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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2016-182
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
https://doi.org/10.5194/bg-2016-182
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Submitted as: research article 01 Jun 2016

Submitted as: research article | 01 Jun 2016

Review status
This discussion paper is a preprint. It has been under review for the journal Biogeosciences (BG). The revised manuscript was not accepted.

Under a new light: validation of eddy covariance flux with light response functions of assimilation and estimates of heterotrophic soil respiration

Georgia R. Koerber1, Wayne S. Meyer1, Qiaoqi SUN1, Peter Cale2, and Cacilia M. Ewenz3,4 Georgia R. Koerber et al.
  • 1Department of Ecology and Environmental Science, School of Biological Sciences, The University of Adelaide, Adelaide, SA 5005, Australia
  • 2Aust ralian Landscape Trust, Riverland, Calperum Station, PO Box 955, SA 5341, Australia
  • 3CSIRO Oceans and Atmosphere Flagship, Yarralumla, ACT 2600, Australia
  • 4Airborne Research Australia / Flinders University, PO Box 335, SA 5106, Australia

Abstract. Estimation of the basal or heterotrophic soil respiration is crucial for determination of whether an ecosystem is emitting or sequestering carbon. A severe bushfire in January 2014 at the Calperum flux tower, operational since August 2010, provided variation in ecosystem respiration and leaf area index as the ecosystem recovered. We propose ecosystem respiration is a function of leaf area index and the y-intercept is an estimate of heterotrophic soil respiration. We calculated an assimilation rate from eddy covariance data for light response functions to calculate ecosystem respiration incorporating suppression of the daytime autotrophic respiration. Ecosystem respiration from light response functions correlated with data processing calculations of ecosystem respiration by OzFluxQC (y0 = 0.161x + 0.0085; Adj. r2 = 0.698). The relationship between ecosystem respiration and leaf area index (y0 = 1.43x +0.398; Adj. r2 = 0.395) was also apparent. When this approach was compared to field measurements of soil respiration and mass balance calculations from destructive leaf area, leaf area index calculations and litter fall, the year of data corresponding to the year of soil respiration measurements, the y-intercept was 0.432 µmol m−2 s−1 or 163.44 gC m−2 year−1 (y0 = 1.37x + 0.432, Adj. r2 = 0.325). The mass balance approach for the net primary productivity when subtracted from the tower NEE estimated heterotrophic soil respiration of 134.59 gC m−2 year−1. This is only 28.9 gC different, therefore the y-intercept approach indeed provides an estimate of heterotrophic soil respiration.

Georgia R. Koerber et al.
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Georgia R. Koerber et al.
Georgia R. Koerber et al.
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Short summary
A severe bushfire in January 2014 at the Calperum flux tower, operational since August 2010, provided variation in ecosystem respiration and leaf area index to estimate the heterotrophic soil respiration from the y-intercept and was 44 % of net ecosystem exchange of carbon dioxide in the year after the bushfire. Light response functions with a calculated assimilation from equalizing the soil temperature and water content in the night and day allowed incorporation of light suppressed autotrophic respiration.
A severe bushfire in January 2014 at the Calperum flux tower, operational since August 2010,...
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