Influence of forest degradation on tree diversity in a forest-savannah transition in Eastern Ivory Coast

This study aimed at determining forest degradation impact on tree diversity in a forest-savannah transition zone in Ivory Coast. Structures of forest patches were given from the comparison of their number, area and index of fragmentation on basis of two land cover maps. Two forest types were identified according to their degradation. Results showed that landscape and forest disturbance, characterized by a forest canopy opening up, led to an increase of light-tolerant species and their richness in degraded forests. Thus, if diversity is summarized to species richness, forest degradation does not lead to a reduction of diversity. In contrast, species in degraded forests are less evenly distributed than those in non-degraded forests. Species abundance distribution in degraded forests indicates that only a few species dominate this zone due essentially to anthropogenic disturbances. In non-degraded forests, abundance distribution shows a relatively stable community in which individuals are more evenly distributed among species. Considering species abundance distribution and evenness index, non-degraded forest has a greater diversity than degraded forest.