Losing uniqueness - shifts in carabid species composition during dry grassland and heathland succession.

Abstract

Dry sand ecosystems, such as dry grasslands and heathlands, have suffered habitat loss and degradation due to land‐use changes and are today among the most endangered habitats in Central Europe. To evaluate the impact of degradation processes on habitat quality, we investigated how succession from sparse vegetated sand ecosystems to grass‐invaded and tree‐dominated ecosystems and the environmental parameters associated with it influences carabid assemblages. We also determined to what extent typical xerophilic species assemblages still exist. Pitfall trapping at 28 study sites in northwestern Germany yielded 111 carabid species that were grouped using Kendall's W coefficient of concordance. Ordination revealed that the differences between the four species groups resulted from vegetation cover and soil humidity, indicating that carabid distribution clearly reflects degradation processes. Our results suggest that areas in which succession proceeds were unsuitable for assemblages typical of dry grasslands and heathlands. In all, 35 species are lost due to succession from dry grassland and heathland to grass‐invaded and tree‐dominated sites. We discuss implications for habitat management and restoration, since dry sand ecosystems comprise a very high number of specialized and endangered species.