From acclimation to risk: Increasing drought vulnerability of introduced Pinus strobus L. across central and Eastern Europe

Climate projections suggest major shifts in tree species distributions, with most conifers expected to lose suitable habitats. In this context, non-native species may offer potential substitutes for native taxa. The introduced Pinus strobus exhibits pronounced variability in growth responses across Europe, reflecting varying levels of adaptation to environmental conditions. The aim of this study was to analyze P. strobus responses to climatic factors along a latitudinal gradient from the Baltic region to the Balkans. The study was based on data from a large tree-ring network comprising >650 trees from 38 sites, divided into four clusters. Summer precipitation emerges as the dominant factor controlling secondary growth with a pronounced latitudinal gradient that is strongest at the southernmost sites and progressively weaker toward the north. The effect of temperature shifts changed from weakly positive in northern sites to strongly negative in southern ones. The growth trend assessments revealed a significant reduction over the last decades at the southern sites, whereas in the central and northern parts of the network, P. strobus basal area increment shows no significant trends. Across the latitudinal gradient, P. strobus exhibits reduced resistance and recovery in the Southern cluster, whereas overall resilience does not differ significantly. These findings demonstrate that P. strobus possesses considerable climatic plasticity but also increasing sensitivity to high temperatures, particularly at the southern margin of the study network. Consequently, progressive warming and the increasing frequency of waves and droughts will reduce growth potential in southern Europe. Despite generally favorable habitat indicators at the northern sites, temporal trends indicate increasingly negative correlations with summer temperatures, indicating increasing heat sensitivity even there.