Eddy Covariance and Static Chamber-Methane and Carbon Dioxide Flux measurement instrument with different environmental parameters measuring sensors installed in a paddy field nearby Bangladesh Agricultural University campus. Methane (CH4) is the predominant hydrocarbon in the atmosphere and the third most important greenhouse gas after water(H2O) and carbon dioxide (CO2); its atmo25 spheric abundance has increased by 150% since the pre-industrial era (Dlugokencky et al., 2009). As of 2010, the radiative forcing of CH4 from anthropogenic emissions was 0.50Wm−2, corresponding to approximately 30% of the radiative forcing from CO2 (Montzka et al., 2011). Estimates of the soil sink for CH4 vary between 15–45 TgCH4 yr−1 (Curry, 2007), making it the second largest sink after tropospheric oxidation. The main losses of atmospheric CH4 in the biosphere are oxidation in upland soils, however the overall 5 magnitude of the soil sink and the factors governing its variability are not well understood. It is believed that between 30–50% of the global CH4 soil sink is in the temperate zone (Price et al., 2004). Natural CH4 emissions are dominated by methanogenesis in wetlands, especially under conditions of high humidity and temperature. Recently, it has been suggested that plants themselves have the potential 10 to emit CH4 depending on environmental conditions (Keppler et al., 2006; Bru¨ggemann et al., 2009; Wang et al., 2011) although the significance of these emissions in natural environments has been disputed (Nisbet et al., 2009). The uncertainties in the global CH4budget result from limited observational data coverage and the large variability in
the factors that influence CH4 fluxes in natural environments (Heimann, 2011).