FLORISTIC COMPOSITION AND STRUCTURAL ANALYSIS OF WOODY VEGETATION IN DIRKI AND JATO FORESTS, WEST SHEWA ZONE OF OROMIA REGION, ETHIOPIA

Abstract

This study was conducted on Dirki-Jato vegetation in Ilu Gelan District, West Shewa Zone of Oromia Region to identify floristic composition and analyze species dominance and diversity in the vegetation. Vegetation data were collected from 54 quadrats of 20 m x 20 m (400 m2) laid systematically along transects. In each quadrat, live woody species were recoded with their local names and scientific names (where possible), numbers counted and DBH measured for those with DBH>2cm. Sample specimens were collected for each species and identified in Haramay University Herbarium using literatures and experts. Quantitative vegetation data such as Shannon-Weiner diversity index, eveness, density, basal area, relative density, relative frequency, relative dominance and importance value index were computed. Sorensens’s similarity index was also computed to compare similarities in family, genera and species with other similar vegetations studied in different parts of the country. Results showed that a total of 106 woody plant species distributed within 84 genera and 49 families were identified. Fabaceae, Rubiaceae, Euphorbiaceae, Combertaceae and Moraceae were the most diverse families with 14, 6, 6, 6 and 6 species, respectively. Overall average Shannon-Wiener diversity index (H`) was 3.23 and the average evenness values (E’) was 0.69 indicating high diversity with more or less even distribution of species. Seven endemic species were recorded from the study area of which three were near threatened. Total density and basal area calculated for woody species were 10202.37 individuals’ ha-1 and 45.87 m2 ha-1, respectively. The densest species in the study area were Maytenus gracilipes, Maytenus arbutifolia and Celtis africana while the dominant species were Cordia Africana, Ficus sycomorus and Ficus vasta. Species with the highest IVI were Cordia africana, Maytenus arbutifolia and Maytenus gracilipes. In spite of its diverse nature, human are interfering with this natural vegetation that needs awarness rising of the locals to maintain the vegetation.