Vegetation ecology of Soetdoring Nature Reserve: pan, grassland and karroid communities

[摘要] English: The main aim of this study was to identify, classify, describe and ecologically interpret the plant communities and their variations for the pans, grassland and karroid grassland of Soetdoring Nature Reserve and to compare it to other similar units where possible. A further aim of the study was to provide the Department of Environmental Affairs & Tourism of a baseline study of the grassland and pan vegetation and to provide results which could serve as an ecological basis for future management, conservation and research.Soetdoring Nature Reserve is situated in the Free State Province, about 35 kilometres north-west of Bloemfontein and covers approximately 6 000 ha. The Modder River divides the reserve in two and the Krugersdrif Dam is also included in the reserve‟s boundaries.The main aim was achieved by undertaking a phytosociological investigation by means of the Braun-Blanquet method. The total data set consists of 229 relevés and 171 species. After refinement, the Braun-Blanquet procedures yielded 17 plant communities. Phytosociological tables were compiled for each of the pan, grassland and karroid grassland, and a synoptic table for the total data set, in order to determine the communities and their variants. An ordination algorithm (DECORANA) (Hill 1979b) was also used to indicate the floristic relationships among the vegetation units.The pan unit was classified into five communities and eleven subcommunities. Two pans are present in the reserve, on the southern and northern side of the Modder River respectively. The northern pan was classified as a Grass Pan and characterised by Cynodon transvaalensis, Panicum schinzii and Echinochloa holubii. The southern pan was classified as a Diplachne Pan and is dominated by Diplachne fusca and Eragrostis bicolor. Two permanent earth dams and a hot spring are also present inside the southern pan basin. Earth Dam A is dominated by Eleusine coracana and Phyla nodiflora, while Earth Dam B is characterised by Cyperus bellus and Eragrostis biflora. The vegetation of the hot spring consists of a dominant zone of Phragmites australis, surrounded by a dense zone of Juncus rigidus.The grassland unit was divided into grassland and karroid communities, due to the state of degradation thereof. The classification resulted in five grassland communities and seven karroid communities. The grassland communities are characterised by climax grasses, with the dominant species being Themeda triandra and Digitaria eriantha. The karroid communities are dominated by dwarf karroid shrubs, like Salsola glabrescens, Rosenia humilis and Felicia muricata, as well as subclimax and pioneer grasses, like Eragrostis obtusa, Chloris virgata and Aristida adscensionis.This study provides important information on especially the pans in the reserve, since little information is available for the vegetation of pans in the Free State. The chapters on pans serve to bring all the available information together and to apply the information to the reserve‟s pans. This study is further of importance in indicating the degree of disturbance in the grassland unit. The impact of the animals and the importance of these mentioned areas for the game in the reserve, were taken into consideration for each vegetation type.

[发布机构] University of the Free State