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，因此它是野火活动的一个很好的指示器。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，植物非常小，像苔藓一样。这些植物需要非常潮湿的环境才能生长和繁殖。植物的小尺寸和它们对潮湿条件的依赖意味着它们应该是野火的不良燃料来源。然而，有相当数量的遗址从这个时候4.2亿至4亿年前，保存木炭，因此证据的古代野火。在接下来的3000万年里，几乎没有木炭被保存下来，这是令人惊讶的，因为世界各地的植被变得更大，更不依赖于水，因此成为更好的燃料来源。该提案旨在调查北美在4.2亿至3.59亿年前（泥盆纪）沉积的岩石，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，以及可能控制它的因素，包括大气中的氧气是否太低而无法支持火灾。本科实习生将参与该项目，并接受与化石木炭研究有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日益增长的时候，这个项目将为这些本科生提供一个机会，与科学界和更广泛的公众分享火灾的热门和令人兴奋的结果。初步证据表明，在泥盆纪早期至中期的全球火灾事件并不主要受燃料的影响，而是由大气中的氧浓度（pO2）的易燃性。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。该提案旨在通过从一系列北美泥盆纪沉积环境中寻找和分离木炭，并根据沉积环境、分类学和岩相学特征对其进行评估，来检验pO2是火灾发生的主要驱动因素这一假设。全面确定早期火灾制度的演变将提供新的见解火反馈到地球化学循环的演变，并允许模型的pO2在泥盆纪进行严格审查。这些数据将共同提供对地球陆地化这一关键时期环境变化的基本见解。本科实习生将参与该项目，并接受与化石木炭研究有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作为顶点，并通过在会议上的演讲和通过科学出版物的合作传播他们的成果。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。

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.