Forest transpiration (T_r) is the major hydrologic flux from terrestrial ecosystems; it dominates the catchment water budget and land surface energy balance and can be used as an index of exchange efficiency between vegetation and the atmosphere. The thermal dissipation method (TDM) is used to obtain the xylem sap flux density (F_d) of individual tree stems; it is among the most powerful tools for estimating forest stand T_r (T_{r_stand}) values. Individual tree T_r values can be upscaled to T_{r_stand} as a product of stand total sapwood area (A_{S_stand}) and stand mean F_d (J_S). In this study, we performed laboratory experiments using Japanese cedar (Cryptomeria japonica D. Don) to examine errors in T_{r_stand} values generated by mis-estimation of A_{S_stand} and/or J_S. We found that simple color identification of the stem hydroactive zone in sapwood and heartwood had little effect on accurate estimation of A_{S_stand} values. Then we examined the effects of mis-estimation of J_S, which is primarily the result of F_d measurement failures. Considering that uncertainties in heat-tracer-derived F_d values using the TDM have been identified in numerous previous studies, we applied calibration to improve the accuracy of TDM-F_d derivation using freshly cut sapwood segments of sample Japanese cedar stems and negative pressure as a driving force to determine F_d within the segments experimentally. The calibration experiment revealed that the calibrated conversion equation for heat-tracer-derived F_d values resulted in values that differed significantly from those determined using the original TDM equation and significant underestimation of T_{r_stand}. The F_d correction increased the annual T_{r_stand} value from 229 to 593 mm year⁻¹, while the corrected value was not significantly different from the T_{r_stand} value obtained from catchment-scale water budget observations. The novel TDM calibration equation improved TDM-based T_{r_stand} estimates dramatically, highlighting the importance of this study's calibration method.

森林蒸腾（Ť _{- [R} ）是从陆地生态系统的主要水文通量; 它支配着流域水预算和地表能量平衡，可以用作植被与大气之间交换效率的指标。用散热法（TDM）求出单个树茎的木质部树液通量密度（F _d）。它是估算林分T _r（T _{r_stand}）值的最强大工具之一。可以将单个树的T _r值_提升为T _{r_stand，}作为林分总边材面积（A _{S_stand}）和林分平均值的_乘积F _d（J _S）。在这项研究中，我们使用日本柳杉（Cryptomeria japonica D. Don）进行了实验室实验，以检查由错误估计A _Sstand和/或J _S产生的T _{r_stand}值的误差。我们发现，边材和心材中茎水活性区的简单颜色识别对A _{S_stand}值的准确估计几乎没有影响。然后，我们检查了J _S误估计的影响，这主要是F _d测量失败的结果。考虑到热示踪剂的不确定性使用TDM的F _d值已在许多先前的研究中确定，我们应用校准来提高TDM- F _d推导的准确性，该方法使用了日本雪松样品的新鲜切材边材段和负压作为驱动力来确定F _d值。实验性细分。校准实验表明，由热示踪剂得出的F _d值的校准换算方程所产生的值与使用原始TDM方程所确定的值显着不同，并且大大降低了T _{r_stand的值}。所述˚F _d校正增加的年Ť_{r_stand}值在229至593 mm年^-1之间，而校正后的值与从集水规模水预算观察中获得的T _{r_stand}值没有显着差异。新颖的TDM校准方程极大地改善了基于TDM的T _r - _stand估计，突出了本研究校准方法的重要性。