Potential for a new interceptometer: Monitoring tree sway as an indicator of interception before, during, and after it rain

Thursday, 17 December 2020: 04:15
Dominick Michael Ciruzzi1, William Alexander Avery2, Harold Barker3, William Selbig4 and Steven P Loheide III1, (1)University of Wisconsin Madison, Civil and Environmental Engineering, Madison, WI, United States, (2)University of Wisconsin Madison, Environment and Resources, Madison, WI, United States, (3)University of Wisconsin Madison, Civil and Environmental Engineering, Madison, United States, (4)USGS - Upper Midwest Water Science Center, Middleton, WI, United States
Interception is the portion of precipitation captured by the foliage of vegetation. Depending on storm intensity and rainfall depth, street trees may capture the majority of precipitation during small storms and attenuate the timing and magnitude of stormwater runoff even in larger, or high intensity storms. The traditional method to quantify interception involves subtracting a point measurement of precipitation recorded at a gauge beneath the canopy from that recorded outside the canopy. This method may over- or underestimate the actual interception by the whole canopy due to heterogeneity of throughfall rates. Here, we aim to measure street tree interception and canopy evaporation by continuously monitoring tree sway period with accelerometers before, during, and after a storm and compare this method with interception quantified using a rain gauge inside and outside the canopy. The tree sway period of any tree is related to its mass, stiffness, height, and diameter, as well as other factors. During the short time frame of a storm, the mass of the tree changes as water is intercepted, but other factors that would influence tree sway period remain constant. We observed increases in tree sway period correlated with increases in gauge-measured interception during rainstorms, which suggests that interception rates and total interception can be quantified from monitoring tree sway motion. Further, we observed decreases in tree sway period following the end of a storm, which indicates the rate of the canopy drying. This research demonstrates the feasibility of a new, independent tool and approach to identify and quantify interception dynamics in trees, which may be more representative of interception at the tree scale.