Cells to ecosystems: fossil xylem is the missing link in reconstructing water use by plants, forests, and global vegetation in deep time

植物群落通过移动和变化来响应气候变化，但目前的预测缺乏植物功能与环境变化之间的机制联系。植物群落的反应在化石记录中被反复观察到，并且可以通过测量植物化石的特征来帮助预测未来的变化。很多研究都集中在研究树叶对环境条件的反应和记录方式上。然而，叶子依赖于长寿命的器官，如茎，来维持植物的功能。本研究将为了解植物群落对古代气候变化主要时期的响应提供新的木质部特征数据库。更广泛地说，该项目将为这项高度跨学科的工作培养新一代地球科学家，并通过创建古生物学和生态系统建模短期课程，对古生物学中代表性不足的群体进行培训和指导，扩大他们对研究的参与。本项目的重点是评估古生代和中生代植物木质部中的水分运输，作为一种适应，影响了两个主要气候变化时期的生存：石炭纪-二叠纪的晚古生代冰期（~3亿年前[Ma]）和三叠纪-侏罗纪的温室气候（~200 Ma）。本项目将集中在三个方面：(1)建立统一的木质部化石功能解剖数据库，以促进(2)预测灭绝类群的水力性状；(3)利用改进的生态系统过程模型（Paleo-BGC）整合化石观察的叶片和木质部性状，预测整个植物的功能。研究人员将使用这种方法来评估在极端全球气候变化时期灭绝的植物的水分胁迫和生态系统功能，并验证在全球变冷和变暖事件中，在植物崩溃和恢复期间，叶和茎水分运输特征的协调将分类群区分为伤亡、幸存者和繁荣者的假设。该项目通过为本科生、研究生和博士后提供培训和指导机会，优先培养新一代跨学科地球科学家。此外，将为未被充分代表和早期职业科学家开设一门短期课程，重点关注古植物学、植物生理学和气候变化之间的联系。课程前和课程后的总结性评估将被应用，目的是改善未来的课程迭代，向目标受众提供以气候变化为重点的跨学科地球科学。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Plant communities respond to climate change by moving and changing, but current predictions lack mechanistic connections between plant function and environmental change. Plant community responses are observed repeatedly in the fossil record, and could help predict future changes by measuring traits from plant fossils. Much effort has focused on the ways that leaves respond to and record environmental conditions. However, leaves depend on long-lived organs, such as stems, to enable plant function. This study will establish a new database dedicated to plant stem traits from fossil xylem to understand plant community responses to major intervals of ancient climate change. More broadly, this project will prepare a new generation of Earth scientists for this highly interdisciplinary work and expand participation in research through training and mentoring targeted towards underrepresented groups in paleontology through the creation of a paleontology and ecosystem modeling short course. This project is focused on assessing water transport in the xylem of Paleozoic and Mesozoic plants as an adaptation that influenced survivorship across two major intervals of climate change: the Late Paleozoic Ice Age of the Carboniferous-Permian (~300 million years ago [Ma]) and the hothouse climate of the Triassic-Jurassic (~200 Ma). This project will focus on three specific aims: (1) establish a unified xylem fossil functional anatomy database to facilitate (2) prediction of hydraulic traits for extinct taxa and (3) integration of fossil-observed leaf and xylem traits to predict whole-plant function using a modified ecosystem process model (Paleo-BGC). Investigators will use this approach to assess extinct plant water stress and ecosystem function through periods of extreme global climate change and test the hypothesis that coordination of leaf and stem water transport traits distinguished taxa as casualties, survivors, and thrivers during floral collapse and recovery during both global cooling and warming events. This project prioritizes training a new generation of interdisciplinary Earth scientists through training and mentoring opportunities for undergraduate, graduate, and postdoctoral scholars. Additionally, a short course for underrepresented and early career scientists focused on linking paleobotany, plant physiology, and climate change will be created. Pre- and post-course summative evaluations will be applied with an aim to improve future course iterations’ delivery of climate-change-focused interdisciplinary geoscience to the target audience.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.