Resource‐based determinants of range sizes of forest vascular plants in Germany

Abstract

AbstractAimTo examining whether niche breadth, niche position and a compound measure of the two variables help to explain the range sizes of forest vascular plants.LocationsDeciduous forests in two regions of Germany, the Weser–Elbe region and Bavarian Alps.MethodsWe compiled range size data for vascular plant species (30 in the Weser–Elbe region, 35 in the Bavarian Alps) on regional, national and continental scales by determining the area of occupancy (number of occupied grid cells) in both regions, Germany and Eurasia. Estimates of realized niche breadth and niche position (ecological optimum) for soil pH and light were based on measurements in 46 sites for all species. Frequency distributions of pH values on regional and national scales served to calculate the ‘available niche breadth’, i.e. niche breadth values corrected for the different availabilities of pH values in the region and country.ResultsRegional range size in the Weser–Elbe region increased with increasing niche breadth for both soil pH and light and with decreasing pH niche position. pH niche breadth was positively correlated to national range size in the Weser–Elbe region and to Eurasian range size in the Bavarian Alps. In the latter region, all other relationships with range size were (partly marginally) non‐significant. Available niche breadth was generally more closely related to the regional and national distribution of species in both regions than either niche breadth or position alone.Main conclusionsNiche breadth and position performed well as predictors of range size only for soil pH and in the Weser–Elbe region, which shows more homogeneous environmental conditions than the Bavarian Alps. If the frequencies of different ranges of pH values can be quantified, the calculation of available niche breadth for soil pH appears to be a promising approach for assessing the possible effects of niche variables on the range sizes of species.