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Research article - Peer-reviewed, 2005

Uncertainties in static closed chamber measurements of the carbon isotopic ratio of soil-respired CO2

Ohlsson KEA, Bhupinderpal-Singh, Holm S, Nordgren A, Lovdahl L, Hogberg P

Abstract

The delta(13)C of soil-respired CO2 (delta(r)) is frequently determined using static closed chamber methods. 6, is obtained as the intercept of the least squares linear regression of delta vs 1/C*, where measured delta(13)C-CO2 (delta) and volume fraction Of CO2 (C*) values of chamber headspace samples are used. Theoretically, we show that the variance of the estimate Of delta(r) can be reduced by extending the 1/C* interval of the regression towards (i) higher or (ii) lower values, or (iii) distributing the 1/C* values optimally within the pre-selected headspace CO2 sampling time period. Experimental applications of these approaches indicated that: (1) lowering the initial CO2 level, thereby increasing 1/C*, yielded a positive bias to the 6, result. (2) It was feasible to obtain lower variance in the 6, estimate by lowering 1/C* values through extended CO2 sampling time. We also recommend that each chamber is sampled only once, mainly because this allows freedom to select the sampling times, in order to optimize the distribution of 1/C* values. (c) 2005 Elsevier Ltd. All rights reserved

Published in

Soil Biology and Biochemistry
2005, Volume: 37, number: 12, pages: 2273-2276
Publisher: PERGAMON-ELSEVIER SCIENCE LTD

    SLU Authors

    • Ohlsson, Anders

      • Department of Forest Ecology, Swedish University of Agricultural Sciences

        • Nordgren, Anders

          • Department of Forest Ecology, Swedish University of Agricultural Sciences

          • Lövdahl, Lars

            • Department of Forest Ecology, Swedish University of Agricultural Sciences

            • Högberg, Peter

              • Department of Forest Ecology, Swedish University of Agricultural Sciences

            UKÄ Subject classification

            Environmental Sciences related to Agriculture and Land-use

            Publication Identifiers

            DOI: https://doi.org/10.1016/j.soilbio.2005.03.023

            Permanent link to this page (URI)

            https://res.slu.se/id/publ/6020