Phytodiversity in nutrient-poor heathlands and grasslands: how important are soil chemical factors?

Central Europe is dominated by intensive farming and the concomitant nutrient input is a main thread to biodiversity in open habitats. The rare case of soils unaffected by agricultural intensification found on a military training area (Grafenwoehr, Bavaria, Germany) was used as an opportunity to study the influence of soil chemical factors on plant species richness in two types of open habitats. Species richness of spermatophytes and soil chemical factors (pH, P, K, Mg ) were assessed on a total of 94 relevés situated in heathlands (40 relevés) and grasslands (54 relevés). Averaging over linear mixed models, we showed a distinct decline of plant species richness with decreasing pH in both habitats. Despite generally low soil P content, species richness declined strongly with increasing soil P in grassland. Consequently, to preserve highly diverse open habitats, it is necessary to spare them from anthropogenic nutrient input.