Seasonal and spatial changes in the composition of the aquatic and semiaquatic vegetation of Lake Chilwa, Malawi

Abstract

Changes in the frequency of individual species, and in the species composition of the vegetation were monitored at monthly intervals at four stations on the shore of Lake Chilwa. The stations formed a transect from land to lake through the littoralTypha swamp. The relationships between seasonal changes in the frequency of individual species and fluctuations in water level were shown. Stand distance indices decreased from land to lake whilst species diversity decreased from land to the central swamp and then rose again on the lake edges. Seasonal changes in the vegetation were more pronounced on the landward edge, which was subjected to alternate wet and dry periods than in the vegetation of the lake edge. The reasons for these spatial and temporal changes are discussed. It is suggested that plant communities occurring in a fluctuating physical environment may behave differently with respect to diversity from those in which the environment is temporally stable.