Growth and productivity of European beech populations show plastic response to climatic transfer at the north-eastern border of the species range

Forest trees facing climate change may persist in a short term through acclimation within the limits of their phenotypic plasticity. In the longer term, however, evolutionary adaptation would be needed for populations to thrive in the changed climate, or species may migrate to new areas as climate becomes favorable there. European beech is one of the most important tree species in western and central Europe, and projections indicate that it may contract its southern range and migrate towards northern and north-eastern Europe in the future climates. It is therefore important to recognize the level of variation in climatic adaptation and climatic responsiveness of populations which are likely the source of genetic material for expanding the species range. In this study we examined variation in growth and productivity among 39 European beech populations, which represent the north-eastern margin of the species distribution range. We employed the transfer function and the Universal Response Function approaches to analyze populations’ performance in response to the climatic transfer across five provenance test sites and in relationship to climate at the populations’ origin and planting sites. We found significant but low variation among tested populations in tree diameter (DBH; cm) and Volume index (m3 ha−1) and significant population × site interaction at age 30 years. That variation, however, was only weakly related to gradients of climatic variables represented by the set of sampled populations. The variable performance of populations across planting sites, and the importance of planting sites’ climate in explaining traits’ variation in this experiment confirm the plastic response of examined populations to climate change. Our findings indicate that beech populations from the analyzed region have a high acclimation potential to the projected changes in climate, although for high-altitude populations (from > 600 m a.s.l) the negative effect of transfers to warmer and drier conditions was observed. Detailed knowledge of the plasticity of response and adaptive potential of marginal beech populations in the longer term would be needed to guide management decisions to help future forests to cope with climate change.