Collaborative Research: Integrated Analysis of Late-Glacial Vegetation and Environments in Eastern North America: How Do Novel Plant Associations Arise?

在美国东部，17000至12000年前存在的森林植物群落不再出现在这片土地上。该项目将确定这些历史上的植被组合是否源于：1)异常高温的季节性，2)大气中二氧化碳浓度低，和/或3)现已灭绝的“大型动物”(如猛犸象、乳齿象)的食草性。该项目综合了古生态数据和机械植被模型。具体地说，该项目将研究从田纳西州到明尼苏达州的七个中大陆地点的湖泊沉积岩心，并模拟气候和二氧化碳对植被组成的控制。将对沉积物进行分析，以推断植被、火灾和大型动物种群密度的生态史，并确定关键生态事件的发生时间。这项对过去环境变化的研究对当前的气候变化问题有着直接的影响。特别是，为了规划的目的，迫切需要准确的生态预测，但目前的生态模型在应用于现代观测范围之外的环境条件时的稳健性，人们知之甚少。此外，21世纪末的气候很可能包括温度和降水的组合，这与今天观察到的任何气候都不同。记录充分的异常晚冰期气候和生态群落是评估当前生态应对复杂环境变化模式的充分性的良好试验场。这项工作将支持学生培训和高中教师和学生的外联活动。

In the eastern United States, forest plant communities that were present 17,000 to 12,000 years ago are no longer represented on the landscape. This project will determine whether these historic assemblages of vegetation arose from: 1) unusually high temperature seasonality, 2) low atmospheric carbon dioxide concentrations, and/or 3) herbivory by now-extinct ''''megafauna'''' (e.g. mammoths, mastodons). This project integrates paleoecological data and mechanistic vegetation models. Specifically, this project will study lake-sediment cores from seven mid-continental sites from Tennessee to Minnesota and model climatic and carbon dioxide controls on vegetation composition. Sediments will be analyzed to infer ecological histories of vegetation, fire, and megafaunal population density and determine the timing of key ecological events. This study of past environmental change has direct implications for current climate-change concerns. In particular, for planning purposes, there is an urgent need for accurate ecological forecasts, but the robustness of current ecological models, when applied to environmental conditions outside the range of modern observations, is poorly understood. Moreover, climates at the end of the 21st century will likely include combinations of temperature and precipitation unlike any observed today. The well-documented anomalous late-glacial climates and ecological communities are a good testing ground for evaluating the adequacy of current models of ecological response to complex environmental change. This work will support student training and outreach activities for high school teachers and students.