Floristic Diversity and Composition of Sheko Forest, Southwest Ethiopia

Abstract

This study presents an analysis of floristic composition, diversity and structure of Sheko forest, southwest Ethiopia. Quadrats of 20 m x 20 m were laid down along line transects in Sheko forest to collect vegetation data. A total of 374 plant species, representing 256 genera and 91 families were recorded. The mean species richness was 45 species per 400 m2, and the highest number of species recorded per plot was 74. The forest had the Shannon diversity index of 2.83 and evenness of 0.54. The family Orchidaceae (28) had the highest number of species followed by Rubiaceae (26), Euphorbiaceae (19), Moraceae (18) and Acanthaceae (16). A total of 24,321 individuals of woody plants (16,433 individuals per ha) were counted in the sampled plots. Twenty plant species alone constituted more than 80% of the absolute density of the forest, of which three species had importance values of greater than 20%. The population distribution patterns of six economically important timber tree species reveals three types of diameter class distribution pattern: inverted J-shaped, J-shaped and bell-shaped. Three plant communities were recognized using hierarchical cluster analysis: Baphia abyssinica-Argomuellera macrophylla, Coffea arabica-Mimusops kummel and Rungia grandis-Croton macrostachyus. A floristic comparison of Sheko forest with other related forests in Ethiopia revealed low floristic similarity. A high diversity associated with the complex and diverse landscape in Sheko forest emphasizes both the botanical uniqueness and conservation value of this remnant forest. Keywords : Biodiversity; Classification; Conservation; Environmental gradient; Ordination; Vegetation structure Ethiopian Journal of Biological Sciences Vol. 6 (1) 2007: pp. 11-42