植物と土壌の炭素貯蔵のトレードオフ
C Terrer1,2, R P Phillips3, B A Hungate4,5
1Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA, USA. terrer@stanford.edu.
Nature
|March 25, 2021
まとめ
陸上の生態系は大量の二酸化炭素 (CO2) を吸収する. しかし,大気中のCO2の増加は,生態系によって土壌の有機炭素 (SOC) に異なる影響を及ぼし,将来の気候予測に影響します.
科学分野:
- 環境科学
- エコロジー
- 気候科学
背景:
- 陸上の生態系は,年間の人為的な二酸化炭素 (CO2) 排出量の約30%を吸収する重要な炭素吸収体として機能します.
- 植物バイオマスと土壌の有機炭素 (SOC) が高濃度のCO2 (eCO2) に反応する様相が異なるため,この炭水化物の長期的安定性は不確実である.
- 過去の実験では,eCO2が SOCに及ぼす影響は一貫していないことが示され,気候変動モデルに重大な不確実性が生じています.
研究 の 目的:
- 多くのeCO2実験から得られたデータを合成し,SOC株の反応に影響を与える要因を理解する.
- 植物バイオマス刺激とeCO2条件下でのSOC貯蔵の関係を特定する.
- SOCのダイナミクスを再現する生態系モデルのパフォーマンスを評価する.
主な方法:
- 108件のeCO2実験のデータを集約したメタアナリシスが行われました.
- この研究では,eCO2による植物バイオマスの変化とSOCの貯蔵量との関係を分析した.
- SOCの反応の主要な要因を特定し,草原と森林の結果を比較するために統計分析が用いられました.
主要な成果:
- 重要なトレードオフが特定されました:eCO2による植物バイオマスの強い刺激はSOC貯蔵の減少をもたらし,弱い刺激はSOCの増加をもたらしました.
- このトレードオフは,植物栄養素獲得戦略と関連しており,バイオマスの増加はSOCを犠牲にすることがあります.
- 草原ではSOCが増加した (8%±2%),森林ではeCO2が増加したにもかかわらず,森林では有意な変化はなかった (0%±2%).
結論:
- この発見は,二酸化炭素のレベルが上昇すると,地上の炭素貯蔵に影響を与える,以前は過小評価されていた重要なメカニズムを明らかにしています.
- 生態系モデルは現在,このバイオマスとSOCのトレードオフを捉えることができず,正確な気候予測を修正する必要があります.
- これらのダイナミクスを理解することは 気候変動を緩和する陸上の生態系の 将来の能力を予測するのに不可欠です
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