Over- and under representation of red list species along abiotic soil gradients

For conservation purposes, but also to understand plant species behavior, knowledge on their abiotic preferences is essential. Based on a large database with vegetation relevés and abiotic soil measurements the general species number and the number of rare species and red list species preferences along abiotic axes were investigated. The ranges of the species, defined as the range between the 5 and 95 percentile of the response curve of the species for an abiotic factor, were used. These ranges were used to calculate the number of species along the abiotic gradient. The abiotic axes, e.g. for soil pH, were cut in small sections and per section the number of species and the number of rare and red list species was counted. Subsequently, the relative red list and rare species number per section was calculated and visualized. The number of species clearly changes along the abiotic axes, with for soil pH high number of species at intermediate pH values and in general for nutrients high number of species at low nutrient levels and low number of species at high nutrient values. For total phosphorous content of the soil also a low number of species is present at very low phosphorous contents. Red list and rare species showed a different pattern along the axes. At low pH values they are underrepresented and at high pH values over-represented. The same pattern appears for chloride content. For nitrate and total phosphorous content of the soil red list and rare species are over-represented at low concentrations and underrepresented at high concentrations.