Nitrogen fixation and its coupling to methane dynamics in the peat moss (Sphagnum) phytobiome of northern peatlands

泥炭地是一种湿地，它以厚厚的泥炭土沉积物的形式锁住了大量的碳。 被称为“碳银行”，科学家认为，储存在泥炭中的碳有可能因环境变化而释放到大气中。 苔藓通常在泥炭地生态系统的植物生产中占主导地位，泥炭地生态系统集中在北方地区，那里的环境可能变得非常寒冷，营养贫乏。 与人类或其他植物类似，苔藓含有多种微生物组，这些微生物与植物密切相关，处于共生关系，有助于宿主在极端条件下生长和茁壮成长。 植物宿主为微生物组提供了一个稳定的生存环境，反过来，微生物被认为有助于苔藓获得氮和碳等营养物质。 例如，一些微生物将大气中的氮气转化为苔藓植物可以使用的形式。 同样，还有一些微生物也可以帮助苔藓从甲烷（湿地土壤中产生的天然气）转化为二氧化碳中获得碳。这项研究将确定泥炭藓微生物代谢氮和碳的数量和速度，以及对明尼苏达州和加拿大北方泥炭地生态系统中泥炭藓生长和碳储存的影响。 该项目将利用大型全生态系统实验，进一步研究泥炭藓及其组成微生物组对环境变化的反应。 该项目将提供关于微生物组如何帮助泥炭藓植物生长的基础研究，泥炭藓植物可能比地球上任何其他植物储存更多的碳。 该项目的结果将用于改善对泥炭地是否将作为净碳源或汇以应对持续的环境变化的预测，以及植物微生物组作为垃圾填埋场产生的甲烷的天然生物过滤器的潜在用途。这项研究还将通过教授下一代科学家湿地提供的重要生态系统服务以及微生物在维持这些服务中的作用来服务社会。 至少有两名研究生，两名本科生和一名博士后研究员将参与该项目的各个方面。 将利用两项签名活动作为向公众宣传项目成果的手段。 在格鲁吉亚湿地举办的为期5天的研讨会将培训16名初中和高中教师，内容是在保护、恢复和全球环境变化的背景下制定生态系统科学教学教案。项目成果将通过亚特兰大科学节（每年有20 000人参加）的年度互动活动向公众传播。研究的总体目标是调查泥炭藓微生物组在调节泥炭地碳（C）和氮（N）循环以及泥炭地对环境变化的适应力中的作用。 目标是：1）量化固氮和甲烷营养的原位速率，并阐明在泥炭藓微生物组中介导这些过程的关键微生物协会的贡献，2）确定固氮及其与甲烷（CH 4）动力学的耦合对实验室和野外大规模整个生态系统实验中环境变化驱动因素扰动的响应，3）利用两个长期实地调查点的数据，估算微生物对生态系统氮和碳收支的贡献，并模拟微生物功能对环境变化驱动因素扰动的响应。工作假设包括：H1：固氮是北方泥炭地的主要氮输入; H2：主要的固氮菌是甲烷营养菌和蓝细菌; H3：也固定氮的甲烷营养菌代表大量的CH 4汇; H4：泥炭藓类的净初级生产直接由固氮获得的N和甲烷营养产生的C支持; H5：泥炭藓的生产力及其对环境扰动的反应将在很大程度上取决于植物-微生物和微生物-微生物的相互作用; H6：温度和CO2的升高将导致泥炭藓生产力下降，从而导致固氮率降低。该奖项反映了NSF的法定使命，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，

Peatlands are wetlands that lock away huge amounts of carbon as thick peat soil deposits. Referred to as a "carbon bank", scientists believe that the carbon stored in peat is at risk of being released to the atmosphere in response to environmental change. Mosses often dominate plant production in peatland ecosystems, which are concentrated in northern regions where the environment can become extremely cold and is nutrient poor. Similar to humans or to other plants, mosses contain a diverse microbiome, microbes that are intimately associated with the plant in a symbiotic relationship, that help the host to grow and thrive under extreme conditions. The plant host provides the microbiome with a stable environment in which to live and in turn the microbes are believed to help mosses acquire nutrients such as nitrogen and carbon. For example, some microbes convert nitrogen gas from the atmosphere into a form that moss plants can use. Similarly, there are microbes that can also help mosses acquire carbon from the conversion of methane (natural gas produced in wetland soils) to carbon dioxide. This research will determine how much and how fast nitrogen and carbon are metabolized by peat moss microbiomes, as well as the implications for the growth of peat mosses and carbon storage in northern peatland ecosystems in Minnesota and Canada. Taking advantage of a large whole ecosystem experiment, the project will further examine the response of peat mosses and their constituent microbiomes to environmental change. This project will provide fundamental research on how microbiomes aid the growth of peat moss plants, which may store more carbon than any other plant on Earth. Results of the project will be used to improve predictions on whether peatlands will act as a net carbon source or sink in response to ongoing environmental change as well as the potential use of plant microbiomes as a natural biofilter for methane produced in landfills. This research will also serve society by teaching the next generation of scientists about the important ecosystem services that wetlands provide and the role of microbes in maintaining these services. At least two graduate students, two undergraduate students, and a postdoctoral researcher will be involved in all aspects of the project. Two signature activities will be used as instruments to communicate project results to the public. A 5-day workshop in a Georgia wetland will train 16 middle and high school teachers on developing lesson plans for teaching ecosystem science in the context of conservation, restoration, and global environmental change. Project results will be disseminated to the public through an annual interactive activity at the Atlanta Science Festival (which reaches 20,000 people per year).The overall goal of the research is to investigate the role of the peat moss microbiome in regulating peatland carbon (C) and nitrogen (N) cycles and the resilience of peatlands to environmental change. Objectives are to: 1) quantify in situ rates of nitrogen fixation and methanotrophy, and elucidate the contribution of keystone microbial associates mediating these processes in the peat moss microbiome, 2) determine the response of nitrogen fixation and its coupling to methane(CH4) dynamics to perturbation of environmental change drivers in the laboratory and in a large-scale whole ecosystem experiment in the field, and 3) leverage datasets from two long-term field sites to estimate the microbiome contribution to ecosystem N and C budgets as well as model the response of microbiome function to perturbation of environmental change drivers. Working hypotheses include: H1: N fixation is a predominant N input to northern peatlands; H2: The dominant nitrogen fixers are methanotrophic bacteria and cyanobacteria; H3: Methanotrophs that also fix N represent a substantial CH4 sink; H4: Net primary production by peat mosses is directly supported by N acquired from nitrogen fixation and methane-derived C from methanotrophy; H5: Peat moss productivity and its response to environmental perturbations will be largely determined by plant-microbe and microbe-microbe interactions; H6: Increases in temperature and CO2 will result in lower rates of N fixation due to decreased peat moss productivity.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.