The Effect of Altitude Gradients in the Species Diversity of Woody Plants of the Natural Grazing Lands of West Shoa, Ethiopia

Abstract

The study was conducted at Meta Robi district, west Shoa zone of Oromia Regional State in October 2015 with the objectives to assess the effects of altitudinal gradients woody species diversity along with different altitudinal gradients of meta-robi district. The latitudinal gradients were divided in to three as 2700msl as upper altitude, 2350 to 2700 as mid altitude and less than 2000 as lower altitude. The Vegetation assessment was conducted with transect walk with in 4-5kms of in 270 quadrat 90 from each three altitudes having 10mx10m (for trees layer) and 5mx5m (for shrubs layer) .The higher diversity species of woody composition appeared with decreasing altitudes. The shrub wood species composition showed higher species diversity than tree wood species composition. A total of 19 wood species belonging to 11 families were identified in the study area, of which eleven were trees (>cm dbh and > 5m height) whereas, the remaining rest eight were shrubs (<2cm dbh and less than 5m height). According to their acceptance by livestock (42.1%) were palatable, (21.1%) were highly palatable and the rest (36.8) were unpalatable.The nineteen woody species recorded from three altitudinal gradients were found to have importance value index of 24.74 to 77.25% for shrubs of woody composition at upper altitude, 29.97 to 75.25% for mid altitude and 11.3 to 92.13% for lower altitudes. Similarly the tree woody species found to have highest in importance value at upper altitude with the dominant tree species.

Keywords: Altitudinal-gradient Woody composition, Species diversity, Similarity Index, Importance Value, Upper altitude, Mid altitude and lower altitude.