Carbon stable isotope-climate association in tree rings of Pinus pinaster and Pinus sylvestris in Mediterranean environments

Abstract

Carbon isotope ratios, recorded as 13C/12C variations in tree rings of woody species, are the result of physiological changes related to environmental conditions. The objective of this work was to analyze the association among carbon thirteen variability (δ13C), climate variables and tree-ring growth of Pinus pinaster and Pinus sylvestris in central Spain. Pulverized woody material from the period 1975-1999 from four trees for each pine species was analyzed. To detect common patterns in δ13C within each species and between δ13C and growth indices, a principal component analysis (PCA) was performed. δ13C of trees and the residual tree-ring chronologies were used at the PCA. Multilevel mixed linear models were applied between intrinsic water use efficiency (iWUE) and climate variables. Our results show an inverse significant correlation between δ13C and tree-ring growth of both species. Winter and spring air moisture was negatively correlated with iWUE of Pinus pinaster. July maximum temperature was positively correlated with iWUE of Pinus sylvestris. As δ13C is significantly related to climate and growth and it may be recommended as a valuable tool for tree growth dynamic analysis to withstand increasingly stressful climate conditions.