ECOLOGICAL STUDY of VEGETATION of ADES FOREST IN TULLO WOREDA WEST HARARGE ZONE OROMIA, ETHIOPIA

Abstract

A study was conducted in Ades forest in Tullo Woreda, which is one of the dry afromontane forests with the objective of documenting species composition and assessing species diversity, dominance, population structure and regeneration status. Vegetation data were collected systematically from 67 quadrants of 20 x 20 m (400 m2) along transects. In each quadrat, parameters such as density and diameter at breast height (DBH) for those with DBH>2cm were measured for all live woody species. Voucher specimens of species were also collected and identified in Haramaya University. Density, frequency, Shannon-Weiner diversity index, evenness, basal area and important value index were computed. Population structure and regeneration status of vegetation of the area were also determined from the densities of individual species falling within different DBH class. Results showed that a total of 57 woody species belonging to 54 genera and 37 families were identified from Ades Forest. Of these, 53.4% of them were trees followed by shrubs (29.3%), lianas with 6.8% and the rest plant species were shrubs or trees. Fabaceae , Euphorbiaceae, Asteraceae, and Rosaceae were with the highest species number(4 spp each) followed by Rubiaceae, Myrsinaceae and Lamiaceae (3 spp each). The Shannon-Wiener Diversity index (H') and evenness values of Ades forest were 1.1 and 0.27, respectively. The mean density of all the woody species with DBH>2 cm was 247.72 individual ha−1. Podocarpus falcatus(73.17 individuals h-1), Maytenus undata (37.98 individuals h-1) and Juniperus procera (25.48 individuals h-1) and Olea europea were the most dense. Basal area of all woody species added up to 12.159m2 ha-1. Hagenia abyssinica, Dombeya torrida and Hymenodictyon spp. accounted for 55% of the total basal area. Podocarpus falctus Olea europea, Juniprus procera, Croton macrostachyus and Maytenus undata.were species with the highest IVI. Population structure of the whole species together and selected individual species with the highest IVI showed stable population with large number of them in the lower DBH classes. Overall the vegetation is under stable situation with some individual species actually deviating from stable. Therefore, monitoring of species with high IVI must be considered so as to maintain the healthy interaction between components of the ecosystem.