Location: Soil and Water Management Research
Title: Data analysis considerations Authors
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: April 1, 2013
Publication Date: June 1, 2013
Citation: Venterea, R.T., Parkin, T.B., Cardebas, L., Petersen, S.O., Petersen, A.R. 2013. Data analysis considerations. In: DeKlein, C., Harvey, M., editors. Global Research Alliance on Agricultural Greenhouse Gas Emissions. New Zealand Ministry for Primary Industries, Wellington, New Zealand. Available: http://www.globalresearchalliance.org/research/livestock/activities/nitrous-oxide-chamber-methodology-guidelines/. Technical Abstract: For the last 30 years static chamber methodologies have been most commonly used to measure N2O fluxes from agricultural soils. The main advantages of this technique are that it is relatively inexpensive, versatile in the field, and the technology is very easy to adopt. Consequently, the majority of our knowledge and understanding of N2O emissions that underpins the estimation of national emission inventories from agricultural soils and efficacies of potential mitigation practices is based on N2O chamber measurements. More than 95% of the thousands of published N2O emission studies used chamber methodologies – in particular, non-flow-through, non-steady-state (NSS) chambers. In 2011/12, the New Zealand Government, in support of the objectives of the Global Research Alliance funded an international collaboration to progress the development of guidelines and recommendations for use of NSS chambers. At an initial workshop in New Zealand in May 2011, leading experts from Alliance member countries reviewed the current state of understanding of N2O chamber methodologies and developed the outlines for this guideline document. Since then, researchers from around the world have been working together to write chapters for the different steps in producing N2O flux data from the use of chambers. The Data Analysis chapter addresses the following issues: Selecting and use of a flux calculation method, Estimation of emissions using non-continuous flux data, Assessment of minimum detectable flux (MDF), Statistical considerations for analyzing inherently heterogeneous flux data, and Estimation of emission factors (EFs). Use of chambers to determine soil-to-atmosphere emissions of N2O is labor intensive and requires collection and processing of relatively large data sets. Due to the inherently variable nature of N2O emissions and the inherent tendency of chambers to alter the quantity being measured, substantial care is required to optimize analysis of the collected data. Careful consideration of appropriate analysis procedures as discussed in this chapter will ensure that upstream efforts with regard to chamber design, sampling regimes, and other aspects of the methodology will generate the most meaningful and statistically valid results. These Guidelines document the current state of knowledge on N2O chamber methodologies and provide internationally agreed standardized guidelines and recommendations for their use that will be useful for researchers around the world.