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Restricting the nonlinearity parameter in soil greenhouse gas flux calculation for more reliable flux estimates

Hüppi, Roman; Felber, Raphael; Krauss, Maike; Six, Johan; Leifeld, Jens and Fuß, Roland (2018) Restricting the nonlinearity parameter in soil greenhouse gas flux calculation for more reliable flux estimates. PLoS ONE, 13 (7), pp. 1-17.

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Online at: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0200876

Summary

The static chamber approach is often used for greenhouse gas (GHG) flux measurements, whereby the flux is deduced from the increase of species concentration after closing the chamber. Since this increase changes diffusion gradients between chamber air and soil air, a nonlinear increase is expected. Lateral gas flow and leakages also contribute to non linearity.
Several models have been suggested to account for this non linearity, the most recent being the Hutchinson±Mosier regression model (HMR). However, the practical application of these models is challenging because the researcher needs to decide for each flux whether a nonlinear fit is appropriate or exaggerates flux estimates due to measurement artifacts. In the latter case, a flux estimate from the linear model is a more robust solution and introduces less arbitrary uncertainty to the data. We present the new, dynamic and reproducible flux calculation scheme, KAPPA.MAX, for an improved trade-off between bias and uncertainty (i.e. accuracy and precision). We develop a tool to simulate, visualise and optimise the flux calculation scheme for any specific static N2O chamber measurement system.
The decision procedure and visualisation tools are implemented in a package for the R software.
Finally, we demonstrate with this approach the performance of the applied flux calculation scheme for a measured flux dataset to estimate the actual bias and uncertainty. The KAPPA.MAX method effectively improved the decision between linear and nonlinear flux estimates reducing the bias at a minimal cost of uncertainty.


EPrint Type:Journal paper
Keywords:greenhouse gases, measurement equipment, simulation and modeling, nonlinear systems
Subjects: Knowledge management > Research methodology and philosophy > Specific methods
Environmental aspects > Air and water emissions
Research affiliation: Germany > Federal Research Institute for Rural Areas, Forestry and Fisheries - VTI
Switzerland > FiBL - Research Institute of Organic Agriculture Switzerland > Soil Sciences
Switzerland > Agroscope
Switzerland > ETHZ - Agrarwissenschaften
DOI:https://doi.org/10.1371/journal.pone.0200876
Deposited By: Krauss, Maike
ID Code:34683
Deposited On:25 Feb 2019 20:32
Last Modified:25 Feb 2019 20:32
Document Language:English
Status:Published
Refereed:Peer-reviewed and accepted

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