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As one of the most significant natural sources of atmospheric methane, wetlands remain a major area of concern with respect to climate change. Wetlands are characterized by water-logged soils and distinctive communities of plant and animal species that have evolved and adapted to the constant presence of water. Due to this high level of water saturation as well as warm weather, wetlands are one of the most significant natural sources of atmospheric methane. Most methanogenesis, or methane production, occurs in oxygen poor environments. Because the microbes that live in warm, moist environments consume oxygen more rapidly than it can diffuse in from the atmosphere, wetlands are the ideal anaerobic, or oxygen poor, environments for fermentation. Fermentation is a process used by certain kinds of microorganisms to break down essential nutrients. In a process called acetoclastic methanogenesis, microorganisms from the classification domain archaea produce methane by fermenting acetate and H2-CO2 into methane and carbon dioxide. H3C-COOH → CH4 + CO2 Depending on the wetland and type of archaea, hydrogenotrophic methanogenesis, another process that yields methane, can also occur. This process occurs as a result of archaea oxidizing hydrogen with carbon dioxide to yield methane and water. 4H2 + CO2 → CH4 + 2H2O ==Natural progressions of wetlands== Many different kinds of wetlands exist, all characterized by unique compositions of plant life and water conditions. To list a few, marshes, swamps, bogs, fens, peatlands, muskegs, and pocosins are all examples of different kinds of wetlands. Because each type of wetland is unique, the same characteristics used to classify each wetland can also be used to characterize the amount of methane emitted from that particular wetland. Any waterlogged environment with moderate levels of decomposition create the anaerobic conditions needed for methanogenesis, but the amount of water and decomposition will affect the magnitude of methane emissions in a specific environment. For example, lower water tables result in lower levels of methane emission because methanotrophic bacteria require oxic conditions to oxidize methane into carbon dioxide and water. Higher water tables, however, result in higher levels of methane emission because there is less habitable area for methanotrophic bacteria to live, and thus the methane can more easily diffuse into the atmosphere without being broken down. Often, the natural ecological progression of wetlands involves the development of one kind of wetland into one or several other kinds of wetlands. So over time, a wetland will naturally change the amount of methane emitted from its soil. For example, Peatlands are wetlands that contain a large amount of peat, or partially decayed plant life. When peatlands are first developing, they often start out as fens, wetlands characterized by mineral rich soil. These flooded wetlands, with higher water tables, would naturally have higher emissions of methane. Eventually, the fens develop into bogs, acidic wetlands with accumulations of peat and lower water tables. With the lower water tables, methane emissions are more easily consumed by methanotrophic, or methane consuming, bacteria and never make it to the atmosphere. Over time, the peatlands develop and end up with accumulated pools of water, which once again increases emissions of methane. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Wetland methane emissions」の詳細全文を読む スポンサード リンク
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