A longstanding assumption of glucose tracing experiments is that all glucose is microbially utilized during short incubations of ≤2 days to become microbial biomass or carbon dioxide. Carbon use efficiency (CUE) estimates have consequently ignored the formation of residues (non-living microbial products) although such materials could represent an important sink of glucose that is prone to stabilization as soil organic matter. We examined the dynamics of microbial residue formation from a short tracer experiment with frequent samplings over 72 h, and conducted a meta-analysis of previously published glucose tracing studies to assess the generality of these experimental results. Both our experiment and meta-analysis indicated 30–34% of amended glucose-C (13C or 14C) was in the form of residues within the first 6 h of substrate addition. We expand the conventional efficiency calculation to include residues in both the numerator and denominator of efficiency, thereby deriving a novel metric of the potential persistence of glucose-C in soil as living microbial biomass plus residues (‘carbon stabilization efficiency’). This new metric indicates nearly 40% of amended glucose-C persists in soil 180 days after amendment, the majority as non-biomass residues. Starting microbial biomass and clay content emerge as critical factors that positively promote such long term stabilization of labile C. Rapid residue production supports the conclusion that non-growth maintenance activity can illicit high demands for C in soil, perhaps equaling that directed towards growth, and that residues may have an underestimated role in the cycling and sequestration potential of C in soil.

中文翻译：

---

评估土壤中作为潜在碳汇和碳利用效率调节剂的微生物残留

葡萄糖追踪实验的一个长期假设是，所有葡萄糖在 ≤ 2 天的短孵育期间都被微生物利用，成为微生物生物量或二氧化碳。因此，碳利用效率 (CUE) 估计忽略了残留物（无生命的微生物产品）的形成，尽管这些材料可能代表葡萄糖的重要汇，易于作为土壤有机质稳定下来。我们通过 72 小时内频繁采样的短示踪剂实验检查了微生物残留物形成的动态，并对先前发表的葡萄糖示踪研究进行了荟萃分析，以评估这些实验结果的普遍性。我们的实验和荟萃分析都表明，在添加底物的前 6 小时内，30-34% 的修正葡萄糖-C（13C 或 14C）以残留物的形式存在。我们扩展了传统的效率计算，将残留物包括在效率的分子和分母中，从而推导出一种新的衡量土壤中葡萄糖-C 作为活微生物生物量加残留物的潜在持久性的指标（“碳稳定效率”）。这一新指标表明，近 40% 的修正葡萄糖-C 在修正后 180 天仍存在于土壤中，其中大部分为非生物质残留。起始微生物生物量和粘土含量成为积极促进不稳定 C 的长期稳定的关键因素。 快速的残留物生产支持以下结论：非生长维持活动可能导致土壤中对 C 的高需求，可能等于针对生长的需求，以及残留物在土壤中碳的循环和封存潜力中的作用可能被低估。