Influence of coarse woody debris on the gastropod community of a managed calcareous beech forest in western Europe

In a managed beech forest a volume of 3-5 m(3)/ha deadwood including coarse woody debris (CWD) was found on the forest floor. The influence of CWD on the gastropod fauna was investigated during three seasons (September, March and June). Samples were taken in two different locations (plateau and SW-exposed slope); in each location, sites close to CWD (c-CWD) and distant from CWD (d-CWD) were distinguished. The results clearly revealed a strong influence of CWD on the fauna that was observed in all seasons, and a Discriminant Analysis showed that the species assemblages differed both between sites and between locations. A three-way ANOVA with single species revealed a strong influence of CWD, a low influence of location and no influence of season. Two dominant species, Punctum pygmaeum and Nesovitrea hammonis, occurred independent of the three factors analysed. Among those species that clearly preferred c-CWD sites were the other three dominant species, Discus rotundatus, Aegopinella pura and Carychium tridentatum, along with Euconulus fulvus, Cochlodina laminata, Monachoides incarnatus and Phenacolimax major. Only three species were also significantly influenced by location, of which C. tridentatum and A. pura preferred the plateau and P. major the slope. Life-stage analysis revealed that C. tridentatum clearly depended on the sheltered microclimate of c-CWD sites for reproduction. The results warrant the change to management practices favouring the availability of CWD as an important structural component, in order to help maintain biodiversity and improve aspects of the biological functioning of the forest floor such as nutrient cycling.