THE INVERTEBRATE ECOLOGY OF FARMLAND AS A MIRROR OF THE INTENSITY OF THE IMPACT OF MAN - AN APPROACH TO INTERPRETING RESULTS OF FIELD EXPERIMENTS CARRIED OUT IN DIFFERENT CROP MANAGEMENT INTENSITIES OF A SUGAR-BEET AND AN OIL SEED RAPE ROTATION INCLUDING SET-ASIDE

The effects of different crop management intensities were investigated on the arthropod community in a sugar beet rotation between 1989-1992 and in an oilseed rape rotation including long-term set-aside between 1992 and 1995. There was a general reduction of arthropod production with increasing intensity of crop management, but very different and s ometimes even opposite reactions at the species level. The intensity o f effects depended on the type of lifecycle (e.g. rove beetles are sen sitive to pesticide applications only during their reproduction period and not during the hatching of their new generation). Certain pest in sect species were enhanced by an increasing intensity of crop manageme nt. Due to harvest and tillage procedures some beneficials were not ab le to build up stable populations in arable crops but did so in long t erm set-aside areas. The activity period of certain beneficials is sho rter the more intensive crop production is conducted. Body length was inversely related to management intensity. Number of individuals, spec ies richness and reproductive rate increased with progressive extensif ication and especially in set-aside areas with natural succession. The percentage of pioneer species of spiders decreased with increasing ex tensification and extension of the crop rotation, and lycosid spiders dominated in the set-aside area with natural succession. The percentag e of euryoecious (spider) species increased with more intensive cultiv ation. The greatest similarity in species composition was between the set-aside area and the more extensively managed crops.