Collaborative Research: How did Terrestrial Ecosystems Rebuild Following the Cretaceous/Paleogene Mass Extinction?

在白垩纪/古近纪(K/PG)大灭绝(约6600万年前)期间，地球上约75%的物种灭绝，特别是包括所有非鸟类恐龙。这一事件彻底改变了生命进化树的轨迹，最终导致了今天以哺乳动物为主的群落的形成。K/PG大灭绝的后果代表着一个自然实验室，可以在其中以高地质分辨率研究生态系统重组。已经开展了一些研究，以考察海洋生态系统是如何重建的，但对陆地环境的反应的记录很少。该项目将研究美国西部落基山脉地区跨越K/PG边界的陆地上发生的生态和环境变化。这项研究将涉及对现有化石收藏进行广泛的古生物学和地球化学分析，并引入新的数据，揭示大灭绝后陆地生态系统重建的时间和模式的变异性。该项目将扩大对地球生命历史上一个重大转折点的认识，这将有助于确定生态系统的生物多样性如何在大陆范围内恢复，以及现代陆地生物群是如何进化的。研究结果还可能为保护生物学家提供数据，以预测当前生物多样性快速变化的长期后果，并帮助为保护优先事项提供信息，以减轻生态系统破坏。该项目将使用教室、博物馆展品和参与机构的外联活动来接触不同年龄和背景的观众。K/PG大灭绝彻底改变了生命树进化的轨迹，大多数研究都集中在海洋系统上。灭绝后陆地生态系统重建的模式是理解哺乳动物和植物现代分类群演化的基础，但由于化石收集、数据和高分辨率年代地层剖面相对较少，因此很少受到关注。该项目将以北美西部内陆三个主要研究地区的大量化石收集为基础，进行新的实地工作，以扩大收集和关键时段的数据，并开发不同的无机和有机地球化学记录，以表征和确定生物模式、当地环境和K/PG灭绝后陆地生态系统重建所涉及的因素。为了实现这些目标，研究小组将：收集和解释来自三个研究良好的地层剖面的大型植物、孢粉、无脊椎动物和脊椎动物的化石和相关背景数据；使用化石树叶外貌特征和有机化合物的地球化学数据来构建温度、降水和火灾频率的记录；整合与这三个研究区域相关的群落结构和环境条件的生态替代物，以确定是否存在任何气候条件、地理位置或营养相互作用，以加强或阻碍K/PG灭绝后生态系统的重建。此外，还将检查火山活动的地球化学指标，以解决德干圈闭的广泛玄武岩喷发对研究区域内生物群的影响。这一裁决反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

During the Cretaceous/Paleogene (K/Pg) mass extinction (ca. 66 million years ago), ~75% of all species on Earth went extinct, notably including all non-avian dinosaurs. This event completely changed the trajectory of the evolutionary tree of life, leading ultimately to the formation of today’s mammal-dominated communities. The aftermath of the K/Pg mass extinction represents a natural laboratory in which ecosystem reorganization can be studied with high geologic resolution. Some studies have been undertaken to examine how marine ecosystems were rebuilt, but the response of terrestrial environments is poorly documented. This project will examine ecological and environmental changes that occurred on land across the K/Pg boundary in the Rocky Mountain region of the western United States. The research will involve extensive paleontological and geochemical analyses of existing fossil collections and introduce novel data that will reveal the variability in the timing and pattern of terrestrial ecosystem rebuilding after the mass extinction. This project will expand knowledge of a major turning point in the history of life on Earth that will help determine how the biodiversity of ecosystems recover at the continental scale and how modern terrestrial biota evolved. The results may also provide data for conservation biologists to predict the long-term consequences of current rapid changes in biodiversity and help inform conservation priorities to alleviate ecosystem disruptions. The project will use established programs in classrooms, museum exhibits, and outreach at the participating institutions to reach audiences of multiple ages and backgrounds.The K/Pg mass extinction completely changed the trajectory of the evolutionary tree of life and most research has focused on marine systems. Post-extinction patterns of ecosystem restructuring on land, fundamental to understanding the evolution of the modern taxa of mammals and plants, have received little attention because fossil collections, data, and high-resolution chronostratigraphic sections are relatively rare. This project will build on extensive fossil collections from three primary study areas in the Western Interior of North America, involve new fieldwork designed to augment collections and data from critical intervals, and develop diverse inorganic and organic geochemical records to characterize and identify biotic patterns, local environments, and factors involved in terrestrial ecosystem restructuring following the K/Pg extinction. To accomplish these goals, the research team will: collect and interpret megafloral, palynological, invertebrate, and vertebrate fossils and associated contextual data from three well-studied stratigraphic sections; use fossil leaf physiognomic traits and geochemical data from organic compounds to construct records of temperature, precipitation, and fire frequency; integrate ecological proxies of community structure and environmental conditions over time and space as they relate to the three study areas, to determine if there are any climatic conditions, geographic locations, or trophic interactions that enhance or impede ecosystem restructuring after the K/Pg extinction. In addition, geochemical proxies for volcanic activity will be examined to resolve the influence of the extensive basalt eruptions of the Deccan Traps on the biota within the study areas.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.