EFFECTS OF 20 YEARS OF GRAZING EXCLUSION IN AN AREA OF THE QUEEN ELIZABETH NATIONAL-PARK, UGANDA

The floristic and structural changes resulting from the long-term excl usion of large herbivores from an experimental area set up in 1971 hav e been analysed, comparing it to two plots in the surrounding grazed a nd trampled area. The vegetation of the area is grassland with thicket clumps, with Sporobolus pyramidalis P. Beauv. dominating the grasslan d and Capparis tomentosa Lam; dominating the thicket layer. The survey showed that long-term exclusion of herbivores results in: (i) higher density and cover in the grass and thicket layer, (ii) lower biodivers ity in the grass layer and in the isolated shrubs, (iii) higher root b iomass, probably due to the absence of trampling. Despite the differen ce in area, no difference was noted between the biodiversity of the th icket clumps of the ungrazed area and the grazed and trampled plots.