Data Sheet 1_Mesotrione alters the structure of network interactions between soil microbes and affects C and N cycling functions.docx

Mesotrione is a widely used herbicide in corn production. However, its persistence in soil following application can cause significant damage to subsequent crops such as tobacco. Despite its widespread use, it remains unclear how mesotrione applications affect soil carbon and nitrogen cycling, as well as whether they alter soil microbial communities. Here, we conducted a 2-month greenhouse experiment to investigate changes in functional C and N cycling genes as well as the structural assembly of soil microbial communities following mesotrione application at 180 (T1) and 900 (T5) g a.i. ha−1. The results showed that total nitrogen, available nitrogen and organic matter in the soil were significantly reduced at both 30 and 60 days after mesotrione application (T1 and T5) compared to untreated control. Mesotrione significantly reduced the α-diversity of soil microbial communities at 10 days, and suppressed metabolic activity across multiple carbon sources over extended periods. The structure of the soil microbial exhibited complex dynamics from 1 to 60 days after mesotrione application, with a significant increase in the relative abundance of Nocardioides observed specifically in the T5 treatment. The effects of mesotrione on functional genes mediating the same C-cycling processes (carbon fixation pathway and methane metabolism) were differential. Mesotrione exhibited inhibitory effects on functional genes involved in nitrification, denitrification, and assimilatory nitrate reduction processes within the soil N-cycling, as well as promoting effects on those mediating nitrogen fixation. Network analyses revealed that soil microbial communities exhibited greater complexity and higher connectivity under high concentrations of mesotrione stress, with low abundance microbial genera forming a highly connected modular center. The number of microbial genera associated with key functional genes involved in soil C and N cycling increased following mesotrione application. Taken together, our findings provide theoretical insights into the microbial mechanisms underlying mesotrione’s impacts on soil carbon and nitrogen cycling.

硝磺草酮（Mesotrione）是玉米种植中广泛使用的除草剂。然而，其施用后在土壤中的残留会对烟草等后茬作物造成显著药害。尽管该药剂应用范围广泛，但目前仍不清楚硝磺草酮施用如何影响土壤碳氮循环，以及是否会改变土壤微生物群落结构。本研究开展了为期2个月的温室培养试验，设置180（T1）与900（T5）g有效成分·公顷⁻¹两个硝磺草酮施用剂量，探究其施用后土壤碳氮循环功能基因的变化，以及土壤微生物群落的结构组装过程。结果显示，与未处理对照组相比，硝磺草酮施用后30天和60天（对应T1和T5处理组）的土壤全氮、速效氮及有机质含量均显著降低。硝磺草酮在施用后10天显著降低了土壤微生物群落的α多样性，并在较长时期内抑制了土壤微生物对多种碳源的代谢活性。硝磺草酮施用后1至60天内，土壤微生物群落结构呈现复杂动态变化，其中仅T5处理组的诺卡氏菌属（Nocardioides）相对丰度显著升高。硝磺草酮对介导同一碳循环过程（固碳途径与甲烷代谢）的功能基因存在差异化影响。在土壤氮循环相关功能基因中，硝磺草酮对参与硝化、反硝化及同化硝酸盐还原过程的基因表现出抑制作用，而对介导固氮过程的基因则具有促进效果。微生物网络分析表明，在高浓度硝磺草酮胁迫下，土壤微生物群落的网络复杂度与连通性更高，低丰度微生物属群构成了连通性极强的模块中心。硝磺草酮施用后，与土壤碳氮循环关键功能基因相关的微生物属数量有所增加。综上，本研究结果为解析硝磺草酮影响土壤碳氮循环的微生物机制提供了理论依据。