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dc.contributor.authorSánchez-Cañete, Enrique P.
dc.contributor.authorScott, Russell L.
dc.contributor.authorvan Haren, Joost
dc.contributor.authorBarron-Gafford, Greg A.
dc.date.accessioned2017-04-11T23:57:39Z
dc.date.available2017-04-11T23:57:39Z
dc.date.issued2017-01
dc.identifier.citationImproving the accuracy of the gradient method for determining soil carbon dioxide efflux 2017, 122 (1):50 Journal of Geophysical Research: Biogeosciencesen
dc.identifier.issn21698953
dc.identifier.doi10.1002/2016JG003530
dc.identifier.urihttp://hdl.handle.net/10150/623105
dc.description.abstractSoil CO2 efflux (F-soil) represents a significant source of ecosystem CO2 emissions that is rarely quantified with high-temporal-resolution data in carbon flux studies. F-soil estimates can be obtained by the low-cost gradient method (GM), but the utility of the method is hindered by uncertainties in the application of published models for the diffusion coefficient. Therefore, to address and resolve these uncertainties, we compared F-soil measured by 2 soil CO2 efflux chambers and F-soil estimated by 16 gas transport models using the GM across 1year. We used 14 published empirical gas diffusion models and 2 in situ models: (1) a gas transfer model called Chamber model obtained using a calibration between the chamber and the gradient method and (2) a diffusion model called SF6 model obtained through an interwell conservative tracer experiment. Most of the published models using the GM underestimated cumulative annual F-soil by 55% to 361%, while the Chamber model closely approximated cumulative F-soil (0.6% error). Surprisingly, the SF6 model combined with the GM underestimated F-soil by 32%. Differences between in situ models could stem from the Chamber model implicitly accounting for production of soil CO2, while the conservative tracer model does not. Therefore, we recommend using the GM only after calibration with chamber measurements to generate reliable long-term ecosystem F-soil measurements. Accurate estimates of F-soil will improve our understanding of soil respiration's contribution to ecosystem fluxes.
dc.description.sponsorshipNSF [1417101, 1331408]; Marie Curie International Outgoing Fellowship within the Seventh European Community, DIESEL project [625988]en
dc.language.isoenen
dc.publisherAMER GEOPHYSICAL UNIONen
dc.relation.urlhttp://doi.wiley.com/10.1002/2016JG003530en
dc.rights© 2016. American Geophysical Union. All Rights Reserved.en
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/
dc.subjectsoil respirationen
dc.subjectdiffusion coefficienten
dc.subjectconservative tracersen
dc.subjectcarbon emissionsen
dc.subjectCO2 sensorsen
dc.subjectsoil CO2 fluxen
dc.titleImproving the accuracy of the gradient method for determining soil carbon dioxide effluxen
dc.typeArticleen
dc.contributor.departmentUniv Arizona, Biosphere 2, Earthsci B2en
dc.contributor.departmentUniv Arizona, Sch Geog & Deven
dc.identifier.journalJournal of Geophysical Research: Biogeosciencesen
dc.description.note6 month embargo; First published: 5 January 2017en
dc.description.collectioninformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.en
dc.eprint.versionFinal published versionen
dc.contributor.institutionB2 Earthscience, Biosphere 2; University of Arizona; Tucson Arizona USA
dc.contributor.institutionSouthwest Watershed Research Center, USDA-ARS; Tucson Arizona USA
dc.contributor.institutionB2 Earthscience, Biosphere 2; University of Arizona; Tucson Arizona USA
dc.contributor.institutionB2 Earthscience, Biosphere 2; University of Arizona; Tucson Arizona USA
refterms.dateFOA2017-07-06T00:00:00Z
html.description.abstractSoil CO2 efflux (F-soil) represents a significant source of ecosystem CO2 emissions that is rarely quantified with high-temporal-resolution data in carbon flux studies. F-soil estimates can be obtained by the low-cost gradient method (GM), but the utility of the method is hindered by uncertainties in the application of published models for the diffusion coefficient. Therefore, to address and resolve these uncertainties, we compared F-soil measured by 2 soil CO2 efflux chambers and F-soil estimated by 16 gas transport models using the GM across 1year. We used 14 published empirical gas diffusion models and 2 in situ models: (1) a gas transfer model called Chamber model obtained using a calibration between the chamber and the gradient method and (2) a diffusion model called SF6 model obtained through an interwell conservative tracer experiment. Most of the published models using the GM underestimated cumulative annual F-soil by 55% to 361%, while the Chamber model closely approximated cumulative F-soil (0.6% error). Surprisingly, the SF6 model combined with the GM underestimated F-soil by 32%. Differences between in situ models could stem from the Chamber model implicitly accounting for production of soil CO2, while the conservative tracer model does not. Therefore, we recommend using the GM only after calibration with chamber measurements to generate reliable long-term ecosystem F-soil measurements. Accurate estimates of F-soil will improve our understanding of soil respiration's contribution to ecosystem fluxes.


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