Fynbos plant communities and vegetation–environment relationships in the Soetanysberg hills, Western Cape

The Cape Floristic Region of South Africa is an area of diverse substrata, high species diversity and complex vegetation patterns. Fynbos vegetation and soils were sampled at 75 sites in a 30-ha study area in the Soetanysberg hills in the south-western part of the Western Cape Province. TWINSPAN, DCA and CCA were used to investigate vegetation patterns and vegetation-environment relationships (with emphasis on soil factors). Classification of the vegetation data, which included 251 species, identified five communities associated with distinct soil types and DCA suggested two main compositional gradients. CCA showed that these two gradients were associated with environmental gradients of pH, soil depth and soil texture. When sites associated with the three substrata, namely, limestone, sandstone and colluvial sand, were analysed separately by CCA, only sandstone and colluvial sand produced significant vegetation-environment relationships. Despite the edaphic complexity of this landscape and the very large number of species, this study showed that there is predictable structure in the vegetation, related to various environmental factors, particularly at the community level. Die Kaapse Floristiese gebied bestaan uit diverse substrata, ‘n hoë spesiediversiteit en komplekse plantegroeipatrone, Fynbos plant- en grondmonsters is op 75 persele in ‘n 30-hektaar gebied in die Soetanysbergheuwels van die Suid-westelike Kaapprovinsie geneem. TWINSPAN, DCA en CCA is gebruik om plantegroeipatrone en piantegroei-omgewingsinteraksies na te gaan met klem op grondfaktore. Die 251 spesies is in vyf gemeenskappe gegroepeer wat met definitiewe grondfaktore geassosieer is, Twee hoofsamestellingsgradiënte is geïdentifiseer, Voigens CCA is hierdie twee gradiënte geassosieer met grond pH, gronddiepte en grondtekstuur. Toe persele wat op die drie substrata (kalksteen, sandsteen en kolluviafe sand) voorkom, afsonderlik met CCA ontleed is, hetslegs sandsteen en kolluviale sand betekenisvolle plantegroei-omgewingsverwantskappe getoon. Ten spyte van die edafiese kompleksi-teit van hierdie gebied en die groot aantal spesies, dui hierdie Studie aan dat, veral op die gemeenskapvlak, die plantegroeistruktuur op grond van verskillende omgewingsfaktore tog voorspefbaar is.