Abstract The potential overestimation of soil microbial biolmass C, using the fumigation-extraction method, arising from the contribution of residual (i.e., non-evacuated) chloroform (CHCl3) to the fumigation flush of C, was recently shown to be minor for agricultural topsoil samples. However, we hypothesized larger flush proportions of residual CHCl3–C, and hence greater biomass overestimations in low-biomass, subsoil samples due to the characteristically lower fumigation flushes of C in subsoils. The depth stratification (0–100 cm) of fumigation-extractable C and CHCl3–C was determined in six soil profiles (three loesses ranging from 6 to 20% clay and three vertisols ranging from 46 to 69% clay). Residual chloroform levels correlated positively with soil organic matter content but not with clay content and decreased down the profiles. Residual chloroform contributed ∼2.0% to biomass-C overestimation, independent of soil type or depth, thus refuting the study hypothesis and supporting the safe use of the fumigation-extraction method also with subsoil samples.

中文翻译：

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使用熏蒸提取法对底土样品中微生物生物量 C 的评估受残留氯仿的影响可忽略不计

摘要 最近表明，由于残留（即非抽空）氯仿 (CHCl3) 对 C 熏蒸冲洗的贡献，使用熏蒸提取方法可能高估了土壤微生物生物量 C，最近表明对农业表土来说是次要的。样品。然而，我们假设残留 CHCl3–C 的冲洗比例更大，因此由于底土中 C 的特征性较低的熏蒸冲洗量，低生物量底土样品中的生物量高估更大。在六个土壤剖面（三个粘土含量从 6% 到 20% 不等的黄土和三个粘土含量从 46% 到 69% 不等的土壤）中确定了熏蒸可提取的 C 和 CHCl3–C 的深度分层（0-100 厘米）。残留氯仿水平与土壤有机质含量呈正相关，但与粘土含量不相关，并且在剖面图上呈下降趋势。