Assessment of Tree Diversity of Riparian Forest Fragments in Omo Biosphere Reserve, Ogun State, Nigeria

Frequently discontinuous landscapes are attributed to various unsustainable human activities all over the world. Increase in population, enclaves and livelihood activities carried out within the reserve over the years is alarming. This study was carried to have a better knowledge of the flora, diversity and ecology of the riparian forests. The study was randomly laid out on various sites of the stratified zone of the reserve namely: Core, Buffer and Transition. Thirty plots (25m ×25m) were selected from each of the zones. A total of 74 tree species belonging to 31 families and 65 genera were identified. The Sorensen index was 90.5%, the evenness of the riparian tree species was 0.056, and the Shannon index ranged from 2.17 to 3.036. Compared to the buffer (587) and transition zones (436), the Core zone (676) has the highest concentration of riparian and upland tree species. The most prevalent species in the core zone is Diospyros dendo. Along the major rivers, Cleistopholis patens is more prevalent in the buffer zone, whereas, Theobroma cacao is more diverse in the transition zone. Low intensity of water flow influenced the abundance of species along streams compared to major rivers. This study revealed that the frequency and intensity of human activities at various levels have an impact on the composition and structure of plant communities.