Gastropods, trees, pH, subsoil and epiphytic lichens

Epiphytic lichens are under considerable grazing pressure due to invertebrate lichenivores, mostly gastropods. Preferences of tree-climbing gastropods affect vertical distribution of lichens, their habitat preferences and whole area of distribution. Higher grazing pressure is expected on sites with basic subsoil and sufficient sources of calcium, where the abundance of gastropods is higher. Most of researches about the topic of grazing pressure were therefore conducted on such sites, although this hypothesis has never been formally tested. Epiphytic communities are also affected by pH and other properties specific to its photophyte. Nevertheless, it is not known, if the same applies for grazing gastropods and how is the grazing pressure affected by tree species. I have addressed these questions in my thesis. I set an 80-days-long field transplantation experiment in the mixed forest of Moravský kras (South Moravia, Czech Republic). Glass fiber meshes with lichen thalli were placed on sixty trunks of three tree species (Carpinus betulus - hornbeam, Abies alba - fir, Fagus sylvatica - common beech) on both calcareous (limestone) and acidic (granodiorite) sites. Abundance and diversity of gastropods were measured. Determined grazing pressure was higher than pressure detected by other authors and was..