酸性稻田全程氨氧化菌对氮肥施加的响应

Response of comammox Nitrospira to nitrogen fertilization in acidic paddy soil

为了揭示酸性稻田全程、半程氨氧化菌对增氮的响应与敏感性差异,通过盆栽实验,设置施加氮肥处理,测定分蘖期、抽穗期、成熟期全程及半程氨氧化菌的丰度,比较全程、半程氨氧化菌对施肥的响应敏感性。结果表明:未施肥与施肥情形下,分蘖期、抽穗期、成熟期土壤氨氧化菌的优势种群均为全程氨氧化菌(Clade A:3.24×10^(8)~7.24×10^(8) copies·g^(-1),Clade B:2.14×10^(8)~1.48×10^(9) copies·g^(-1))而非半程氨氧化菌(AOA:2.00×10^(7)~4.37×10^(7) copies·g^(-1),AOB:1.35×10^(7)~3.31×10^(7) copies·g^(-1))。施肥的主效应(Clade A:P=0.762,Clade B:氮素利用率=0.398)、生育期的主效应(Clade A:P=0.264,Clade B:P=0.237)、施肥与生育期的交互效应(Clade A:P=0.316,Clade B:P=0.294)均不显著,即全程氨氧化菌两大分支A和B季节变化并不显著,二者对尿素施加的响应并不敏感。未施氮肥与施加氮肥的情形下全程氨氧化菌丰度的环境调控因子可能有所不同。未施氮肥情形下,全程氨氧化菌的2个分支A(Clade A:R=-0.73,P=0.027)和B(Clade B:R=-0.75,P=0.019)的丰度均与土壤总氮含量呈负相关,预示着无外源性氮输入情形下,全程氨氧化菌的生长受土壤有机氮、氨化作用和游离氨负向调控。施加氮肥情形下,全程氨氧化菌尤其是分支A的丰度可能更多地受土壤pH、氧化还原电位(Eh)及NH_(4)^(+)-N含量的影响。氮肥的施加显著影响全程、半程氨氧化菌的群落共变性,致使Clade B丰度与AOA、AOB丰度的正向共变趋势消失。

In order to reveal the differences in response and sensitivity of comamox Nitrospira and incomplete nitrifiers to nitrogen addition in acidic rice fields,a pot experiment was conducted to investigate the impact of urea fertilization,in conjunction with growth stage,on complete nitrifiers,and to compare their responsiveness to nitrogen(N)fertilization with that of incomplete nitrifiers in acidic paddy soils.The research results revealed that irrespective of fertilization conditions,comammox Nitrospira(Clade A:3.24×10^(8)-7.24×10^(8) copies·g^(-1),Clade B:2.14×10^(8)-1.48×10^(9) copies·g^(-1))rather than ammonia‐oxidizing archaea(AOA:2.00×10^(7)-4.37×10^(7) copies·g^(-1))and nitriteoxidizing bacteria(AOB:1.35×10^(7)-3.31×10^(7) copies·g^(-1)),were the dominant ammonia oxidizers across tillering,heading,and maturity stages.Neither urea fertilization(Clade A:P=0.762,Clade B:P=0.398)nor growth stage(Clade A:P=0.264,Clade B:P=0.237),nor their interaction(Clade A:P=0.316,Clade B:P=0.294),significantly influenced comammox Nitrospira clades A and B,as their populations remained consistent across the fertilizer treatments and seasons.It is plausible that the environmental factors governing comammox bacterial abundance in urea‐fertilized and unfertilized soils may vary.In the absence of urea,the abundance of comammox Nitrospira clades A(R=-0.73,P=0.027)and B(R=-0.75,P=0.019)exhibited a negative correlation with soil N,suggesting that increased ammonia,ammonification,and organic N may not be conducive to comammox bacterial growth and activity in unfertilized soils.Conversely,in the presence of urea,comammox bacteria,especially clade A,were notably influenced by soil pH and redox potential(Eh).Notably,urea application had the potential to alter the interplay between complete and incomplete nitrifiers,as evidenced by the absence of a positive mode of population co‐variation of clade B with AOA and AOB following urea application.