Alien tree species in the northern part of the Niepolomice Forest

In spite of the fact that the selection of introduced species in Poland is limited and their proportion in forest stands is in fact insignificant, the threat of launching the invasive processes on a large scale is highly probable. The Niepołomice Forest was selected as a study area because the species occurring in the stands are of alien origin and can be a source of diaspores for a spontaneous, natural regeneration of these species. The studies were conducted in the moist broadleaved forest habitat featuring high trophic and moisture conditions, thus being more susceptible to non−indigenous species invasion. At the study plots three of fourteen woody species occurring across the Forest i.e. red oak, and black cherry were described. So far, the occurrence of alien species in the study area has been on an insignificant scale when compared with the regeneration of native species. Currently, they occupy nearly 11% of the plots, representing about 3% of the total share in the regeneration of the main forest tree species