Objective Clarifying nocturnal water allocation patterns (transpiration vs. recharge) in plants and their driving factors is essential for developing effective forest management strategies to enhance forest resilience under climate change.

Method This study was conducted at the Liupan Mountain Forest Ecological Positioning Station of the National Forestry and Grassland Administration. We monitored sap flow rate (J_s) and environmental factors of Larix principis-rupprechtii Mayr. plantation in the Xiangshui River small watershed of Liupan Mountain throughout the growing season of 2022 (from May 13 to October 13). We analyzed the dynamic changes of nocturnal transpiration (T_n) and stem refilling (R_e) during the growing season and their responses to environmental factors and canopy stomatal conductance (G_s).

Results (1) During the whole growing season, the nocturnal water use of Larix principis-rupprechtii Mayr. was dominated by R_e, with T_n accounting for 34.2% and R_e accounting for 65.8%. (2) The dominant factors affecting T_n were G_s, vapor pressure deficit (VPD) and air temperature (T_a), while the dominant factors affecting R_e were VPD, relative humidity (RH) and volumetric water content (VWC). (3) When the wind speed (WS) and G_s reached 1.00 m·s⁻¹ and 0.31 mol·m⁻²·s⁻¹, they gradually promoted T_n. When T_a, VPD and VWC reached 11.81 °C, 0.43 kPa and 17.98%, they gradually inhibited T_n. When T_a and VPD reached 12.88 °C, and 0.25 kPa, they gradually promoted R_e. When WS, RH, VWC and G_s reached 0.30～1.10 m·s⁻¹, 95.00%, 17.65% and 0.30 mol·m⁻²·s⁻¹, they inhibited R_e.

Conclusion Nocturnal water use in Larix principis-rupprechtii Mayr. during the growing season was dominated by R_e, and T_n and R_e were regulated by different factors, and the response thresholds to each influencing factor were different.