VEGETATION UNDER DIFFERENT TREE SPECIES IN ACACIA WOODLAND IN THE RIFT VALLEY OF ETHIOPIA

Abstract

Under-canopy vegetation was investigated in Senkele Sanctuary,
Habemosa Cattle Ranch, Abjata-Shalla and Awash National Parks in the Rift Valley of Ethiopia to study the influence of some tree species on the environment under their canopies. Ten species of trees were selected for their relatively bigger canopy size and structure as subjects of the study. The relative abundance of the species in the herbaceous layer under the tree canopy were estimated and subjected to various multivariate numerical data analyses. Patchiness of the habitat on the tree canopy scale aggregated into five distinct groups with little
overlap on the landscape scale suggesting that the vegetation beneath the tree canopy responded to environmental variables both under the tree canopies and in the landscape. The landscapes considered showed variation, among other things in altitude, temperature and precipitation. The vegetation under the tree canopies and the aggregations referred to as stratocoena, showed variations in cover,
species richness and diversity. Economic implications were drawn for the variations in the herbaceous vegetation across tree canopy and landscape scale. It is argued that suitability of a tree for a particular purpose may depend on the environmental variables across the landscape scale as it does across tree canopy scale. Tree species suitable for agroforestry, developing grazing areas, creating patchy habitats and hence promoting biodiversity could be specific for each landscape considered.