VEGETATION RESPONSE TO CATTLE GRAZING IN THE ETHIOPIAN HIGHLANDS

The effect of grazing cattle on vegetation was studied on a natural pa sture during the rainy and dry seasons of 1995 in the Ethiopian highla nds. The study used 0.01 ha plots, established on 0-4% and 4-8% slopes located close to each other at Debre Zeit research station, 50 km Sou th of Addis Ababa. The grazing regimes were: light grazing stocked at 0.6 animal-unit-month per hectare (AUM ha(-1)); moderate grazing stock ed at 1.8 AUM ha(-1); heavy grazing stocked at 3.0 AUM ha(-1); very he avy grazing stocked at 4.2 AUM ha(-1); very heavy grazing on ploughed pasture stocked at 4.2 AUM ha(-1); and a control of 'no grazing'. Heav y grazing significantly reduced vegetative cover and biomass yields, e specially on steeper slopes, Light to heavy grazing did not affect the botanical composition of the vegetation at both sites, but very heavy grazing resulted in species normally less preferred by animals domina ting the botanical composition. Grazing did not have significant effec t on ground vegetative cover on the 0-4% slope except at very heavy gr azing pressure, but on the 4-8% slope even moderate grazing significan tly reduced vegetative cover. Light to moderate grazing at the beginni ng of the dry period enhanced plant biomass productivity, while any gr azing reduced plant productivity during the periods of reduced growth. Species richness increased with increasing grazing pressure compared with no grazing, but decreased sharply at very heavy grazing pressure. We concluded that there is need for developing 'slope and time specif ic' grazing management practices, and to assess short and long term ef fects of grazing and trampling on vegetation. (C) 1997 Elsevier Scienc e B.V.