关键词: 蒸腾, 水分利用, 水分关系, 热扩散, 杨树

Abstract: Aims To systematically understand the applicability of Granier's original equation to Populus tomentosa and clarify the necessity of its calibration. Methods Taking Populus tomentosa as the experimental material, this study used the stem weighing method and the whole-tree potometer method to evaluate the accuracy of Granier's original equation for different types of TDP, and compared the application effects of different methods. Important findings Compared with the measured values by the stem weighing method, the sap flux density calculated by Granier's original equation was underestimated by 52.3%–61.4% on average. The calibrated equa-tions obtained by the stem weighing method and the whole-tree potometer method are Fd = 0.0362K1.870 and Fd = 0.0105K0.976, respectively. The calibrated equation by one method has a large deviation when applied to other methods. Compared with Granier's original equation, the average sap flux density of seven trees in the field growth state calculated by the whole-tree potometer method calibrated equation did not change significantly (P> 0.05). But the calculation results of the stem weighing method and other studies were significantly larger (P<0.05). Compared with the data of the whole-tree potometer method, the accuracy of Granier's original equation is considerably higher than that of other calibrated equations, and the relative average absolute error and root mean square error is 10% and 0.0005 cm/s, respectively. In addition, the coefficients of the calibrated equation were obviously different among different trees, but their values were significantly negatively correlated with the ratio of probe insertion into sapwood without water conduction function (P<0.001). In summary, Correcting the original Granier's equation may be necessary when using TDP to measure the sap flux density. However, the application effects of different calibrated equations vary greatly, indicating that the calibrated equations obtained in previous studies have sig-nificant limitations. This study did not find sufficient evidence to support the view that it is necessary to use a calibrated equation to estimate the sap flux density of Populus tomentosa. Therefore, it suggested continuing to use the calibrated equation of Granier for this tree species.

Key words: transpiration, water use, water relation, heat dissipation, poplar