| Autor: |
Stalmans, M., Mentis, M. T. |
| Zdroj: |
African Journal of Range & Forage Science; December 1993, Vol. 10 Issue: 3 p129-134, 6p |
| Abstrakt: |
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 × 30 m 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. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
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