Wildfires decrease forest aboveground biomass and have long-term legacy effects on carbon (C) stocks in soil via alterations of microbial communities and functions. However, the interactions between soil organic C (SOC) chemodiversity and bacterial communities that drive C decomposition remain unclear. Soils from two boreal forest sites, 3 months (S1) and 15 years (S2) after fire events, were incubated for 53 days to quantify the mineralization of sucrose (mimicking rhizodeposits, δ13C = −11.97‰) and SOC priming. To reveal SOC-bacterial interactions that regulate SOC decomposition, the isotopic abundance, SOC chemical composition (¹³C NMR), and associated bacterial community structure (16S rRNA gene sequencing) were analyzed. The best multivariate model (DISTLM) analysis indicated that aromatic C (phenolic-C and aryl-C) in S1 and di-O-alkyl C in S2 were the largest contributors to bacterial community structure. The co-occurrence network confirmed SOC-bacteria interactions, and revealed the highly co-occurrent groups, i.e. Paenibacillus in S1 and Bacillus in S2, both of which belong to the Firmicutes, correlated with recalcitrant C and labile C, respectively, and are potentially linked to decomposition. For example, Firmicutes (as well as Proteobacteria and Actinobacteria) were correlated with aryl-C and phenolic-C in S1 and highly correlated with SOC priming intensity. The limited C resources (enriched refractory components, i.e. phenolic substances) in S1 favored oligotrophs to outcompete other bacterial groups, which likely aided decomposition of more recalcitrant SOC via co-metabolisms. The slow decomposition of sucrose and large soil priming effects observed in S1 suggested a faster SOC turnover via bidirectional processes of additional sucrose-C gain and native soil-C loss. Collectively, changes in SOC chemistry were coupled with an altered bacterial community, and their interactions might further correlate to decomposition, with implications for C sequestration in the post-fire boreal forest soils.

野火减少了森林地上生物量，并通过改变微生物群落和功能对土壤中的碳 (C) 储量产生长期遗留影响。然而，土壤有机碳 (SOC) 化学多样性与驱动碳分解的细菌群落之间的相互作用仍不清楚。火灾事件发生后 3 个月 (S1) 和 15 年 (S2) 的两个北方森林地点的土壤被培养 53 天，以量化蔗糖的矿化（模拟根系沉积物，δ13C = -11.97‰）和 SOC 引发。为了揭示调节 SOC 分解的 SOC-细菌相互作用、同位素丰度、SOC 化学成分 ( ¹³C NMR）和相关的细菌群落结构（16S rRNA基因测序）进行了分析。最佳多元模型 (DISTLM) 分析表明，S1 中的芳族 C（酚-C 和芳基-C）和 S2 中的二-O-烷基 C 是细菌群落结构的最大贡献者。的同现网络确认SOC-细菌相互作用，并揭示了高度共正在发生的基团，即类芽孢杆菌S1和芽孢杆菌在 S2 中，两者都属于厚壁菌门，分别与顽固的 C 和不稳定的 C 相关，并且可能与分解有关。例如，厚壁菌门（以及变形杆菌和放线菌）与 S1 中的芳基-C 和酚-C 相关，并且与 SOC 引发强度高度相关。S1 中有限的 C 资源（富集的难降解成分，即酚类物质）有利于寡营养菌与其他细菌群竞争，这可能有助于通过共代谢分解更顽固的 SOC。在 S1 中观察到的蔗糖缓慢分解和大土壤启动效应表明，通过额外的蔗糖-C 增加和天然土壤-C 损失的双向过程，SOC 周转速度更快。总的来说，SOC 化学的变化与细菌群落的改变相结合，