Use of bromide as a tracer to demonstrate uptake of groundwater by trees

Bromide, a tracer present in plant tissues, is used for demonstrating the uptake of groundwater by trees. Analysis of bromide in leaves could serve as a simple tool to demonstrate that high water-uptake trees are tapping into groundwater augmented with bromide. An experiment was conducted using three eucalyptus and three poplar trees, employing three types of irrigation namely, bottom irrigation without bromide, bottom only bromide irrigation, and bottom and surface irrigation with bromide. The daily irrigation volume was 0.5 L for the first ten days of treatment and 1 L for the last seven days. Bromide uptake was observed in poplars after 17 days of irrigation while no uptake was observed in eucalyptus. The method demonstrates the effectiveness of use of trees for hydraulic control of groundwater.