title: Agricultural peatland restoration: effects of land-use change on greenhouse gas (CO2 and CH4) fluxes in the Sacramento-San Joaquin Delta.
abstract: Agricultural drainage of organic soils has resulted in vast soil subsidence and contributed to increased atmospheric carbon dioxide (CO2) concentrations. The Sacramento-San Joaquin Delta in California was drained over a century ago for agriculture and human settlement and has since experienced subsidence rates that are among the highest in the world. It is recognized that drained agriculture in the Delta is unsustainable in the long-term, and to help reverse subsidence and capture carbon (C) there is an interest in restoring drained agricultural land-use types to flooded conditions. However, flooding may increase methane (CH4) emissions. We conducted a full year of simultaneous eddy covariance measurements at two conventional drained agricultural peatlands (a pasture and a corn field) and three flooded land-use types (a rice paddy and two restored wetlands) to assess the impact of drained to flooded land-use change on CO2 and CH4 fluxes in the Delta. We found that the drained sites were net C and greenhouse gas (GHG) sources, releasing up to 341 g C m(-2) yr(-1) as CO2 and 11.4 g C m(-2) yr(-1) as CH4. Conversely, the restored wetlands were net sinks of atmospheric CO2, sequestering up to 397 g C m(-2) yr(-1). However, they were large sources of CH4, with emissions ranging from 39 to 53 g C m(-2) yr(-1). In terms of the full GHG budget, the restored wetlands could be either GHG sources or sinks. Although the rice paddy was a small atmospheric CO2 sink, when considering harvest and CH4 emissions, it acted as both a C and GHG source. Annual photosynthesis was similar between sites, but flooding at the restored sites inhibited ecosystem respiration, making them net CO2 sinks. This study suggests that converting drained agricultural peat soils to flooded land-use types can help reduce or reverse soil subsidence and reduce GHG emissions.
authors.affiliation: Ecosystem Science Division, Department of Environmental Science, Policy and Management, University of California at Berkeley, Berkeley, CA, USA.
authors.forename: Sara Helen
authors.initials: SH
authors.lastname: Knox
authors.forename: Cove
authors.initials: C
authors.lastname: Sturtevant
authors.forename: Jaclyn Hatala
authors.initials: JH
authors.lastname: Matthes
authors.forename: Laurie
authors.initials: L
authors.lastname: Koteen
authors.forename: Joseph
authors.initials: J
authors.lastname: Verfaillie
authors.forename: Dennis
authors.initials: D
authors.lastname: Baldocchi
mesh_terms: D000383:Agriculture; D000393:Air Pollutants / Q000032:analysis*; D002140:California; D057486:Carbon Cycle; D002245:Carbon Dioxide / Q000032:analysis*; D003247:Conservation of Natural Resources; D004784:Environmental Monitoring; D008697:Methane / Q000032:analysis*; D012987:Soil / Q000737:chemistry*; D053833:Wetlands
chemical_list: D000393:Air Pollutants; D012987:Soil; D002245:Carbon Dioxide; D008697:Methane
keywords: carbon flux; drained; eddy covariance; greenhouse gas balance; land-use change; methane; peatland; restored; rice; wetland