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List of Abstracts 20(total 18 days) during the experimental period. As soon as set-up the static chamber onto agricultural soil, 50ml of air was drawn from inside of the chamber by syringe 3 times with 15 minute interval (e.g. 0min,15min, 30min). GHG emission is calculated by use of a formula derived from mass balance of GHGbetween in and out of the chamber. Time change of the GHG gas concentration must be required to calculatethe gas emission. In addition, soil parameters (e.g. soil moisture, soil temperature, soil pH, total organic insoil, soil N and C) were monitored and measured at the same site. The gas samples in syringes were analysedby gas chromatography (equipped with ECD/FID). The average soil pH during the experimental period was~pH5.7 at the plot. The average fluxes and ranges of GHG during the experimental period were 0.002±0.09mg-m-2 hr-1 (-0.036 ~ 0.045 mg-m-2 hr-1) for CH4, 23.854±170.61 mg-m-2 hr-1 (-73.109 ~ 139.379 mgm-2hr-1) for CO2, and 0.317±0.48 mg-m-2 hr-1 (-0.082 ~ 1.144 mg-m-2 hr-1) for N2O, respectively.Monthly base flux measurement results revealed that monthly mean GHG flux during October wassignificantly higher than those during November and January when soil temperatures during these monthswere significantly low. Soil temperature during the experimental periods were ranged from 0.2 to 18.8oC(17.5±1.2oC for October; 12.4±2.4oC for November; 1.1±0.7oC for January). It seems that soil temperaturehas significant role in controlling the soil GHG emission, and low temperature during November andJanuary could weaken microbial activity in soil and now turn soil GHG emission decrease. Other soilparameters were also correlated with GHG emissions and discussed. Negative gas fluxes for both CH4 andCO2 were observed during these measurements, but not for N2O. CH4 and CO2 gases seem to be emitted ordeposited depending on other factors such as background concentrations and physicochemical soilconditions. However, still there are uncertainties in their determination. Improvement of measurementtechniques and well-understanding of relationships between gas emission and controlling factors in suchenvironments need to be required.P-Sources.23 ID:4585 15:35Methane emission from natural wetlands: what are wetlands and where are they?Elaine MatthewsNASA Goddard Institute for Space StudiesContact: ematthews@giss.nasa.govNatural wetlands are the world's largest source of methane. Their emission dynamics are strongly influencedby inter-annual variations in climate and, together with wild fires, control inter-annual variations in thegrowth rate of atmospheric methane concentrations. About half of the world's wetlands are north 50˚N wheretemperature, permafrost, and peaty soils dominate. Another ~40% is in low latitudes governed primarily bylarge-scale riverine flooding in forested environments. Wetlands display exceptional variability invegetation, hydrological regime and seasonality which means that defining wetlands is not straightforward.In fact, there is no consensus on what a wetland is for methane or any other studies. Existing classificationsystems reflect regional complexes and are not globally applicable. Meaningful distinctions among wetlands,rivers and lakes are impossible in some regions and seasons which further complicates defining, mapping,monitoring and modeling wetlands.Models simulating methane dynamics in natural wetlands, developed since the mid-1990s, are usuallyapplied to an independent wetland data set due to difficulties in modeling the distribution of wetlandsthemselves although researchers are now attempting to predict methane-producing wetland distributionsfrom climate variables.While models evolve, wetlands remain undefined. We found that distributions and areas of wetland data setsprimarily reflect the strengths and weaknesses of the instruments and approaches employed to develop them.Therefore, apparent discrepancies among data sources mostly represent methodological differences ratheriCACGP-IGAC 2010 12 July, 2010