Drought increased the response sensitivity of tree-ring δ18O for Qinghai spruce to climate change at different elevations in the eastern Tibetan Plateau

The frequency and duration of drought events are gradually increasing with global warming, which leads to widespread forest decline and mortality, affecting the stability of forest ecosystems. It is therefore of particular importance to gain an understanding of the response mechanisms of trees to drought. In this study, tree rings of the Qinghai spruce (Picea crassifolia) were collected at different elevations in the eastern Tibetan Plateau. The responses of tree ring stable oxygen isotopes (δ¹⁸O_tr) to climate factors and soil moisture were investigated at different elevations and periods. The results demonstrated that 1) there were no notable discrepancies in the δ¹⁸O_tr values of Qinghai spruce at varying elevations. 2) The response of δ¹⁸O_tr to climate factors increased significantly during the dry period, exhibiting a strong positive correlation with growing season temperature and a negative correlation with precipitation, scPDSI, and relative humidity. 3) The sensitivity of δ¹⁸O_tr to climatic factors increased with increasing drought intensity and the water use strategies of trees were changed at different elevations. This is mainly manifested in trees using deep soil moisture during and before the growing season to cope with drought. Therefore, the monitoring of climatic factors at different elevations should be enhanced in subsequent forest management and protection, while soil moisture management should be strengthened in different soil layers at different elevations to decrease the impact of drought on the growth of trees.