Etude de l'écologie des communautés macrophytiques en vue de fournir des indicateurs paléo-environnementaux pour les lacs-cratères d'Afrique de l'Est

This research is part of an integrated paleoecological project which aims at coupling reconstructions of past vegetation and water-quality changes with climate variability. Crater-lakes from East Africa are favourable to the conservation of proxy indicators such as plant macrofossils used to reconstruct the lake ecosystem. The study of modern macrophytic communities in relationship with present environmental parameters was the first step of this research. Eventually, it will allow us to select species with high proxy-indicator value. Phytosociologic and environmental data were collected in 18 crater-lakes in South-western Uganda. In each relevé, species abundance and habitat conditions were described. Environmental parameters were used to develop a lake typology. A cluster analysis identified 6 aquatic and semi-aquatic communities and the indicator species were highlighted. The CA ordination emphasized the importance of geography, physico-chemistry and trophic level in the community structure. Temperature, pH, sediment type, depth and slope were the most correlated parameters to floristic variation in the CCA ordination. These preliminary results give some trends about the ecology of macrophytes communities. A complete dataset and the study of species ecological range will allow us to go further in the ecological significations of macrofossils.