Vegetation Composition, Biomass Production, Carrying Capacity and Grassland Types in Odolla Area of Shinile Zone, Eastern Ethiopia

A study was conducted to characterize vegetation composition and grassland types as well as to estimate biomass production and carrying capacity of the rangeland in Ordolla areas of Shinile zone, eastern Ethiopia in October 2004. The Ordolla grasslands covered 22,621ha on alluvial plain composed of sand and silt texture and clay in minor cases in small hydromorophic depressions. Seventeen vegetation types are identified in Orodolla areas based on soil types, vegetation structure and density, and drainage pattern described using LANDSAT image and geographical map of the area. The dominant grass species were Cynodon dactylon, Cynodon nlemfuensis, Eragrostis cilianensis, Cenchrus ciliaris, Andropogon greenwayii, Brachiaria leersiodes, Setaria pumila and Sorghum arundinaceum. Acacia tortilis, Acacia nilotica, Acacia mellifera and Acacia seyal were the most dominant shrubs with scattered Caddaba rotundifolia, Caddaba furmisa, Seddera bagshawei, Tamarix nilotica, Dobera glabra and abundant Parthenium hysterophorus, Cissus rotundifolia and C. quadrangularis . The grass biomass estimated in enclosed site near Ordolla village was 4.5 t DM/ha/yr and the total grass biomass produced in Ordolla rangeland was estimated around 27 534 t DM/year. The theoretical, dry and wet seasons carrying capacities were 0.16, 0.06 and 0.09 TLU/ha, respectively. There were good grazing lands in hydromorphic depression and well drained facets in Ordolla areas but the palatable grasses, trees and shrubs are decreasing due to overgrazing, runoff and drought and replaced by Parthenium, Calotropis, Solanum and Xanthium species, which are invader category of the plant community, indicating overgrazing and rangeland degradation. Keywords : Biomass Production; Carrying Capacity; Grassland Types; Grazing Lands; Vegetation Composition East African Journal of Sciences Vol. 1 (2) 2007: pp. 148-159