Vegetation and flora of the Southern Drakensberg escarpment and adjacent areas

Abstract

The grasslands of South Africa, and especially the higher altitudinal grasslands, are under increasing human pressure. In this study a floristic-ecological account of the vegetation of the southernmost Drakensberg and its foothills is given. This is the first comprehensive botanical study undertaken in this floristically poorly known region. The study area is situated in the magisterial districts of Barkly-East, Elliot and Maclear between 30° 40' and 31 °35' S, and 27°25' and 28°35' E. In the study area afforestation is the greatest threat at lower altitudes, whereas at the higher altitudes overgrazing, trampling and invasion by exotic plant species impact negatively on the native vegetation. A brief review of the history and previous botanical exploration of the area, as well as the physical environment are given. Four main plant communities -- the Maytenus undata -Rhus dentata woodland and forests communities, Harpechloafalx - Pycreus cooperi hygrophilous communities, Themeda triandra - Alloteropsis semialata high altitude communities and Alloteropsis semialata - Rendlia altera Afromontane grassland communities, with various sub-communities and variants are identified and described. An annotated check-list of the plant species collected in the study area and distribution maps of all the Drakensberg Alpine Region and local endemic species found in the study area are given. Twenty two local endemic species and 74 rare and threatened taxa were identified. During the study 1 991 species and infraspecific taxa of vascular plants were collected or listed. Most of the endemic species in the study area are located above 1 500 m altitude. Due to the relatively low number of local endemic species (22) the study area can at best be considered as a weak centre of endemism. However, it is clearly linked with two other major centres of plant endemism, namely the Drakensberg Alpine Region (DAR) and Maputaland-Pondoland Region (MPR). Within the study area 194 DAR and 86 MPR endemic species were recorded. No local endemic species occur in the forest and wetland communities. Most of the rare and threatened species are found in open grassland which are the areas most suitable for afforestation. This causes a major conflict between the forestry industry and conservation agencies in the area. All grasslands situated at an altitude of above 1 600 m are floristically very diverse and adequate representative areas should be protected, especially the areas of Tentkop and Elands Heights. Soils here are highly erodible and forestry and trampling in these areas should therefore be avoided at all costs. The higher lying grasslands and, to a lesser extent, the lower lying grasslands are ecologically sensitive areas. This is particularly so where the underlying mother rock is basalt, which weathers into highly erodible soils. It is suggested that all areas above 1 600 m be declared "no-go" areas for afforestation. This is based on not only the number of endemic and rare species found in these areas, but also because of the floristic diversity and aesthetic value they hold for eco-tourism. All habitats are sensitive to some degree, but the most threatened areas are the higher lying and open grasslands. Areas that are generally unsuitable for afforestation include rocky outcrops, vleis, drainage lines and forests. Most of these areas are protected by law, albeit for reasons not to do with biodiversity or endangered species.