The impact of increasing amounts of labile C input on priming effects (PE) on soil organic matter (SOM) mineralization remains unclear, particularly under anoxic conditions and under high C input common in microbial hotspots. PE and their mechanisms were investigated by a 60-day incubation of three flooded paddy soils amended with¹³C-labeled glucose equivalent to 50–500% of microbial biomass C (MBC). PE (14–55% of unamended soil) peaked at moderate glucose addition rates (i.e., 50–300% of MBC). Glucose addition above 300% of MBC suppressed SOM mineralization but intensified microbial N acquisition, which contradicted the common PE mechanism of accelerating SOM decomposition for N-supply (frequently termed as “N mining”). Particularly at glucose input rate higher than 3 g kg⁻¹ (i.e., 300–500% of MBC), mineral N content dropped on day 2 close to zero (1.1–2.5 mg N kg⁻¹) because of microbial N immobilization. To cope with the N limitation, microorganisms greatly increased N-acetyl glucosaminidase and leucine aminopeptidase activities, while SOM decomposition decreased. Several discrete peaks of glucose-derived CO₂ (contributing >80% to total CO₂) were observed between days 13–30 under high glucose input (300–500% of MBC), concurrently with CH₄ peaks. Such CO₂ dynamics was distinct from the common exponential decay pattern, implicating the recycling and mineralization of ¹³C-enriched microbial necromass driven by glucose addition. Therefore, N recycling from necromass was hypothesized as a major mechanism to alleviate microbial N deficiency without SOM priming under excess labile C input. Compound-specific ¹³C-PLFA confirmed the redistribution of glucose-derived C among microbial groups, i.e., necromass recycling. Following glucose input, more than 4/5 of total ¹³C-PLFA was in the gram-negative and some non-specific bacteria, suggesting these microorganisms as r-strategists capable of rapidly utilizing the most labile C. However, their ¹³C-PLFA content decreased by 70% after 60 days, probably as a result of death of these r-strategists. On the contrary, the ¹³C-PLFA in gram-positive bacteria, actinomycetes and fungi (K-strategists) was initially minimal but increased by 0.5–5 folds between days 2 and 60. Consequently, the necromass of dead r-strategists provided a high-quality C–N source to the K-strategists. We conclude that under severe C excess, N recycling from necromass is a much more efficient microbial strategy to cover the acute N demand than N acquisition from the recalcitrant SOM.

不稳定的碳输入量的增加对土壤有机质（SOM）矿化作用的引发效应（PE）的影响仍然不清楚，特别是在缺氧条件下和微生物热点中常见的高碳输入下。通过对三种淹水的水稻土进行60天的温育研究，对土壤的PE及其机理进行了研究，这些土壤用¹³ C标记的葡萄糖（相当于微生物生物量C（MBC）的50–500％）进行了改良。PE（未改良土壤的14-55％）在中等葡萄糖添加速率（即MBC的50-300％）达到峰值。MBC含量超过300％的葡萄糖添加抑制了SOM的矿化作用，但增加了微生物对氮的吸收，这与加速N供给的SOM分解的普通PE机制（通常称为“ N开采”）相矛盾。特别是在葡萄糖输入速率高于3 g kg ^{-1的情况下}（即MBC的300–500％），由于固定化了微生物，第2天的矿物质N含量下降到接近零（1.1–2.5 mg N kg ^-1）。为了应对氮的限制，微生物大大增加了N-乙酰氨基葡萄糖苷酶和亮氨酸氨基肽酶的活性，而SOM分解却降低了。在高葡萄糖输入（MBC的300-500％）下的第13-30天之间，观察到了葡萄糖衍生的CO _2的几个离散峰（占总CO _2的> 80％），同时还有CH ₄峰。这种CO ₂动力学不同于普通的指数衰减模式，这暗示了¹³的再循环和矿化。通过添加葡萄糖驱动富含C的微生物坏死。因此，从坏死中回收氮被认为是缓解微生物氮缺乏而在不稳定的C输入下无需SOM引发的主要机制。特定于化合物的¹³ C-PLFA证实了葡萄糖衍生的C在微生物组之间的重新分布，即坏死物质再循环。葡萄糖输入后，总的¹³ C-PLFA中超过4/5位于革兰氏阴性菌和一些非特异性细菌中，表明这些微生物是能够快速利用最不稳定C的r-策略家。然而，它们的¹³ C- PLFA内容后60天下降了70％，可能是因为这些死亡的结果[R -strategists。相反，这¹³革兰氏阳性细菌，放线菌和真菌（K-策略家）中的C-PLFA最初很小，但在第2天和60天之间增加了0.5-5倍。因此，死亡的r-策略家的坏死提供了高质量的C-N来源给K战略家。我们得出的结论是，在严重的碳过量下，死灵中的氮再循环比满足顽固性SOM的氮要有效得多，可以满足急性氮需求。