Water Use Adaptations of <scp> <i>Platycladus orientalis</i> </scp> Under Varying Soil Moisture in the Loess Plateau, China

ABSTRACT Quantifying tree transpiration variability across soil volumetric water content (VWC) is vital for understanding tree water use strategies and developing effective forest management in dryland areas. However, the complicated interaction of soil moisture and meteorology on tree water use is still indistinct, resulting in challenges for water resource management in arid and semiarid regions. To examine the impacts of environmental factors on tree water use, canopy transpiration ( T ) and canopy conductance ( G c ) of Platycladus orientalis plantation were quantified through Granier‐type thermal dissipation probes and the Penman‐Monteith equation, respectively, in a semiarid area of the Loess Plateau throughout the growing seasons (May–September) of 2020–2022. Average T increased with increasing VWC, while the peak value and growth rate of T decreased due to relatively low vapour pressure deficit (VPD) even when VWC was at the highest level (0.105–0.127 m 3 m −3 ). The ratio of stomatal sensitivity to reference G c decreased from 0.89 to 0.52 with increasing VWC, indicating a shift from more to less strict stomatal regulation. The decoupling coefficient increased simultaneously with rising VWC, indicating an enhanced effect of solar radiation ( R s ) and a decreased stomatal limitation on transpiration. VWC exceeded 0.094 m 3 m −3 in more than 50% of the instances. Under these conditions, there was a significant increase ( p &lt; 0.05) in the sensitivity of G c to VPD and R s as VWC increased. These results suggest that P. orientalis adapts to drought by reducing stomatal conductance and water loss through transpiration during soil droughts. Given increasing drought events and accelerated soil water depletion in the arid region, heightened water stress will impair tree gas exchange and hinder vegetation growth. This study reveals an adaptive mechanism of P. orientalis in semiarid areas and advances understanding of plant water use strategies in water‐limited ecosystems. Given frequent droughts and increasing soil water depletion worldwide, extra attention on drought impacts on the water use of forests is crucial in the Loess Plateau and similar drought regions.