A better understanding of the respective role of key climatic variables on tree growth is crucial for an accurate assessment of how ongoing global changes may affect both dynamics and distribution of forest tree species in the future. The aim of this study was (i) to explore growth patterns of European larch (Larix decidua Mill.) through a network of tree-ring chronologies developed for the French Alps and (ii) to identify the main climatic drivers explaining radial growth. Climate-growth relationships were coupled with a hierarchical analysis. This relationship revealed significant variability expressed spatially by the existence of five clusters, initially discriminated by an elevational contrast related to (i) a negative correlation between summer temperatures and larch growth at lower elevations and (ii) a stronger response of low-elevation larch stands to winter precipitation. In the high-elevation clusters, tree growth depends on previous autumn and current summer temperatures and water supply in July. The differentiation, that portrays a strong geographical coherence, is mainly related to the latitudinal gradient; (i) the northwestern stands are mostly sensitive to high temperatures in summer; (ii) the growth of the southernmost clusters is equally driven by temperatures during autumn, winter, and summers; (iii) the populations of a cluster located in a transitional zone of the inner French Alps, subject to both Mediterranean and Continental influences, exhibit negative correlations to late winter and early spring precipitation. This significant spatial heterogeneity of climate-tree ring relationships in L. decidua clearly underlines the high plasticity of the species to adapt its growth to local climate conditions.
Keywords: Climate-growth relationships; Clustering analysis; Dendrochronology; French Alps; Larch.
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