稻田是温室气体甲烷的重要来源之一，其每年甲烷排放量约占全球排放总量的10~20%。以亚硝酸盐和硝酸盐为电子受体的甲烷厌氧氧化反应是全球氮循环与碳循环关键过程的新内容，是控制稻田甲烷排放的新途径。施用氮肥是提高稻田产量的一项必要而有效的措施，同时该措施可能对亚硝酸盐和硝酸盐型甲烷厌氧氧化产生促进或者抑制效应，从而改变两者在控制稻田甲烷排放中的作用。本项目拟采用稳定性同位素示踪、现代分子生物学和室内培养等多种手段，对不同施肥措施下（包括无肥对照，单施化肥，中量有机肥+化肥和高量有机肥+化肥）稻田土壤中亚硝酸盐和硝酸盐型甲烷厌氧氧化的反应速率，及其功能微生物关键基因的转录活性、组成特征和丰度等进行系统研究，探明不同施肥措施对这两类甲烷厌氧氧化过程的影响及其作用机理。本项目研究结果有助于丰富稻田土壤甲烷循环的内容，深入认识稻田土壤甲烷氧化的微生物机制，为控制稻田甲烷排放提供科学依据。

Paddy fields are one of the most significant sources of atmospheric methane, which are responsible for 10~20% of the global annual methane emissions. The processes of nitrite- and nitrate-dependent anaerobic methane oxidation are two new additions to the global nitrogen and the carbon cycles, and also act as new pathways for reducing methane emissions from paddy fields. Fertilization is a necessary and effective practice for paddy fields to achieve high crop yields. In the meantime, this practice may stimulate or inhibit the nitrite- and nitrate-dependent anaerobic methane oxidation and therefore could have a great impact on the significance of the two processes in reducing methane emissions from paddy fields. This project will investigate and compare the potential rates of the two processes, the gene transcription, community composition and abundance of the nitrite- and nitrate-dependent anaerobic methanotrophs in paddy soils that under different fertilization regimes (including an unfertilized control, chemical fertilizer, medium level of organic fertilizer + chemical fertilizer, and high level of organic fertilizer + chemical fertilizer) by using stable isotope techniques, molecular biology techniques, and incubation experiments. The main objective of the current project is to reveal how different fertilization regimes will affect the nitrite- and nitrate-dependent anaerobic methane oxidation processes and the influence mechanisms. The results of this project can help to better understand the soil methane cycle, the mechanism of methane oxidation, and provide a scientific basis for reducing methane emissions from paddy fields.