The objective of this study was to partition tree T under shallow groundwater table conditions into groundwater (T_gw) and soil water (T_sw). Three indigenous trees growing in lysimeters were installed with the compensation heat pulse velocity method to measure stem sap flow half‐hourly. Soil water content was monitored using HydraSCOUT probes. A groundwater table of 20 cm depth was maintained, and daily water replenishment to maintain a constant groundwater table was monitored using a graduated automatic supply bucket system. The contribution of T_gw towards total T for the investigated trees ranged from 31% when the topsoil was wet to 97% when it was dry. The contribution of T_sw ranged from 3% when the topsoil was dry to 69% after an irrigation event. It was concluded that trees switch to source water from superficial soil layers when the topsoil is wet and from groundwater during dry conditions.

中文翻译：

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地下水在干湿土壤条件下对树木蒸腾作用的贡献*

这项研究的目的是在浅层地下水位条件下将树T分为地下水（T _gw）和土壤水（T _sw）。用补偿热脉冲速度法安装了三棵在蒸渗仪中生长的本地树，以半小时测量茎汁流动。使用HydraSCOUT探针监测土壤水分。维持20厘米深的地下水位，并使用带刻度的自动供水桶系统监控每日的水补充量以维持恒定的地下水位。T _gw对总T的贡献被调查树木的水分含量从表土潮湿时的31％到干燥时的97％不等。T _sw的贡献范围从表土干燥时的3％到灌溉事件后的69％。结论是，当表土潮湿时，树木从表层土壤中获取水，而在干燥条件下则从地下水中获取水。