The importance of field boundaries for earthworms (Lumbricidae) in the Swedish agricultural landscape

Abstract

The aim of this study was to find out if field boundaries are refuges for earthworms from where they can spread out into the agricultural fields, thereby keeping up their abundance and biodiversity. The earthworm community was studied in: (1) a 640 m long field boundary; (2) the adjacent arable field at different distances from the boundary; (3) a pasture adjoining to the opposite side of the field near Uppsala in Sweden. Sampling was done in May and September. In contradiction to what was preconceived, the abundance and biomass of earthworms, both in the boundary and the pasture, was significantly lower than that in the agricultural field. The density increased towards the centre of the field. The trends were similar for both spring and autumn. The same species were found in the field, boundary and pasture, but Aporrectodea caliginosa was more dominant in the field than in the other habitats. The conclusion is that agriculture with manure, fertilisers, moderate soil cultivation and varying crops, in general, is favourable for earthworms, except for certain species. However, situations can occur when the earthworm populations in the field decline, and then boundaries may serve as sources from where re-immigration can take place.