Effects of forest management on alien plant invasion of woodlands

In the Silesian Upland (southern Poland) in the years 1997-2001 total 283 phytosociological releves were taken using commonly applied Braun-Blanguet method. The geobotanical survey was carried out in natural, semi-natural, as well as in disturbed forest communities. The woodlands were chosen systematically and randomly within the study area and the patches in them were chosen in relation to presence and different cover-abundance of a neophyte i. e. alien invasive species introduced after 1500. Of total 18 alien plant species found during physociological research in the study area only 3 are very frequent: woody species Quercus rubra, Padus serotina and herbaceous annual Impatiens parviflora. PCA analysis confirmed the biggest mean cover and the widest synecological amplitude of these species. The alien trees are used as productive admixtures to tree stands in forest management. The most vulnerable forest communities to invasions are those which are also frequently exploited by forestry i.e. Leucovryo-Pinetum, Querco roboris-Pinetum and Tilio-Carpinetum. Such species as Impatiens parviflora, Solidago gigantea, Reynoutria japonica are manly connected with mesic forest communities of Querco-Fagatea class, which are dominated by the former. Impatiens parviflora also occurs in mixed coniferous forest and communities of Alnetea glutinosae class. The representatives of neophytes recorded in woodlands occur basically in various types of plant communities, however their cover increases with decreases in number and cover of native species