Edyta Adamska and Dariusz Kamiński
Faculty of Biology and Environmental Protection, Chair of Geobotany and Landscape Planning, Nicolaus Copernicus University, Lwowska 1, PL-87-100 Torun, Poland
Invasive alien species affect the ecosystem at various levels of its organization. The effect of the invasion can be, among others, change in the species composition of different groups of organisms caused by the transformation of biotic and abiotic properties of the habitat. Bark of trees is a substrate for lichens and there is a strong correlation between epiphytic lichens and phorophytes, which result from the physico-chemical properties of the bark. Trees in natural riparian forests are phorophytes for the group of stenotopic lichens defined as indicators of naturalness of forests and common eurytopic. A good example of negative impacts may be the invasion of Acer negundo in Poland, which is particularly well spread in river valleys in riparian forest habitats. It occurs as an admixture in natural willow and poplar forests, it can also form almost single-species communities. In this study, we explored the relationship between kind of native and invasive phorophytes and biota of epiphytic lichens. Our research on the lichens species composition were conducted in the Vistula River Valley in the city of Toruń and in its vicinity in riparian forests with the participation of Acer negundo. On the bark of Salix spp. and Populus spp., we found a total of 50 stenotopic lichen species (e.g. Bacidia incompta, Chaenotheca brachypoda, Ch. trichialis, and Ch. chrysocephala). On the Acer negundo bark, 13 species of lichens occurred, mainly toxitolerant – nitrophilous, photophilous and coniophilous (e.g. Phaeophyscia orbicularis, Physcia tenella, Ph. adscendens, Physconia grisea; and Xanthoria parietina). On the bark of A. negundo, the lichens were abundant, while on native phorophytes they covered a small percentage of the bark’s surface. The Acer negundo invasion causes qualitative and quantitative changes in the lichen species list. The availability of substrates for stenotopic species is reduced while the abundance of toxitolerant species is increasing. It can be assumed that replacing natural forests by xenospontaneous A. negundo communities will result in the disappearance of stenotopic lichen species.