A Seasonally Varying Tree Physiological Response to Environmental Conditions: Results From Semi‐Arid China

Abstract

AbstractDrought is the primary limiting factor for tree growth in water‐stressed regions through its effects on xylem development. In this study, we developed intra‐annual series of tree‐ring stable carbon (δ13C) and oxygen (δ18O) isotopes from Chinese pine (Pinus tabuliformis) to investigate the ecophysiological responses of trees to drought during the growing season in a climatic transition zone between arid and semi‐arid areas in north‐central China. Distinct intra‐annual patterns of δ13C and δ18O were revealed, with average annual amplitude of 0.26 and 2.72‰, respectively. Tree‐ring δ13C values increased from the early‐ to mid‐growing season, peaked in the mid‐to‐late‐growing season, and decreased at the end of the growing season. In contrast, δ18O values continuously decreased throughout the growing season. As expected, drought significantly increased δ13C and altered its intra‐annual pattern, particularly toward the end of the growing season. However, there was no significant difference in the average intra‐annual pattern in δ18O between dry and wet years. The tree‐ring δ18O at the end of the growing season was significantly correlated with the September to October average soil water δ18O, as simulated by a global isotope‐enabled climate model, which is consistent with the high proportion of exchangeable oxygen atoms predicted by previous studies for cellulose synthesis in the late growing season.