土壌の肥沃性は,CO2濃縮された大気中の森林生態系による炭素吸収を制限する
R Oren1, D S Ellsworth, K H Johnsen
1Nicholas School of the Environment and Earth Sciences, Duke University, Durham, North Carolina 27708, USA. ramoren@duke.edu
Nature
|May 25, 2001
まとめ
大気中の二酸化炭素を吸収する森林の能力は,土壌の栄養素によって制限されています. 栄養素の添加は,樹木,特に貧しい土壌における炭素吸収を大幅に増加させ,楽観的な気候変動緩和見積もりに異議を唱える.
科学分野:
- 森林生態学 森林生態学 森林生態学
- バイオジオケミストリー バイオジオケミストリー
- 気候変動科学 気候変動科学
背景:
- 北中緯度の森林は,地球上の重要な炭素吸収源である.
- 大気中の二酸化炭素 (CO2) の増加は,森林の炭素吸収を強化すると予想されています.
- 森林の肥沃性,特に窒素の利用可能性は,しばしば木の成長と炭素の吸収を制限します.
研究 の 目的:
- 森林におけるCO2誘発の炭素結合に対する栄養素制限の影響を調査する.
- 森林の炭素貯蔵に対する高濃度のCO2と栄養素添加の相乗効果を評価する.
- 森林ベースの気候変動緩和戦略をめぐる楽観性を再評価する.
主な方法:
- 大気中の高濃度のCO2にさらされた熟成中の松の木の樹木を用いて2つの森林実験を実施した.
- 実験用プロットに栄養素を加えることで栄養素の利用可能性を操作する.
- 測定されたCO2誘発バイオマスによる炭素増加が,土壌の肥沃度が異なる場所において時間とともに増加した.
主要な成果:
- 栄養素が添加されていない栄養素が少ない場所では,CO2誘発の炭素封じ込めは検出できませんでした.
- 栄養素の添加は,より貧しい場所でのより大きな利益で,重要なシナージー効果を明らかにしました.
- 炭素結合に対する高濃度のCO2のポジティブな効果は,栄養素が添加されていない,適度な肥沃な場所では一時的で限界的であった.
結論:
- 土壌の肥沃性,特に窒素の利用可能性は,大気中のCO2の上昇に反応して,森林が炭素を吸収する能力を大幅に制限しています.
- 森林の炭素収縮の可能性に関する現在の推定は,栄養素の制限を考慮しない場合,過度に楽観的かもしれません.
- 炭素収縮の将来の評価は,土壌の肥沃性の制約と窒素堆積との相互作用を考慮する必要があります.
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