title: Effects of seasonality, transport pathway, and spatial structure on greenhouse gas fluxes in a restored wetland.
abstract: Wetlands can influence global climate via greenhouse gas (GHG) exchange of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Few studies have quantified the full GHG budget of wetlands due to the high spatial and temporal variability of fluxes. We report annual open-water diffusion and ebullition fluxes of CO2, CH4, and N2O from a restored emergent marsh ecosystem. We combined these data with concurrent eddy-covariance measurements of whole-ecosystem CO2and CH4exchange to estimate GHG fluxes and associated radiative forcing effects for the whole wetland, and separately for open-water and vegetated cover types. Annual open-water CO2, CH4, and N2O emissions were 915 ± 95 g C-CO2m-2yr-1, 2.9 ± 0.5 g C-CH4m-2yr-1, and 62 ± 17 mg N-N2O m-2yr-1, respectively. Diffusion dominated open-water GHG transport, accounting for >99% of CO2and N2O emissions, and ~71% of CH4emissions. Seasonality was minor for CO2emissions, whereas CH4and N2O fluxes displayed strong and asynchronous seasonal dynamics. Notably, the overall radiative forcing of open-water fluxes (3.5 ± 0.3 kg CO2-eq m-2yr-1) exceeded that of vegetated zones (1.4 ± 0.4 kg CO2-eq m-2yr-1) due to high ecosystem respiration. After scaling results to the entire wetland using object-based cover classification of remote sensing imagery, net uptake of CO2(-1.4 ± 0.6 kt CO2-eq yr-1) did not offset CH4emission (3.7 ± 0.03 kt CO2-eq yr-1), producing an overall positive radiative forcing effect of 2.4 ± 0.3 kt CO2-eq yr-1. These results demonstrate clear effects of seasonality, spatial structure, and transport pathway on the magnitude and composition of wetland GHG emissions, and the efficacy of multiscale flux measurement to overcome challenges of wetland heterogeneity.
authors.affiliation: Department of Environmental Science, Policy, and Management, University of California at Berkeley, Berkeley, CA, 94720, USA.|Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA.
authors.forename: Gavin
authors.identifier: 0000-0002-6655-8045
authors.initials: G
authors.lastname: McNicol
authors.affiliation: National Ecological Observatory Network, Boulder, CO, 80301, USA.
authors.forename: Cove S
authors.initials: CS
authors.lastname: Sturtevant
authors.affiliation: Department of Environmental Science, Policy, and Management, University of California at Berkeley, Berkeley, CA, 94720, USA.
authors.forename: Sara H
authors.initials: SH
authors.lastname: Knox
authors.affiliation: Department of Landscape Architecture and Environmental Planning, University of California at Berkeley, Berkeley, CA, 94720, USA.
authors.forename: Iryna
authors.initials: I
authors.lastname: Dronova
authors.affiliation: Department of Environmental Science, Policy, and Management, University of California at Berkeley, Berkeley, CA, 94720, USA.
authors.forename: Dennis D
authors.initials: DD
authors.lastname: Baldocchi
authors.affiliation: Department of Environmental Science, Policy, and Management, University of California at Berkeley, Berkeley, CA, 94720, USA.
authors.forename: Whendee L
authors.initials: WL
authors.lastname: Silver
mesh_terms: D002245:Carbon Dioxide; D017753:Ecosystem; D017752:Greenhouse Effect; D008697:Methane; D009609:Nitrous Oxide; D053833:Wetlands
chemical_list: D002245:Carbon Dioxide; D009609:Nitrous Oxide; D008697:Methane
keywords: carbon dioxide; gas flux; greenhouse gas; methane; nitrous oxide; redox; restoration; seasonality; wetland