The relationship between snails, soil factors and calcitic earthworm granules in a coppice woodland in Sussex

A variety of environmental parameters including soil aggregate size and earthworm granules were examined in relationship to snail abundance and diversify in different aged coppice compartments in a deciduous woodland in Sussex, England. The results indicate, in general, a positive relationship between snail abundance and intermediate sized aggregates (5mm and 2 .36mm) and a negative relationship with 0.6mm and 20mm. Several individual species also followed this trend. The reason for this correlation is not clear.
Ordination of snails, sites, soil fractions and other environmental variables achieves a clear geographical site separation. Soil aggregate sizes are the principal components along with pH and earthworm calcitic granules. It is clear that the soil aggregate size proportions vary substantially between coppice compartments and this may be an important factor in explaining variation in snail distribution in the study area. Earthworm granules correlate strongly with certain factors such as pH and chalk, and also with certain snail species. This link is likely to be caused by similar environmental preferences such as with pH and litter depth. Earthworms may facilitate favourable conditions for certain snails by aggregate production and litter breakdown.