サバンナと森林が代替バイオーム状態として地球規模に及ぶ範囲と決定要因

A Carla Staver¹, Sally Archibald, Simon A Levin

¹Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA. astaver@princeton.edu

Science (New York, N.Y.)

|October 15, 2011

まとめ

火災と木の覆いのダイナミクスは,世界中で独特のサバンナと森林の生態系を作り出します. これらのバイオームは,特に中間気候では,変化が急激で不可逆的であり,代替的な安定状態を表す可能性があります.

科学分野:

エコロジーエコロジーエコロジー
バイオジオグラフィーバイオジオグラフィー
気候科学気候科学

背景:

火の木の覆いのフィードバックは,理論的には,サバンナと森林を代替的な安定した状態としてサポートします.
季節性や土壌を考慮して,火災による樹木覆いの不連続性の世界的な範囲は,ほとんど不明のままです.

研究の目的:

絶え間ない樹冠の地球規模分布を調査する.
サバンナと森林のバイオームの区別における気候,季節性,火,土壌の役割を決定する.
サバンナと森林が,世界的に別の安定した状態を表しているかどうかを評価する.

主な方法:

樹木の覆い,気候,火災発生,土壌特性のグローバルデータセットを利用した.
樹木覆いの不連続性のパターンを特定するために,統計分析を用いた.
異なる降雨量および季節性条件下でのバイオームの差異化を調べた.

主要な成果:

樹木の覆いは,気候の影響で,世界的に不連続です.
穏やかな季節性 (<7ヶ月) の中間の降雨量 (1000-2500ミリメートル) で,樹木の覆いはバイモダリティを示します.
火は,これらの中間条件でサバンナと森林を区別する重要な要因であり,代替的な安定した状態を示唆しています.

結論:

サバンナと森林は,アマゾンやコンゴを含む広範囲の地域で,代替的な安定した状態として存在することがあります.
気候によるサバンナの断片化や森林の喪失など,バイオームの分布の変化は,急激で逆転が困難である可能性が高い.

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