Real-Time Soil Flux Measurements and Calculations with Crds + Sfp: Comparison Among Flux Algorithms and Derivation of Whole System Error.

The selection of the correct empirical model applied to soil flux rate analysis in soil chamber experiments has been a topic of debate and research for many years (Mosier, A.R. and Hutchinson, G.L. 1981, Healy et al. 1996, Wagner, S.W., 1997, GraceNET, Livingston et al. 2006, Venterea, R.T. et al. 2009). As well, chamber flux values have been primarily reported without estimation of measurement error. Understanding chamber flux model fitting and measurement error is key to scaling soils GHG emissions and resolving the primary uncertainties in climate and management feedbacks at regional and global scales. Recently, Picarro has released a new software tool, the “Soil Flux Processor” (SFP), which links the power of Cavity Ring-Down Spectroscopy (CRDS) technology with an easy-to-use GUI interface. The SFP has been designed to provide a very flexible sample-ID and run-scheme GUI interface, a highly practical real-time monitoring of chamber measurement GUI interface, and a sophisticated flux analysis GUI interface. The SFP offers a user-defined model selection which includes three predominant fit algorithms as default, and an open-code interface for user-composed algorithms. The Soils Flux Processor is designed to couple with the Picarro G2508 system, an analyzer which radically simplifies soils flux studies by simultaneously measuring primary GHG species -- N2O, CH4, CO2 and H2O. In this study, we present experimental demonstrations of chamber flux analysis using the different modeling algorithms available with the Soils Flux Processor, and we demonstrate the assessment of measurement error using a whole system “Boot Strap” Monte Carlo analysis.