Masters Degrees (Animal, Wildlife and Grassland Sciences)
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Browsing Masters Degrees (Animal, Wildlife and Grassland Sciences) by Advisor "Du Preez, P. J."
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Item Open Access The ecological planning of Doornkloof Nature Reserve, Northern Cape Province(University of the Free State, 2014-01) Smit, Zacharias Martinus; Smit, G. N.; Du Preez, P. J.The successful and effective management of conservation areas can only be achieved with access to sound environmental data. The Doornkloof Nature Reserve (DNR) in the Northern Cape Province, was in need of such data which was essential for the development of proper management policies. The objectives of this study were to identify, describe and measure the most important environmental characteristics of the reserve, which will be used as the baseline data for the refinement of management policies. This included the identification and description of the plant communities; the demarcation of management units; determining the botanical composition and the veld condition of each management unit; quantifying the density; species composition and above-ground biomass of woody plants; calculating the carrying capacity (graze and browse); determining the seasonal habitat selection, group sizes and social structures of the ungulate species of DNR and developing a suitability index to assists management decisions. The Braun-Blanquet method was used to identify the plant communities of DNR. A total of 204 reléves were sampled and upon analysis six major plant communities and 14 sub-communities were identified. The plant communities and sub-communities were grouped into seven management units. Due to the heterogeneous landscape of the reserve, the vegetation of DNR was relatively diverse, consisting of grasslands, shrublands and riverine communities. A step point-method and the Ecological Index Method were used to determine the species composition and veld condition of the herbaceous layer of each management unit respectively. The grazing capacity of each management unit was determined by two separate methods. The floristic diversity differed substantially between topographical features, rather than between management units. The mountainous areas were in excellent veld condition and had a high grazing capacity, while the more degraded lower regions were in poor to good condition and had substantially lower grazing capacities. Rainfall and grazing played an important role in the study area and indicated that the vegetation of Doornkloof Nature Reserve displays both equilibrial and non-equilibrial trends. A quantitative description technique, (BECVOL3-model), was used to quantify the plant densities, species composition and above ground biomass of the woody plants of each management unit. Browsing capacities were calculated for different browsing heights (1.5m, 2m and 5m). Both plant densities and browsing capacities differed substantially between the various units. Plant densities varied from 40 plants/ha to 1 120 plants/ha, while browsing capacity varied from 4 ha/Bu to 157 ha/BU at a browsing height of 2 m. The browsing capacity did not decline substantially from the wet to the dry season, predominantly due to the abundance of evergreen species. The habitat selection of seven ungulate species was investigated by recording sightings of game species within each habitat unit. A goodness-of-fit test was applied to the data to determine if habitat selection of game species differed from being random. Habitat selection was found not to be random. Confidence intervals were calculated by means of the Bonferroni method to determine the habitat preference of each game species. The results indicated that species had clear habitat preferences and that some species showed seasonal changes in habitat selection. Species such as buffalo and mountain reedbuck were found to be habitat specialists, while species such as eland were more habitat generalist. The results indicated that eland, kudu and warthog were thriving in the environment, while the gemsbok and mountain reedbuck population were not adapting as well as expected. An alternative approach to conventional habitat suitability models was attempted in this study. The proposed suitability model proved to be relatively accurate in predicting both the habitat selection of game species and the quality of the habitats of DNR. The potential use of similar suitability models holds potential as a tool in assisting with objective management decisionsItem Open Access A plant ecological evaluation of mechanical bush thinning in Marakele Park, Limpopo Province(University of the Free State, 2008-01-19) Pienaar, Francina Christina; Smit, G. N.; Du Preez, P. J.English: Bush encroachment is currently of great concern in Marakele Park. The main motivation for this study, conducted during the 2003/2004 and 2004/2005 seasons, was to determine whether mechanical bush thinning, executed with a mechanical mulc her, namely the Barko Tractor, was successful in solving the bush encroachment problem in the areas where it was applied. The specific objectives of this study were to identify, describe and interpret the plant communities of a section of Marakele Park, and to establish the influences of the thinning treatments on the dynamics of the ecosystem, more specifically the