Old selectively cut forests can host rich lichen communities - lessons from an exhaustive field survey

Lichens comprise a significant part of forest biota, but their diversity patterns are poorly known at medium spatial scales, which are most relevant for management planning. We carried out exhaustive lichen surveys in two 2-ha plots of old, weakly harvested herb-rich forests in Estonia; the field effort exceeded 500 hours for each plot. We recorded 222 species (194 lichens, 14 lichenicolous and 14 saprobic fungi traditionally treated by lichenologists), including 57 species of conservation concern. Those numbers form ca. one-third of forest species known in this fungal group in Estonia and were very similar in the two plots. Bacidia hemipolia f. Czarnota & Coppins, Lecanora farinaria Boner. Porina borreri (Trevis.) D.Hawksw. & P.James and Phaeocalicium tremulicola (Norrl. ex Nyl.) Tibell are reported as new to Estonia, and several other rare or little-known species were found. Many putative 'old-growth indicator species' formed local populations of substantial size. Using a fixed-effort approach (based on 4 survey hours per 2 ha) we demonstrate that the species richness in the studied stands exceeds that previously found in conventionally managed 2-ha stands and is not smaller than in old growth of similar site type. These results indicate that old selectively cut forests can provide valuable microhabitats and host rich lichen communities, and they represent a useful option for enhancing biodiversity in forest landscapes managed predominantly by even-aged systems.