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

该项目的目标是更好地了解树木在全球水和甲烷循环中的作用，并通过有关水和树木的实践活动吸引小学生学习环境科学。甲烷是一种强效的温室气体，每个甲烷分子造成的全球变暖效应是二氧化碳的30倍。目前已知的是，甲烷可以从树木的树干中释放出来，但尚不清楚甲烷是来自土壤，并随着树木从地下吸收水分而被输送到树木中，还是来自树木内部。了解水和环境因素对树木甲烷排放的影响可以改善气候预测，并可能帮助人们有意识地管理森林和森林湿地，以减少其天然甲烷排放。该项目还将与当地一所小学合作，为主要来自代表性不足的群体（黑人、拉丁裔）的天才和天才学生提供服务。大约200名二年级学生将访问美国大学，在那里他们将学习流域、树木和可持续性，并参加培养科学身份的活动。这项研究将使用氡作为水和气体在树木中运动的示踪剂。氡是研究海洋、河口、河流、土壤和地下水中水流和气体交换的既定工具。来自树木的氡、甲烷和水通量将在湿地-高地梯度上同时测量，以确定树木排放的甲烷是来自土壤水还是树木内部产生的。将同时测量土壤水分、水势、土壤甲烷和氡浓度、地下水位高度、气孔导度和树液流量，以描述树木生理、水流和茎干气体排放之间的关系，并区分地形效应。现场数据将用于开发数值模型，模拟通过土壤-植物-大气连续体的动态气体输送，考虑溶解气体和气泡，并包括白天和夜间的瞬态水势梯度和输送。最后，研究结果将被扩大，以评估气候变化的直接和间接影响（例如，温度升高、海平面上升、降水模式、土壤湿度和树木用水的变化、一些沿海森林从高地向湿地的转移）如何影响树木甲烷排放。该奖项由地球科学部的水文科学和仪器与设施项目以及环境生物学部的生态系统科学项目共同资助。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.