Interrelationships Between Fire, Grazing and Grass Cover at the Bontebok National Park

Abstract

Point surveys of permanently marked plots were conducted with the aim of (i) determining the change in grass height, cover and degree of defoliation with increasing time after veld burning and (ii) determining which plant species are most intensively defoliated by herbivores (mainly bontebok and grey rhebok). Grass was the most heavily defoliated component of the vegetation, whereas Restionaceae and Cyperaceae were generally avoided. No grass species was consistently avoided by herbivores, and no species was consistently favoured. Instead selection among species varied with growth stage. The tall, coarse species were favoured on new burns when the vegetation was still short. The short species came into favour once the sward had grown taller. Defoliation was heaviest within the first year after burning and thereafter decreased substantially. The introduction of coarse grass grazers such as mountain zebra to the park might lead to greater use of the mature veld. Those grass species that underwent the heaviest defoliation on new burns (over 50 of leaves severed) showed three- to seven-fold increases in canopy spread cover over subsequent years. Thus heavy use of recently burnt veld is not necessarily deleterious.