Obce gatunki drzewiaste w południowym kompleksie Puszczy Niepołomickiej

Managed forests are likely to be exposed to uncontrolled, spontaneous spread of alien/invasive species as a result of a frequently conscious introduction of alien species to forests in order to achieve economic gains. Unfortunately, we still lack data on the intensity of such invasions to forests on a larger scale. The aim of the paper is to provide a detailed qualitative and quantitative description of the existing regeneration of tree species, particularly the alien ones, and to determine the impact of selected factors on the regeneration of introduced species. The research was carried out in a mixed coniferous forest habitat in the "Uroczysko Główne". Particular focus was on the regeneration of alien species. Eight tree species were found to be regenerating naturally on the examined plots of which two were alien species. The scale of occurrence of alien species in comparison with native ones, particularly the black cherry, may now become a problem. Alien species accounted for nearly 25% of all tree species regeneration in the examined area and were noted in over half of the plots. It can therefore be said that the conditions occurring in the southern complex of the Niepołomice Forest have a great impact on tree regeneration and may favour spontaneous spread of alien species. The research helped to quantified and qualified the intensity of forest colonisation by the two most frequently occurring alien species.