This diploma thesis focuses on the research of non-native tree species in areas where they occur more frequently. Non-native tree species like to inhabit degraded areas or areas affected by various disturbances, as well as areas where human influence is strong. As such, we chose the urban forests of the Tivoli, Rožnik and Šišenski hrib Landscape Park. The aim of this research was to identify which non-native tree species are present and at which locations, to determine their condition in the stand and, to check whether they are potentially invasive or not. We studied their appearance in different stand layers (lower, middle and upper layer), the light conditions in these layers and regeneration. Finally, we determined the potential invasiveness of individual non-native tree species present in the park and listed possible silvicultural measures where necessary. Measurements were performed in the field, and data was analyzed using basic computer software. The proportion of plots with regeneration was significantly higher in open parts of the stand compared to more shaded areas, especially for shade-intolerant species: black locust, wild chestnut and black walnut. Moderately shade- tolerant species such as red oak and white pine regenerated even in heavily shaded areas. The non-native tree species s that showed signs of potential invasiveness were: black locust and red oak, Other observed non-native tree species did not show signs of potential invasiveness in our study area or we were not able to obtain sufficient sample size for them to be able to conclude about their invasiveness.
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