regrowth and browse production of the woody plants, the species composition and dry matter (DM) yield of the herbaceous layer and the short term changes in the soil. Eight experimental plots (3 treatments, 3 controls, 2 coppice) were selected in three veld types (Acacia mellifera – Grewia flava, Combretum apiculatum – Grewia flava and Acacia erubescens – Dichrostachys cinerea), in which tree thinning was applied during 2002 and 2003. Each plot was 100 m x 200 m (20 000 m2 = 2 ha) in size. The vegetation of the plots was phytosociologically studied during the 2003/2004 season with the aid of the Braun-Blanquet vegetation sampling method. A total of 80 relevés were surveyed and upon analysis 3 major communities, 7 communities, 6 sub-communities and 3 variants were identified. The woody layer was quantified with a quantitative description technique, which is incorporated in the BECVOL-model. A step point-method and the Ecological Index Method were used to determine the species composition and veld condition of the herbaceous layer, respectively, and a harvesting method was used to determine the DM yield and the associated grazing capacity. The thinning treatments resulted in an initial decreased number of woody plants, but since no follow-up treatments were applied, a large number of new seedlings have since established and the majority of cut-plants coppiced vigorously. However, approximately three years after the thinning treatments the leaf biomass (ETTE ha-1) of the woody layer increased due to regrowth and re-encroachment to a point where negative interactions between the woody and herbaceous plants, as a result of competition for soil water and nutrients, were evident again. The species diversity of the herbaceous layer increased after the thinning treatments, but species normally associated with disturbed and overgrazed veld still dominated. It was concluded that the herbaceous layer of Marakele Park is in a poor ecological state and indications are that it is still deteriorating. The herbaceous DM yield did not respond to the thinning treatments as expected, except in areas protected from grazing herbivores. As a result, the grazing capacity of the Park was comparatively low. It is clear that Marakele Park is currently overstocked with various game species, especially of high density, selective short grass grazers. Thinning treatments will therefore not be successful unless the herbivore game numbers are reduced. Few soil variables changed significantly as a result of the thinning treatments, but in view of the fact that soil enrichment is a slow process, monitoring of the soil variables is recommended. The specific soil propertie s did, however, have a decisive influence on the vegetation type. The Combretum apiculatum – Grewia flava plots occurred on relatively shallow, gravelly soil, while the Acacia dominated plots occurred on deeper, more fertile soil. It was also concluded that the Barko Tractor, due to its size and weight, had a negative impact on the soil, mainly in the form of soil compaction. Subhabitat differentiation, rainfall and herbivory played an important role in the study area and indicated that the vegetation of Marakele Park displays both equilibrial and non-equilibrial trends. The high grazing pressure, together with the high incidence of coppice and re-encroachment of woody plants after the initial thinning treatments, as well as the lack of follow-up treatments, effectively neutralised the success of the mechanical bush thinning treatments. In order to restore these thinned areas from re-encroachment it will be necessary to cut the plants again and combine this effort with a cut-stump treatment (chemical herbicide). Due to the negative impact of the Barko Tractor, it should not be used again during any follow-up operation.Item Open Access A plant ecological study of the Rietvlei Nature Reserve, Gauteng Province(University of the Free State, 2004-11) Marais, Riaan; Smit, G. N.; Du Preez, P. J.English: This study was undertaken with the objective to identify and quantify different homogeneous management units on the Rietvlei Nature Reserve to facilitate more effective management as far as grazing utilization, burning and monitoring are concerned. Vegetation units had to be identified and mapped. From the communities different management units could be identified. The study area of 3 870 hectares is a proclaimed nature reserve and is situated southeast of Pretoria in the Gauteng Province. A phytosociological study of the vegetation was done using the Braun-Blanquet method. A total of 184 plots were sampled and classified using the Braun-Blanquet method and TWINSPAN. This study revealed that the vegetation of the Rietvlei Nature Reserve could be divided into six main communities, each with a number of sub-communities and some with variants. The communities identified were: Andropogon schirensis – Aristida congesta Community, Gladiolus crassifolius – Brachiaria serrata Community, Eragrostis chloromelas - Setaria sphacelata var sphacelata Community, Eragrostis chloromelas - Cynodon dactylon Community, Setaria verticillata – Phragmites australis Community and Arundinella nepalensis – Eleocharis dregeana Community. The different communities described were used as a basis for the representation of a vegetation map of the reserve and the demarcation of management areas for the Rietvlei Nature Reserve.