Factors affecting the distribution of lumbricids (Oligochaeta) in associations at peat and mineral sites in northern England

Summary

• 1. Earthworms were collected in pitfall traps from 46 moorland sites over a period of two years; mineral moorland sites were sampled by formalin solution and gave density estimates of 40–100 worms per square metre.

• 2. Thirteen species were found and A. chlorotica and A. caliginosa were most abundant. Sites were clustered on the basis of species present and showed mineral and peat sites clearly separate. Six species were almost confined to mineral sites and B. eiseni was virtually confined to peat sites.

• 3. Environmental factors measured at the sites were used in multiple regression analysis to identify those significant in governing the distribution of each species; pH, loss in wieght on ignition of soil, plant association and dominant plant were among those significant.

• 4. Cluster analysis showed only one cluster of seven species. The distribution of most of these had been shown to be determined by dominant plant species (or a factor associated with this) or by soil pH.

• 5. Species in a cluster are largely responding to the same group of environmental factors but detailed investigation of microdistribution and laboratory experiments to identify other factors which affect their population dynamics are needed to fully explain the geographical distribution of earthworms.