Abiotic processes dominate CO2 fluxes in Antarctic soils
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TitleAbiotic processes dominate CO2 fluxes in Antarctic soilsAbstractEcosystems within the McMurdo Dry Valleys of Antarctica are highly sensitive to environmental change. Increases in soil temperature and/or moisture content may dramatically change rates of soil respiration and soil carbon (C) turnover. Present estimates of soil respiration rates and C turnover times are based on surface carbon dioxide (CO2) fluxes and soil organic C content. However, the assumption that surface CO2 fluxes are purely biological in origin has not been rigorously tested. We use concentration and, for the first time, the stable C isotopic composition of surface soil CO2 fluxes and subsurface CO2 profiles to: 1) examine mechanisms of soil CO2 uptake and release, 2) identify the location of potential CO2 sources and sinks within the soil profile, and 3) discriminate between biotic and abiotic contributions to CO2 fluxes in soils of Taylor Valley. Surface CO2 fluxes and subsurface CO2 profiles confirm that these soils take up and release CO2 on a daily basis (during the austral summer), associated with small changes in soil temperature. Shifts in the C isotopic composition of soil CO2 are inconsistent with biological mechanisms of CO2 production and consumption. Instead, the isotopic shifts can be accounted for by HenryÅ› Law dissolution and exsolution of CO2 into a solution of high pH, driven by changes in soil temperature. Our results constrain the biological component of soil CO2 fluxes in Taylor Valley to less than 25% (and likely to be significantly less). This finding implies that previous measurements of surface soil CO2 fluxes are overestimates of soil respiration, thus C turnover times calculated from them are underestimates. Discriminating between biotic and abiotic contributions to CO2 fluxes in Antarctic dry valley soils is essential if the effects of climate change on these sensitive ecosystems are to be accurately identified. â"' 2012 Elsevier Ltd.AcknowledgementsWe thank Prof. James Bockheim for his assistance and enthusiasm in the field, Neil Smith for his expert technical help with data logger and field equipment set-up, and Roger Cresswell for his invaluable assistance with sample analyses. We gratefully acknowledge the excellent logistical support provided by Antarctica New Zealand. Operational support was provided by the Lincoln University Research Fund. F.L.S thanks Helicopters New Zealand, the William Machin Trust, Freemasons New Zealand and the Kate Sheppard Memorial Trust for financial support. We also thank two anonymous reviewers for their constructive comments on the manuscript.
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1st AuthorShanhun, F.AuthorShanhun, F.Almond, P.Clough, T.Smith, C.Year2012JournalSoil Biology and BiochemistryVolume53Pages99-111DOI10.1016/j.soilbio.2012.04.027URLhttps://www.scopus.com/inward/recor.....0db82f95ee975f82e7972dd3cKeywordsAntarcticaAustral summersBiological componentsBiological mechanismsDry valleyEnvironmental changeExsolutionHenry's lawHigh pHInorganic CIsotopic compositionIsotopic shiftOrganic CSoil carbonSoil COSoil organic CSoil profilesSoil respirationSoil respiration ratesSoil temperatureSurface carbonSurface soil, Climate changeEcosystemsForestryIsotopesLandformsSoil surveysSoilsTemperature, Carbon dioxide, biotic factorcarbon dioxidecarbon fluxcarbon isotopeclimate changeenvironmental changeinorganic carbonisotopic compositionorganic carbonpHsoil carbonsoil moisturesoil profilesoil temperature, AntarcticaEast AntarcticaMcMurdo Dry ValleysTaylor Valley, rank5Author Keywordsδ 13C CO2Antarctic soilsInorganic CMcMurdo Dry ValleysOrganic CSoil respiration
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TypeArticleCitationShanhun, F., Almond, P., Clough, T. and Smith, C. (2012) Abiotic processes dominate CO2 fluxes in Antarctic soils. Soil Biology and Biochemistry, 53: 99-111 doi:10.1016/j.soilbio.2012.04.027 IdentifierShanhun2012Relevancerank5
Smith, C., Abiotic processes dominate CO2 fluxes in Antarctic soils, [Shanhun2012]. Antarctica NZ, accessed 04/09/2026, https://adam.antarcticanz.govt.nz/nodes/view/63765, 10.1016/j.soilbio.2012.04.027