SEASONAL DYNAMICS OF PLANT DIVERSITY ON INSELBERGS IN THE IVORY-COAST(WEST-AFRICA)

Inselbergs are isolated monolithic outcrops which are characterized by large areas of exposed crystalline rock. Due to harsh edaphic and mic roclimatic conditions, inselbergs are completely differentiated from t heir surroundings. Consequently they host a very distinct vegetation w hich is being investigated on a global scale over a six year period. T he seasonal dynamics of selected plant communities (Afrotrilepis pilos o mat, shallow depression, ephemeral flush vegetation) on granitic ins elbergs in the Comoe National Park (NE Ivory Coast) were studied durin g the rainy period from May to November 1991 by recording all vascular plant species at 12 intervals. For the habitats investigated, the sea sonal vegetation dynamics were related to the rainfall pattern. Maximu m values both in species diversity and richness were attained in the f irst third of the rainy period. Drought in August and September caused a decline in species number and diversity in the shallow depression a nd ephemeral flush vegetation, resulting in mortality of more than 20% of the species. The individual communities studied differed considera bly in species diversity and richness. We conclude that ephemeral flus h and shallow depression communities are more species rich than the ma t community which is dominated by the highly competitive and specializ ed K-strategist Afrotrilepis piloso (a poikilohydric Cyperaceae) due t o stochastic climatic perturbations which allow the maintenance of spe cies rich non-equilibrium assemblages with r-strategists as major comp onents.