Microbial necromass substantially contributes to soil organic carbon (SOC) sequestration. However, the response of soil microbial necromass to fresh labile carbon (C) inputs and the underlying microbial mechanisms are poorly understood. In this study, we investigated the dynamics of soil microbial necromass following single and repeated labile C inputs in two typical agricultural soils, black soil (Mollisol) and red soil (Ultisol). Our results showed that labile C inputs triggered the decomposition of soil native microbial necromass, regardless of soil type and C input frequency. Following repeated glucose pulses, the microbial necromass decreased by 75 % and 41 % in black and red soils, respectively, in a week. While a single glucose pulse triggered a comparable decline in soil microbial necromass, which occurred gradually over an incubation period of 3–4 weeks. In contrast, the priming effect following a single glucose pulse was 2–3 fold higher than repeated pulses. Repeated glucose pulses increased microbial α-diversity and temporal succession of various K-strategists, enhanced the network complexity and the potential hierarchical interactions between bacteria, fungi and protists, but yielded 1.66 fold less microbial biomass compared to a single pulse. These changes explained variations in soil microbial necromass after glucose pulses. Furthermore, repeated glucose pulses enhanced the linkages between microbial attributes and the degradation of soil microbial necromass. MicroResp assay revealed that the capacity of microbial communities to degrade microbially derived residues was 1.29 and 3.60 fold higher in black and red soils with repeated glucose pulses, respectively, compared to a single pulse. Our findings provide comprehensive insights into the microbially-mediated processes that influence soil microbial necromass degradation following labile C inputs, with important implications for understanding the dynamics and stabilisation of soil microbial necromass.

中文翻译：

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重复的不稳定碳输入通过增加微生物多样性和分层相互作用触发土壤微生物坏死物分解

微生物坏死物对土壤有机碳（SOC）的固存有很大贡献。然而，人们对土壤微生物坏死物对新鲜不稳定碳（C）输入的反应以及潜在的微生物机制知之甚少。在本研究中，我们研究了黑土（Mollisol）和红土（Ultisol）这两种典型农业土壤中单次和重复不稳定碳输入后土壤微生物坏死物的动态。我们的结果表明，无论土壤类型和碳输入频率如何，不稳定的碳输入都会引发土壤原生微生物坏死物的分解。重复葡萄糖脉冲后，一周内黑土和红土中的微生物坏死物分别减少了 75% 和 41%。而单个葡萄糖脉冲引发了土壤微生物坏死物的类似下降，这种下降在 3-4 周的潜伏期内逐渐发生。相比之下，单次葡萄糖脉冲后的启动效应比重复脉冲高 2-3 倍。重复的葡萄糖脉冲增加了微生物 α 多样性和各种 K 策略的时间连续性，增强了网络复杂性以及细菌、真菌和原生生物之间潜在的层次相互作用，但与单次脉冲相比，产生的微生物生物量减少了 1.66 倍。这些变化解释了葡萄糖脉冲后土壤微生物坏死物的变化。此外，重复的葡萄糖脉冲增强了微生物属性与土壤微生物坏死物降解之间的联系。MicroResp 测定显示，与单次脉冲相比，重复葡萄糖脉冲的黑土和红土中微生物群落降解微生物衍生残留物的能力分别高出 1.29 倍和 3.60 倍。我们的研究结果提供了对不稳定碳输入后影响土壤微生物坏死物降解的微生物介导过程的全面见解，对于了解土壤微生物坏死物的动态和稳定性具有重要意义。