Overestimation of closed-chamber soil CO<sub>2</sub> effluxes at low atmospheric turbulence
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Published:2017-03-28
Issue:6
Volume:14
Page:1603-1616
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ISSN:1726-4189
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Container-title:Biogeosciences
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language:en
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Short-container-title:Biogeosciences
Author:
Brændholt Andreas, Steenberg Larsen KlausORCID, Ibrom AndreasORCID, Pilegaard KimORCID
Abstract
Abstract. Soil respiration (Rs) is an important component of ecosystem carbon balance, and accurate quantification of the diurnal and seasonal variation of Rs is crucial for a correct interpretation of the response of Rs to biotic and abiotic factors, as well as for estimating annual soil CO2 efflux rates. In this study, we measured Rs hourly for 1 year by automated closed chambers in a temperate Danish beech forest. The data showed a clear diurnal pattern of Rs across all seasons with higher rates during night-time than during daytime. However, further analysis showed a clear negative relationship between flux rates and friction velocity (u∗) above the canopy, suggesting that Rs was overestimated at low atmospheric turbulence throughout the year due to non-steady-state conditions during measurements. Filtering out data at low u∗ values removed or even inverted the observed diurnal pattern, such that the highest effluxes were now observed during daytime, and also led to a substantial decrease in the estimated annual soil CO2 efflux. By installing fans to produce continuous turbulent mixing of air around the soil chambers, we tested the hypothesis that overestimation of soil CO2 effluxes during low u∗ can be eliminated if proper mixing of air is ensured, and indeed the use of fans removed the overestimation of Rs rates during low u∗. Artificial turbulent air mixing may thus provide a method to overcome the problems of using closed-chamber gas-exchange measurement techniques during naturally occurring low atmospheric turbulence conditions. Other possible effects from using fans during soil CO2 efflux measurements are discussed. In conclusion, periods with low atmospheric turbulence may provide a significant source of error in Rs rates estimated by the use of closed-chamber techniques and erroneous data must be filtered out to obtain unbiased diurnal patterns, accurate relationships to biotic and abiotic factors, and before estimating Rs fluxes over longer timescales.
Publisher
Copernicus GmbH
Subject
Earth-Surface Processes,Ecology, Evolution, Behavior and Systematics
Reference61 articles.
1. Aubinet, M., Grelle, A., Ibrom, A., Rannik, U., Moncrieff, J., Foken, T., Kowalski, A. S., Martin, P. H., Berbigier, P., Bernhofer, C., Clement, R., Elbers, J., Granier, A., Grunwald, T., Morgenstern, K., Pilegaard, K., Rebmann, C., Snijders, W., Valentini, R., and Vesala, T.: Estimates of the Annual Net Carbon and Water Exchange of Forest: The EUROFLUX Methodology, Adv. Ecol. Res., 30, 114–173, 2000. 2. Anthony, W. H., Hutchinson, G. L., and Livingston, G. P.: Chamber measurement of soil-atmosphere gas exchange: linear vs diffusion-based flux models, Soil Sci. Soc. Am. J., 59, 1308–1310, 1995. 3. Brændholt, A., Steenberg Larsen, K., Ibrom, A., and Pilegaard, K.: Raw data for “Overestimation of closed-chamber soil CO2 effluxes at low atmospheric turbulence” [Data set], Zenodo, https://doi.org/10.5281/zenodo.438015, 2017. 4. Brooks, J. R., Flanagan, L. B., Varney, G. T., and Ehleringer, J. R.: Vertical gradients in photosynthetic gas exchange characteristics and refixation of respired CO2 within boreal forest canopies, Tree Physiol., 17, 1–12, 1997. 5. Conen, F. and Smith, K. A.: A re-examination of closed flux chamber methods for the measurement of trace gas emissions from soils to the atmosphere, Eur. J. Soil Sci., 49, 701–707, https://doi.org/10.1046/j.1365-2389.1998.4940701.x, 1998.
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