文章基本信息

标题：Effect of Soil Texture on Estimates of Soil-Column Carbon Dioxide Flux Comparing Chamber and Gradient Methods
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作者：Xiaoli Yang ; Jun Fan ; Scott B. Jones 等
期刊名称：Vadose Zone Journal
电子版ISSN：1539-1663
出版年度：2018
卷号：17
期号：1
页码：1-8
DOI：10.2136/vzj2018.05.0112
出版社：Soil Science Society of America, Inc.
摘要：Core Ideas Carbon dioxide efflux from soil of different textures was compared. The dominant mechanism of CO 2 efflux changed from coarse to fine soil. The gradient method should be used very carefully in coarse soils. A key component of the global C balance includes soil CO 2 emissions. Both chamber‐ and gradient‐based methods have been effectively used for determination of soil CO 2 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 2 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 ( D P /D 0 ). The gradient‐based CO 2 effluxes were compared with estimates derived from the CO 2 –efflux chamber. Soil CO 2 effluxes estimated using the gradient method approximated those using the chamber for all three soil textures. The particle shape factor ( p ) in the SAPHIR model varied with silt content of the three soils. The SAPHIR model's water blockage factor ( w ) 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 2 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.
关键词：NMSE; normalized mean square error; SAPHIR; Soil Air Phase Individual Resistances; TDR; time-domain reflectometry; VWC; volumetric soil water content.