Organic versus conventional arable farming systems: Functional grouping helps understand staphylinid response

The response of different feeding groups of staphylinid beetles to organic management, distance to perennial boundary and landscape context was studied in 42 paired organic and conventional winter wheat fields. Management effects were found to strongly depend on feeding group. While the activity-density of predators was higher in the conventional fields, both activity-density and species richness of detritivores were higher in the organic fields. Activity-density and species richness of detritivores were positively correlated to crop yield in the conventional but not in the organic fields. Unexpectedly, species richness as high as in the less productive organic fields was thus found in intensified conventional systems. No significant effects of landscape context could be found on activity-density or species richness of the different feeding groups. More species were caught near the field edge than in the middle, showing the importance of spill-over from field boundaries into arable crops for diversity. In conclusion, separation of species into feeding groups revealed patterns that have not been shown before. Decomposer diversity (but not that of predators and fungivores) was higher in organic fields, but reached similar levels in high-yielding conventional fields. Thus resource quality (purely organic or organic/synthetic fertiliser) and quantity appear to play a major role for this functional group.