Rangeland evaluation in the middle Awash valley of Ethiopia: II. Woody vegetation

摘要

Although a few studies have reported an increase of woody plants in the rangelands of Ethiopia during the last few decades, most studies related to the importance of tree canopies have been conducted in lightly grazed areas that have suffered little disturbance. The woody vegetation composition, density, evapotranspiration tree equivalent (ETTE), browse production, browsing capacity and bush encroachment were therefore studied in a part of the Middle Awash Valley of Ethiopia with the objective of determining the condition and contribution of woody vegetation as a source of feed to animals. Accordingly, 7 and 8 rangeland sites in Kereyu-Fantale and Awash-Fantale districts, respectively, were identified. The data collected was analyzed using the Biomass Estimates from Canopy Volume model. The dominant sources of browse and the encroacher woody plants in the study districts were species of Acacia (A. Senegal and A. nubica). In both districts, the browse production ranged from as low as 194-3 311 kg ha~(-1) with most of the leaf dry mass found above the height of 1.5 m. Some of the possible factors contributing to bush encroachment in the study area are heavy grazing pressure, expansion of cultivation and reduced mobility of animals due to many factors.