Development and monitoring procedures for the herbaceous layer on the northeastern Transvaal escarpment

Abstract

A step-wise approach was followed towards the design of a monitoring system for the herbaceous layer on the escarpment of the Drakensberg mountains in the Transvaal, South Africa. The parameter of concern was proportional species composition. In a first phase, the plot size and number of point observations required to achieve a repeatable assessment of a single plot at a predetermined precision level were investigated. The Chapman-Richards three-parameter model was fitted to similarity values obtained from comparisons between successively larger sets of points. This resulted in 140 points being required within a 30 x 30 plot in order to recover 95% of the internal association of the composition data. In a second phase, the number of plots required for a repeatable assessment of a large stratum was determined. Successively larger nested areas were sampled. Monitoring of a large stratum at 95% of asymptotic replicate similarity would require sets of 21 randomly selected plots. The third and final phase was concerned with the development of a procedure for detecting change. A similarity test made it possible to detect change between successive surveys with a known degree of precision.

Keywords: botany; composition; drakensberg mountains; herbaceous layer; internal association; model; monitoring; precision; procedure; replicate similarity; sourveld; south africa; species composition; survey; transvaal; wheel-point apparatus

African Journal of Range & Forage Science, 10(3): pp. 129-134