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Global Research Alliance N 2 O chamber methodology guidelines: Flux calculations
Author(s) -
Venterea Rodney T.,
Petersen Søren O.,
Klein Cecile A. M.,
Pedersen Asger R.,
Noble Alasdair D. L.,
Rees Robert M.,
Gamble Joshua D.,
Parkin Timothy B.
Publication year - 2020
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.1002/jeq2.20118
Subject(s) - sampling (signal processing) , flux (metallurgy) , selection (genetic algorithm) , calibration , basis (linear algebra) , set (abstract data type) , accuracy and precision , computer science , algorithm , mathematical optimization , environmental science , mathematics , statistics , chemistry , geometry , organic chemistry , filter (signal processing) , artificial intelligence , computer vision , programming language
A critical step in determining soil‐to‐atmosphere nitrous oxide (N 2 O) exchange using non‐steady‐state chambers is converting collected gas concentration versus time data to flux values using a flux calculation (FC) scheme. It is well documented that different FC schemes can produce different flux estimates for a given set of data. Available schemes differ in their theoretical basis, computational requirements, and performance in terms of both accuracy and precision. Nonlinear schemes tend to increase accuracy compared with linear regression but can also decrease precision. The chamber bias correction method can be used if soil physical data are available, but this introduces additional sources of error. Here, the essential theoretical and practical aspects of the most commonly used FC schemes are described as a basis for their selection and use. A gold standard approach for application and selection of FC schemes is presented, as well as alternative approaches based on availability of soil physical property data and intensity of sample collection during each chamber deployment. Additional criteria for scheme selection are provided in the form of an error analysis tool that quantifies performance with respect to both accuracy and precision based on chamber dimensions and sampling duration, soil properties, and analytical measurement precision. Example error analyses are presented for hypothetical conditions illustrating how such analysis can be used to guide FC scheme selection, estimate bias, and inform design of chambers and sampling regimes.