Coupled anaerobic methane oxidation and metal reduction in soil under elevated CO2 |
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| Authors: | Chenchao Xu Naifang Zhang Kaihang Zhang Shuyao Li Qing Xia Jing Xiao Maojun Liang Weilei Lei Junpan He Gaiping Chen Chengjun Ge Xunhua Zheng Jianguo Zhu Shuijin Hu Roger T. Koide Mary K. Firestone Lei Cheng |
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| Affiliation: | 1. MOE Key Laboratory of Biosystems Homeostasis & Protection, College of Life Sciences, Zhejiang University, Hangzhou, China;2. College of Ecology and Environment, Hainan University, Haikou, China;3. Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China;4. State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, China;5. Department of Plant Pathology, North Carolina State University, Raleigh, North Carolina, USA;6. Department of Biology, Brigham Young University, Provo, Utah, USA;7. Department of Environmental Science, Policy and Management, University of California, Berkeley, California, USA |
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| Abstract: | Continued current emissions of carbon dioxide (CO2) and methane (CH4) by human activities will increase global atmospheric CO2 and CH4 concentrations and surface temperature significantly. Fields of paddy rice, the most important form of anthropogenic wetlands, account for about 9% of anthropogenic sources of CH4. Elevated atmospheric CO2 may enhance CH4 production in rice paddies, potentially reinforcing the increase in atmospheric CH4. However, what is not known is whether and how elevated CO2 influences CH4 consumption under anoxic soil conditions in rice paddies, as the net emission of CH4 is a balance of methanogenesis and methanotrophy. In this study, we used a long-term free-air CO2 enrichment experiment to examine the impact of elevated CO2 on the transformation of CH4 in a paddy rice agroecosystem. We demonstrate that elevated CO2 substantially increased anaerobic oxidation of methane (AOM) coupled to manganese and/or iron oxides reduction in the calcareous paddy soil. We further show that elevated CO2 may stimulate the growth and metabolism of Candidatus Methanoperedens nitroreducens, which is actively involved in catalyzing AOM when coupled to metal reduction, mainly through enhancing the availability of soil CH4. These findings suggest that a thorough evaluation of climate-carbon cycle feedbacks may need to consider the coupling of methane and metal cycles in natural and agricultural wetlands under future climate change scenarios. |
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| Keywords: | anaerobic oxidation of methane Candidatus Methanoperedens nitroreducens free-air CO2 enrichment metal reduction methane cycle paddy rice |
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