长期大气CO_(2)浓度升高对稻田CH_(4)排放的影响

Effect of Long-term Elevated CO_(2) Concentration on CH_(4) Emissions from Rice Paddy Fields

大气CO_(2)浓度升高可直接或间接影响稻田CH_(4)排放。深入研究长期大气CO_(2)浓度升高对稻田CH_(4)排放及其相关微生物的影响,对评估和应对未来气候背景下稻田CH_(4)排放的响应具有重要意义。为探明长期大气CO_(2)浓度升高对稻田CH_(4)排放的影响及其机制,依托连续运行10年以上的中国稻田FACE(free-air CO_(2) enrichment)平台,观测2016—2017年正常大气条件(ACO_(2))和大气CO_(2)浓度升高200µmol·mol^(-1)条件(ECO_(2))下稻田CH_(4)排放通量、产甲烷菌和甲烷氧化菌群落丰度,并采用Meta分析方法定量研究CO_(2)熏蒸年限对稻田CH_(4)排放及其相关微生物群落丰度的影响。结果表明:对比ACO_(2)处理,长期ECO_(2)处理使稻田CH_(4)排放降低28%(P<0.05),产甲烷菌群落丰度降低39%(P<0.05),同时甲烷氧化菌群落丰度增加21%(P>0.05)。Meta分析结果发现,随着CO_(2)熏蒸年限的增加,大气CO_(2)浓度升高对稻田CH_(4)排放和产甲烷菌群落丰度的促进作用逐渐减弱,对甲烷氧化菌群落丰度的促进作用却逐渐增大。因此,未来气候条件下,长期大气CO_(2)浓度升高会降低稻田CH_(4)排放,这对缓解水稻种植带来的温室效应具有重要意义。

【Objective】Increases in atmospheric CO_(2) concentration have certain direct or indirect impacts on CH_(4) emission from rice paddy fields.So it is of great significance to have an in-depth study on impacts of long-term elevated atmospheric CO_(2) concentration on CH_(4) emission and related microorganisms for assessing and managing CH_(4) emissions from rice paddy fields in the context of future climate.【Method】To investigate effects of long-term elevated atmospheric CO_(2) concentration on CH_(4) emission and its mechanism,CH_(4) emission fluxes and abundance of the methanogens and methanotrophs under ambient CO_(2)(ACO_(2))and elevated CO_(2) conditions(ECO_(2))in rice paddy fields were monitored during the 2016-2017 season,with the aid of the Chinese rice FACE platform that has been operating for more than 10 years.Moreover,meta-analysis was conducted to determine quantitatively effects of elevated CO_(2) relative to duration on CH_(4) emission from and the abundances of methanogens and methanotrophs in rice paddy fields.【Result】Results show that compared with ACO_(2),long-term ECO_(2) significantly reduced CH_(4) emission and the abundance of methanogens by 28%and 39%,respectively(P<0.05),but increased the abundance of methanotrophs by 21%(P>0.05).Meta-analysis shows that with the increase in duration of CO_(2) elevation,the effect of elevated atmospheric CO_(2) concentration promoting CH_(4) emission and the abundance of methanogens gradually decreased,while the effect on the abundance of methanotrophs gradually increased.【Conclusion】Therefore,it could be concluded that under future climate conditions,long-term elevated CO_(2) will reduce CH_(4) emission from rice fields,which is of great significance for mitigating the greenhouse effect brought about by rice cultivation.