Links between lateral vegetation zones and river flow02 September 2015
Plant species are known to be distributed on river banks in a sequence of community zones from the water’s edge to the outer riparian area. The interplay between flow and landscape is thought to drive the existence of these zones, and specifically, between a lower zone that is inundated most years and an upper zone that is inundated less frequently. There remains no consensus on the number of zones present, what their links to flow might be or whether the same zones occur in different basins. This paper reports on the number and nature of vegetation zones along South African rivers in different geographical areas and their relationship to the flow regime. River bank sites in four climatic areas of South Africa were found to support four vegetation zones (in two groups) despite major differences in vegetation community types, climate and patterns of river flow. The Wet bank and Dry Bank zones were separated at an elevation that correlated well with the 1:2 year flood line. If vegetation zones along rivers can be linked in this generic way to the flow regime of a river, it will strengthen our ability to predict vegetation changes likely to occur with flow modifications.