Diversity of epiphytic lichens in boreo-nemoral forests on the North-Estonian limestone escarpment: the effect of tree level factors and local environmental conditions

Abstract The species richness and composition of lichens was quantified for four temperate broad-leaved tree species ( Acer platanoides, Fraxinus excelsior, Tilia cordata and Ulmus glabra ) in boreo-nemoral forests on the talus slope of the North-Estonian limestone escarpment (North-Estonian Klint). Thirteen study sites were distributed along the klint on a west to east gradient. The effects of tree and stand characteristics and geographical location of a stand on composition and diversity of epiphytic lichens were evaluated by multivariate analyses (DCA, CCA, pCCA) and by general linear mixed models (GLMM). Tree level variables (e.g. bark pH, bryophytes cover and host tree species) explained the largest fraction of the variation in lichen species composition. However, species richness and composition were significantly influenced also by the unique habitat conditions of klint forest (length of the forest fragment, proximity of the stand to the sea and height of the escarpment). A significant correlation between stand locality and lichen diversity on the tree bole was found which is most likely related to local air pollution gradients caused by alkaline cement dust and acid pollutants in the north-eastern part of Estonia.