Effect of Soil Texture on Estimates of Soil-Column Carbon Dioxide Flux Comparing Chamber and Gradient Methods

• Main Authors: Xiaoli Yang, Jun Fan, Scott B. Jones
• Format: Article
• Language: English
• Published: Wiley 2018-12-01
• Series: Vadose Zone Journal
• Online Access: https://dl.sciencesocieties.org/publications/vzj/articles/17/1/180112

A key component of the global C balance includes soil CO emissions. Both chamber- and gradient-based methods have been effectively used for determination of soil CO efflux. The gradient-based method, however, is installed belowground and requires assessment of the soil gas diffusion coefficient, which varies with soil properties such as soil texture. We hypothesized that the gradient and chamber methods would yield similar results when soil texture was appropriately accounted for. Our objective was to evaluate soil gas efflux by applying both methods in three different soil textures (loam, silty loam, and silty clay loam) packed in laboratory soil columns. Water was incrementally applied to soil surfaces while volumetric soil water contents (VWC) and CO concentrations were continually monitored at target locations in parallel with surface chamber measurements. The Soil Air Phase Individual Resistances (SAPHIR) model was used to determine the relative gas diffusion coefficients (). The gradient-based CO effluxes were compared with estimates derived from the CO–efflux chamber. Soil CO effluxes estimated using the gradient method approximated those using the chamber for all three soil textures. The particle shape factor () in the SAPHIR model varied with silt content of the three soils. The SAPHIR model’s water blockage factor () also varied with soil texture to a lesser extent. Under the repacked soil condition, these results confirm that the gradient method can provide consistent CO measurements in comparison with chamber-based results from soils of varied texture when the diffusion coefficient takes into account the effects of soil texture. The gradient method should be used cautiously in coarse-textured soils.