CAREER: Developing a Fire Ecology Framework for Soil Bacteria

野火造成了重大的生态和经济混乱。它们在世界许多地区的频率和严重性都在增加，每年烧毁数亿公顷的土地。烧毁的地貌导致生态系统碳和氮的大量损失。土壤中的微生物通过其在养分循环中的作用以及它们与植物的相互作用，在受野火影响的生态系统的恢复中发挥关键作用。野火对植物生命的生态影响在某种程度上是可以理解的。土壤微生物的情况并非如此。NSF这个职业项目的目标是为细菌开发一个火生态框架，以提高对为什么某些细菌是“易燃”的理解--即为什么它们在暴露在火中后茁壮成长。该方法将借鉴对北部森林野火和受控草原燃烧的实地研究、实验室实验和基因测序。从本质上讲，提高我们对细菌对火灾反应的理解将有助于加强我们对火灾和不断变化的火灾制度将如何影响气候这一具有重大社会意义的问题的理解。该项目将通过其与每个研究目标紧密结合的教育目标实现无数更广泛的影响。在整个拨款过程中，本科生将在实验室接受培训，与威斯康星大学-麦迪逊大学本科生研究学者计划合作，该计划将帮助支持女性和代表不足的群体成员全面参与STEM领域。与生命科学传播专业的本科生合作开发的关于火生态的播客，以及一个新的公共外展摊位--《火灾期间地下会发生什么？》--都将有助于提高公众的科学素养，并参与科学和火生态。拟议的研究将建立在PI之前的结果的基础上，以加强和整合对细菌对火的反应的基于特征的理解。最重要的假设是，火灾发生后不久(~1年)，火灾的存续将是最重要的，快速增长将在更长的时间尺度上(~5年)相关，热源有机物的降解将在更长的时间段(~10年)内相关。第一个主题将讨论土壤嗜热细菌的模式和特征。为了确定哪些细菌和遗传特征与燃烧的土壤有关，研究团队将在40个地点的野火现场实验中，在目前的一年和五年时间点上增加一个十年的时间点，最终将成为一项关于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一种基于元基因组学的非靶向方法来表征火灾后的功能潜力。拟议的加强细菌火灾生态框架的方法的一部分在于通过实验研究细菌通过其单独的组成部分(如耐热性)做出的火灾反应。第二个主题集中在温度和干旱对细菌存活和火灾后碳(C)矿化的交互影响。该方法将使用细菌分离、完整的土壤岩心和气体通量跟踪的实验室实验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细菌在高温下的生存，并影响火灾后的碳矿化速率。第三个主题将致力于发展对土壤细菌火生态的综合理解。在这里，研究小组将利用当前和新兴的数据集以及跨领域的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变化方面的相对重要性。研究将比较使细菌成功应对火灾的特征如何与其他生物体中相同的策略相对应(或相反)。总体而言，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角色。本科培训将与博士生和研究技术人员的导师培训相结合，帮助他们成为更好的未来教育工作者。为了帮助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元基因组学教程，向学生提供尖端生物信息学技能。这些教程将与博士后研究员一起开发，博士后研究员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教育和教育者发展。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.