Permalink : http://hdl.handle.net/2115/49057

KEYWORDS : 湿地;雪;メタン;温室効果ガス;微生物;wetlands;snow;methane;greenhouse gases;microorganisms

北方の湿地やツンドラは, 地球の全土壌炭素の約30％が蓄積する場であり, メタンの主要発生源である. 本稿では, 積雪が北方の湿地におけるメタン放出やメタンの代謝に関わる微生物に及ぼす影響を概説, 以下のように要約した. １）積雪によって冬期のメタン放出量は低下するが, その間湿地土壌中にメタンが蓄積し, 春の融雪とともに急激に大気へ放出される. ２）積雪による保温効果や不凍水における栄養塩やその他基質の濃縮効果により, 微生物の活性が高くなる. ３）大気との遮断や地下水位の上昇により湿地土壌中の嫌気環境が拡大しメタン生成が促進される. ４）積雪の影響は冬季ばかりでなく夏季のメタン放出にも及ぶ.
Northern wetland and tundra regions store approximately 30% of the world organic soil carbon and function as a major source of atmospheric methane. In this article, the impact of snow on methane emission and microorganisms in northern wetlands is reviewed. In summary, 1)Methane emission from northern wetland is reduced in winter partly by snowpack and methane is accumulated in the soil under snow;snow melt causes a “burst”of methane emission in spring. 2)Microbial activities in wetland soil are enhanced by snow cover that keeps the underlying surface soil warmer (around 0 ℃) and causes concentrated nutrients and substrates for microorganisms in unfrozen soil water. 3)Snow pack suppresses gas exchange between wetland soil and the atmosphere and melted snow may raise the level of water table, both of which expand anoxic area in soil and enhance methane production. 4)Snow can also give an impact on methane emission in a vegetative season of summer.