Collaborative Research: Megaherbivore and climatic controls on fire and vegetation dynamics during the last deglaciation

长期以来，生态学家一直试图了解物种是如何在重大环境变化期间重新洗牌进入新的生态群落的，以及这种重新洗牌对这些生态群落为人类社会提供的服务的影响。这个项目利用了一个重大的历史事件——大约17000年前植物群落的巨大变化——来确定气候变化、物种相互作用和火灾在新群落的形成中所起的相对作用。这项研究的结果将为当代关于气候变化创造“无模拟”社区的可能性的辩论提供信息，这些社区在结构、功能和向社会提供的服务方面存在根本差异。它们还将指导旨在将社区恢复到以前状态的管理实践，并提高我们对大范围灭绝后果的理解。该项目建立在先前证据的基础上，该证据表明，由于大型食草动物的灭绝使植物从食草动物的压制中解放出来，植物群落在上一次冰川消退期间发生了巨大变化。新的研究将通过评估气候和物种相互作用对植被和火灾动力学的相对重要性来测试新的巨型动物释放假说。研究人员将收集和分析美国东部的一系列湖泊沉积物岩心，并量化各个地点内部和不同地点之间独立的气候和生态指标之间的关系，以检验巨型动物释放假说。将分析8个新湖泊遗址的过去植被组成（化石花粉）、火情（沉积木炭）、巨型动物丰度（粪便中发现的真菌孢子）和温度（有机地球化学）指标。更广泛的影响包括指导和培训一名博士后研究科学家、一名研究生和几名本科生，以及扩大古生物学家、地理学家和生态学家之间的合作，以了解未来的环境变化。所有数据都将通过标准的社区数据存储库公开提供。

Ecologists have long sought to understand how species reshuffle into novel ecological communities during periods of major environmental change, and the consequences of this reshuffling for the services that those ecological communities provide for human society. This project capitalizes on a major historical event - massive changes in plant communities roughly 17,000 years ago - to determine the relative roles that climate change, species interactions, and fire played in the creation of novel communities. Results from this research will inform contemporary debates about the potential for climate change to create 'no analog' communities that differ fundamentally in their structure, function, and the services they provide to society. They will also guide management practices intended to restore communities to prior states and improve our understanding of the consequences of widespread extinctions.This project builds on prior evidence that plant communities changed dramatically during the last deglaciation because the extinction of large grazers released plants from herbivore suppression. New research will test the novel Megafaunal Release Hypothesis by assessing the relative importance of climate and species interactions on vegetation and fire dynamics. The investigators will collect and analyze a series of lake-sediment cores in the eastern US, and quantify relationships among independent climatic and ecological proxies within and across sites in order to test the Megafaunal Release Hypothesis. Eight new lake sites will be analyzed for indicators of past vegetation composition (fossil pollen), fire regime (sedimentary charcoal), megafaunal abundance (spores from fungi found in dung), and temperature (organic geochemistry). Broader impacts include the mentoring and training of a postdoctoral research scientist, a graduate student, and several undergraduates, and the expansion of collaborations among paleontologists, geographers, and ecologists to understand future environmental change. All data will be made publicly available through standard community data repositories.