A CARBON DIOXIDE FLUX GENERATOR FOR TESTING INFRARED GAS ANALYZER-BASED SOIL RESPIRATION SYSTEMS

摘要

An artificial flux generation device was developed to test the accuracy of a closed-dynamic soil respiration system (LICOR 6400). The device consisted of an enclosed reservoir with a porous top; the reservoir contained a volume of CO₂ enriched air, which was monitored by an infrared gas analyzer (IRGA). When the internal CO₂ concentration within the reservoir was elevated, diffusion rates through the porous medium were measured by recording changes in CO₂ concentration within the reservoir. This diffusion-based artificial flux mimics natural soil respiration, and allows an independent verification of the accuracy of soil respiration measurement systems. We tested a LI-COR 6400 portable photosynthesis system fitted with a 6400-09 soil CO₂ flux chamber. On average, this system overestimated high flux rates by 2 to 4% and underestimated low flux rates by 4 to 20% over five independent trials. Soil respiration appeared to be sensitive to boundary layer mixing, and ambient CO₂ concentrations.