PNNL

Abstract

Tidal wetlands provide valuable ecosystem services, including storing large amounts of carbon in their sediments. However, the net exchange of carbon dioxide (CO2) and methane (CH4) in tidal wetlands are highly uncertain. While several biogeochemical models can operate in tidal wetlands, they have yet to be trained and validated against high-frequency, ecosystem-scale CO2 and CH4 flux measurements across diverse sites. We paired the Cohort Marsh Equilibrium Model (CMEM) with a version of the PEPRMT model called PEPRMT-Tidal that considers the effect of water table height and sulfate and nitrate availability on CO2 and CH4 emissions. Using a model-data fusion approach, we trained the model against three tidal wetland sites and validated with two independent sites, encompassing the three oceanic coasts of North America. Gross primary productivity (GPP) and ecosystem respiration (Reco) modules explained on average 59% of the variation in CO2 exchange with consistently low model error (normalized RMSE