Roots, Weathering, and the Terrestrial Phosphorus Cycle of the Late Devonian

晚泥盆世的根源、风化和陆地磷循环

• 批准号: 1850878
• 负责人: Gabriel Filippelli
• 金额: $ 30.54万
• 依托单位: Indiana University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-08-15 至 2025-01-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1850878&HistoricalAwards=false
• 关键词: Roots; Weathering; Terrestrial; Phosphorus; Cycle

For the first 4 billion years of Earth history, the land surface was devoid of biological activity. There were no plants, no forests, no roots, and little to no soil. Then, in a geologic blink of an eye, a whole series of evolutionary advances began on land about 400 million years ago. Plants evolved to make harder, more rigid cell structures, allowing them to reach above their neighbors to catch sunlight and downward with roots to both capture more energy and to develop stabilizing structures. These early roots weathered the crust and formed the first soils on Earth; however, the areal distribution of plants was sparse and early soils were rarely retained. Eventually, in the late Devonian period (roughly 330 million years ago), a forest ecosystem of an ancient fern-like tree, known as Archaeopteris, emerged, and the Earth's surface never lost its forest cover or soils since that time. The development of soil fundamentally changed the way weathering and erosion occurs, as the newly evolved plant acids enhanced the chemical weathering of rock into sediment. The ramifications of this massive transformation of the earth surface have been explored from several fronts, including mass extinctions in the oceans by a weathering pulse and release of phosphorus from land inducing a fertilization effect, similar to the excessive algal growth from fertilizer runoff and the modern Gulf of Mexico Dead Zone. But the scenario of a phosphorus-driven mass extinction in the ocean has never been corroborated at the source?namely using land-based records to see if soil development really did result in a dramatic loss of phosphorus from the landscape, and if so, whether this amount of phosphorus was adequate to drive a global "Dead Zone" in the ocean. Investigators will explore this critical interval by examining nutrient geochemical records stored in ancient lake sediments nearer the weathering sources. This work will involve an international collaboration and will train graduate and undergraduate students in geochemistry, geobiology, and earth history. Additionally, researchers will develop learning exercises for elementary and junior high students to explore the modern environmental issues of the Gulf of Mexico Dead Zone by looking through the lens of past examples of eutrophication. Investigators will quantify what impacts the proliferation and declines of various root-based ecosystems had on soil weathering and terrestrial cycling of the key global nutrient phosphorus. They will additionally examine relationships between carbon/nitrogen/phosphorus, carbon and nitrogen isotopic compositional changes, and geochemical proxies of weathering intensity during these terrestrial evolutionary steps to explore how the emergence of the modern soil systems impacted total soil nutrient and carbon balances. They will constrain terrestrial phosphorus mass balances to provide quantitative estimates of phosphorus export to the oceans, key evidence by which to test extant models of mid-late Devonian episodic oceanic anoxia. Their results will be coupled with complementary work done on palynology and isotope geochemistry by colleagues at the University of Southampton. The overarching hypothesis is that a temporal record of soil phosphorus transformations can be resolved from the sedimentary record of lacustrine systems in the mid-late Devonian. The intellectual merits of this work are to: (1) constrain terrestrial nutrient evolution during the late Devonian in reference to the extant paleobotanical record in a stratigraphic manner (which paleosols, as time-integrated records, do not independently do), (2) explore the potential role of nutrient limitation in driving evolution and extinction during one of the most dynamic transitions in terrestrial weathering and erosion conditions in Earth history, and (3) develop critical input data to constrain ocean reconstructions. Broader impacts include: (1) a significantly greater understanding of terrestrial nutrient dynamics, thus informing the broader geobiological community, (2) advanced training for a PhD student in biogeochemistry and Earth history, (3) facilitating research collaborations between IUPUI and Southampton, and informing several educational endeavors, including targeted class content applications and a science outreach program for 3rd ? 9th grade students with inadequate access to STEM resources at their schools.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.

