Epiphytic macrolichens as conservation indicators: successional sequence in Populus tremula stands.

摘要

We studied the species composition of epiphytic macrolichens in 18 aspen (Populus tremula) stands located in boreal forest around Lake Tunsjon, Angermanland, central Sweden. Stand age varied from about 20 to 130 years old. In total, 51 macrolichen species were found, 15 of which were aspen specialists. Qualitative features, e.g., identifying signal species, showed a stronger correlation than quantitative features, e.g. total number of species, to increasing stand age. Aspen specialists showed a significant difference in dispersal mode, early colonizers were mainly sexually dispersed and late colonizers were mainly asexually dispersed. Cyanolichens were confined to late-successional stands, and did not occur in adjacent younger stands. It is concluded that late-successional aspen stands in the forest must be conserved to function as core habitats for dispersal to young stands. Thus, such young stands have to be continuously created in order to retain the unique lichen flora associated with aspen stands in the forest landscape.