Seasonality in embolism resistance and hydraulic capacitance jointly mediate hydraulic safety in branches and leaves of oriental cork oak (Quercus variabilis Bl.).

This article focuses on the seasonal variation of drought-related hydraulic traits and hydraulic safety margins (SMs) in oriental cork oak (Quercus variabilis Bl.), a keystone tree species dominant in Chinese temperate forests. The study found significant seasonal changes in branch and leaf embolism resistance (P50), sapwood capacitance, and leaf pressure–volume traits, with branches exhibiting relatively stable and high embolism resistance (P50_branch < −3 MPa) and consistently positive typical hydraulic SMs (~2 MPa), indicating strong hydraulic safety throughout the year. Vulnerability segmentation between leaves and branches was prevalent, supporting a "safety valve" function where leaves are more vulnerable to embolism to protect branches. Despite its overall hydraulic safety, Q. variabilis may be susceptible to sudden summer droughts under climate change, highlighting the importance of monitoring and conservation efforts.