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Chamber Measurements of Soil Nitrous Oxide Flux: Are Absolute Values Reliable?
Author(s) -
Rochette Philippe,
Eriksen-Hamel Nikita S.
Publication year - 2008
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2007.0215
Subject(s) - flux (metallurgy) , confidence interval , environmental science , reliability (semiconductor) , soil science , statistics , mathematics , chemistry , physics , thermodynamics , power (physics) , organic chemistry
The vast majority of soil N 2 O flux data reported in the literature was obtained using non‐flow‐through non‐steady‐state (NFT‐NSS) chambers. Considerable variation in chamber methodology may influence N 2 O flux measurements, however, raising concerns about the reliability and accuracy of these measurements. The objectives of this study were to determine criteria for assessing the quality of soil N 2 O flux measurements made using NFT‐NSS chambers, to evaluate NFT‐NSS chamber methodologies used in the scientific literature, and to propose a minimum set of criteria for NFT‐NSS chamber design and deployment methodology. We identified 16 characteristics of chamber methodology and developed four factors contributing to the quality of N 2 O flux measurements made using NFT‐NSS chambers. We compiled a data set of 356 studies and evaluated the quality of each study against the set of characteristics and factors to determine the confidence in the reported N 2 O flux. Confidence in the absolute flux values reported in about 60% of the studies was estimated to be very low or low due to poor methodologies or incomplete reporting. The confidence in flux measurements improved with time; however, there were still about 50% of recent studies (2005–2007) with low or very low confidence levels. This study has shown that the quality of soil N 2 O flux measurements reported in the literature is often poor. While the flux data obtained may be valid for comparisons between situations (e.g., treatments) within a given study, they are often biased estimates of actual fluxes. We propose a minimum set of criteria for reliable soil N 2 O flux measurements using NFT‐NSS chambers.