Improving the accuracy of the gradient method for determining soil carbon dioxide efflux
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S-nchez-Ca-ete_et_al-2017-Jour ...
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FInal Published Version
Affiliation
Univ Arizona, Biosphere 2, Earthsci B2Univ Arizona, Sch Geog & Dev
Issue Date
2017-01Keywords
soil respirationdiffusion coefficient
conservative tracers
carbon emissions
CO2 sensors
soil CO2 flux
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AMER GEOPHYSICAL UNIONCitation
Improving the accuracy of the gradient method for determining soil carbon dioxide efflux 2017, 122 (1):50 Journal of Geophysical Research: BiogeosciencesRights
©2016. American Geophysical Union. All Rights Reserved.Collection Information
This 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.Abstract
Soil 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.Note
6 month embargo; First published: 5 January 2017ISSN
21698953Version
Final published versionSponsors
NSF [1417101, 1331408]; Marie Curie International Outgoing Fellowship within the Seventh European Community, DIESEL project [625988]Additional Links
http://doi.wiley.com/10.1002/2016JG003530ae974a485f413a2113503eed53cd6c53
10.1002/2016JG003530