Patterns of Plant Species Diversity in Fynbos Vegetation, South Africa

Abstract

Fynbos is the broad category of sclerophyllous shrublands which dominate the vegetation of the southwestern Cape, South Africa (see Kruger 1979 & Taylor 1978 for detailed descriptions). Plant species diversity both at the landscape level (gamma diversity) and at the community level (alpha diversity) is, supposedly, exceptionally high. Kruger & Taylor (1980) suggest that gamma diversity is apparently much higher than in any of the other world's biogeo graphic zones, except the tropical rain forest zones and other South African sites of about 1 km2. Kruger (1977) states that fynbos communities are probably the richest shrubland communities in the world. He states further that with the exception of plant communities in extreme habitats (for example, where soils are alternatively water logged and droughted), alpha diversity is consistently high and some record figures are 83 species on 50 m2 and 121 species on 100 m2 (data from Taylor 1977, 1978). These figures exclude annuals and geophytes. Kruger et al (1977) suggest that 'it could be that fynbos community diversity is exceeded only by that of tropical rain forests, if at all". A major goal of ecologists working towards a theory of community organization is to understand the causes of patterns of plant species diversity (Hutchinson 1959, Whittaker 1972, Menge & Sutherland 1976, Peet 1978). There are only a few references to plant species diversity in fynbos, despite its supposed richness. In view of the present interest in plant species diversity patterns we studied the alpha (within-habitat) diversity and the beta (between habitat) diversity of a small area of mountain fynbos (sensu Taylor 1978) in relation to altitude and fire. These two factors appear to be of major importance in deter mining fynbos physiognomy.