The Accuracy of the Step Point Vegetation Sampling Method for Herbaceous Layer Monitoring in South African Savannas
Armand A. Biko’o | Willem J. Myburgh | Brian K. Reilly
Robust monitoring techniques, capable of showing change in the savanna when change has occurred, are a prerequisite for better managing this ecosystem. The Step Point Method is a well-established technique in South African range surveys (Short and Morris 2016). However, it is often considered inaccurate in describing vegetation dynamics in the savanna herbaceous layer due primarily to issues with sample sizes and cover estimates, its inability to capture the spatial heterogeneity and patchy distribution typical of these ecosystems, sensitivity to observer bias, reliance on relative values and poor inclusion of sparse or less common species. This study aimed to test the effectiveness and accuracy of the Step Point Method for monitoring the herbaceous layer of savanna by comparison to absolute densities of plants. The results show that the Step Point Method only recorded 41–50% of species richness. It overestimated the relative species richness of grasses by 17.4% while underestimating that of forbs by 13.8% on average. The relative abundance of grasses was overestimated by 32.4%, while that of forbs was underestimated on average by 28.4%. Dominance was overestimated by 115.5% on average, and species diversity was underestimated by 15%. Considering these shortcomings, the Step Point Method should be used with extreme caution in studies focusing on monitoring temporal and spatial changes in veld condition and for biodiversity management.
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