Anthropic influences on earthworm distribution, Isle of Rum National Nature Reserve, Scotland

Earthworm surveys were conducted on the Isle of Rum (NNR), Inner Hebrides, Scotland. Fifteen species were located representing all three ecological groups of earthworm. Most species have a very limited distribution, around current or former centres of human habitation and are associated with anthropic activity. Bulk addition of mainland soil at Kinloch provided conditions that now support 12 species (greatest diversity recorded). Three species Dendrodrilus rubidus, Dendrobaena octaedra, and Lumbricus rubellus are almost ubiquitous across Rum, occurring on acidic moorland and to the summit of the highest peak (812 m). Fertiliser addition at such altitude to patchy, herb-rich Calluna heath, has led to greater earthworm numbers but no more species. Where woodland has been re-established on moorland, earthworm communities showed significantly increased numbers (up to 170 m–2 with a mass of 25 g m–2) and increased diversity compared with associated moorland (approximately 10 m–2). It is suggested that selected earthworms, such as Aporrectodea caliginosa and L. rubellus may have a role in assisting soil development and woodland establishment, so their use in the continuing Rum afforestation programme ought to be considered.