干旱区生态环境知识资源中心

This study investigated the impact of rainfall and herbivory by indigenous herbivores over five years (2004-2008) on the vegetation of the Sanbona Wildlife Reserve (SWR), a 54 000 ha privately owned conservation area in the Little Karoo. Changes in floristic composition, species richness, aerial plant cover and grazing capacity were determined using drop-point surveys in fenced and open (i.e. grazed) plots in four dominant vegetation types. Annual and seasonal rainfall totals, herbivore stocking rate and herbivore utilisation patterns were also measured. Ordination analyses showed that fenced plots did not develop a fundamentally different successional trajectory from open plots over time. There were also no significant differences in species richness, plant cover and grazing capacity between fenced and open plots in all vegetation types. This lack of indigenous herbivore impact is ascribed to the relatively low stocking rates that were maintained on SWR during most of the study period. Species richness, plant cover and grazing capacity also did not differ significantly between years in all vegetation types except for the highly disturbed Old Land sites. The existing monitoring programme provides a useful tool for assessing the impact of indigenous herbivores and should be supported at local and provincial levels.