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Abstract：
The nitrification inhibitors (NIs) 3,4-dimethylpyrazole (DMPP) and dicyandiamide (DCD) can effectively reduce N2 O emissions; however, which species are targeted and the effect of these NIs on the microbial nitrifier community is still unclear. Here, we identified the ammonia oxidizing bacteria (AOB) species linked to N2 O emissions and evaluated the effects of urea and urea with DCD and DMPP on the nitrifying community in a 258 day field experiment under sugarcane. Using an amoA AOB amplicon sequencing approach and mining a previous dataset of 16S rRNA sequences, we characterized the most likely N2 O-producing AOB as a Nitrosospira spp. and identified Nitrosospira (AOB), Nitrososphaera (archaeal ammonia oxidizer) and Nitrospira (nitrite-oxidizer) as the most abundant, present nitrifiers. The fertilizer treatments had no effect on the alpha and beta diversities of the AOB communities. Interestingly, we found three clusters of co-varying variables with nitrifier operational taxonomic units (OTUs): the N2 O-producing AOB Nitrosospira with N2 O, NO3 - , NH4 + , water-filled pore space (WFPS) and pH; AOA Nitrososphaera with NO3 - , NH4 + and pH; and AOA Nitrososphaera and NOB Nitrospira with NH4 + , which suggests different drivers. These results support the co-occurrence of non-N2 O-producing Nitrososphaera and Nitrospira in the unfertilized soils and the promotion of N2 O-producing Nitrosospira under urea fertilization. Further, we suggest that DMPP is a more effective NI than DCD in tropical soil under sugarcane.
摘要：
硝化抑制剂（NIs）3,4-二甲基吡唑（DMPP）和双氯胺（DCD）可以有效减少N2O的排放；但是，哪些物种是目标，这些NIs对微生物硝化群落的影响尚不清楚。这里,我们确定了与N2O排放相关的氨氧化细菌（AOB）物种，并在甘蔗下进行了258天的田间试验，评估了尿素和尿素与DCD和DMPP对硝化群落的影响。使用amoAAOB扩增子测序方法并挖掘以前的16SrRNA序列数据集，我们将最可能产生N2O的AOB鉴定为亚硝基螺旋体。并鉴定了亚硝基螺旋体(AOB)，Nitrososphaera（古细菌氨氧化剂）和Nitrospira（亚硝酸盐氧化剂）是最丰富的，目前的硝化。肥料处理对AOB群落的α和β多样性没有影响。有趣的是,我们发现了三个具有硝化操作分类单位（OTU）的共同变量簇：具有N2O的产生N2O的AOB亚硝基螺旋体，NO3-,NH4+,充满水的孔隙空间（WFPS）和pH；AOA含NO3-，NH4+和pH；以及AOA亚硝基螺旋体和NOB亚硝基螺旋体与NH4+，这表明不同的驱动程序。这些结果支持在未施肥的土壤中同时出现不产生N2O的亚硝基螺旋体和亚硝基螺旋体，并在尿素施肥下促进产生N2O的亚硝基螺旋体。Further,我们建议在甘蔗下的热带土壤中，DMPP比DCD更有效。
