Abstract

The article presents the results of instrumental measurements of stem sap flow with the use of sap-flowmeters in the trunks of white fir (Abies nephrolepis), the analysis of the main factors of the process of moisture transport in tree trunks, and the results of modeling hourly series of xylem flow rates. The analysis of factors was made with the use of the method of principal components, and the reproduction of individual series of xylem consumption was based on a multiple linear regression model. The evaluated volume of the transported moisture flux in fir trees over the vegetation period in 2020 varied from 1720 to 5620 L, depending on tree diameter, and the mean daily velocity of stem sap flow in the xylem varied from 0.3 to 1.0 cm/h. Regression analysis was used to find the optimal structure of the empirical model, which includes two predictors—air temperature and humidity. The empirical coefficients of regression equations were determined for each tree based on calibration samples. The results of testing on long enough test samples showed that the model series of xylem discharge on a complete sample (from May to October) for three test trees out of four are close to the measured values: the coefficient of correlation is 0.79–0.88, Nash–Sutcliffe coefficient is 0.62–0.85. The simulation efficiency improves significantly when samples for individual months are used: the correlation coefficient is 0.87‒0.94, the Nash–Sutcliffe coefficient is 0.73‒0.97.

中文翻译：

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液流测量作为评估河流流域水平衡研究中蒸腾作用的工具

摘要

本文介绍了利用液流计对白冷杉树干树干液流进行仪器测量的结果，分析了树干水分输送过程的主要因素，并给出了结果。对木质部流速的每小时序列进行建模。采用主成分法进行因素分析，并基于多元线性回归模型再现木质部消耗量的个体序列。评估的2020年植被期内冷杉树输送水分通量的量在1720至5620L之间变化，具体取决于树径，木质部茎液流的平均日流速在0.3至1.0cm/h之间变化。回归分析用于找到经验模型的最佳结构，其中包括两个预测变量——空气温度和湿度。根据校准样本确定每棵树的回归方程的经验系数。对足够长的试验样本进行测试的结果表明，四棵试验树中的三棵在完整样本（5月至10月）的木质部排放模型系列与实测值接近：相关系数为0.79-0.88，纳什-萨克利夫系数为 0.62-0.85。使用单月样本时，模拟效率显着提高：相关系数为0.87-0.94，Nash-Sutcliffe系数为0.73-0.97。