Evaluation of three objective point-sampling techniques to measure utilization of karoo bushes.

Abstract

Three techniques to measure utilization of karoo bushes were evaluated. Precision, accuracy and consistency were measured on three species at different times and levels of utilization. The percentage-cover technique was less sensitive and less efficient than the percentage-edible-strikes and percentage-twigs-grazed techniques. It required samples that were 25% larger than those needed for the other two techniques to achieve equivalent levels of precision. For any single technique, precision was consistent for different species. Provided samples exceeded 30 bushes all techniques were consistent over time. No improvement in accuracy was measured for samples greater than 20 bushes. While similar levels of accuracy were achieved on the three species, the lack of consistency of the percentage-cover technique for different levels of utilization, limits the usefulness of the technique. To estimate utilization of a single species using any of the techniques with adequate precision and accuracy, approximately 25 minutes with two operators was required.Language: English

Keywords: accuracy; botany; karoo bushes; percentage-cover technique; percentage-edible-strikes technique; percentage-twigs-grazed technique; Point-sampling techniques; precision; repeatability; sampling; south africa; techniques; utilization