Classification and habitat characteristics of plant communities invaded by the non-native Rosa rugosa Thunb. in NW Europe
The Japanese Rose (Rosa rugosa) an invasive neophyte in Europe, builds up large dominant shrublands especially in coastal areas. To describe the vegetation invaded by R. rugosa 383 relevés out of NW Europe with R. rugosa were collected from literature and from vegetation databases. Different plant communities were evaluated by TWINSPAN classification, and two main groups were distinguished: wood- and shrublands, grass- and heathlands. Rosa rugosa builds up dominant stands that are assigned to the corresponding higher syntaxon. The main variation in vegetation composition was studied with a Detrended Correspondence Analysis and related to Ellenberg indicator values. Furthermore, Ellenberg indicator values were used to compare the environmental conditions in different plant communities containing Rosa rugosa. Environmental conditions changed with the development and spread of R. rugosa. Effects of R. rugosa invasion on species richness of different lifeform groups, native species and neophytes were analysed. The study shows, that the expansion of R. rugosa changes the species composition of the invaded vegetation. Species richness, especially of herbaceous plants, decreased with increasing cover of R. rugosa. Furthermore, Rosa dominated plots have a higher percentage number of neophytes and a lower percentage number of native species than the corresponding not invaded plant communities. In comparison to its native range, R. rugosa establishes in various plant communities, at a wide range of environmental conditions. Therefore it appears that the shrub has a broader environmental niche in its new range. According to the presented environmental gradient, moderate conditions of nutrients, soil pH and water content, and both lighter and dryer sites were preferred. Considering environmental requirements, open dry grasslands as well as heathlands especially with bare patches are probably very endangered by R. rugosa invasion.