The spatial and temporal pattern of carabid beetles on arable fields in northern Germany (Schleswig-Holstein) and their value as ecological indicators

Ground beetles have been often used as indicators for agricultural practices in ecological studies, but little is known about the spatial and temporal variation independent from the agricultural practices. Between 1985 and 1995 the ground beetles (Carabidae) of 53 fields in Schleswig-Holstein (northern Germany) were investigated using three replicate pitfall traps at each site. One field was studied over a period of 9 years from 1988 to 1996, and in addition two adjacent fields subjected to ecological or conventional farming methods were investigated in 1999 using 12 pitfall traps each. Overall, five assemblages of ground beetles could be differentiated, primarily by sand content of the soils and field size. The separation of the assemblages was weak (eigenvalue of 1st axis: 0.39) compared to natural ecosystems. The most common assemblage on loamy soils was dominated by Pterostichus melanarius. On both sandy soils and loamy soils in small fields the species Poecilus versicolor and Platynus dorsalis, Bembidion lampros, respectively, dominated. Eight ecologically differentiated groups of ground beetles were found. Most species correlated positively with the sand content of the soils. Only two species, P. melanarius and Loricera pilicornis showed a positive correlation with the field size. A higher species richness was observed on fields which have practised for 30 years ecological farming. Comparing the two adjacent fields with ecological and conventional farming, no difference in species richness was detected. Four species showed higher abundance on the field with ecological farming. In this analysis of a long-term dataset ground beetles did not respond to the cultivated plants, but only to the yearly climate conditions.