氷河期と氷河期間のC3とC4の植物の豊富さの変動に対する支配的なコントロールとして,気候変動
Y Huang1, F A Street-Perrott, S E Metcalfe
1Department of Geological Sciences, Brown University, Providence, RI 02912, USA.
まとめ
低大気中の二酸化炭素だけでは,C4植物の拡大を説明することはできません. 湿度や気温などの気候要因は,C4の植物生長に不可欠であり,C3とC4の植物種のバランスに影響を与えます.
科学分野:
- 古代植物学と古代気候学
- 植物生態 植物生態学
- イソトープ地球化学 イソトープ地球化学
背景:
- ミオセンの末期におけるC4植物の拡大は既知の現象だが,その要因については議論が続いている.
- 降水量,気温,大気中の二酸化炭素 (PCO2) を含む過去の環境条件の再構築は困難です.
- C3およびC4の植物の分布に影響を与える要因を理解することは,過去の陸上の生態系を解釈する鍵です.
研究 の 目的:
- C4植物の拡大の主な要因を,古気候のプロキシを用いて調査する.
- C3 vs. C4の植物の豊富性を制御する際にPCO2,水分,および温度が相対的に重要であることを評価する.
- 最後の氷河期最大期以来,メソアメリカにおける地域的な気候の変動を再構築する.
主な方法:
- 湖の堆積物から採取した葉のn-アルケンの炭素同位体組成 (δ13C) の分析.
- 異なる湿度の歴史を持つメソアメリカにおける2つの遺跡を利用した.
- 同位体傾向をC3およびC4植物の相対的な豊富さの指標として解釈する.
主要な成果:
- 衝突する同位体傾向が2つの研究された場所間で観察され,地域気候に対する異なる反応を反映しています.
- これらの相反する傾向は,地域の気候,特に水分利用量が,C3とC4の植物比率に大きく影響することを示しています.
- 低PCO2レベルだけでは,湿度や温度条件が最適でない場合,C4プラントの拡大を促進するには不十分でした.
結論:
- 地域の気候,特に湿度が,C3とC4の植物の相対的な豊富さを制御する主要な要因です.
- 過去のC4プラントの拡張は,大気中のPCO2.2の減少にのみ帰結することはできない.
- 温度と湿度の好ましい状態は,C4植物の大幅な増殖の必要条件である.
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