Dynamics of methanogenesis and methanotrophy in tropical paddy soils as influenced by elevated CO2 and temperature interaction

Response of methanogenesis and methanotrophy to elevated carbon dioxide (CO2) could be affected by changes in soil moisture content and temperature. In soil microcosms contained in glass bottles and incubated under laboratory conditions, we assessed the impact of elevated CO2 and temperature interactions on methanogenesis and methanotrophy in alluvial and laterite paddy soils of tropical origin. Soil samples were incubated at ambient (370 mu mol mol(-1)) and elevated (600 mu mol mol(-1)) CO2 concentrations at 25, 35 and 45 degrees C under non-flooded and flooded conditions for 60 d. Under flooded condition, elevated CO2 significantly increased methane (CH4) production while under non-flooded condition, only marginal increase in CH4 production was observed in both the soils studied and the increase was significantly enhanced by further rise in temperature. Increased methanogenesis as a result of elevated CO2 and temperature interaction was mostly attributed to decreased soil redox potential, increased readily mineralizable carbon, and also noticeable stimulation of methanogenic bacterial population. In contrast to CH4 production, CH4 oxidation was consistently low under elevated CO2 concentration and the decrease was significant with rise in temperature. The low affinity and high affinity CH4 oxidation were faster under non-flooded condition as compared to flooded condition. Admittedly, decreased low and high affinity CH4 oxidation as a result of elevated CO2 and temperature interaction was related to unfavorable lower redox status of soil and the inhibition of CH4-oxidizing bacterial population. (C) 2011 Elsevier Ltd. All rights reserved.