Comparative analysis of three methods for quantifying shrub and herbaceous stratum cover in eight major silvopastoral ecosystems in Morocco (Argan Forest, Alfa Steppe, Suberaie Forest, Tetraclinis Forest)
Abstract
The present study consists in comparing three methods of quantifying the vegetation cover: Intercept point method, Simple quadratic points method and the combined method, at the level of eight silvopastoral ecosystems of Morocco. The objective of this study is to find a method that objectively and more reliably approaches the cover of vegetation at the level of Mediterranean multi-strata pastoral ecosystems. To do this, we compared the results of these three methods, applying them to species cover measures for each ecosystem and for all ecosystems, stratum cover for each ecosystem, and for all ecosystems and the overall cover of all strata. The investigation method, which concerns eight natural ecosystems spread over the regions of Essaouira, Maâmora, Tendrara and Adrej, is based on the stratification of vegetation from satellite images. In each stratum, an inventory of the vegetation and the station’s factors was made simultaneously by the same methods. The analysis of the data was done by the Factorial Correspondence Analysis (AFC) to characterize the typology of the targeted ecosystems in question, highlighting the relations between these ecosystems and the ecological factors which prevail there. Then, through the application of an independence test, One-way analysis of variance (ANOVA1) and multiple analysis of variance (ANOVAM), we were able to compare the efficiency of these three methods, the results of which differ according to the structure of the vegetation. For the species (herbaceous and shrub species) considered at the level of each ecosystem and at the level of all the ecosystems, the results differ from one method to another. It is the same for the strata considered individually. For all ecosystems, the analysis of coverings of the herbaceous stratum shows no difference for the three methods; on the other hand, for shrub coverings, the combined method differs from the other two methods. Based on the overall cover, we have shown that the combined method is distinctly different from the other two methods which give the same results.
Keywords: ANOVA1, ANOVAM, Ecosystem, Cover quantification methods, Vegetation cover, Strata