Objective Investigating the dynamic characteristics of sap flow velocity of Salix psammophila branches and their response to environmental factors is essential for guiding effective tending, regeneration, and sustainable management of S. psammophila plantations in arid regions.

Methods In this study, a plant-wrapped sap flow sensor, a fully automatic portable weather station, and soil temperature and moisture sensors were used to continuously monitor the sap flow velocity of S. psammophila branches, meteorological factors, soil temperature, and soil volumetric water content in a plantation located at the southeastern margin of the Mu Us Sandy Land. The objective was to elucidate the mechanisms by which environmental factors influenced the sap flow velocity of S. psammophila branches during the observation period (April to October 2024).

Results 1) The diurnal variations in sap flow velocity of S. psammophila branches exhibited a broad bimodal curve, with peaks occurring at around 10:00 and 16:00. 2) On a daily scale, sap flow velocity showed highly significant positive correlations (P < 0.01) with air temperature, vapor pressure deficit (VPD), solar radiation, and soil volumetric water content, and highly significant negative correlations (P < 0.01) with precipitation, air humidity, and soil temperature. 3) On a monthly scale, sap flow velocity also demonstrated highly significant positive correlations (P < 0.01) with air temperature, VPD, solar radiation, and soil volumetric water content, and significant negative correlations (P < 0.01) with air humidity and soil temperature. Among the major environmental factors in the study area, solar radiation and VPD exhibited the highest explanatory power for the sap flow velocity of S. psammophila, with coefficients of determination (R²) of 0.695 and 0.319, and correlation coefficients (r) of 0.809 and 0.560, respectively.

Conclusions Sap flow velocity of S. psammophila branches in this region is primarily influenced by air temperature, VPD, solar radiation, and air humidity. Among these, solar radiation and VPD are the dominant direct drivers, whereas air humidity and air temperature indirectly regulate sap flow by modulating VPD. These findings provide a scientific basis for formulating strategies to improve the quality and efficiency of S. psammophila plantations in the Mu Us Sandy Land.