EFFECTS OF MANAGEMENT ON SPIDER COMMUNITIES OF HEADLANDS IN CEREAL FIELDS

The effects of different management regimes on spider communities of c ereal headlands in the Breckland Environmentally Sensitive Area were i nvestigated. Mean species richness, catch biovolume and the number of agile hunting spiders caught were significantly greater on uncropped h eadlands than on conservation (selectively sprayed) headlands, fully s prayed headlands and in the adjacent crops. Vegetation structural comp lexity (VSC) on the different headlands and crops was quantified by a principal components analysis based on measurements of peak vegetation height, stem density and the density of angled stems. The numbers of nocturnal hunters, agile hunters and ambushers caught were all signifi cantly positively correlated with VSC. It is concluded that VSC is an important environmental determinant of spider community structure and functional organisation. Species richness and catch biovolume increase d with time on uncropped headlands, probably as a result of increasing VSC, the lack of physical disturbance and the lack of fertiliser and pesticide application. The regulation of pesticide application on cons ervation headlands had no beneficial effect on the spider community pr esent on those headlands. Uncropped headlands are potentially of consi derable value to the biological control of aphids and the conservation of spiders.