自然湿地甲烷排放时空变化规律研究(英文)

Spatial and Seasonal Variability of Methane Emission from Natural Wetlands

对三江平原沼泽湿地甲烷排放时空变化规律及其影响因素进行了研究．自然湿地甲烷排放存在着明显的季节性变化，即随着植物生长甲烷排放量不断增加，在8月达到最大值，而后下降．这一变化特点主要受温度和沼泽静水层深度所控制．春季低温不仅直接降低了甲烷的产生强度，而且也降低了其他好氧微生物的活性，使得沼泽水中存留较多的氧气，这些氧气直接加速了沼泽水中甲烷氧化，同时又提高了沼泽水的氧化还原电位，后者反过来进一步减缓甲烷的产生．三江平原不同植被生长的沼泽甲烷排放通量呈如下特点：毛果苔草＞乌拉苔草＞小叶章．莎草科植物生长的沼泽中，72％～86％的甲烷通过植物排放进人大气，而小叶章生长的沼泽只有28％～31％．毛果苔草促进了沼泽水中甲烷的氧化而不是产生，相反小叶章通过释放根系分泌物刺激甲烷产生的能力大于分泌氧气促进甲烷氧化的能力．毛果苔草沼泽水中更高的甲烷浓度是由于深的静水层淹没更多的植物立枯，从而为产甲烷菌提供充足的底物所致．

Spatial and seasonal variabilities in methane emission from natural wetlands in the Sanjiang Plain, China were studied in the years 2001 - 2002 and the factors influencing methane emission were also evaluated. A seasonal variability of methane emission that increased with the plant growth, reached maximum in August and then decreased was identified in freshwater marshes. This pattern was mainly affected by temperature and depth of standing water. Low methane emission at the early growth stage was due to low temperature rather than deficiency of substrate for methane production. Low temperature not only directly reduced methane production but also lowered the activity of aerobic microbes; the latter in turn left more oxygen in the rhizosphere for methanotrophs resulting in more methane to be oxidized. Methane emission in the freshwater marsh showed the following order： Carex lasiocarpa 〉 Carex myeriana 〉 Deyeuxia angustifolia. The Carex plants transported 72% - 86% of total methane emission, but only 28% -31% for Deyeuxia angustifolia. Carex lasiocarpa accentuated methane oxidation rather than methane production in the rhizopshere and by contrast, Deyeuxia angustifolia stimulated methane production by excreting root exudates instead of methane oxidation by releasing oxygen. The higher methane concentration in porewater in the Carex lasiocarpa marsh than in Deyeuxia angustifolia marsh was mainly because of the deep standing water, which inundated more plant litters resulting in more organic carbon to be provided for methane production.