Princess tree is a fast-growing non-native tree species that has started to spread locally within managed forests in Slovenia. We were interested in which environmental factors influence the regeneration of princess tree in managed forests. We analyzed the regeneration of princess tree at 13 different sites in the Posavje region, setting up 5 × 5 m research plots in areas with the highest density of princess trees. We concluded that princess trees appear in forests where sudden forest stand openings have occurred due to logging or storms. Due to its rapid growth, it cannot be detected in the lower height classes; it was recorded in classes above 50 cm and the average height increment of princess trees was 1.3 m. We tested whether the density and height increment of princess trees are influenced by the size of forest stand gaps. The results showed no correlation, but the graphs in both cases indicated that the density and the height increment of princess trees were higher in larger forest stand gaps. In the future, more attention will have to be paid to this species, especially as climate change and storms are improving the conditions for its growth and expansion. We have proposed some preventive silvicultural measures that are already being used to prevent the spread of similar species such as the black locust and the tree of heaven.
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