The ecological planning of Doornkloof Nature Reserve, Northern Cape Province

[摘要] 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 decisions

[发布机构] University of the Free State