Abstract: Abstract: Background Accurate measurement of tree transpiration is critical for understanding plant-water interactions and ecosystem water budgets. The Granier equation, widely used in thermal dissipation probe (TDP) systems, was developed for temperate conifers but exhibits significant errors when applied to other species.项目名称：河北省林业和草原局“三北工程区植被恢复关键技术创新写示范”(2025JBGS0001) 第一作者简介：白宇(2000—)，男，硕士研究生。主要研究方向：植物蒸腾耗水和森林培育。E-mail：2567000898@qq.com †通讯作者简介：马长明(1980—)，男，博士，副教授。主要研究方向：植物蒸腾耗水和森林培育。E-mail：machangming@126.com Pinus tabuliformis, a keystone species in northern China’s ecological restoration, lacks validation of TDP accuracy under field conditions. This study, conducted in Baoding, Hebei Province—a region characterized by a warm-temperate monsoon climate—aimed to evaluate and recalibrate the original Granier formula for P. tabuliformis to address systematic underestimation issues in sap flow measurements. Methods Three healthy P. tabuliformis trees were transplanted into controlled containers to minimize root damage. Sap flow was monitored using TDP sensors (AV-3665R) installed in the sapwood, while transpiration rates were simultaneously measured via a whole-tree weighing system (precision: 20 g). Data from July 11–15, 2023, were analyzed using regression modeling to correlate thermal dissipation coefficient (K) with gravimetric transpiration. The original Granier formula (Fd=0.0119K1.231) was recalibrated, and its accuracy was validated against weighing-derived values. Results The original Granier formula systematically underestimated sap flow density by 69.1% (absolute error: 0.691 cm³·cm⁻²·s⁻¹), with poor alignment to gravimetric data. A species-specific correction was derived: Fd=0.0126K0.6697. Validation using independent datasets (July 14–15) confirmed the corrected model’s superiority, reducing the mean error to -0.43% and achieving high consistency with weighing results. Diurnal sap flow patterns aligned across methods, peaking at 11:00–12:00. The recalibration addressed parameter discrepancies linked to P. tabuliformis’s xylem anatomy, resolving the original formula’s underestimation bias. Conclusions In future thermal dissipation-based sap flow measurements, the corrected Granier formula will enable more accurate estimation of P. tabuliformis sap flow rates. This advancement provides methodological support for precise evaluation of forest transpiration and holds significant value for improving the accuracy of soil and water conservation benefit assessments.