Vegetation of road verges on an urbanisation gradient in Potchefstroom, South Africa

A vegetation survey of road verges along an urban to rural gradient in the Potchefstroom Municipal Area was conducted. Important applications of these studies include understanding of the role of indigenous (native) and exotic species in the overall synanthropisation of vegetation. The present study forms part of a research programme on spontaneous vegetation in urban open spaces in the North-West Province of South Africa. A numerical classification technique (TWINSPAN) was used as a first approximation and the classification was refined using Braun-Blanquet procedures. The result is a phytosociological table from which 13 plant communities and seven sub-communities were recognised. Although some of these communities and sub-communities are similar to previously described vegetation types in natural and disturbed areas, most of them were not described before in South Africa. Two ordination scatter diagrams show the distribution of the plant communities along gradients which were related to the depth of the soil water table, habitat type, trampling, soil compaction and percentage of gravel in the soil surface. Similarities between roadside vegetation in this study and those overseas are discussed, as well as the possible role of road verges as dispersal corridors between natural and disturbed areas.