On the combination of species cover values from different vegetation layers

Abstract

Abstract Phytosociological relevés consist of lists of species occurring on certain plots and their cover values in different vegetation layers. When combining the cover values of two layers into a unique value, the overlap between the layers must be taken into account. With two layers this can easily done by subtracting the product of the cover values from their sum. A general formula to estimate the combined cover for any number of layers, assuming independence of the layers, is presented. This is especially useful for large databases where rich data sets have to be compiled that were originally recorded from different numbers of vegetation layers.