Responses of radial growth and stable carbon isotopes to climate in the northern Tianshan Mountains

Climate change has profound effects on forest ecosystems. Schrenk spruce (P. schrenkiana) is a natural conifer species endemic to the arid inland areas of Asia. In this study, the relationship between tree-ring parameters of P. schrenkiana and major meteorological factors were analyzed, and the main limiting factors for tree radial growth and stable carbon isotope fractionation were explored. Our results indicate that moisture stress before and during the growing season have an important influence on radial growth of P. schrenkiana, especially, the correlation coefficient between tree-ring width and vapor pressure deficit (VPD) from previous August to current July is as high as −0.622 (n = 51, p < 0.01). Collinearity analysis further supports the conclusion that the limiting factor for the radial growth of P. schrenkiana is moisture. Although the correlation analysis results show that the tree-ring δ¹³C_corr is significantly positively correlated with sunshine duration (SD), additional analysis based on first order difference variables suggests that the climate factor may not be the only limiting factor for the stable carbon isotope fractionation of tree rings in the Sayram Lake Basin. This lays the foundation for the assessment of forest management practices and carbon sink capacity in light of future climate change.