Climatic signals of tree-ring width and intra-annual density fluctuations in Pinus pinaster and Pinus pinea along a latitudinal gradient in Portugal

摘要

Tree-ring width integrates the prevailing environmental conditions during the whole growing season (annual resolution). Other wood anatomical traits, like intra-annual density fluctuations (IADFs), imprint environmental conditions within the growing season (sub-annual resolution). IADFs are anatomically characterized by latewood-like cells within earlywood or earlywood-like cells within latewood. Under climate change scenarios, it is increasingly important to understand which traits are more relevantin the adjustment of long-lived species. We established a latitudinal transect along Portugal and compared tree-ring width and the frequency of IADFs in Pinus pinaster growing under temperate and Mediterranean climate, and of P. pinaster and P. p/'nea growing under Mediterranean climate. Pinus pinaster growing under temperate and Mediterranean climate showed similar correlations between climate and tree-ring width, whereas P. pinaster and P. pinea under Mediterranean climate presented a different pattern of climate-growth correlations. We therefore suggest that the climate-growth response is species dependent. However, the climate-IADFs correlation was driven by site conditions and less related to the species. We propose that the correlations betweenclimate and growth are conserved within the distribution range of a species, whereas IADFs function as a finer morphological adjustment to the environmental conditions during the growing season.