Although controlled burning has been used to manage Highland Sourveld grasslands, little was known of its effects on the vegetation. This study examined the effects of past fire treatments on veld condition, species composition, dry matter production, quality and canopy recovery growth rates of these grasslands. Also, six techniques of estimating the species composition of grasslands were compared in order to decide on a standard technique for monitoring these grasslands. From this work it was concluded that the wheel point method is the most satisfactory. Veld condition scores were significantly lower in grassland protected from fire than where veld had been burnt or burnt and grazed at regular intervals. Frequent defoliation was found to maintain the grassland composition largely unchanged over a period of 30 years. Individual species were, however, found to react strongly to defoliation frequency. Plant demographic studies were therefore carried out to explain this differential response to burning. Three Decreaser and two Increaser I species were studied. In all species examined, recruitment of secondary tillers was stimulated by regular burning, each species being well adapted to a regular fire regime. Differential responses to burning were best explained by the combined effects of the different reproductive capacities and mortality rates of tillers of these species. A biennial spring burning regime was shown to be most suitable for maintaining the most important grass species at their present levels of abundance. Annual winter and biennial spring burning did not result in significant differences in dry matter production. Maximum net productivity was approximately 230 g/m² in both treatments, placing them amongst the more productive areas of Southern Africa. Examination of canopy recovery growth rates showed that there is little difference in the percentage canopy cover at the end of the growing season when veld is burnt annually in winter or biennially in spring. However, differences in season of burn resulted in exposure to erosive forces at different times of the year. The results of this investigation have highlighted the importance of regular burning during the dormant period in the montane grasslands of Natal. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1985.

Contemporary and historical studies of the flora of the Hluhluwe Game Reserve (HGR), have emphasised the woody component whilst little work has been performed on the herbaceous vegetation. This is particularly true with regard to the responses of grasses to historical fire and bush clearing. This study attempted to elucidate some of these responses. Of all the variables considered in this study, woody cover, altitude, the number of fire events, geological and soil parent material are the most important affecting the abundance of grasses in this reserve. Most of these variables are not independent in their effects on grass abundance, with varying degrees of correlation between each other. Certain species appear to be restricted to particular geological substrates. Along with successional changes in the composition and cover of the woody community, due to seemingly inevitable bush encroachment, there is a parallel change in grassland communities in this reserve. In the absence of clearing, numerous fires, higher altitudes, igneous geology and soils derived from igneous parent material delays this succession, whilst sedimentary geology at lower altitudes and fire frequencies accelerates the trend to high woody cover and associated grass species. The grass communities in HGR were shown to be significantly affected by bush clearing and fire. Specifically the number of clearings and fire events, physical bush clearing during 1957 - 1963 and chemical bush clearing during 1968 - 1978. From the responses of species in relation to the various key environmental variables, viz. geological substrate, woody cover and burning and clearing, a model of species response to these variables was developed. With increased fire and bush clearing frequency, the grass communities shift from closed woodland, shade tolerant species through to more open fire climax grassland. These are also more productive communities producing palatable grasses. Validation of aspects of the model were successful - the model having a relatively high predictive capability. Further testing of the model over different substrates and under different clearing regimes is necessary. With regular fires and re-clearing in some bush cleared areas, the vegetation of this reserve should be able to be maintained as productive and diverse grasslands. In the absence of this management, the grass communities will shift towards species associated with woodlands. Bush clearing activities would appear to be most effective over sites on igneous substrate, at higher altitudes, where successional rates are slowest. This is in comparison to sites at lower altitudes over sedimentary geology. / Thesis (M.Sc.)-University of Natal, Durban, 1992.