Collaborative Research: EAR-Climate: Hydraulic and Hydrologic Regulation of Greenhouse Gas Emissions From Forest Soils and Trees and Detection With Radon As a Novel Tracer

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The goals of this project are to better understand the role of trees in the global water and methane cycles and to attract elementary-school age students to environmental science through hands-on activities about water and trees. Methane is a potent greenhouse gas, causing about 30 times as much global warming per molecule as carbon dioxide. It is currently known that methane can be emitted from the trunks of trees, but it is unknown if the methane originates in the soil and is transported into the tree along with tree water uptake from below ground, or if the methane originates inside the tree. Understanding what water and environment factors influence methane emissions from trees can improve climate predictions and may help people manage forests and forested wetlands deliberately to reduce their natural methane emissions. The project will also work with a local elementary school serving talented and gifted students primarily from underrepresented groups (Black, Latinx). About 200 second-grade students will visit American University, where they will learn about watersheds, trees, and sustainability and participate in activities to develop a science identity.This research will use radon as a tracer of the movement of water and gases through trees. Radon is an established tool for studying water flows and gas exchange in the ocean, estuaries, rivers, soil, and groundwater. Radon, methane, and water fluxes from trees will be simultaneously measured across a wetland-upland gradient to determine whether the methane emitted from trees comes from soil water or is produced within the tree. Soil moisture, water potential, soil methane and radon concentrations, water table height, stomatal conductance, and sap flow will be measured concurrently to delineate the relationships between tree physiology, water flows, and stem gas emissions and to distinguish topographic effects. Field data will be used to develop numerical models that simulate dynamic gas transport through the soil-plant-atmosphere continuum, account for both dissolved gas and bubbles, and include both daytime and nighttime transient water potential gradients and transport. Finally, the results will be scaled up to assess how direct and indirect effects of climate change (e.g., temperature increase, sea level rise, changes in precipitation patterns, soil moisture, and tree water use, shift of some coastal forests from upland to wetland) may affect tree methane emissions.This award is co-funded by the Hydrologic Sciences and Instrumentation and Facilities programs in the Division of Earth Sciences, as well as the Ecosystem Science program in the Division of Environmental Biology.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.