Distribution, prevalence and intensity of earthworm populations in arable land and grassland in Scotland

Summary. The earthworms of arable and pasture fields from 100 randomly chosen arable farms were identified and counted and their relationship with soil factors examined. Thirteen species of earthworm were recorded includingLumbricus friendifrom Scotland for the first time. The most prevalent and numerous species wereAporrectodea longa, Aporrectodea caliginosaandLumbricus terrestris.All earthworm species had cosmopolitan distributions apart fromAporrectodea nocturnaandLumbricus festivuswhich were confined to southern/central Scotland. Four soil characteristics (% moisture, % sand, % organic matter and pH) shared no relationship with species recorded but tillage may have had a detrimental effect on species composition and size of population. It is suggested that the magnitudes of the earthworm populations found, particularly in permanent pasture, were important in maintaining soil structure and fertility, and the spread of the New Zealand flatworm(Artioposthia triangulata), an obligate predator of earthworms, could have a considerable impact on agricultural productivity and wildlife in Scotland.