Effect of Altitudinal Gradient on Herbaceous Species Composition, Herbaceous Biomass and grassland Condition in North-Eastern Ethiopia

Abstract

Species composition, biomass yield and grassland condition of four grazing land types (both communally and privately owned grazing areas; riverside grazing sites and grazing reserves, as bench mark areas) were studied along three altitudinal gradients (highland: >2600, medium altitude: 2300-2600, and bottomland: 1900-2300 meter above sea level) in north-eastern highlands of Ethiopia. Grassland condition assessment was based on grass layer composition, basal and litter covers, number of seedlings, age distribution of grasses and soil erosion according to previously developed methodologies. A total of 32 species were identified, of which 18 grasses, 7 legumes and 7 forbs. Benchmarks and private grazing areas had higher number of desirable grasses but the riverside and communal grazing areas dominated by undesirable grasses during the study. Similarly, benchmarks and private grazing areas were found in good and fair grassland condition, respectively, whereas the riverside and communal grazing areas were found in poor condition. Moreover, benchmark areas had a higher biomass yield of herbaceous species compared to the heavily grazed riverside and communal grazing areas. Our results confirmed that species composition, biomass yield and grassland condition in the benchmark areas were found in good condition, whereas riverside and communal grazing areas were highly deteriorated in the Ethiopian highlands, and resulted in severe soil and vegetation degradation. We suggested appropriate grazing land policy, destocking and pasture improvement technologies to improve the condition of the grasslands on the heavily grazed riverside and communal grazing areas in the north-eastern highlands of Ethiopia.