Other Theses
Permanent URI for this collection
Browse
Recent Submissions
- ItemOpen AccessA study of bush encroachment in Hluhluwe National Park, using aerial photographs within a GIS framework(2003) Aston, TimBush encroachment has been an ongoing process since the proclamation of the Hluhluwe Reserve. In this paper, I assess both the total extent of bush encroachment over the last 40 years for a section of the reserve (9.1 %}, as well as which landscape factors pre-dispose areas to encroachment in that section. Aerial photographs from 1960 were linked together and aligned to an orthorectified Image from 2000, which had been georeferenced and aligned to the GIS database that exists for the area. Areas of closed canopy vegetation were converted into polygons, and the physical attributes of the areas that had been encroached Upon were extracted from the GIS database that exists for the area. Classification trees were used for the analysis of landscape correlates of encroachment. Fire frequency and the area of forest within 200m of a point in? 1960 were Identified as being the main factors determining which areas had been encroached upon
- ItemOpen AccessAre animals choosing foraging patches according to spatial scaling laws or predator avoidance arguments? : a study on grazing ungulates in Hluhluwe Imfolozi(2004) Ballantyne, Fiona; Bond, WilliamSpatial scaling laws predict that patch choke in animals in determined by body size, with smaller animals utilising smaller patches. However, this theory does not take into consideration the potential impact predator avoidance behaviour may have on patch choice. Smaller animals are more at risk from predation; thus they have to choose grazing patches that meet their nutritional requirements without exposing themselves to an added risk of predation
- ItemOpen AccessCan nitrogen isotopes be used to detect the effects of burning on nitrogen cycling? A study on Pinus resinosa in Minnesota, USA(2004) Ballantyne, Fiona; Craine, JosephPinus resinosa stands in Minnesota, USA were surveyed and fine and coarse roots from stands were analysed for nitrogen isotopes in an attempt to determine if fire effects nitrogen cycling. Fire increased the % nitrogen of coarse roots and changed the ratio of C: N. It may also decrease the depth of the A-horizon. It did not however affect the nitrogen isotope ratio of stands. Isotope values of coarse roots were affected by the depth of the A-horizon, which is consistent with other studies. A correlation between the 15N values of course and fine roots was found however fine roots were enriched proportionately to coarse roots. This suggests that they may be using a more enriched source of nitrogen such as ammonia although this is not conclusive. A PCA performed on site variables and isotope values determined the two major axes for sites were bum history and nitrogen cycle openness but that burning did not affect the second axis. A stepwise backwards regression showed the best predictors of a root's isotope value were, in decreasing order, the isotope value of coarse roots for fine roots and vice versa, the % nitrogen of roots and the age of stands. Coarse and fine roots showed opposite trends with % nitrogen. As the % nitrogen increased, fine roots were more 15 N enriched, again pointing to different nitrogen sources for coarse and fine roots. Older stands do appear to have a more open nitrogen cycle, as roots were 15N enriched in these stands. The availability of different forms of nitrogen may influence the 15N signal of roots especially if fine roots are preferentially using ammonia. Therefore, it is not possible to say if isotope values are due to stand openness, or due to different resources use by roots.
- ItemOpen AccessMollecular Phylogeny of tribolium (Danthoniodeae: Poaceae) and its taxonomic implications(2003) Ntsohi, Refiloe; Verboom, TonyMolecular sequence data from two noncoding regions of D A (ITS AND TRNL-F) Were used to produce a phylogeny for the genus Tribolium and its African and Australasian allies. Topological comparisons of the combined molecular data with the appended existing morphological tree were made. A significant incongruence was revealed. Molecular data indicate that Tribolium is paraphyletic. The formally defined sections: Uniolae, Acutiflorae and Tribolium have been retrieved by the molecular data. The analysis retrieved Karroochloa as polyphyletic. Monophyly of Schismus is strongly supported. The Australasian species form a monophyletic clade. Data support early divergence of the Merxmuellera species and Pseudopentameris macrantha.
- ItemOpen AccessIsolepis R.Br. (Cyperaceae) revisited : a phylogeny based on plastid and nuclear ribosomal DNA data(2006) Wiswedel, Stefan; Muasya, MuthamThe approximately 75 species of Isolepis R Br. are currently described as annual or short lived perennials with predominantly terete spikelet's