The effects on butterfly abundance of the management of uncropped edges of arable fields.
Abstract
The abundance and species richness of butterflies [Rhopalocera] on expanded-width uncropped arable field edges, which were subject to 10 contrasting, experimental management regimes, were measured using transects in 1989, 1990 and 1991 in Oxford, UK. The effects of the management regimes on a number of botanical variables, likely to be of importance to butterflies, were measured. On the experimental field edges, butterfly abundance and species richness fluctuated between years and peaked at different times each year. Butterfly abundance and species richness differed between experimental treatments. Plots which were either cut in the spring and autumn, or not cut at all, attracted more individuals and species of butterfly than did plots cut in the summer. Sowing with a grass and wild flower seed mixture increased butterfly abundance. Butterfly abundance declined on swards sprayed once annually with herbicide. Mowing, sowing and spraying had significant effects on mean flower abundance, on the annual and perennial components flowering in the sward, and on the abundance of commonly used nectar sources and larval host-plants. Stepwise multiple regression analyses on butterfly and plant data showed that the abundance of adults of most butterfly species was most closely associated with the abundance of flowers of key nectar source species. The results are discussed in relation to resource provision for larval and adult butterfly stages. Recommendations are made for the conservation management of butterflies on arable farmland.