THE EFFECTS OF ARABLE FIELD MARGIN MANAGEMENT ON THE ABUNDANCE AND SPECIES RICHNESS OF ARANEAE (SPIDERS)

The effects of ten different management regimes on the abundance and s pecies richness of Araneae on pre-existing and newly expanded zones of field margins surrounding arable fields are compared in a large-scale experiment conducted between 1987 and 1991. Most of the management re gimes involved varying the timing and frequency with which the field m argins were cut. There was no evidence of consistent temporal trends i n the abundance and species richness of Araneae on either the existing or expanded zones of the field margins during the first four years of the experiment. However, lowest numbers were recorded before expansio n of the margins in 1987, and highest numbers in the final sample, in 1991. Araneae remained less abundant, and less species rich, on the ne wly expanded than on the existing zones of the field margins four year s after they were 'set-aside'. Cutting reduced both abundance and spec ies richness. Regimes which included cutting in mid-summer had a great er impact which persisted for longer than did those involving cutting in spring and autumn. Removal of cut material was associated with lowe r species richness than leaving it in situ. Sowing the margins with a wild flower seed mixture was associated with increased abundance and s pecies richness of Araneae, Annual spraying with a broad-spectrum, non -persistent herbicide reduced the abundance of Araneae but the effect was not detectable until several months after the application of the s pray. Both the species richness and abundance of Araneae were positive ly correlated with a measure of vegetation height made on the field ma rgins in September, on both the pre-existing and newly expanded zones of the margins. The extent to which management practices which benefit Araneae are compatible with both the management requirements for vari ous other taxa, and the overriding constraint of effective pernicious weed control on field margins, is discussed.