Mechanism of Evapotranspiration from Forest Floor based on Soil Moisture Changes and its Evaluation Method

本文以原状土柱蒸发试验为基础，分别探讨了蒸散量的可能估算方法。为了估算入渗和干燥过程中的水分运动量，在森林中选取了原状土柱进行试验。在试验过程中，测定了土柱的压力水头变化和水分平衡。通过上、下边界的水量与实测值和估算值比较，两者吻合较好。为了分别估算土壤表面蒸发量和假根系统的吸水量，对侧插假根的原状土柱进行了土柱压力水头的测定。结果表明，各土层体积含水量的减少量之和与土柱的失重量基本一致。从柱的顶部表面的蒸发被评价为在柱的顶部表面的蒸发量的减少量。 关于我们 f第1层的体积含水量。假根的吸水量评估为柱第2层至第6层体积含水量减少的总和。其次，通过求解理查兹方程和非饱和流动分析得到的顶部表面的蒸发，被评估为通过柱的顶部边界的水通量。假根的吸水量计算为边界处上下层之间的通量差。估算的蒸发量和假根吸水量之和与土柱重量损失吻合较好。最后，将非饱和流分析应用于天山南坡土壤水分变化的实测研究。富士。结果，蒸腾速率被评估为平均1.7mm/天。林下蒸发速率平均为1.0 mm/d，树木蒸散速率平均为2.7 mm/d。少

This paper examines possible evaluations on the amount of evapotranspiration separately, based on evaporation experiments with an undisturbed soil column.To evaluate the amount of water movement during infiltrating and drying, experiments were performed by using a Kuroboku column picked out under undisturbed conditions on the forest. In the experiments, the pressure heads changes and water balance of the soil column were measured. In comparison with the measured and evaluated amount of water through the upper and lower boundary, the two were in close agreement. To estimate the surface evaporation and the water uptake by pseudo-root system separately, pressure heads in the undisturbed soil column with inserting pseudo-roots on the side were measured. In consequence, the sum of the decrease of volumetric water content in each layer was in good agreement with the loss in weight of the soil column. Evaporation from the top surface of the column was evaluated as the amount of the decrease o … More f volumetric water content in the 1st layer. Water uptake by pseudo-roots was evaluated as a sum of the decrease of volumetric water content from 2nd to 6th layers of the column. Secondly, evaporation from the top surface obtained by solving Richards' equation with the unsaturated flow analysis, was evaluated as the water flux through the top boundary of the column. Water uptake by pseudo-roots was calculated as the difference in the flux between upper and lower layer at the boundary. The sum of estimated amount of evaporation and water uptake by pseudo-roots was in good agreement with the loss in weight of the soil column. Finally, the unsaturated flow analysis applied to the soil moisture changes measured in the southwest slope of Mt. Fuji. As a result, the transpiration rate was evaluated 1.7 mm/day on the average. The evaporation rate from forest floor was evaluated 1.0 mm/day on the average, and the evapotranspiration rate by trees was estimated 2.7 mm/day by adding transpiration rate and evaporation rate. Less