Site factors controlling epiphytic lichen abundance in northern coniferous forests

Epiphytic lichens are an important part of the vegetation of northern coniferous forests of Eurasia and North America. Much progress has been made during recent decades at disentangling relevant site factors, which control the diversity and distribution of epiphytic lichens in boreal and oroboreal forests. The present paper aims at summarizing the present state of knowledge. Relevant site factors include the microclimate, nutrient supply, structural diversity and, if applicable, air pollution. The continuity of site conditions decides over the presence of species with dispersal limitations. The effects of fire on epiphytic lichens are largely unstudied, although fire is an important ecological factor in boreal forests.