Tritiated Water as a Tool for Ecological Field Studies.

Tritium was used to investigate the withdrawal by small trees of water from soil at three depths. Within 4 hours of placement at each depth, tritium was detected in the transpired water from nearby trees. On the 3rd day after application, 38 times more tritium (per unit volume) was present in transpired water drawn from soil at a depth of 0 to 30.5 centimeters than in water drawn from the 61- to 91.5-centimeter level.