CAREER: A research foundation to improve understanding of the post-thaw permafrost microbiome via collaboration networks and experiential learning

北极的变暖速度比地球上其他地方快四倍，导致北极许多地区的永久冻土融化。永久冻土层位于北半球大约四分之一的陆地表面之下，含有与整个大气一样多的碳（以未分解的有机物质的形式储存）。当永久冻土融化时，微生物（如真菌和细菌）分解并将这种有机物质转化为二氧化碳和甲烷，这是我们大气中最重要的两种温室气体。这种机制被称为积极的气候反馈，因为永久冻土变暖会使大气中二氧化碳和甲烷的浓度更高，从而进一步提高大气温度。这种永久冻土-气候反馈是最不为人所知的全球气候反馈之一，部分原因是我们对永久冻土微生物群落缺乏了解。关于永久冻土融化如何影响微生物群落或微生物组的数据有限，包括永久冻土融化后支撑微生物群落组成的生态过程。新的证据表明，微生物群落不仅受其生存环境的影响，而且随机的机会或巧合也决定了在任何给定时间存在哪些微生物。巧合的程度影响了我们预测微生物群及其功能的能力。所提出的工作将加深对形成解冻后土壤微生物组成和活动的生态过程的理解。与此同时，该项目将培养下一代极地研究人员（博士后、研究生和本科生），并建立一个永久冻土微生物学家网络，以解决微生物在永久冻土气候反馈中的作用问题。由于北极气候变暖的扩大，冻土景观正在迅速变化，拟议的工作将提高人们对冻土景观中解冻后微生物群动态的了解。这项工作的目标是通过一系列高度综合的研究、教育和更广泛的影响活动来解决这一知识差距。具体而言，该项目将(1)合成全球永久冻土解冻后微生物群的公开可用和尚未发表的DNA序列数据；(2)采用野外采样方法，利用生态模型评估解冻后微生物组组成随空间、时间和干扰强度变化的随机性贡献；(3)在多个生态轴高度控制的实验室孵育中测试解冻后微生物组的组装机制；(4)通过培养一名博士后研究员、一名博士生、一名本科生和研究生，使下一代北极学者和/或自然资源管理者具备在科学研究、网络和协作以及科学传播方面取得卓越成就所需的技能；(5)建立一个专业的冻土微生物生态学家网络，以阐明冻土和解冻后微生物群落的复杂未知；(6)支持继续开展使极地和生物地球科学更加多样化和包容性的工作。总之，这些活动将有助于增进对永久冻土-气候反馈的理解，这将指导规划和政策。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。

The Arctic is warming about four times faster than elsewhere on Earth, resulting in thaw of permafrost—permanently frozen soil underlying many Arctic landscapes. Permafrost occurs under approximately one fourth of the northern hemisphere's land surface and contains as much carbon (stored as undecomposed organic material) as the entire atmosphere. When permafrost thaws, microorganisms (such as fungi and bacteria) decompose and convert this organic material to carbon dioxide and methane, two of the most important greenhouse gases in our atmosphere. This mechanism is referred to as positive climate feedback because the warming of permafrost generates higher concentrations of carbon dioxide and methane in the atmosphere which increases atmospheric temperatures even further. This permafrost–climate feedback is one of the least well-understood global climate feedbacks, partially due to our lack of understanding of permafrost microbial communities. There is limited data about how permafrost thaw affects the microbial community—or microbiome—including the ecological processes underpinning the composition of the microbial community after permafrost thaws. New evidence shows that microbial communities are not only shaped by the environment in which they live, but that random chance—or coincidence—also determines which microbes are present at any given time. The degree of coincidence influences our ability to predict microbiomes and their functions. The proposed work will deepen the understanding of the ecological processes that are shaping the post-thaw composition and activity of soil microorganisms. At the same time this project will train the next generation of polar researchers (at the postdoctoral, graduate, and undergraduate levels) and build a network of permafrost microbiologists able to address questions about the role of microorganisms in the permafrost–climate feedback. The proposed work will improve understanding of the poorly known dynamics of post-thaw microbiomes in permafrost landscapes, which are rapidly changing due to the amplification of Arctic climate warming. The goal of the work is to address this knowledge gap through a series of heavily integrated research, education, and broader impacts activities. Specifically, this project will (1) synthesize publicly available and as-yet-unpublished DNA sequence data on post-thaw microbiomes from permafrost across the globe; (2) use ecological modeling to assess the contribution of stochasticity to the post-thaw microbiome composition over space, time, and disturbance intensity using a field sampling approach; (3) test mechanisms of assembly in post-thaw microbiomes in highly controlled laboratory incubations performed across many ecological axes; (4) equip the next generation of Arctic scholars and/or natural resource managers with the skills necessary to excel in scientific research, networking and collaboration, and science communication by training a postdoctoral researcher, a PhD student, and undergraduate and graduate students; (5) develop a professional network of permafrost microbial ecologists to elucidate the complex unknowns of permafrost and post-thaw microbiomes; and (6) support efforts to continue work in making polar and biogeosciences more diverse and inclusive. Together, these activities will contribute to enhanced understanding of the permafrost–climate feedback, which will guide planning and policy.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.