Inverse Determination of Subsurface CO2 Production and Temperature Sensitivity from Continuous Efflux Measurements

English Abstract:

High-frequency CO₂ soil flux measurements offer enhanced resolution of terrestrial carbon cycling. However, understanding the sensitivity of emissions to environmental conditions is complicated by vertically heterogeneous soil properties. In this study, we describe a new inverse modeling technique to determine distributed soil profile CO₂ production and its temperature sensitivity (Q₁₀) from high-frequency CO₂ soil flux. Quantitative uncertainties that arise from input data are presented. Using field data, we explore natural trends and show the utility of the physically based technique to isolate the effects of CO₂ driving variables. Results demonstrate that accuracy and precision of soil environmental measurements are critical issues for resolving depth dependant soil properties. It is further shown that depth resolved soil CO₂ production and Q₁₀ are dynamic, and deep soil CO₂ production was regularly but not always more sensitive to temperature. Although computationally intensive, the inversion of distributed soil profile CO₂ production and Q₁₀ is theoretically valid, and may be applicable to most soil conditions.