Groundwater contribution to transpiration of trees under wet and dry soil conditions*

Abstract

AbstractThe objective of this study was to partition tree T under shallow groundwater table conditions into groundwater (Tgw) and soil water (Tsw). 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 Tgw towards total T for the investigated trees ranged from 31% when the topsoil was wet to 97% when it was dry. The contribution of Tsw 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.