RUI: The Timing and Evolution of Devonian Fire Systems and Their Implications for Atmospheric Oxygen Concentration

木炭可以保存在岩石记录中，因此它是深时间野火活动的一个很好的指标。已知最早的野火木炭证据可以追溯到大约4.2亿年前，当时没有树木，植物也非常小，像苔藓一样。这些植物的生长和繁殖需要非常潮湿的环境。植物的体积小，对潮湿环境的依赖意味着它们不适合作为野火的燃料来源。然而，在4.2亿至4亿年前的这段时间里，有相当多的遗址保存着木炭，从而成为古代野火的证据。在接下来的3000万年里，很少有木炭被保存下来，这令人惊讶，因为世界各地的植被变得越来越大，越来越不依赖水，因此成为了更好的燃料来源。这项提议旨在调查在4.2 - 3.59亿年前（泥盆纪）沉积的北美岩石，当时缺乏野火的证据。这项研究将评估这种火灾丰度的异常是否真的存在，以及哪些因素可能控制了它，包括大气中的氧气是否太低而无法支持火灾。本科生实习生将参与该项目，并接受与化石木炭研究相关的实地工作和实验室技术培训。在火灾对许多社区的全球影响越来越大的时候，这个项目将为这些本科生提供一个机会，与科学界以及通过在线内容与更广泛的公众分享有关火灾的热门和令人兴奋的结果。初步证据表明，早至中泥盆世全球火灾的发生主要不受燃料的影响，而是受大气氧浓度（pO2）的影响。这个地球系统的主变量被认为深刻地影响了后生动物的进化，但其在深时间的量化是不确定的。本研究旨在通过在北美泥盆纪沉积环境中寻找和分离木炭，并根据沉积环境、分类和岩石学特征对其进行评估，从而验证pO2是该时期火灾发生的主要驱动因素的假设。全面确定早期火情演变将为火情反馈到生物地球化学循环的演变提供新的见解，并将使泥盆纪的pO2模型得到严格的检验。这些数据将共同为地球地球化这一关键时期的环境变化提供基础水平的见解。本科生实习生将参与该项目，并接受与化石木炭研究相关的实地工作和实验室技术培训。这些本科生将在学年期间继续他们的项目，并通过在会议上的演讲和科学出版物上的合作来传播他们的成果。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。

Charcoal can be preserved in the rock record, and so it is an excellent indicator of wildfire activity in deep-time. The earliest known charcoal evidence of wildfires dates from about 420 million years ago when there were no trees and plants were extremely small and moss-like. These plants required very wet environments for growth and reproduction. The small size of plants and their dependence on moist conditions means that they should be a poor source of fuel for wildfires. However, there are a significant number of sites from this time 420-400 million years ago that preserve charcoal and thus evidence of ancient wildfires. There are very few charcoals preserved over the following 30 million years, which is surprising since vegetation around the world became larger and more independent of water and so a better source of fuel for fire. This proposal aims to investigate rocks from North America deposited during the time interval from 420-359 million years ago (the Devonian Period) when evidence of wildfires is lacking. This study will assess whether this anomaly in fire abundance really exists and what factors may have controlled it, including whether oxygen in the atmosphere may have been too low to have supported fires. Undergraduate interns will be engaged in the project and trained in fieldwork and laboratory techniques related to the study of fossil charcoal. At a time when the global impact of fires on many communities is growing, this project will provide these undergraduates an opportunity to share topical and exciting results on fires in deep time with both the scientific community and, through online content, the broader general public. Preliminary evidence indicates that global fire occurrences during the Early to Mid-Devonian were not affected primarily by fuel but rather, flammability was governed by atmospheric oxygen concentration (pO2). This master variable of the Earth system is considered to have profoundly impacted metazoan evolution, but its quantification in deep time is uncertain. This proposal aims to test the hypothesis that pO2 was the primary driver of fire occurrence at this time by seeking and isolating charcoal from a range of North American Devonian-age sedimentary settings and assessing it in terms of sedimentary setting, taxonomy and petrographic characteristics. Comprehensively determining early fire regime evolution will afford new insights into the evolution of fire feedback into biogeochemical cycles and will permit models of pO2 during the Devonian to be critically examined. These data will collectively provide base level insights into environmental change during this key interval in the terrestrialization of Earth. Undergraduate interns will be engaged in the project and trained in fieldwork and laboratory techniques related to the study of fossil charcoal. These undergraduates will continue their projects during the academic year as capstones and disseminate their results through presentations at conferences and through collaboration in scientific publications.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.