Vegetation of high-altitude fens and restio marshlands of the Hottentots Holland Mountains, Western Cape, South Africa

Abstract

Seepages occurring at high altitudes in the Hottentots Holland Mountains (HHM) (Western Cape Province. South Africa) were subject to a phytosociological survey. Relevé sampling method and classification procedures of the floristic-sociological (Braun-Blanquet) approach as well as numerical data analyses (numerical classification and ordination) were used to reveal syn- taxonomic patterns and characterize the position of the syntaxa along major environmental gradients. Nine plant communities were recognized, three of which were classified as associations, following formal syntaxonomic and nomenclatural rules of the floristic-sociological approach Most of the studied mire communities were dominated by low-growing clonal restios (Restionaceae). whereas some consisted of other types of graminoids. The most important species determining the structure (and function) of the mire communities on sandstones of the HHM include restios Anthochortus crinalis, Chondropetalum deustum.C. mucronatum, Elegia intermedia. E. thyrsifera. Restio subtilis. R. purpurascens. cyperoids Epischoenus villosus. Ficinia argy-ropa, grasses Ehrharta setacea subsp. setacea. Pentameris hirtiglumis as well as shrubs Berzelia squarrosa. Cliffortia tricuspi- data. Erica intenallaris and Grubbia rosmarinifolia. Protea lacticolor and Restio perplexus dominate a rare shale band seep­age community. There are two major groups of communities—the fens (dominated by carpets of Anthochortus crinalis and other low-growing species) and the restio marshlands (mosaics of low tussocks of Restio subtilis and tall Chondropetalum mucrona­tum). The degree of soil (and water) minerotrophy was found to be the most important differentiating feature between the mire (fen and restio marshland) communities studied. The soils in the centre of mires were found to have high contents of peat and showed very little influence from the underlying sandstone. The soils along the mire margins had a greater admixture of mineral soil derived from the sandstone or shale bedrock.