Trees as urban heat and water regulators - a study of canopy interception and transpiration in the City of St Paul, Minnesota
Abstract
Urban trees are widely planted for their aesthetics and their functional benefits (e.g. regulating temperature and hydrology) and recognized as a climate adaptation strategy across the US. However, largely due to the costliness, accessibility, and instrumentation complexity of long-term monitoring, we know little to quantify either the horizontal or the vertical extents of urban tree canopies' diverse benefits.
To understand how urban canopies function with respect to water, we designed and implemented a low-cost, Arduino-based sensing system for urban trees in the City of St Paul. Through multi-year monitoring at a tree and plot-level, we want to gain insights into the plant-soil-water dynamics, the urban canopy's feedback to surface air temperature, and the interactions between these hydrological and climate processes. We measured evapotranspiration rate (via lab-assembled Granier-type sap flux probes) and canopy interception in trees (via throughfall, the precipitation that passes directly through a canopy), root-infiltration-runoff dynamics in soil (via soil moisture at multiple depths below and away from the canopy), and temperature and relative humidity of ambient air. This presentation evaluates both within-site and cross-site variability across the city. The variability of canopy interception may depend on tree traits (such as LAI and canopy coverage) and environmental variables (such as rainfall intensity). The different degrees of water stress response are controlled by sensitivity to soil moisture content and vapor pressure deficit, and this sensitivity may depend on the tree species. Additionally, land cover profile as well as canopy coverage contribute to a canopy's effectiveness in mitigating urban heat islands. Understanding the variability in trees' abilities to regulate urban heat and reduce stormwater will provide empirical guidelines for integrating municipal forestry and water resources management.- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFM.H22Y1170C