TREE SPECIES DIVERSITY AND SOIL STATUS OF PRIMARY AND DEGRADED TROPICAL RAINFOREST ECOSYSTEMS IN SOUTH-WESTERN NIGERIA

We investigated the tree species diversity and soil properties of primary (Queen’s) and degraded (Elephant and Oluwa) rainforests in south-western Nigeria. Results revealed that differences in soil properties of the sites could not be attributed to the effect of forest degradation since there was no discernable pattern between properties of primary and degraded forest soils. A total of 31 families (26, 24 and 22 in Queen’s, Oluwa and Elephant forests respectively) were encountered. Species diversity index, species richness and species evenness were in the order Queen’s Oluwa Elephant forests and decreased as the level of forest degradation increases, thus indicating that these indices depended on site conditions. Queen’s forest had the highest species diversity (51), followed by Oluwa (45) and Elephant forests (31). About 30% of tree species in the three sites were among the endangered tree species in Nigeria, a situation that calls for urgent conservation measures. The similarity of diversity index of the once highly degraded Oluwa forest with that of the primary forest indicates that rainforests have the ability to return to their original ‘species rich’ situation even after significant degradation, provided that the physical factors of the forest are intact, seed dispersal is present, the site does not become invaded by aggressive weed species and all forms of degradation activities cease or are controlled.