Abstract Asymbiotic nitrogen fixation in the subsurface of mine soils is often neglected despite it playing an important role in the ecological restoration of mine soils. Here, we examined the effect of artificial root exudates on the community structure of asymbiotic diazotrophs in the subsurface of mine soils by simulating the oxygen conditions in the root zone of mine soils via application of three artificial root exudates under two oxygen states (oxygen deficiency with 10% oxygen and anaerobic) in microcosm experiments and 16S rRNA and nifH mRNA transcript analysis. The results showed that the three artificial root exudates significantly increased the nitrogen fixation ratio in mine soils under both the anaerobic and oxygen deficiency conditions, and the mine soils treated with the same artificial root exudates showed a higher nitrogen fixation ratio in the oxygen deficiency condition than in the anaerobic condition. The effects of different artificial root exudates on the bacterial and diazotrophic α-diversity indexes were significantly different. In addition, artificial root exudates can change the structures of bacterial and diazotrophic communities. Furthermore, artificial root exudates significantly increased the abundance of Clostridium, which are not the dominant bacteria responsible for asymbiotic nitrogen fixation in subsurface mine soils. In parallel, artificial root exudates mainly stimulated sulfate-reducers and uncultured bacteria for nitrogen fixation. This study is of great importance to strengthen our understanding of the nitrogen fixation dynamics in the ecological restoration of abandoned mining lands.

中文翻译：

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人工根系分泌物激发矿井土壤地下的细菌固氮作用

摘要 矿区土壤次表层非共生固氮作用在矿区土壤生态修复中发挥着重要作用，但往往被忽视。在这里，我们通过在两种氧状态（缺氧和缺氧）下应用三种人工根系分泌物来模拟矿井土壤根区的氧气条件，研究了人工根系分泌物对矿井土壤地下非共生固氮菌群落结构的影响。 10% 氧气和厌氧）在微观实验和 16S rRNA 和 nifH mRNA 转录分析。结果表明，在厌氧和缺氧条件下，三种人工根系分泌物均显着提高了矿区土壤的固氮率，用相同的人工根系分泌物处理的矿井土壤在缺氧条件下比在厌氧条件下表现出更高的固氮率。不同人工根系分泌物对细菌和固氮菌α-多样性指数的影响存在显着差异。此外，人工根系分泌物可以改变细菌和固氮群落的结构。此外，人工根系分泌物显着增加了梭状芽孢杆菌的丰度，梭状芽孢杆菌不是负责地下矿井土壤非共生固氮的主要细菌。同时，人工根系分泌物主要刺激硫酸盐还原剂和未培养的细菌进行固氮。