关键词: 水力导度, 自然恢复, 木质部储水能力, 空气干旱, 栓塞疲劳

Abstract: Abstract Aims With climate change, extreme drought events occur frequently around the world, and there is an urgent need to understand the resilience and influencing factors of trees after extreme drought. Methods Seven dominant tree species in karst evergreen and deciduous broad-leaved mixed forest in Guilin, Guangxi were selected to analyze the dynamic differences of xylem water transport function and its correlation with xylem characteristics and environmental factors at the end of extreme drought and after drought. Important findings (1) At the end of extreme drought, the percentage loss of xylem hydraulic conductivity (PLC) of all tree species except Cinnamomum camphora was higher than or close to 50%, and the highest was 87.92%.PLC of all species decreased linearly with the increase of xylem saturation water content at the end of extreme drought. PLC of porous species had significant positive and negative correlations with xylem density (WD) and xylem saturation water content (SWC), respectively, indicating that xylem water storage capacity was an important factor affecting water transport function of karst trees under extreme drought. (2) PLC of Fraxinus chinensis decreased significantly for the first time in the spring of the following year after extreme drought, and the formation of new vessels may be the strategy for restoring water transport function after extreme drought. The PLC of Choerospondias axillaris and Quercus acutissima, Quercus glauca, Boniodendron minius and Machilus calcicola decreased significantly for the first time on the 3rd and 13th day after extreme drought, respectively. The refilling of embolized vessels may be the strategy to restore water transport function of these species. (3) After the extreme drought event, the PLC recovery degree of all tree species at the last 6 sampling times was significantly positively correlated with the mean saturated water vapor pressure deficit (VPD) within 3 days before the current sampling time, indicating that the degree of air dryness had an important effect on the hydraulic function recovery of karst trees after extreme drought after the soil moisture condition recovered. (4) During the recovery process after extreme drought, many tree species showed embolism degree close to or even higher than that at the end of extreme drought, and the embolism fatigue degree of annular porous wood species was higher than that of loose porous wood species.

Key words: hydraulic conductance, spontaneous recovery, xylem water storage capacity, air drought, embolic fatigue