The vegetation ecology of the Witteberg and Dwyka Groups south of Worcester, Western Cape Province, South Africa

Abstract

The vegetation supported by the Witteberg and Dwyka Groups south of Worcester is a diverse mosaic of fynbos-, renosterveld- and succulent karoo vegetation units sustained by a winter-rainfall pattern. Elytropappus rhinocerotis (renosterbos) dominated plant communities are found on finer grained soils derived from the various mudrock-dominated formations of the Witteberg Group, a Passerina truncata (gonnabos) dominated shrubland with large Protea shrubs and / or small Protea trees where the substrate is largely influenced by the sandstone-dominated formations of the Witteberg Group, a grass dominated Capeochloa arundinacea (Olifantgras) shrubland where both mudrock-dominated and sandstone-dominated formations influence the substrate as a result of folding, a karoo Hirpicium integrifolium (Haarbossie) dominated shrubland where succulents are in abundance on the Dwyka tillite, and a distinct Thamnochortus bachmannii restio-dominated sandveld in areas where deep aeolian sand had accumulated. The differences in vegetation communities are mainly based on geology with consequent soil characters and degree of rockiness, as well as topography, moisture availability and the water holding capacity of the soil. Although slope, aspect and elevation can sometimes be associated with specific plant communities, geology, soil pH and rock cover are the principal elements responsible for shaping the vegetation mosaic. Rather than a broad ecotone, the vegetation of the study area is understood as a complex mosaic mountain vegetation entity.