Carabid communities in the spatio-temporal mosaic of a rural landscape

The effect of landscape dynamics on carabid communities was investigated using a chronosequence of managed grassland sites. A total of 52 carabid species was found. Species richness was significantly higher in early than in later stages of grassland succession. The change from an arable land to a grassland carabid community was almost complete 10 years after the conversion to grassland. The accompanying change in the dominant feeding mode indicates a marked shift in the functional structure of the carabid community from arable land to grassland. Correlation analysis revealed a positive response of phytophagous species to dense and species-rich grassland vegetation that was only loosely related to grassland age. Invasion of grassland species was largely confined to the early stages of carabid succession. On the other hand, loss of species continued until the latest stage of the chronosequence, though many species preferring arable land had already vanished a short time after the conversion to grassland. The species turnover was independent of the dispersal abilities of the carabid species involved. This is probably due to the high spatial connectivity of suitable habitats in the small-scale landscape mosaic of the Lahn-Dill-Bergland. It is concluded that the variety of land use (arable land versus grassland) contributes considerably more to the species richness of carabids at the landscape level than the simultaneous availability of grassland sites of different age, provided that areas converted to grassland are allowed to persist for at least 10 years. The missing invasion of additional species into later stages of grassland succession can partly be explained by the premature state that is maintained at the older sites by management.