Microbial versus non-microbial methane releases from fresh soils at different temperatures

•Microbial versus non-microbial methane.•Response of methane releases to temperature.•Microbial methane was largely released from wet soils.•Non-microbial methane was mainly released from dry soils.•Methane was predominately produced by microbial mechanism in soils.

Methane (CH4) production in soils can occur by microbial and non-microbial processes. We postulated that there exist the mixed microbial and non-microbial CH4 emissions from fresh soils in nature. To test both emissions and their importance, this study examined CH4 releases from fresh soils of forest, orchard, croplands, grasslands, and wetland. By designing the treatments with or without inhibitor(s) in the laboratory conditions, we used inhibition method to compare/distinguish microbial and non-microbial CH4 releases from fresh soils at a series of temperatures. Microbial CH4 release occurred mainly in wetland soils and moist upland soils, with the peak rates of 101-103 ng gdw− 1 h− 1 around 40 °C. Non-microbial CH4 release occurred mainly in upland soils and usually increased with temperature, showing negligible rates at ambient temperatures of 0-40 °C and detectable rates of approximately 0.2-0.7 ng gdw− 1 h− 1 at high temperatures of 50-70 °C. Microbial CH4 release was much more important than non-microbial CH4 release from fresh soils at different temperatures, when all land uses were considered together. In nature, soils are frequently exposed to various forms of environmental stress. Besides temperature fluctuation examined in the present study, solar ultraviolet radiation, soil water deficit and flooding, hypoxia and hyperoxia, tillage, and herbicide may also affect non-microbial CH4 production. Thus, more measurements are required for understanding the contribution of non-microbial CH4 emission to the total from soils.

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