Woody Species Composition, Diversity, and Vegetation Structure of Kolbu Forest, Maji District, South West Ethiopia

The study was conducted in Kolbu Forest in Maji District Southwest Ethiopia. The general objective of this study was investigating woody plant species Composition, Vegetation Structure and plant diversity of Kolbu Forest. Systematic sampling technique was used within 8 Transect lines of fixed distance interval 600m apart to record vegetation data. A Sample quadrat of 20m x 20 metre for Trees and 5m x 5 metre for Shrubs were laid in the main plot. Five (1m*1m) sub plots were laid to collect seedling and sapling to the regeneration status of the forest. A total of 56 quadrants were laid along transects. Each plots was laid at distance of 400 metre and the distance between the transect lines was 600 metre apart from each other. The data of vegetation structure was analyzed using excel spread sheet whereas Plant community determination was performed based on the dendrogram output of cluster analysis and synoptic values of species obtained using R version 3.0.2 statistical software. Shannon –Wiener Diversity Index was used to analyze the species diversity, species richness and evenness of the vegetation. A total of 73 woody species representing 63 genera and 34 families were recorded from the 56 sample plots in the forest. Euphorbiaceae and Rubiaceae were the dominant family followed by Celasteraceae. Three community types were identified by Agglomerative Hierarchical Clustering using Similarity ratio and synaptic values of each species in each plot. The total density of tree species with DBH greater than 2.5cm in the Kolbu forest was 4291individuals (1915.63ha<sup>-1</sup>). The most dense species in the study area were Psydrax parviflora with density of 874.11 ha<sup>-1</sup> followed by Syzygium guineense and Elaedendron buchananii with density of 197.32 ha<sup>-1</sup> and 172.32 ha<sup>-1</sup> respectively. The most frequently observed species in the study area were Elaedendron buchananii and Syzygium guineense with a total frequency of 41 out each of the 56 quadrate with frequency of 73.21%. The total basal area of the trees forest was 65.68m<sup>2</sup>ha<sup>-1</sup>. DBH and height class profile indicated that the greater number of individuals were in the lower class than higher classes. This shows older trees in forest were continuously removed by anthropogenic activity. Therefore, creating awareness for the community on the conservation and sustainable use of the forest was recommended based on the finding of the study.