CAREER: Developing a Fire Ecology Framework for Soil Bacteria

野火造成了严重的生态和经济混乱。在世界许多地区，它们的频率和严重程度都在增加，每年烧毁数亿公顷的土地。被烧毁的景观导致生态系统中大量的碳和氮流失。土壤中的微生物通过循环养分和与植物的相互作用，在受野火影响的生态系统的恢复中发挥着关键作用。野火对植物生命的生态影响已有所了解。这与土壤微生物的情况不同。这个NSF CAREER项目的目标是为细菌开发一个火生态学框架，以提高对为什么某些细菌是“嗜火性”的理解——也就是说，为什么它们在接触火后会茁壮成长。该方法将利用对北方森林野火和可控草原大火的实地研究、实验室实验和基因测序。其核心是，提高我们对细菌对火灾反应的理解将有助于我们理解火灾和变化的火灾制度如何影响气候，这是一个具有重大社会意义的问题。该项目将通过其教育目标实现无数更广泛的影响，这些目标与每个研究目标紧密结合。本科生将在整个资助期间在实验室接受培训，与威斯康星大学麦迪逊分校本科生研究学者项目合作，这将有助于支持女性和代表性不足群体成员充分参与STEM领域。一个关于火灾生态学的播客，是与生命科学传播项目的本科生合作开发的，还有一个新的公共宣传摊位，“火灾期间地下发生了什么？”，这将有助于提高公众的科学素养和对科学和火灾生态学的参与。拟议的研究将以PI先前的结果为基础，加强和整合基于特征的对细菌对火反应的理解。总体假设是，火灾生存将在火灾发生后不久（~1年）最相关，快速增长将在较长时间尺度（~5年）相关，而热生有机物降解将在较长时间（~10年）相关。第一个主题将讨论嗜热性土壤细菌的模式和特征。为了确定哪些细菌和遗传特征与燃烧的土壤有关，研究小组将在40个地点的野火现场实验中，在现有的1年和5年的时间点上增加一个10年的时间点，最终将成为对北方森林野火的长期现场研究。此外，研究小组将在多个时间点应用基于非靶向宏基因组学的方法来表征火灾后的功能潜力。加强细菌火灾生态框架的部分建议方法是通过实验研究细菌的火灾反应，通过其单独的组成部分，如耐热性。第二个主题侧重于温度和干旱对细菌存活和火灾后碳(C)矿化的相互作用。该方法将使用分离细菌的实验室实验、完整的土壤岩心和气体通量追踪来确定嗜热细菌可以生存的温度范围，以及先前的干旱胁迫是否会影响高温下的细菌存活，并影响火灾后的C矿化率。第三个主题将旨在发展对土壤细菌的火生态学的综合理解。在这里，研究小组将利用当前和新兴的数据集和跨领域合作来确定不同特征在确定火灾后嗜热细菌随时间和烧伤严重程度的成功方面的相对重要性。研究将比较使细菌成功应对火灾的特征如何对应（或对比）其他生物的等效策略。总的来说，该项目将促进我们对火灾对细菌影响的基本问题的理解，细菌是火灾后生态系统恢复的关键参与者。本科生培训将与博士生和研究技术人员的导师培训相结合，帮助他们自己成为更好的未来教育工作者。为了支持具有全球竞争力的STEM劳动力，PI将为土壤微生物学课程开发新的宏基因组学教程，这将为学生提供尖端的生物信息学技能。这些教程将与博士后研究员一起开发，他还将参加威斯康星大学麦迪逊分校的教学研讨会，进一步帮助改善STEM教育和教育工作者的发展。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。

Wildfires cause major ecological as well as economic disturbances. They are increasing in frequency and severity in many regions of the world and burn hundreds of millions of hectares of land every year. The burned landscape results in large losses of carbon and nitrogen from ecosystems. Microorganisms in the soil play a critical role in the recovery of wildfire-affected ecosystems through their roles in cycling nutrients and their interactions with plants. The ecological impacts of wildfires on plant life are somewhat understood. This is not the case for soil microbes. The goal of this NSF CAREER project is to develop a fire ecology framework for bacteria, to improve understanding of why certain bacteria are “pyrophilous” – i.e., why they thrive following exposure to fire. The approach will draw on field research on northern forest wildfires and controlled prairie burns, laboratory experiments, and genetic sequencing. At its core, improving our understanding of bacterial response to fires will help underpin our understanding of how fires and changing fire regimes will affect the climate, an issue of great societal importance. This project will realize a myriad of broader impacts through its education goals, which are tightly integrated with each research goal. Undergraduates will be trained in the lab throughout the grant, working with the University of Wisconsin-Madison Undergraduate Research Scholars program, which will help support full participation of women and members of underrepresented groups in STEM fields. A podcast about fire ecology, developed in collaboration with undergraduates in the Life Sciences Communication program, and a new public outreach booth, “What happens belowground during a fire?”, will both help increase public scientific literacy and engagement with science and fire ecology.The proposed research will build on the PI’s prior results to strengthen and integrate a trait-based understanding of bacterial responses to fire. The overarching hypothesis is that fire survival will be most relevant shortly after wildfires (~1 year), fast growth will be relevant over longer timescales (~5 years), and pyrogenic organic matter degradation will be relevant over longer periods of time (~10 years). The first theme will address the patterns and traits of pyrophilous soil bacteria. In seeking to determine which bacteria and genetic characteristics are associated with burned soils, the research team will add a ten-year timepoint to a current one- and five-year timepoints in a 40-site wildfire field experiment, building toward what will ultimately become a long-term field study of boreal forest wildfires. In addition, the research team will apply an untargeted metagenomics-based approach at multiple time points to characterizing post-fire functional potential. Part of the proposed approach to strengthening a fire ecology framework for bacteria lies in experimentally investigating bacterial fire response through its separate components, such as heat tolerance. The second theme focuses on the interactive effects of temperature and drought on bacterial survival and post-fire carbon (C) mineralization. The approach will use laboratory experiments with bacterial isolates, intact soil cores, and gas flux tracing to determine the temperature ranges that pyrophilous bacteria can survive and whether prior drought stress affects bacterial survival of high temperatures and influences post-fire C mineralization rates. The third theme will aim to develop an integrative understanding of fire ecology for soil bacteria. Here, the research team will draw on current and emerging datasets and cross-domain collaborations to determine the relative importance of different traits in determining post-fire success of pyrophilous bacteria over time and across burn severities. Studies will compare how the traits that make bacteria successful fire-responders correspond to (or contrast with) equivalent strategies in other organisms. Overall, the project will advance our understanding of fundamental questions about the effects of fire on bacteria – critical players in post-fire ecosystem recovery. Undergraduate training will be coupled with mentorship training for a PhD student and a research technician, helping them become better future educators, themselves. To help support a globally competitive STEM workforce, the PI will develop new metagenomics tutorials for soil microbiology courses, which will provide cutting-edge bioinformatics skills to students. These tutorials will be developed with a postdoctoral researcher, who will also participate in UW-Madison teaching workshops, further helping to improve both STEM education and educator development.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.