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.

博宁； ATM 9912052本研究提出了一种新方法，通过对从沉积物核心提取的化石草和花粉进行碳同位素分析，重建 C3 与 C4 草分布的过去变化。 这种方法的优点是 C3 和 C4 植物很容易通过碳同位素特征来区分，并且草花粉忠实地记录了寄主植物的碳同位素特征。 因此，草花粉同位素记录将记录过去 C3 与 C4 植物的变化。 由于草花粉记录的变化将与冰芯 pCO2 估计值结合使用，以提供热带地区末次盛冰期大陆温度变化的独立于水分的、受限的估计值。 该工作计划包括对来自热带东非的已识别现代草的花粉进行分析，以测试新方法并确认草花粉碳同位素信号的完整性。 对乌干达西部四个湖泊的表面沉积物样本进行分析，结合对向这些盆地提供花粉的低地环境中草物种丰度的半定量估计，将为与化石值进行比较提供必要的现代模拟。 过去的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本中的草花粉来评估，这些样本取自至少一个火山口湖收集的岩芯。 拟议研究的结果将完善对末次盛冰期期间东非热带地区变冷的估计，并将通过提供古生态数据来改进对末次盛冰期至今陆地碳库变化的模型预测，从而为全球碳预算估算做出贡献。