在地球历史的前40亿年里，陆地表面没有生物活动。没有植物，没有森林，没有根，几乎没有土壤。然后，在地质学的一瞬间，大约4亿年前，一系列的进化进程开始在陆地上进行。植物进化成更坚硬、更刚性的细胞结构，使它们能够到达邻居的上方以捕捉阳光，并向下延伸根部以捕获更多能量并发展稳定的结构。这些早期的根风化了地壳，形成了地球上的第一批土壤;然而，植物的区域分布稀疏，早期的土壤很少被保留下来。最终，在泥盆纪晚期（大约3.3亿年前），一种古老的蕨类植物，被称为古羊齿树的森林生态系统出现了，从那时起，地球表面从未失去过森林覆盖或土壤。土壤的发展从根本上改变了风化和侵蚀发生的方式，因为新进化的植物酸增强了岩石的化学风化作用，使其成为沉积物。地球表面的这种巨大变化的后果已经从几个方面进行了探索，包括风化脉冲引起的海洋大规模破坏，以及从陆地释放的磷引起的施肥效应，类似于肥料径流和现代墨西哥湾死区的藻类过度生长。但是，磷驱动的海洋大规模灭绝的情景从未在源头得到证实？也就是说，利用陆地记录来观察土壤的发展是否真的导致了景观中磷的急剧流失，如果是的话，这些磷的数量是否足以在海洋中形成一个全球性的“死亡区”。研究人员将通过检查储存在靠近风化源的古湖泊沉积物中的营养元素地球化学记录来探索这一关键区间。这项工作将涉及国际合作，并将培养研究生和本科生在地球化学，地球生物学和地球历史。此外，研究人员将为小学和初中学生开发学习练习，通过观察过去富营养化例子的透镜，探索墨西哥湾死区的现代环境问题。研究人员将量化各种基于根系的生态系统的增殖和衰退对土壤风化和关键的全球营养磷的陆地循环的影响。他们还将研究碳/氮/磷，碳和氮同位素组成变化之间的关系，以及这些陆地演化步骤中风化强度的地球化学代理，以探索现代土壤系统的出现如何影响土壤总养分和碳平衡。他们将限制陆地磷质量平衡，提供定量估计磷出口到海洋，关键证据，以测试现存的模型中晚泥盆世情节海洋缺氧。他们的研究结果将与南安普顿大学同事在孢粉学和同位素地球化学方面所做的补充工作相结合。总体假设是，土壤磷转化的时间记录可以从中晚泥盆世的湖泊系统的沉积记录解决。这项工作的智力价值是：（1）参照现存的古植物记录，以地层学的方式限制晚泥盆世期间陆地营养盐的演化（古土壤作为时间综合记录，并不独立地这样做），（二）探索在陆地风化和侵蚀条件最动态的转变过程中，营养限制在推动进化和灭绝方面的潜在作用，地球历史，（3）开发关键输入数据，以约束海洋重建。更广泛的影响包括：（1）陆地营养动态的显着更好的理解，从而通知更广泛的地球生物学社区，（2）在地球化学和地球历史博士生的高级培训，（3）促进IUPUI和南安普顿之间的研究合作，并通知几个教育工作，包括有针对性的课程内容应用程序和第三届科学推广计划？该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

项目成果

Enhanced terrestrial nutrient release during the Devonian emergence and expansion of forests: Evidence from lacustrine phosphorus and geochemical records

泥盆纪森林出现和扩张期间陆地养分释放增强：来自湖相磷和地球化学记录的证据

• DOI: 10.1130/b36384.1
• 发表时间: 2022
• 期刊: GSA Bulletin
• 作者: Smart, Matthew S.;Filippelli, Gabriel;Gilhooly III, William P.;Marshall, John E.A.;Whiteside, Jessica H.
• 通讯作者: Whiteside, Jessica H.