INCREASING SUSTAINABILITY AND MITIGATING GREENHOUSE GAS EMISSIONS OF FOOD AND BIOFUEL PRODUCTION SYSTEMS OF THE UPPER MIDWEST U.S.
Location: Soil and Water Management Research
Title: Quantifying biases in non-steady state chamber measurements of soil-atmosphere gas exchange
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: July 14, 2011
Publication Date: June 20, 2012
Citation: Venterea, R.T., Parkin, T.B. 2012. Quantifying biases in non-steady state chamber measurements of soil-atmosphere gas exchange. In: Liebig, M., Follett, R., Franzluebbers, A., Editors. Managing Agricultural Greenhouse Gases: Coordinated Agricultural Research through GRACEnet to Address our Changing Climate. Waltham, MA: Academic Press. p. 327-343.
Limitations of non-steady state (NSS) chamber methods for determining soil-to-atmosphere trace gas exchange rates have been recognized for several decades. Of these limitations, the so-called “chamber effect” is one of the most challenging to overcome. The chamber effect can be defined as the inherent tendency for NSS gas flux chamber methods to produce a biased estimate of the actual pre-deployment flux (PDF), where the PDF is defined as the flux occurring immediately prior to placement of the chamber on the soil surface. This effect can be particularly important for greenhouse gases (GHGs) like nitrous oxide (N2O) which often require more prolonged chamber deployment periods in order to facilitate analytical measurement. Despite widespread recognition of this limitation, there is little consensus regarding practical approaches to either estimating the magnitude or reducing the significance of this effect. There is wide variation in method protocols used to determine soil N2O flux, details of which can directly affect chamber-induced bias. Recent analysis has shown that intra- and inter-site flux comparisons can be confounded by chamber-induced artifacts. Since NSS chambers generally tend to underestimate the actual PDF, this raises the likelihood that current emissions assessments at the regional, national, and global scale are negatively biased. This has important implications for effective management and mitigation of GHG emissions. The main objectives of this chapter are to (i) present an overview of the problem, (ii) describe currently available options for quantifying and minimizing flux estimation errors resulting from the chamber effect, and (iii) briefly discuss the path toward ultimate solutions to this problem.