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

Abstract

Abstract Frequently discontinuous landscapes are attributed to various unsustainable human activities all over the world. These activities result to poorer diversity and reduced quite a lot of landscape The study was laid out on various sites of the stratified zone of the reserve namely: Core, Buffer and Transition. Riparian forests along Major River and Streams were sampled. Ninety plots (25m × 25m) were selected for the study. Sites were chosen based on accessibility within the zones and it was ensured that a variety of physiognomy were well represented. In all, 74 tree species, 31 families 65 genera were identified. Shannon index varied from 2.17 to 3.036, evenness of the riparian tree species was 0.056 and Sorensen index was 90.5%. The Core zone of the reserve has the highest occurrence of riparian and upland tree species in comparison with the buffer and transition zone. Diospyros dendo is the most occurring species in the core zone and more species were found along major rivers. In the buffer zone, tree species along the stream had higher representation with Cleistopholis patens observed while in the transition zone, higher diversity was found in species along the major rivers with Theobroma cacao having the highest occurrence. This study shows that the composition and plant community structure is affected by a range of disorders such as frequencies and magnitude of human activities at different levels. Species along streams had higher abundance than those along Major Rivers due to low intensity in the rate of flow of water which enables inundation and support of seed settlement for germination.