A plant ecological survey of the Umfolozi Game Reserve, Zululand.
Downing, Brian Harvey.
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A landscape unit approach based on use of airphotos was used for investigation of Deciduous Acacia Woodland in the Reserve. The approach was useful for indicating that a quantity of as few as 531 samples could be suitable for sampling woody vegetation over the large, 493 km² area, and for showing where the samples might advantageously be distributed. Use of the approach minimised the extrapolation of community boundaries for mapping purposes. Normal association analysis of the samples revealed the nine woody consociations present and provided quantitative data on species constancy and fidelity. These data were used towards explaining low levels of homogeneity within consociations, as well as some close floristic similarities found between consociations. The successful emergence of a species to dominance in a consociation was ascribed to the presence of a particular, described soil series or rock substrate. The distribution pattern of the consociations resembled a soil-vegetation catena on the landscape. The consociations were grouped into defined physiognomic categories of Open, Closed and Riverine Woodland Associations that were distributed according to three soil associations. The effects of soil factors, fire and the biota on physiognomy, notably secondary thicket encroachment, were discussed; and the relationship between climate and phenology was mentioned. A quantitative description of the grass communities based on normal analysis of stratified sample data revealed a retrogression whereby climax grasses are being replaced by mid-seral and pioneer grasses. The retrogression was ascribed to selective grazing by an increasingly large biomass of enumerated, indigenous herbivores. Some of the management recommendations offered were based on empirically calculated estimates of the weights of dry grass required annually by the grazing animals. Copies of topography, place names, geology, land surface and vegetation maps are provided. The text is supplemented by check lists of plants and animals recorded, by eight figures, 33 tables and 54 photos.