Aims

N rhizodeposition plays a vital role in regulating rhizosphere soil N dynamics. However, its effects on the rhizosphere soil N cycle in clonal plants and the underlying mechanism remain unclear.

Methods

¹⁵N solutions with different concentrations were injected into young or connected mature ramets of Moso bamboo (Phyllostachys edulis), respectively, in the field, to explore the response of rhizosphere N transformation to N rhizodeposition.

Results

¹⁵N injection increased the ¹⁵N abundance in the rhizosphere soil of both young and mature ramets, with higher ¹⁵N abundance in 20–40-cm layer than that in 0–20-cm layer. Functional genes involved in nitrification and denitrification in the rhizosphere were upregulated when young ramets received low- and medium-N solutions. However, the genes showed diverse responses to high-N treatment in young ramets, with increased abundances of ammonia-oxidizing bacteria and decreased levels of ammonia-oxidizing archaea, comammox, and denitrifiers. In contrast, the functional genes involved in denitrification in the 20–40-cm layer of rhizosphere soil were upregulated by high-N treatment in mature ramets. Additionally, partial-least-squares path modeling revealed ¹⁵N abundance in the soil indirectly affected N mineralization, N mineralization directly affected nitrification, and nitrification directly affected denitrification in a positive manner.

Conclusion

The variations of N rhizodeposition and transformation process in both connected ramets is highly consistent in responding to different N treatments, but the nitrifiers and denitrifiers in the deeper rhizosphere soil were more sensitive to N rhizodeposits than those in the upper rhizosphere soil.

中文翻译：

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毛竹林无性系根际氮沉积对根际氮素转化的影响

目标

根际氮沉积在调节根际土壤氮动态中起着至关重要的作用。然而，其对克隆植物根际土壤氮循环的影响及其潜在机制仍不清楚。

方法

^{田间将不同浓度的15} N溶液分别注入毛竹幼龄或相连的成熟分株中，探讨根际氮素转化对根际氮素沉积的响应。

结果

¹⁵ N注射增加了幼龄和成熟分株根际土壤¹⁵ N丰度， 20~40 cm层^{15 N丰度高于0~20 cm层。}当幼苗接受低氮和中氮溶液时，根际硝化和反硝化相关的功能基因上调。然而，这些基因在幼年分株中对高氮处理表现出不同的反应，氨氧化细菌的丰度增加，氨氧化古菌、comammox 和反硝化细菌的水平降低。相比之下，成熟分株的高氮处理使根际土壤20-40厘米层反硝化相关的功能基因上调。此外，偏最小二乘路径模型显示，土壤中^{15 N丰度间接影响氮矿化，氮矿化直接影响硝化作用，硝化作用直接影响反硝化作用。}

结论

两个相连分株的氮根际沉积和转化过程的变化对不同氮素处理的响应高度一致，但根际深层土壤中的硝化细菌和反硝化细菌对根际氮沉积的敏感度高于根际上部土壤的硝化细菌和反硝化细菌。