Abstract The water balance of tropical dry deciduous forests is less well understood than some other forest ecosystems. To help close this knowledge gap, we separately measured the evapotranspiration from the whole ecosystem (ETW), transpiration (TR) and interception loss (IL) from overstory trees, and evapotranspiration from the understory vegetation (ETU) in a tropical dry deciduous forest in Cambodia. It was found that ETW was equivalent to 73.7% of rainfall (P) at the annual scale. In the dry season, ETW corresponded to 120.1% of P, which indicates the utilization of soil water replenished during the wet season. The sum of transpiration estimated by the thermal dissipation (TD) method with the original coefficient (TRG), IL, and ETU was smaller than ETW, except for the middle of the dry season, due to an underestimation of TRG. Although recently reported calibration coefficients can reasonably correct TRG, future calibrations of the TD method are highly recommended for the precise evaluation of single-tree-scale transpiration in tropical dry forests. The annual contribution of the understory vegetation to ETW (ETU/ETW) was 34.6%, leading to the conclusion that the understory vegetation cannot be ignored when trying to gain a comprehensive understanding of the hydrologic cycle in tropical dry forests. The seasonal variations in ETU/ETW were mainly controlled by the leaf area index (LAI) of overstory trees, resulting from the overall stability of ETW and decreasing trend of ETU with increasing LAI in the wet season, with the opposite holding true in the dry season, i.e., decreasing ETW with the decline of LAI and less variations of ETU. Thus, LAI influenced both the seasonality and the annual contribution in ETU/ETW, exerting a notable influence on hydrological cycling in this forest.

中文翻译：

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柬埔寨热带干燥落叶林林下的蒸发量

摘要 与其他一些森林生态系统相比，对热带干燥落叶林的水平衡了解较少。为了帮助缩小这一知识差距，我们分别测量了热带干燥落叶林中整个生态系统 (ETW) 的蒸散量、上层树木的蒸腾量 (TR) 和截留损失 (IL) 以及下层植被 (ETU) 的蒸散量。柬埔寨。结果表明，ETW相当于年尺度降雨量（P）的73.7%。旱季ETW对应于P的120.1%，说明雨季补给的土壤水分得到了利用。由于TRG的低估，热耗散（TD）方法与原始系数（TRG），IL和ETU的蒸腾总和小于ETW，除了旱季中期。尽管最近报告的校准系数可以合理地校正 TRG，但强烈建议未来对 TD​​ 方法进行校准，以精确评估热带干旱森林中单树尺度的蒸腾作用。林下植被对 ETW 的年贡献率（ETU/ETW）为 34.6%，由此得出的结论是，要想全面了解热带干旱森林的水文循环，就不能忽视林下植被。ETU/ETW 的季节性变化主要受林木叶面积指数（LAI）控制，这是由于 ETW 整体稳定，ETU 在雨季随 LAI 的增加呈下降趋势，而在旱季则相反。季节，即随着 LAI 的下降和 ETU 的变化较小，ETW 减少。因此，