B038-0013
United States Methane Budget from Tidal Wetlands: Developing an Open-source Database of Methane Measurements and Process-based Models

Wednesday, 9 December 2020
Poster
Patty Y Oikawa1, James Robert Holmquist2, Patrick Megonigal3, Sarah Russell4, Sara Knox4, Michael Najarro5, Lisamarie Windham-Myers6, Ellen JoAnne Stuart-Haëntjens7, Gavin McNicol8, Brian Needelman9, Debjani Sihi10, Inke Forbrich11, Jianwu Tang12, Scott D Bridgham13, Michael Lonneman14, Jaxine Wolfe14, Etienne Fluet-chouinard15 and Ariane Arias Ortiz16, (1)California State University East Bay, Hayward, CA, United States, (2)University of California Los Angeles, Los Angeles, CA, United States, (3)Smithsonian Env Research Ctr, Edgewater, MD, United States, (4)University of British Columbia, Geography, Vancouver, AB, Canada, (5)California State University East Bay, Statistics, Hayward, CA, United States, (6)U.S. Geological Survey, Water Mission Area, Menlo Park, CA, United States, (7)Virginia Commonwealth University, Integrative Life Sciences, Richmond, VA, United States, (8)Stanford University, Stanford, CA, United States, (9)University of Maryland, Environmental Science and Technology, College Park, MD, United States, (10)University of Florida, Ft Walton Beach, FL, United States, (11)Marine Biological Lab, Woods Hole, MA, United States, (12)MBL, The Ecosystems Center, Woods Hole, MA, United States, (13)University of Oregon, Eugene, OR, United States, (14)Smithsonian Environmental Research Center Edgewater, Edgewater, United States, (15)Stanford University, Earth System Science, Stanford, CA, United States, (16)University of California Berkeley, Environmental Sciences, Policy, and Management, Berkeley, CA, United States
Abstract:
Tidal wetlands are biogeochemical reactors where carbon is transformed at the interface of land, ocean, and atmosphere. In this context, methane (CH4) emissions are complex and have a wide range in magnitude, which result in budgets from these ecosystems being poorly constrained. The Coastal Carbon Research Coordination Network (CCRCN) Methane Working Group is focused on establishing an open-source database and a synthesis of CH4 measurements from tidal wetlands across the continental United States to improve our process based understanding of CH4 fluxes. This includes eddy covariance and chamber-based flux measurements along with ancillary environmental covariates such as salinity, water table, inundation time, vegetation cover, soil carbon and porewater electron acceptors. Over 76 sites are being included in the database covering tidal wetlands of the Gulf of Mexico, Atlantic and Pacific coasts ranging from 0.2 ppt to 34 ppt salinity, with annual CH4 budgets from -5 to 160 g CH4-C m-2 yr-1. We are using this database to establish quantitative relationships for scaling‐up and to train and test a set of process-based models that are being modified from the Marsh Equilibrium Model (MEM), the Peatland Ecosystem Respiration and Methane Transport (PEPRMT) model and the Dual Arrhenius and Michaelis-Menten Greenhouse Gas (DAMM-GHG) model. Preliminary results developed and tested in a brackish tidal marsh in the San Francisco Bay-Delta region show modelling ability to capture interannual variability in CH4 budgets (cumulative 4-yr observed: 3.37g CH4-C and cumulative 4-yr modeled: 3.04g CH4-C 4yrs-1). After parameterization and validation using the database, we plan to use our models to provide a CH4 budget for tidal wetlands across the United States and to identify main sources of error in CH4 budgets and the data streams that are needed to improve predictions. Our work so far highlights the importance of salinity and water table height, which are variables not often reported within open databases such as the Ameriflux Network but that are critical to improving CH4 budgets. We acknowledge the CCRCN data contributors for the data provided.
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