Growth-climate sensitivity of two pine species shows species-specific changes along temperature and moisture gradients in southwest China

Abstract

A better understanding of tree growth-climate sensitivity across regions and species may reduce uncertainties in simulating forest carbon budgets. We studied the spatial heterogeneity of growth-climate sensitivity of Pinus yunnanensis and Pinus kesiya across temperature and moisture gradients in the complex mountain regions of Southwest China. We developed tree ring-width chronologies from 22 sites for P. yunnanensis and 20 sites for P. kesiya, totaling 903 trees (1684 cores). We applied generalized additive mixed models (GAMMs) on basal area increment (BAI) series to remove the age and size effects on tree growth, and correlated BAI residual chronologies with climate variables. Radial growth of P. yunnanensis and P. kesiya at most sites (> 75%) were positively correlated with precipitation and one-month Standardized Precipitation-Evapotranspiration Index (SPEI1) during the early growing season. In contrast, high precipitation and SPEI1 during the late growing season reduced tree growth of both pine species. The growth-climate sensitivity of both pine species varied along the temperature and moisture gradients, i.e., moisture sensitivity of tree growth decreased along a dry-to-humid moisture gradients for P. kesiya during early growing season, whereas temperature sensitivity of P. yunnanensis shifted from positive (beneficial) to negative (limitative) along cold-to-warm gradients. Our results indicate that the growth-climate sensitivity of both pine species varies with site-specific environmental conditions. These findings contribute to improve our understanding about the spatial patterns of tree growth-climate responses of these economically important conifer species in Southwest China.