Study on Floristic Composition, Diversity and Structure of Woody Plant Species in Geba Moist Evergreen Afro - montane Natural Forest, Sigmo Woreda, Jimma Zone of Oromia Regional state, Southwest Ethiopia.

Abstract

This study was conducted in Geba Forest Sigmo district in Jimma Zone Southwest Ethiopia. The study was conducted with the objective to determine floristic composition, diversity, structure and regeneration status of the Forest. Systematic sampling method was used to collect vegetation data from 57 (20 m x 20 m). All trees and shrubs with Diameter at Breast height (DBH) ≥ 2cm were measured for height and diameter. Shannon - Wiener diversity index was applied to quantify species diversity and richness. A total of 118 woody plants species were recorded and identified in the study forest. Rubiaceous and Asteraceae are the most dominant family represented each with 15 genera, 15 species (12.71%) and 5 genera, 11 species (9.32%) respectively. The Shannon –Wiener diversity index shows that quadrats number 11, 24, 4 and 33 are the richest, while the lowest number of species (16) was recorded for quadrat 56. Out of 118 woody species twelve species (52.2%) major commercial indigenous tree species of them were recorded from the study area and 12 were endemic species of the study forest. The total stem density calculated for individuals of woody species in hectare was 2856.6 ha-1 . The most frequent woody species of the forest were Ilex mitis 55 plots (96.5%), Celtis africana and Schefflera abyssinica were 54 plots (94.7%). About 85 woody tree species having 4136 individuals were selected to describe height distribution in eight different classes. A total of 4079 individuals whose height >2 m and DBH >2.5 cm was recorded and seven DBH classes are established in the forest for DBH analysis. The total Basal Area of forest was 965.2 ha-1 . About 14.81% of the total species was dominated by only five woody species of the forest. IVI combines data from three parameters, which include Relative Frequency, Relative Density and Relative Basal area. Six IVI classes were established in the forest. Percentages of species in the IVI classes were 15.58%, 27.27%, 31.16%, 11.68%, 5.19%, and 9.09% for classes 6, 5, 4, 3, 2, and 1 respectively. Regeneration status of the forest was analyzed by comparing saplings and seedlings with the matured trees. In this study the regeneration status of 55 woody species were analyzed. 10211 seedlings (4478 seedling/ha), 8089 saplings (3548 sapling/ha) and 6513 (2856.6 matured/ha) were recorded from 57 sample plots. This result indicates that regeneration status of the Geba forest was in good regeneration status or good health potential. Geba forest is one of the governments mapped forest in Ethiopia. Geba forest are the most species rich and dense moist evergreen afro mountain forest which have a different endemic and commercially important tree. The forest needs conservation and awareness in the community on biodiversity conservation and sustainable use of the forest resource. Geba forest has highly affected by the local community in and out of the forest by expansion of agricultural lands, grazing animals, tree cutting for different purposes, forest fire, charcoal and timber and the seedling and sapling of the forest are highly affected or damaged by fattening livestock in the forest. In this study area some forest parts are highly affected in the different parts by surrounding community in Gejo direction, Suba Direction, Ulma’i direction affected due to different reason. Based on the result of the study, research and Ethnobotanical studies to explore the indigenous knowledge on the diverse uses of plants and its conservation, and Participatory management of the forest were recommended.