Collaborative Research: Are Amazonian and Andean ecosystems close to a tipping point?

合作研究：亚马逊和安第斯生态系统是否已接近临界点？

• 批准号: 2029615
• 负责人: Liviu Giosan
• 金额: $ 13.13万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-06-01 至 2024-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2029615&HistoricalAwards=false
• 关键词: Collaborative; Research; Amazonian; Andean; ecosystems

Amazonian rainforests are famous for the immense biological and cultural diversity they support. These forests are also a vital part of global recycling of freshwater, and their loss has implications for food security for millions of people as well as global climate dynamics. Climate change is threatening these systems and there are concerns that as temperatures rise and rainfall becomes less reliable, these forests might be replaced by low-diversity grasslands. However, it is unclear what level of climate change might trigger a forest-to-grassland transition. Paleoecology can provide information about biological diversity in the past, and how biodiversity patterns changed during past warming events. This research project will investigate two periods of climate warming, one that lasted from about 8000 to 5000 years ago, and another even warmer time that lasted from 128,000 to 120,000 years ago. Ancient lakes build up sediments through time, and by taking a drill-core down through the sediment the history of the region can be captured in the lake mud. The researchers will analyze the fossil and chemical content of lake sediment cores from seven locations in the Amazon and Andes to establish how much the climate changed in the past, and whether those changes were enough to induce a shift from forest to grassland. By looking at a range of locations that vary in moisture, from very wet to quite dry, and degree of warming, the researchers will estimate how close the modern rainforest is to a forest-to-grassland transition. Additionally, new interactions between the collaborating research groups will include a co-taught paleoecology/paleoclimatology course, a sponsored category in a local film festival, and training of at least 10 undergraduates, two doctoral students, and one postdoctoral researcher. The research will address a number of hypotheses relating to climate-vegetation responses such as flickering, teleconnections, ecosystem buffering, and tipping points. By using organic geochemical data to estimate paleotemperature, leaf wax isotopes to estimate precipitation, sediment chemistry to characterize droughts, fossil pollen to reconstruct vegetation, and charcoal to reconstruct fire frequency, the researchers will investigate ecosystem change under conditions as much as 2 degrees C (4 degrees F) warmer than the present. The Last Interglacial will provide an index of scale of change in traits, fire prevalence and community composition in a climate 1-2 degrees C warmer than modern. In the directly-dated Holocene, the data will assess sub-decadal variance in ecosystem indicators, and allow rates of change to be investigated. Currently, no high-resolution records of Amazonian temperature exist, so the novel approach of separating climatic change from that of ecological proxies will be transformational for quantitative neotropical paleoecology.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

亚马逊雨林以其支持的巨大生物学和文化多样性而闻名。这些森林也是全球淡水回收的重要组成部分，它们的损失对数百万人以及全球气候动态的粮食安全产生了影响。气候变化正在威胁到这些系统，人们担心随着温度升高和降雨的可靠性，这些森林可能被低多样性的草原所取代。但是，目前尚不清楚什么水平的气候变化可能会引发森林到格拉斯兰的过渡。古生态学可以提供有关过去生物多样性的信息，以及在过去的变暖事件中生物多样性模式如何变化。该研究项目将调查两个持续时间从8000年前的气候变暖，一个持续时间为5000年，还有另一个持续时间从128,000到120，000年前的时间。古老的湖泊会随着时间的流逝而产生沉积物，通过将钻头沿沉积物进行钻探，可以在湖泥中捕获该地区的历史。研究人员将分析来自亚马逊和安第斯山脉七个地点的湖泊沉积物岩心的化石和化学含量，以确定过去气候发生了多少变化，以及这些变化是否足以引起从森林转移到草原的转变。通过查看一系列水分的不同位置，从非常潮湿到非常干燥，以及变暖的程度，研究人员将估计现代雨林与森林到格拉斯兰的过渡有多近。此外，协作研究小组之间的新互动将包括一个共同教授的古生态学/古气候学课程，当地电影节中的赞助类别，以及对至少10名本科生的培训，两个博士生和一名博士后研究员。这项研究将解决与气候植被反应有关的许多假设，例如闪烁，远程连接，生态系统缓冲和临界点。通过使用有机地球化学数据来估算古温过温，叶蜡同位素以估计降水量，沉积物化学以表征干旱，化石花粉以重建植被以及重建火频率，研究人员将在与现在的温度相比2摄氏度（4摄氏度）中调查生态系统变化。最后一次冰川间将在气候1-2摄氏度中比现代化的特征，火灾患病率和社区成分的变化规模指数。在直接日期的全新世中，数据将评估生态系统指标的子差异差异，并允许研究变更速率。当前，没有亚马逊温度的高分辨率记录，因此将气候变化与生态代理分离的新方法将是定量新型新热带古生物学的转变。该奖项反映了NSF的法定任务，并认为通过使用该基金会的智力和更广泛的影响来评估CRITERIA的评估。