DRYLAND WOODY VEGETATION ALONG AN ALTITUDINAL GRADIENT ON THE EASTERN ESCARPMENT OF WELO, ETHIOPIA

Abstract

Vegetation data from plots (20 m X 20 m) on the eastem escarpment in Welo between
750 m and 1780 m a.s.l were analyzed. We found 216 species distributed in 61 families found out of
which 104 were woody species and used for vegetation classification using Two-way Indicator Species
Analysis (TWINSPAN). Seven woody plant community types were distinguished. Woody individuals
were counted and higher Importance Value Indices (IVl) were calculated for Euclea racemosa ssp.
schimperi (27.7), Dodonaea angustifolia (22.8), Acacia asak (21.9) and Grewia bieolour (14.4). The diversity
and evenness of each community were compared using Shannon-Weiner diversity and evenness index.
Pearson's correlation results reveal a strong correlation between altitude and soil depth an~ Tukey's W:~!
showed that the distribution of plant communities has strong correlation with altitude/soil depth ~a'
slope. Communities at inaccessible hill-slopes and protected areas are relatively species rich, while
communities under high grazing pressure and other disturbance are poor in species richness. Most of
the vegetation was observed highly disturbed except along inaccessible steep slopes, and in few
protected and privately owned areas indicating some implications of conservation and management.
The vegetation was compared with seven other vegetation types using Sorensen's similarity analysis
and general description of the vegetation was made.