Plants can influence soil microbes through resource acquisition and interference competition, with consequences for ecosystem function such as nitrification. However, how plants alter soil conditions to influence nitrifiers and nitrification rates remains poorly understood, especially in the subsoil. Here, coupling the N isotopic pool dilution technique, high throughput sequencing and soil O monitoring, we investigated how a deep-rooted perennial grass, miscanthus, versus an adjacent shallow-rooted turfgrass reference shapes nitrifier assembly and function along 1 m soil profiles. In topsoil, the suppression of ammonia (NH) oxidizing archaea (AOA) and gross nitrification rates in miscanthus relative to the reference likely resulted from nitrifiers being outcompeted by plant roots and heterotrophic bacteria for ammonium (NH). The stronger tripartite competition under miscanthus may have been caused in part by the lower soil organic matter (SOM) content, which supported lower gross nitrogen (N) mineralization, the major soil process that produces NH. In contrast, below 10 cm soil depth, significantly greater gross nitrification rates were observed in miscanthus compared to the reference. This was likely driven by the significantly lower oxygen (O) in miscanthus than reference subsoil, which selected against aerobic heterotrophic bacteria but in favor of AOA. Overall, we found that plants can regulate AOA community structure and function through different mechanisms in topsoil and subsoil, with suppression of nitrification in topsoil and enhancement of nitrification in subsoil.

中文翻译：

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不同的机制驱动表土和底土中植物与硝化菌的相互作用

植物可以通过资源获取和干扰竞争来影响土壤微生物，从而对硝化等生态系统功能产生影响。然而，人们对植物如何改变土壤条件以影响硝化菌和硝化速率仍然知之甚少，尤其是在底土中。在这里，结合氮同位素池稀释技术、高通量测序和土壤氧监测，我们研究了深根多年生草类芒草与邻近的浅根草坪草参考如何沿着 1 m 土壤剖面塑造硝化菌组装和功能。在表土中，相对于参考值，芒草中氨（NH）氧化古菌（AOA）和总硝化率的抑制可能是由于硝化细菌在铵（NH）方面被植物根部和异养细菌击败所致。芒草下三方竞争的加剧可能部分是由于土壤有机质 (SOM) 含量较低，从而支持了较低的总氮 (N) 矿化，而总氮 (N) 是产生 NH 的主要土壤过程。相反，在 10 厘米土壤深度以下，与参考相比，在芒草中观察到显着更高的总硝化率。这可能是由于芒草中的氧 (O) 显着低于参考底土，后者不利于需氧异养细菌，但有利于 AOA。总体而言，我们发现植物可以通过不同的机制调节表土和底土中AOA群落的结构和功能，抑制表土硝化作用并增强底土硝化作用。