Tree Species Diversity and Distribution in the Natural Forest of Onigambari Forest Reserve, Oyo State, Nigeria

Abstract

Anthropogenic activities has caused depletion of majority of Nigeria forest reserves, reducing forest lands to agricultural lands and grasslands. These prompted this study to consider the diversity of species as well as their species composition in the forest in February 2021. Four sub-plots were established in a cluster with an area of 50m by 50m, with 20m distance between each plots and 10m as edge effect. Twenty five tree species belonging to fifteen families were found in the study site. Family Malvaceae was the most represented. Triplochiton scleroxylon recorded the highest relative importance value (11.23). The diversity indices across the study plots assessed were species richness, evenness, Shannon index and dominance. Dominance indices across the study plots were low, asides for Plot 4 where. Triplochiton scleroxylon was dominant. Simpson index was highest in Plot 1 and lowest at Plot 4. Shannon index was highest, though in moderation in Plot 1 and relatively low in the remaining plots. Evenness indices across the four plots were high. However, the summarized diversity indices for the study site reflected dominance was generally low, Simpson index was high, Shannon index was moderate and Evenness index was moderate. The dendrogram depicted the relationship among  the tree species population based on similarities and dissimilarities. Triplochiton scleroxylon belonged to a cluster while every other species with close similarity were categorized under cluster 2.