Paleodistributions of C3 and C4 Grasses in Tropical East Africa- Climatic Implications

热带东非 C3 和 C4 草的古分布 - 气候影响

• 批准号: 9912052
• 负责人: Kristina Beuning
• 金额: $ 13.03万
• 依托单位: Wesleyan University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-04-01 至 2001-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9912052&HistoricalAwards=false
• 关键词: Paleodistributions; C3; C4; Grasses; Tropical

Beuning; ATM 9912052This study proposes a new methodology to reconstruct past changes in C3 vs C4 grass distributions by carbon isotopic analysis of fossil grass and pollen extracted from sediment cores. The advantage of this methodology is that C3 and C4 plants are easily distinguished by their carbon isotopic signatures, and grass pollen faithfully records the carbon isotopic signature of the host plant. Therefore, past shifts C3 vs. C4 plants will be recorded by the grass pollen isotopic record. As shifts recorded by the grass pollen will be used in conjunction with ice core estimates of pCO2 to provide moisture-independent, constrained estimates of LGM continental temperature change in the tropics. The work plan includes analysis of pollen from identified modern grasses from tropical East Africa to test mew methodologies and confirm integrity of the grass pollen carbon isotopic signal. Analysis of surface sediment samples from four lakes in western Uganda in conjunction with semi-quantitative estimates of grass species abundance in the lowland environments contributing pollen to these basins will provide necessary modem analogs for comparison with fossil values. Impacts of past climate change on the grassland communities will be assessed through analysis of grass pollen preserved in Last Glacial sediment samples from a core collected in at least one crater lake. Results of the proposed research will refine estimates of tropical East African cooling during the LGM and will contribute to global carbon budget estimates by providing paleoecological data to improve model predictions of change in terrestrial carbon reservoirs from the LGM to present day.

Beuning; ATM 9912052这项研究提出了一种新的方法来重建过去的变化C3与C4草分布的化石草和花粉提取的沉积物芯的碳同位素分析。 这种方法的优点是C3和C4植物很容易通过它们的碳同位素特征来区分，并且草花粉忠实地记录了宿主植物的碳同位素特征。 因此，过去的变化C3与C4植物将记录的草花粉同位素记录。 由于草花粉记录的变化将与冰芯pCO 2估计值结合使用，以提供独立于水分的热带LGM大陆温度变化的约束估计值。 这项工作计划包括分析来自东非热带地区已确定的现代草的花粉，以测试新方法并确认草花粉碳同位素信号的完整性。 从四湖在乌干达西部的表面沉积物样品的分析，结合半定量估计的草物种丰富的低地环境贡献花粉这些盆地将提供必要的现代类似物与化石价值的比较。 过去气候变化对草原群落的影响将通过分析保存在末次冰期沉积物样品中的草花粉进行评估，这些样品来自至少一个火山口湖的核心。 拟议研究的结果将完善对LGM期间热带东非冷却的估计，并将通过提供古生态数据来改善对LGM至今陆地碳库变化的模型预测，从而有助于全球碳预算估计。