Effects of precipitation changes and drought events on sap flow density of Lannea coromandelica in a Savanna ecosystem in Southwest China

The Yuanjiang Savanna ecosystem (YSE) located in Southwest China. The Lannea coromandelica tree species in YSE would be more sensitive to changing precipitation regime, yet its response to this regime has not been adequately evaluated. To address this gap, we explored the effects of 30%, 50%, 70% precipitation exclusion (PE) and 30%, 50%, and 70% precipitation addition (PA) and control (CK) experiments on sap flow density (J s ) of L. coromandelica in YSE. Results show that the precipitation changes significantly enlarged the J s in the PE50, PA30, and PA70 plots ( P <0.01), and changed the start time (ST), maximum occurrence time (MT), end time (ET), and duration time (DT) of diurnal J s ( P <0.0001). The full random forest model of six environmental factors showed that the soil water content (SWC), air temperature, and photosynthetically active radiation were more important for J s (R 2 =0.725, P <0.001), with the IncMSE values were 41.77%, 37.51% and 20.18%, respectively. The relative drought year of a natural climatic anomaly significantly not only decreased the J s in the PE50, PE30, CK, and PA70 plots ( P <0.05), but postponed the ST, MT, and ET of J s , prolonged the DT of J s ( P <0.0001), and resulted in relying heavily of J s on SWC on the diurnal time scale ( P <0.001). Our findings provide new insights into the physiological adjustments, adaptations and environmental responses on an hourly time scale to future precipitation changes in YSE. • Sap flow of Lannea coromandelica to water pulse was immediate in Savanna ecosystems. • Sap flow of L. coromandelica in Savanna was regulated by SWC, T a , and PAR. • The relative drought year disturbed sap flow dynamic and its environmental responses. • Sap flow severely relied on soil water content during the relative drought year. • Sap flow gradually adjusted its diurnal time parameters to adapted to precipitation changes.