The Effects Of Fire And Grazing On Grasslands Of Nairobi National Park

Abstract

The object of this study was to investigate the effects of burning, grazing and habitat on species composition, nutritional quality of the grasses, and the vegetation and grazing herbivore biomass. Comparisons of the above variables were made between burnt and lightly grazed plots inside the park and heavily grazed areas outside. Comparisons of quality between the treatments showed that quality was highest in the burnt areas, followed by heavily grazed and was lowest in the lightly grazed areas. Species composition varied between the treatments. Pennisetum mezianum, a coarse and unpreferred species and Eragrostis tenuifolia, a species which has been suggested as being highly successful in heavily grazed areas were abundant. Early burning affected species composition by changing the relative contribution of the different species to the total biomass. In some habitats, .- certain forbs were eliminated by burning. Biomass quickly increased to amounts found before burning except where grazing pressure was high. Outside the park, where there was heavy and continuous grazing, biomass remained low, but quality was sufficiently high. Animal counts at two-week intervals showed that animals particularly grazing herbivores preferred the burnt areas where the nutritional quality was high. Most animals moved out of the burned areas when grasses became tall and f1l1alitydeclined. Results of the controlled experiments showed that heavy simulated grazing reduced total production of the plant. There was no significant difference between no grazing though the results showed a slight stimulation peak at moderate levels of grazing.