中文摘要：

利用江都市小记镇的稻-麦轮作FACE平台，采用最大可能（MPN）法，在2005年水稻生长季研究了不同施肥（常规N量和低N量）、不同秸秆还田（秸秆今还田和秸秆不还田）处理土壤中的产甲烷菌和甲烷氧化菌数量在大气CO2浓度升高（FACE）条件下随时间的变化情况，并且借助气相色谱测定了土壤的产甲烷潜力和甲烷氧化潜力。结果表明：在秸秆全还田情况下，FACE对于产甲烷菌在分蘖期具有促进作用，而在抽穗期与收获期具有抑制作用。这种作用在低N条件下达到显著性（P〈0，05）水平。而秸秆不还田情况下，FACE对产甲烷菌无明显促进作用：在低量N的施用情况下，FACE对于土壤甲烷氧化菌的活性具有刺激作用，在水稻抽穗期土壤甲烷氧化菌数量明显地高于对照，达到显著性水平（P〈0．05）；而常规施N量秸秆全还田的情况下，在水稻的分蘖期、拔节期和收获期FACE土壤中的甲烷氧化菌数量却受到一定程度的抑制。土壤的产甲烷潜力测定结果表明，FACE能促进土壤的CH4释放，尤其是在常规N量施用条件下。当底物（加入外源CH4）充足时，FACE条件下能使土壤具有较高的氧化CH4的能力，其CH4氧化潜力明显大于对照土壤，并且这种作用在常规N肥施用条件下尤为明显，达极显著性水平（P〈0．01）。

英文摘要：

A free-air CO2 enrichment （FACE） experiment was conducted during rice-growing season in 2005 in paddy fields at Jiangdu of Jiangsu province with two different N fertilization levels （Usual N - UN and Low N - LN） and two levels of rice-straw-returning-back-to-field （HR, NR） to evaluate population changes of methanogens and methanotrophs by the most-probable-number （MPN） method as well as methane production and oxidizing potential by gas chromatography. Results showed that elevated atmospheric CO2 concentrations increased methanogens population at tillering stage, but restrained methanogens activity at heading and harvest stages under HR condition. Rising atmospheric CO2 concentrations increased methanotrophs activity under LN condition, and methanotrophs population in FACE condition was significantly higher than that of Ambient in heading stage. But methanotrophs activities under UN and HR conditions were restrained except at heading stage. Methane production potential showed that FACE promoted methane release, especially under UN condition. High methane oxidizing activity was found under UN condition with enough exterior-CH4 and rising atmospheric CO2 concentrations.