Impacts of introduced dwarf pine (Pinus mugo) on the diversity and composition of alpine vegetation

Dwarf pine (Pinus mugo) is a successful pioneer tree, but also an invader of the subalpine belt in Central-European mountains. In the Hrubý Jeseník Mts. (Czech Republic), dwarf pine was introduced at the end of the 19th century by humans into alpine communities. To analyse the influence of non-native woody species on species diversity, vegetation composition and the ecological bioindication of invaded alpine communities, three habitats (non-invaded alpine grasslands, gaps of alpine grasslands within dwarf pine stands and closed dwarf pine stands) were compared at two localities (Keprník, Tabulové kameny) using the space-for-time substitution approach. Plant species composition was assessed by means of phytosociological relevés, and bioindication by means of Ellenberg indicator values. At both localities, both beta and gamma diversity were lower, and species composition more uniform in dwarf pine plantations in contrast to the gaps within and alpine grasslands outside of dwarf pine stands. At Keprník, alpha diversity was lower in the dwarf-pine plantation than outside of it, while at Tabulové kameny no significant differences were found. This is probably due to the somewhat different spatial structure of the dwarf pine stands and the different timing of dwarf pine introduction at these localities. Bioindication showed that dwarf-pine stands were drier, more shaded and had a higher soil fertility than alpine grasslands. Dwarf pine colonisation of alpine grasslands causes the extinction of many endangered plant species, complicating conservation goals. Because of the limited size of alpine areas, changes caused by dwarf pine in medium-high mountains might be more significant than in mountains with large alpine forest-free areas