Weather–Growth Responses Show Differing Adaptability of Scots Pine Provenances in the South-Eastern Parts of Baltic Sea Region

Local adaptation and plasticity of growth play important roles in the adaptability of trees to changing conditions. Under accelerating climatic changes, the adaptive capacity of metapopulations can be exceeded, implying a necessity for assisted gene flow to sustain the productivity of forests. Such management is knowledge intensive, and information on the responsiveness of metapopulations (provenances) across the climatic gradient can aid more comprehensive projections of their performance. The plasticity of growth responses to weather conditions of five provenances of Scots pine with differing field performance across the climatic gradient of the south-eastern Baltic Sea region was assessed using dendrochronological methods and generalized additive models. Weather conditions related to water availability in summer, as well as during dormancy, were the main regional drivers of an increment in the provenances. The provenances differed by the plasticity of responses according to field performance, indicating adaptation in terms of growth sensitivity and uneven adaptability. The weather–growth responses of the top-performing provenances to summer weather were more plastic, providing advantages under a changing climate. Accordingly, regional sensitivity and plasticity of growth responses could be used for the screening of genotypes best suited for the projected climates. In addition, the estimated growth responses encourage supplementation of the local breeding populations with the top-performing provenances originating from sites with the projected climates.