Differential response of radial growth and δ13C in Qinghai spruce (Picea crassifolia) to climate change on the southern and northern slopes of the Qilian Mountains in Northwest China

Tree radial growth can have significantly different responses to climate change depending on the environment. To elucidate the effects of climate on radial growth and stable carbon isotope (δ13C) fractionation of Qinghai spruce (Picea crassifolia), a widely distributed native conifer in northwestern China in different environments, we developed chronologies for tree-ring widths and δ13C in trees on the southern and northern slopes of the Qilian Mountains, and analysed the relationship between these tree-ring variables and major climatic factors. Tree-ring widths were strongly influenced by climatic factors early in the growing season, and the radial growth in trees on the northern slopes was more sensitive to climate than in trees on the southern. Tree-ring δ13C was more sensitive to climate than radial growth. δ13C fractionation was mainly influenced by summer temperature and precipitation early in the growing season. Stomatal conductance more strongly limited stable carbon isotope fractionation in tree rings than photosynthetic rate did. The response between tree rings and climate in mountains gradually weakened as climate warmed. Changes in radial growth and stable carbon isotope fractionation of P. crassifolia in response to climate in the Qilian Mountains may be further complicated by continued climate change.