ABSTRACT Background: Soil N2-fixing bacterial (SNB) communities may play a vital role in plant invasion. Two or more invasive plant species (invaders) may coexist in the same ecosystem. Thus, it is important to assess the effects of co-invasion on SNB communities to elucidate the ecological mechanisms of plant invasion. Aims: The effects of two co-occurring invaders (Erigeron annuus and Solidago canadensis) with different coverage classes on SNB communities were evaluated via a comparative study. Methods: SNB communities were assessed using a high-throughput sequencing approach. Results: The invasion of E. annuus and/or S. canadensis, regardless of coverage, did not pose pronounced effects on soil physicochemical properties and the diversity of SNB. Soil electrical conductivity was the most important environmental factors explaining the variation in SNB composition. This phenomenon may be chiefly attributed to the fact that the shifts in soil electrical conductivity can recruit obvious variations in the resource utilisation and acquisition patterns of carbon for the metabolism of soil microorganisms. Plant Shannon’s diversity was also one key factor influencing the community structure of SNB, but its direct effects are less powerful than soil electrical conductivity. However, the negatively indirect effects of plant Shannon’s diversity on the Shannon index, ACE index, and Chao1 index of SNB were noticeably greater than soil electrical conductivity. Therefore, the effects of plant Shannon’s diversity on the community structure of SNB may largely be attributed to the variation in soil electrical conductivity via the released root exudates and then modify the resource availability pattern of SNB. Conclusions: SNB diversity is more influenced by changes in soil variables like soil electrical conductivity than by the presence/coverage of invasive plant species.

中文翻译：

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独立或共同发生的入侵植物物种不会改变土壤固氮细菌群落的多样性

摘要背景：土壤固氮细菌（SNB）群落可能在植物入侵中起重要作用。两个或多个入侵植物物种（入侵者）可能共存于同一个生态系统中。因此，重要的是评估共同入侵对 SNB 群落的影响，以阐明植物入侵的生态机制。目的：通过比较研究评估具有不同覆盖等级的两种同时发生的入侵者（Erigeron annuus 和 Solidago canadensis）对 SNB 群落的影响。方法：使用高通量测序方法评估 SNB 社区。结果：E. annuus 和/或 S. canadensis 的入侵，无论覆盖范围如何，都不会对土壤理化性质和 SNB 的多样性产生显着影响。土壤电导率是解释 SNB 组成变化的最重要的环境因素。这种现象可能主要归因于土壤电导率的变化可以招募土壤微生物代谢的碳资源利用和获取模式的明显变化。植物香农的多样性也是影响SNB群落结构的关键因素之一，但其直接影响不如土壤电导率强。然而，植物香农多样性对SNB香农指数、ACE指数和Chao1指数的负面间接影响明显大于土壤电导率。所以，植物香农多样性对 SNB 群落结构的影响可能很大程度上归因于通过释放的根系分泌物改变土壤电导率，进而改变 SNB 的资源可用性模式。结论：SNB 多样性受土壤电导率等土壤变量变化的影响比受入侵植物物种的存在/覆盖率的影响更大。