Black walnut (Juglans nigra L.) is a non-native tree species from North America, valued for its fast growth, high economic value of wood, and adaptability to various site conditions. The aim of this thesis was to analyze the growth and quality of black walnut in two plantations in the Pišece and Ravna gora forest districts and to test the proposed hypotheses. The results showed that crown suppression has a statistically significant effect on diameter growth: trees with less suppressed crowns achieved larger diameters, confirming the importance of thinning and the social position of trees. The analysis of stem quality revealed that the share of the first quality part of the stem increases with age. In the older stand it amounted to 79.8%, while in the younger stand it was 71.2%. In addition, trees with defects, especially dead and decayed branches, were more common in the younger stand. The comparison of micro-sites confirmed the influence of soil conditions, as trees growing on deeper and better-drained soils grew faster and reached larger dimensions than those on wetter sites. The results support the conclusion that black walnut is a promising tree species in Slovenia, whose success depends on appropriate site selection and proper silvicultural management.
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