Ordination of the herbaceous stratum of savanna in the Nylsvley Nature Reserve, South Africa

The purpose of the study was to determine the ecological status of representative herbaceous species with respect to environmental factors and subhabitats of which the spatial and temporal pattern could be elucidated.The basal cover of the herbaceous vegetation was determined by means of the wheel-point method. Frequency data in each of 200 1 m2 contiguous quadrats were ordinated by means of detrended correspondence analysis (DECORANA).The distribution of the species along the first axis is a function of conditions representing an open habitat with full sunlight and somewhat drier conditions to the left and a denser and/or shrub habitat with more shade and wetter, more favourable conditions to the right. The gradient along the second axis is that of undisturbed conditions with more perennials at the lower end to disturbed conditions with more annuals at the upper end. From the scatter diagrams it can be concluded that the herbaceous layer is functionally homogeneous, that it represents a seral stage and that Eragrostis pallens and Digitaria eriantha, both with the highest basal cover in the study area, are representative of a seral stage rather than of the climax. The lack of pattern in the herbaceous layer can be attributed mainly to the large number of annual and perennial pioneer and disturbance-indicating species. In a similar study Whittaker et al. (in press) concluded that the woody vegetation dominates the pattern