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dc.contributor.authorRaczka, B.en
dc.contributor.authorBiraud, S. C.en
dc.contributor.authorEhleringer, J. R.en
dc.contributor.authorLai, C.-T.en
dc.contributor.authorMiller, J. B.en
dc.contributor.authorPataki, D. E.en
dc.contributor.authorSaleska, S. R.en
dc.contributor.authorTorn, M. S.en
dc.contributor.authorVaughn, B. H.en
dc.contributor.authorWehr, R.en
dc.contributor.authorBowling, D. R.en
dc.date.accessioned2017-10-06T18:58:22Z
dc.date.available2017-10-06T18:58:22Z
dc.date.issued2017-08
dc.identifier.citationDoes vapor pressure deficit drive the seasonality of δ 13C of the net land-atmosphere CO2 exchange across the United States? 2017, 122 (8):1969 Journal of Geophysical Research: Biogeosciencesen
dc.identifier.issn21698953
dc.identifier.doi10.1002/2017JG003795
dc.identifier.urihttp://hdl.handle.net/10150/625792
dc.description.abstractThe seasonal pattern of the carbon isotope content (delta C-13) of atmospheric CO2 depends on local and nonlocal land-atmosphere exchange and atmospheric transport. Previous studies suggested that the delta C-13 of the net land-atmosphere CO2 flux (delta(source)) varies seasonally as stomatal conductance of plants responds to vapor pressure deficit of air (VPD). We studied the variation of (source) at seven sites across the United States representing forests, grasslands, and an urban center. Using a two-part mixing model, we calculated the seasonal delta(source) for each site after removing background influence and, when possible, removing delta C-13 variation of nonlocal sources. Compared to previous analyses, we found a reduced seasonal (March-September) variation in delta(source) at the forest sites (0.5 parts per thousand variation). We did not find a consistent seasonal relationship between VPD and delta(source) across forest (or other) sites, providing evidence that stomatal response to VPD was not the cause of the global, coherent seasonal pattern in (source). In contrast to the forest sites, grassland and urban sites had a larger seasonal variation in (source) (5) dominated by seasonal transitions in C-3/C-4 grass productivity and in fossil fuel emissions, respectively. Our findings were sensitive to the location used to account for atmospheric background variation within the mixing model method that determined (source). Special consideration should be given to background location depending on whether the intent is to understand site level dynamics or regional scale impacts of land-atmosphere exchange. The seasonal amplitude in delta C-13 of land-atmosphere CO2 exchange (delta(source)) varied across land cover types and was not driven by seasonal changes in vapor pressure deficit. The largest seasonal amplitudes of delta(source) were at grassland and urban sites, driven by changes in C-3/C-4 grass productivity and fossil fuel emissions, respectively. Mixing model approaches may incorrectly calculate delta(source) when background atmospheric observations are remote and/or prone to anthropogenic influence.
dc.description.sponsorshipCenter for High Performance Computing at the University of Utah; US Department of Energy (DOE), Office of Science, Office of Biological and Environmental Research, Terrestrial Ecosystem Science (TES) Program [DE-SC0010625]; US National Science Foundation Macrosystems Biology Program [EF-1137336]; Atmospheric Radiation Measurement Program (ARM) [DE-AC02-05CH11231]; NOAA Climate Program Office's Atmospheric Chemistry, Carbon Cycle, and Climate Program [NA14OAR4310178]; U.S. Department of Energy's Office of Science; NSF as part of the Harvard Forest LTER; DOE TES program [DE-SC0006741]en
dc.language.isoenen
dc.publisherAMER GEOPHYSICAL UNIONen
dc.relation.urlhttp://doi.wiley.com/10.1002/2017JG003795en
dc.rights©2017. American Geophysical Union. All Rights Reserved.en
dc.subjectstable carbon isotopesen
dc.subjectland-atmosphere exchangeen
dc.subjectC3 discriminationen
dc.subjectvapor pressure deficiten
dc.titleDoes vapor pressure deficit drive the seasonality of δ 13C of the net land-atmosphere CO2 exchange across the United States?en
dc.typeArticleen
dc.contributor.departmentUniv Arizona, Dept Ecol & Evolutionary Biolen
dc.identifier.journalJournal of Geophysical Research: Biogeosciencesen
dc.description.note6 month embargo; published online: 10 August 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.institutionDepartment of Biology; University of Utah; Salt Lake City Utah USA
dc.contributor.institutionEarth and Environmental Sciences Area; Lawrence Berkeley National Laboratory; Berkeley California USA
dc.contributor.institutionDepartment of Biology; University of Utah; Salt Lake City Utah USA
dc.contributor.institutionDepartment of Biology; San Diego State University; San Diego California USA
dc.contributor.institutionEarth System Research Laboratory; NOAA; Boulder Colorado USA
dc.contributor.institutionDepartment of Biology; University of Utah; Salt Lake City Utah USA
dc.contributor.institutionDepartment of Ecology and Evolutionary Biology; University of Arizona; Tucson Arizona USA
dc.contributor.institutionEarth and Environmental Sciences Area; Lawrence Berkeley National Laboratory; Berkeley California USA
dc.contributor.institutionInstitute for Arctic and Alpine Research; University of Colorado Boulder; Boulder Colorado USA
dc.contributor.institutionDepartment of Ecology and Evolutionary Biology; University of Arizona; Tucson Arizona USA
dc.contributor.institutionDepartment of Biology; University of Utah; Salt Lake City Utah USA
refterms.dateFOA2018-02-10T00:00:00Z
html.description.abstractThe seasonal pattern of the carbon isotope content (delta C-13) of atmospheric CO2 depends on local and nonlocal land-atmosphere exchange and atmospheric transport. Previous studies suggested that the delta C-13 of the net land-atmosphere CO2 flux (delta(source)) varies seasonally as stomatal conductance of plants responds to vapor pressure deficit of air (VPD). We studied the variation of (source) at seven sites across the United States representing forests, grasslands, and an urban center. Using a two-part mixing model, we calculated the seasonal delta(source) for each site after removing background influence and, when possible, removing delta C-13 variation of nonlocal sources. Compared to previous analyses, we found a reduced seasonal (March-September) variation in delta(source) at the forest sites (0.5 parts per thousand variation). We did not find a consistent seasonal relationship between VPD and delta(source) across forest (or other) sites, providing evidence that stomatal response to VPD was not the cause of the global, coherent seasonal pattern in (source). In contrast to the forest sites, grassland and urban sites had a larger seasonal variation in (source) (5) dominated by seasonal transitions in C-3/C-4 grass productivity and in fossil fuel emissions, respectively. Our findings were sensitive to the location used to account for atmospheric background variation within the mixing model method that determined (source). Special consideration should be given to background location depending on whether the intent is to understand site level dynamics or regional scale impacts of land-atmosphere exchange. The seasonal amplitude in delta C-13 of land-atmosphere CO2 exchange (delta(source)) varied across land cover types and was not driven by seasonal changes in vapor pressure deficit. The largest seasonal amplitudes of delta(source) were at grassland and urban sites, driven by changes in C-3/C-4 grass productivity and fossil fuel emissions, respectively. Mixing model approaches may incorrectly calculate delta(source) when background atmospheric observations are remote and/or prone to anthropogenic influence.


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