Organic amendments can stimulate soil organic carbon (SOC) mineralization and soil aggregation simultaneously, which can improve C sequestration and soil fertility. However, the microbial mechanism governing C mineralization at the aggregate level remains uncertain. Here, we investigate how long-term organic amendments change SOC mineralization via affecting the microbial community composition and their co-occurrence pattern from micro-to macroaggregates. Four fertilization regimes from an 8-year field experiment were selected to study this mechanism, i.e., no fertilization (CK); inorganic NPK fertilizer (NPK); NPK + straw (NS); and NPK + straw and manure (NSM). Our results indicated that organic amendments significantly modified the C dynamics, bacterial and fungal community composition and network topological patterns in all aggregate sizes. Specifically, for microbial community composition, organic amendments increased the relative abundance of most Gram-negative bacteria and saprotrophic fungi. For microbial network relationships, organic amendments shifted keystone taxa from oligotrophs to copiotrophs in the bacterial network, and from Eurotiales to Sordariales in the fungal network, respectively. In addition, organic amendments alleviated competitive interactions coupled with keystone taxa in the bacterial network. These microbial changes were responsible for the increase of C mineralization in all aggregates, but the dominant microbial mechanisms varied with aggregate size. The alleviated competitive interactions coupled with keystone taxa of the bacterial network dominated the increases of C mineralization in macroaggregates, while the bacterial community composition did so in microaggregates. However, the fungal community composition only showed a significant impact on altering C mineralization in macroaggregates. Overall, our study provides a fundamental understanding of the microbial regulation of C dynamics at the aggregate level and highlights the importance of network topological patterns.

有机改良剂可同时刺激土壤有机碳（SOC）矿化和土壤聚集，从而改善固碳和土壤肥力。然而，在总体水平上控制碳矿化的微生物机制仍然不确定。在这里，我们研究了长期的有机修饰物如何通过影响微生物群落组成及其从微观聚集体到大型聚集体的共生模式来改变SOC矿化。从一项为期8年的田间试验中选择了四种施肥方案来研究这种机理，即不施肥（CK）；不施肥（CK）。无机氮磷钾肥（NPK）; NPK +稻草（NS）; 以及NPK +秸秆和肥料（NSM）。我们的结果表明，有机修饰剂在所有聚集体大小中均显着修饰了C动力学，细菌和真菌群落组成以及网络拓扑模式。具体而言，对于微生物群落组成，有机修饰物增加了大多数革兰氏阴性细菌和腐生真菌的相对丰度。对于微生物网络关系，有机修饰将梯形分类群从细菌网络中的寡养生物转变为番茄属，并从Eurotiales飞往Sordariales在真菌网络中。此外，有机改良剂减轻了细菌网络中的竞争性相互作用以及梯形分类群。这些微生物的变化是所有骨料中碳矿化增加的原因，但主要的微生物机制随骨料大小而变化。缓解的竞争相互作用加上细菌网络的梯形分类群，控制了大聚集体中碳矿化的增加，而细菌群落组成在微聚集体中却如此。但是，真菌群落组成仅对改变大型聚集体中的C矿化作用有显着影响。总体而言，我们的研究提供了总体水平上微生物对碳动力学的调控，并强调了网络拓扑模式的重要性。