A Method for Determining Water Transport in Trees

Abstract

A new form of heat—flow analysis was developed to measure water transport in tree trunks. The application of the energy budget required the installation of heat—flow plates and thermocouples under the bark to measure the natural heat exchange between the water—conducting layer of xylem and the adjacent parts of the tree. The equipment was installed on two large branches of an ash tree and on the main trunk below. Over an extended period of time the sum of the flow through the two branches was equal to than through the main trunk, but early in the morning water loss was so high from the branch on the west side of the tree that water must have moved to it from the protected branch on the east. Immediately following sunrise, water loss from the east side was greater. During rain there was reversed transport, indicating that water was absorbed through the leaves. This method permits practically instantaneous measurement of transpiration losses from large trees with no disturbance of the environment of the crown.