Biotic and abiotic edge effects in highly fragmented heathlands adjacent to cropland and forest

The aims of this study were to examine how adjacent land use, in this case cropland and forest, affects the heathland plant community and soil chemical composition, and whether potential edge effects differ according to adjacent land use type or edge orientation. Therefore mixed modeling was applied on vegetation and soil data gathered from 20 heathland edges adjacent to cropland or forest. Plant community composition showed a clear gradient across the heathland edge, both for cropland and forest as adjacent land use. Heathland soil nutrient content also varied with edge distance. No effects of heathland orientation with respect to forest could be found. For both types of adjacent land use, edge effects were limited in their extent to a zone of ca. 8 m into the heathland patch. Within this zone however, eutrophicating effects of cropland on the heathland vegetation and soil were more pronounced than the effects of the presence of an adjacent forest. From these results, it could be concluded that heathland flora and soil were significantly altered in a zone of ca. 8 m from the heathland edge. Eutrophication was the driving force behind this change, both for heathland adjacent to cropland and heathland adjacent to forest. Especially in the heathland–cropland edges this eutrophication has resulted in an almost complete replacement of the characteristic dwarf shrub vegetation by grasses and species typical for nutrient-rich habitats.