB) (Morrey et al., 1992; Williamson, 1994; Balkwill et al., 1997; Williamson et al., 1997; Changwe & Balkwill, 2003; Williamson & Balkwill in prep.). There are around 40 larger outcrops of ultramafic soil in the BGB, the largest of which are shown in Figure 1.1, and to date 29 endemic taxa have been discovered, 5 of which hyperaccumulate Ni (Williamson & Balkwill, in prep). Using IUCN criteria 21 of these taxa have recommended conservation status in the vulnerable categories and four are data deficient. With a number of threatened taxa and scientifically interesting and potentially useful Ni hyperaccumulators on the South African part of the BGB, it was likely that there were additional endemic taxa in Swaziland or additional populations of species collected in South Africa. The ultramafic sites in Swaziland (Figure 1.2) range in altitude from 4750 m above sea level (Figure 1.3) in the south to below 2250 m in the Komati River valley (Figure 1.4), higher than the South African sites which range from 354 – 1648 m above mean sea level (Balkwill et al., 1997). The Swaziland sites thus provide an opportunity to discover the effect of altitude on the vegetation of ultramafic soils in the BGB. The higher sites are cooler than the lowveld sites, with frost at night in winter and even snow on rare occasions. Rainfall averages 127 to 152 mm per year, the highest rainfall being recorded at the higher altitudes, where frequent fog also supplements the rainfall (Compton, 1966). The Swaziland sites also show a range of topography with the lower altitude sites often situated on the slopes of mountains, but higher altitude sites comparatively level. Very little of the ultramafic area in Swaziland has any form of protection and half the area has already been lost to agriculture and forestry. A previous study (Witkowski et al., 2001) identified Kniphofia umbrina Codd. as a critically endangered ultramafic endemic. There was thus an urgent need to study the remaining ultramafic areas and document the vegetation before more of this unique and important habitat is lost, and possibly some endemic plant species too. High population growth, expanding forestry and black wattle encroachment could all impact negatively on the remaining diversity of the ultramafic areas.Item Potential Symmetries and Conservation Laws for p.d.e.s including Perturbations(2006-03-13) Kiguwa, Ronald ItoRelationships between symmetries and conservation laws of perturbed partial differential equations are reviewed. Potential symmetries and their applications to perturbed partial differential equations and conservation laws are presented in detail. An example of a perturbed wave equation for an inhomogeneous medium is solved in detail. Proofs of some of the lesser-known theorems are outlined. A wide range of examples is given to further explain these concepts.