The effect of rainfall on the vegetation of the grassland plateaus of the Mountain Zebra National Park

Abstract

The vegetation of permanently marked plots distributed within a grassland plateau of the Mountain Zebra National Park was monitored by means of point surveys for canopy cover for a six-year period from 1980 to1986 and also in 1989. The observed changes conformed in some respects to the successional model that forms the basis of veld condition assessment for the Karoo Biome. Unpalatable species decreased after rains while palatable species increased after rains. The nature of the rainfall-induced changes differed between different communities with the climax grasses never becoming dominant. As part of a longer-term project on the vegetation of the Park, the monitoring of these areas was repeated in 2001 in order to determine whether any further change in canopy cover has taken place since 1989, and if good rainfall had an effect on the vegetation. The preliminary data confirms the previous results and indicates that rainfall has an effect on the total vegetation with a shift towards a more grassy system in high rainfall years with certain grass species changing their ecological status in dry and wet periods.