NSF Award
2420261
Modern Earth is covered by lush tropical forests, extensive grasslands, and soaring redwoods—in striking contrast to landscapes through much of Earth’s early history that consisted largely of bare rock and microbial mats. Plants have dramatically altered Earth’s landscape and climate (like the shapes of rivers and patterns of rainfall). However, there is currently little consensus on how the development of plants, starting with the first ground-hugging mosses and liverworts around 470 million years ago, followed by the eventual rise of trees around 380 million years ago, affected nutrient and oxygen levels both on land and in the oceans. This research combines field, laboratory, and modeling approaches to examine the effects of early land plants on the Earth system. This study focuses on the Canadian Arctic Archipelago which contains some of the best-preserved sedimentary rocks chronicling this key time period of early plant evolution. The team of researchers are studying fossil plants, pollen, and spores and geochemical elements to understand how weathering changed on land, how plant material was delivered to the ocean, how the availability of critical nutrients like phosphorus changed on the land and in the oceans, and how oxygen and sulfur levels changed in the ocean. The broader impacts activities stemming from the research include educational and mentorship opportunities for students in middle-school through graduate school. Graduate students will be co-mentored by the Principal Investigators, and undergraduates will also be recruited to analyze collected samples. The Yale Peabody Museum and the Yale Pathways to Science program will provide platforms for community-oriented outreach efforts, including educational events fostering scientific literacy and engagement in local middle-school students of diverse racial, gender and socioeconomic backgrounds. The team will also take advantage of the unique opportunity provided by recent Peabody renovations to develop a new public-facing exhibit on “Ecosystem Engineering” focused on land plants and their impacts on Earth’s landscapes and ecosystems. The University of California, Riverside’s Camp Highlander program is fostering local high-school student engagement with Earth sciences. Finally, field-conducted telepresence outreach through the new “Annals of the Arctic” program, integrated with existing summer programs at Stanford, Yale, and UCR, will provide public-facing exposure to day-by-day realities of geologic fieldwork in remote terrains. This will increase the accessibility of geologic research and provide a venue for direct illustration of geologic concepts, human experiences of the dynamic nature of polar ecosystems, and their vulnerability to ongoing environmental change.<br/><br/>Reconstructing the biotic, biogeochemical and climatic impacts of the evolution of land plants has been hampered by the commonly fragmentary and disassociated records of geochemical and paleontological change across the lower-middle Paleozoic transition, and by the limited integration of empirical observations with the mechanistic framework that can be provided by biogeochemical and Earth-system models. To address these fundamental questions, we are generating new, high-resolution field-based geochemical data (biomarker, programmed pyrolysis, carbon isotope, lithium isotope, osmium isotope, phosphorus speciation and phosphate-oxygen isotope, iron speciation, and trace metal abundances) and sedimentological and paleontological (plant body fossils, palynomorphs, graptolite and conodont biostratigraphy) records from key sections in the Canadian Arctic to reconstruct first-order ecological and environmental changes—in both continental and marine settings—concurrent with the radiation of early land plants. The Silurian–Devonian transition is an under-characterized but key interval for both land plant evolution and marine redox state, and these data will be integrated with long-term records to distinguish perturbations from more permanent state shifts. These new empirical records will be coupled to biogeochemical modeling over a range of scales—from local critical zone and seafloor diagenetic processes to continental climate and ocean and atmospheric carbon-oxygen cycle modeling—to develop a more robust process-based understanding of plant-biogeochemical feedbacks and reconstruct the long-term consequences of early land plant evolution for the broader Earth system.<br/><br/>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.
