Doctoral Dissertation Research: Assessing the impacts of Pleistocene megaherbivores on vegetation stability and resilience in the Arctic

大型食草动物通过促进植物生长、多样性和营养循环，在塑造现代北极生态系统方面发挥着重要作用。它们还可以通过减少冻土融化和灌木的扩张来缓冲气候变化对冻土带生态系统的影响。直到大约12,000年前，北极一直是各种食草动物(猛犸象、野牛、野马、驯鹿和麝牛)的家园，共存于一个被称为“猛犸象草原”的环境中。人们认为，这种环境是由大型食草动物维持的，类似于现代的非洲稀树草原。因此，一些人提出，将大型食草动物重新野化可能是北极可行的管理策略。然而，我们对这些生态系统特性在多大程度上依赖于草食动物多样性知之甚少，因为今天很少有高纬度系统支持大量的多种物种。化石记录提供了一个自然档案，记录了大型食草动物和气候变化如何随着时间的推移影响北极植物群落。该项目建立在论文级研究的基础上，研究了阿拉斯加松鼠湖的古生态记录，以了解史前食草动物多样性对北极生态系统长期稳定性的影响，并确定组成冰河时代食草动物群落的物种。该项目通过创建从今天到距今约55,000年的松鼠湖(阿拉斯加Kotzebue Sound)周围动植物多样性的多代理沉积物记录，调查大型食草动物多样性对北极生态系统属性的影响。沉积的古代DNA和放射性碳年代动物遗骸的密度将被用来研究随着时间的推移湖泊周围巨型食草动物和植物多样性的模式。植被、巨型食草动物的存在和古气候的替代物将为重建大型动物的存在和环境变化的年表提供信息。这个数据集将被用来衡量草食动物多样性对生态系统稳定性的不同组成部分(抵抗力、恢复力、恢复力和纬度)的影响，为理解这些动物的影响提供一个量化框架。这项研究将为当前关于重新引入食草动物作为北极生态系统管理工具的辩论提供信息，并提供有关形成巨大草原的过程的数据。这项研究的结果将在Kotzebue Sound地区的公共互动展览中与当地社区分享，并用于构建针对阿拉斯加和缅因州中学生的虚拟现实体验。该奖项反映了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。

Large herbivores play an important role in shaping modern-day Arctic ecosystems by promoting plant growth, diversity, and nutrient cycling. They may also buffer the effects of climate change on tundra ecosystems by reducing permafrost thaw and the expansion of shrubs. Until ~12,000 years ago, the Arctic was home to a diverse array of herbivores (woolly mammoths, bison, wild horses, caribou, and muskoxen) coexisting in an environment called “mammoth steppe.” It is thought that this environment was maintained by large herbivores, similar to modern African savannas. As a result, some have suggested that “rewilding” large herbivores could be a viable management strategy for the Arctic. However, we know little about how much these ecosystem properties rely on herbivore diversity because few high-latitude systems support multiple species in high numbers today. The fossil record provides a natural archive of how large herbivores and climate change influenced Arctic plant communities through time. This project builds on dissertation-level research examining a paleoecological record from Squirrel Lake, Alaska to understand the effect of prehistoric herbivore diversity on the long-term stability of Arctic ecosystems and identify the species that made up the ice age herbivore community. This project investigates the role of large herbivore diversity on Arctic ecosystem properties by creating a multi-proxy sediment record of the plant and animal diversity that surrounded Squirrel Lake (Kotzebue Sound, Alaska) in a period spanning from today to ~55,000 years before present. Sedimentary ancient DNA and density of radiocarbon dated animal remains will be used to investigate patterns of megaherbivore and plant diversity surrounding the lake through time. Proxies for vegetation, megaherbivore presence, and paleoclimates will inform the reconstruction of a chronology of megafaunal presence and environmental change. This dataset will be used to measure the effect of herbivore diversity on different components of ecosystem stability (resistance, resilience, recovery, and latitude), providing a quantitative framework to understand the impacts of these animals. This research will inform the current debate about herbivore reintroductions as a management tool for Arctic ecosystems and contribute data on the processes that shaped the mammoth steppe. The results of this study will be shared with local communities in the Kotzebue Sound area in a public, interactive exhibit, and used to build a virtual reality experience aimed at middle schoolers in Alaska and Maine.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.