アマゾンのメタン予算は,洪水平原の木々からの大量排出によって縮小する.
Sunitha R Pangala1, Alex Enrich-Prast2,3, Luana S Basso4
1School of Environment, Earth and Ecosystem Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK.
Nature
|December 7, 2017
まとめ
アマゾン湿地の木々は大気中のメタン (CH4) の主要な源であり,地域の排出量を大幅に過小評価しています. アマゾンの湿地のCH4の半分は木の幹の排出量で,これは世界のメタン予算を理解するために不可欠です.
科学分野:
- 環境科学
- 生地化学
- 大気科学
背景:
- 湿地は,大気中のメタン (CH4),強力な温室効果ガスの主な地球規模の源です.
- トロピカルCH4の主要な源であるアマゾン流域の既存のメタン排出量インベントリは,大気中のCH4の負荷を過小評価しています.
- この不一致は,アマゾンの湿地が世界のCH4排出量に与える影響を理解する上で重要な知識のギャップを浮き彫りにしています.
研究 の 目的:
- アマゾン流域の樹幹からメタン (CH4) の流れを定量化するためです.
- アマゾンのCH4予算における湿地の木々の役割を特定する.
- 地域のCH4排出量の"ボトムアップ"と"トップダウン"の見積もりを調整する.
主な方法:
- アマゾン流域の13箇所の2357本の木の幹から 測定されたCH4の流れ
- 発射されたCH4の安定炭素同位体値 (δ13C) を分析して起源を決定する.
- "上から下へ"の大気プロファイル (2010年−2013年) を用いた地域的なCH4排出量と"下から上へ"のフクロス測定値との比較.
主要な成果:
- アマゾンの樹幹からのメタンの流出量は 温帯や泥沼林の 200倍にも達しました
- 樹幹の排出量は地域のCH4の主な源で,年間15.1〜21.2Tgと推定されています.
- 同位体シグネチャー (δ13C = -66.2 ± 6.4‰) は,木から排出されるCH4の土壌生物学的起源を確認している.
結論:
- アマゾンのCH4排出の主な原因は湿地の木々を通過する土壌ガスの排出です.
- アマゾンの木は地域の湿地のCH4排出量の約半分を占め,世界のメタン予算に大きな影響を与えています.
- アマゾンのCH4排出量の過小評価を解決するために,上から下へ"と"下から上へ"の見積もりをうまく調和させました.
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