Naturalization Without Extensive Invasion: Non-Native Tree Species in Lithuanian Forests Within a European Context

The use of non-native (alien) tree species in forestry involves trade-offs between ecological risks and potential economic benefits. This study assesses the distribution, naturalization, and invasion potential of non-native tree species in Lithuanian forests within a European context. The analysis integrates national forest inventory data with European datasets and applies a trait-based invasiveness assessment framework. Non-native tree species occupy only 0.6–0.7% of Lithuanian forest area, markedly lower than the European average (~4%). Only a small subset of species shows the capacity to transition from naturalization to invasion, with Acer negundo exhibiting the highest invasiveness potential. Most species remain confined to the naturalized stage and do not exhibit extensive spread under current conditions. The results demonstrate that invasiveness and silvicultural performance are not necessarily linked, as several species with high productivity exhibit limited invasion potential. These findings highlight the context-dependent role of non-native tree species in forest ecosystems and support the need for differentiated evidence-based approaches that integrate invasion risk, ecological characteristics, and management objective under changing environmental conditions.