Revegetation of Artificial Disturbances in Grasslands of the Serengeti National Park, Tanzania: II. Five Years of Successional Change

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Abstract
(1) The effects of disturbance-depth and grazing on succession, spatial heterogeneity and species revegetation patterns were investigated in four grasslands (short, mid, tall and mosaic) in the Serengeti National Park, Tanzania. Successional trajectories of vegetation on disturbed and control plots in grazed and ungrazed blocks and plot variability were derived from detrended correspondence analysis. (2) All disturbances were revegetated by species of the original community and returned to their previous compositions 1-3 yr after disturbance. (3) After the elimination of grazing, short and sexually-reproducing species disappeared from the short- and mid-grass communities, which became dominated by tall, vegetatively-reproducing species. The mosaic and tall-grass communities were unchanged. Vegetation on the disturbed plots in both grazed and ungrazed blocks resembled the species composition and structure of the surrounding undisturbed vegetation. (4) Within-treatment plot heterogeneity increased over 5 yr in a community that was dominated by vegetatively-spreading species but decreased in communities dominated by caespitose species. (5) Patterns of colonization and succession in the undisturbed plots supported Gleason's `individualistic' concept.