The active fraction of soil organic carbon is an important component of soil health and often is quickly assessed as the pulse of CO₂ released by re-wetting dried soils in short-term (24–72 h) assays. However, soils can lose carbon (C) as they dry and, if soil samples vary in moisture content at sampling, differential C loss during the pre-assay dry-down period may complicate the assay's interpretations. We examined the impact of pre-assay CO₂ loss in a long-cultivated agricultural soil at initial moisture contents of 30 %, 50 %, and 70 % water-filled pore space (WFPS). We found that 50 % and 70 % WFPS treatments lost more C during drying than did those in the 30 % WFPS treatment and that dry-down losses led to a 26 %–32 % underestimate of their CO₂ pulses. We developed a soil-specific correction factor to account for these initial soil moisture effects. Future C mineralization studies may benefit from similar corrections.

中文翻译：

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量化和校正短期碳矿化测定中的测定前CO ₂损失

土壤有机碳的活性成分是土壤健康的重要组成部分，通常可以通过在短期（24-72小时）测定中通过重新润湿干燥的土壤而迅速释放出 的CO _2来评估。但是，土壤在干燥过程中可能会损失碳（C），如果土壤样品在采样时含水量发生变化，则在分析前的干燥期间差异C的损失可能会使分析的解释复杂化。我们检查了测定前CO _2的影响在初始水分含量分别为30％，50％和70％的充满水的孔隙空间（WFPS）中，长期耕作的农业土壤中的水分损失。我们发现，与30％WFPS处理相比，50％和70％WFPS处理在干燥过程中损失的碳更多，并且干燥损失导致其CO ₂脉冲低估了26％–32％。我们开发了一种土壤特定的校正因子，以解决这些最初的土壤水分影响。未来的C矿化研究可能会受益于类似的修正。