The York Research Database

The effects of different management regimes on spider communities of cereal headlands in the Breckland Environmentally Sensitive Area were investigated. Mean species richness, catch biovolume and the number of agile hunting spiders caught were significantly greater on uncropped headlands than on conservation (selectively sprayed) headlands, fully sprayed headlands and in the adjacent crops. Vegetation structural complexity (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 significantly 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 increased 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 conservation headlands had no beneficial effect on the spider community present on those headlands. Uncropped headlands are potentially of considerable value to the biological control of aphids and the conservation of spiders.