396 - Throughfall and Stemflow Measurements of Three Different Sized Trees

Throughfall and stemflow were measured for three different sized trees at the Edison Environmental Center in Edison, New Jersey over three growing seasons. Stemflow measurements expectedly indicate that larger trees collect more rain as stemflow. The smallest rainfall events did not produce measurable stemflow for the largest tree measured, indicating that there is an “initial abstraction” or loss of runoff down the trunk of the tree. This wetting front (water must first wet surface before flowing over bark of trunk) down the trunk of any size implies that besides interception and redirection of rainfall to the trunk and tree pit, there is also a lag in runoff that is provided by the movement of this wetting front down the trunk. Besides the use of tipping bucket rain gauges placed under each tree in the study, on the largest tree a Parsivel optical disdrometer was used to measure rain drop size and energy using laser light and photodiode detection. Results of observations are presented along with design guidance for rain fall capture for tree pits.