Collaborative Research: Microbial processes and carbon transformation in the thawing permafrost

合作研究：融化的永久冻土中的微生物过程和碳转化

• 批准号: 2029585
• 负责人: Robert Spencer
• 金额: $ 9.97万
• 依托单位: Florida State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-07-01 至 2025-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2029585&HistoricalAwards=false
• 关键词: Collaborative; Research; Microbial; processes; carbon

As a result of global warming, arctic ecosystems have reached a ‘new normal’ characterized by the loss of sea ice, retreating glaciers, and the beginning of widespread permafrost thaw. Permafrost (i.e., permanently frozen soil) contains an enormous amount of carbon, much of it in the form of detrital plant material. Subzero temperatures have protected this plant-derived carbon from microbial decomposition. Warming thaw removes this protection, exposing permafrost carbon to the action of microbial communities that will degrade it and ‘breathe’ globally significant amounts of carbon dioxide and methane (greenhouse gases) into the atmosphere. This release of permafrost carbon into the atmosphere could lead to even faster and greater climate change. Details of how this will play out are not well understood. The goal of this research is to understand how microbial communities function and degrade carbon during permafrost thaw. To achieve this goal, thaw will be simulated by transplanting permafrost into soil that overlays the permafrost and thaws annually during the summer months. Samples will be harvested at multiple time scales (weeks, months, and years). Microbial communities and soil carbon chemistry will be evaluated before and after transplantation to determine how communities change, function, and degrade carbon during thaw. The knowledge that will be generated by this research project is critically important to understanding how greenhouse gas production from thawing permafrost will contribute to future climate change. In addition to training a graduate student and postdoctoral researcher the project will also implement a novel "adopt a microbe" program as part of an undergraduate lab course. Estimates are that permafrost contains 25-50% of the total global soil carbon pool. As a result of global warming, up to 40% of northern latitude permafrost may disappear due to thaw by the end of the century. Permafrost thaw will unlock previously frozen carbon making it amenable to microbial community decomposition. Millennia-old organic matter will get converted to CO2 and CH4. The resulting production of globally significant quantities of CO2 and CH4 is likely to cause a positive feedback loop amplifying the effects of climate change. The overarching goal of this research is to more precisely determine the magnitude of this microbe-mediated feedback loop through understanding the rules governing microbial community composition, function, and carbon turnover in the thawing permafrost. To address this a series of novel, in situ thaw experiments will be performed. Permafrost of different ages (from the Holocene and Pleistocene) will be transplanted into the active layer (soil overlaying the permafrost that freezes and thaws annually) to simulate thaw. Prior to transplantation, soils will be sterilized and then inoculated with microbial communities from the active layer, from permafrost of different ages, or from a combination of communities and then sampled at different time intervals. Community structure, (taxonomic marker genes), functional potential (metagenomes), function (metatranscriptomes), and soil chemistry (FT-ICR MS, physicochemical measurements) will be evaluated. The outcome of this research will be an integrated conceptual model that relates community assembly and function to carbon turnover during thaw at multiple time scales. The project will include training in microbial ecosystem ecology research at the undergraduate, graduate and postdoctoral levels.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.

由于全球变暖，北极生态系统已达到“新常态”，其特征是海冰消失、冰川后退以及大面积永久冻土（即永久冻土）开始融化，其中含有大量碳。其中大部分以碎屑植物材料的形式存在，零下的温度保护了这种植物来源的碳免遭微生物分解，而变暖的解冻消除了这种保护作用，即永久冻土碳。微生物群落的作用将使其降解，并将全球大量的二氧化碳和甲烷（温室气体）“吸入”到大气中，这种向大气中释放永久冻土碳的现象可能会导致更快、更严重的气候变化。这项研究的目的是了解微生物群落在永久冻土融化过程中如何发挥作用并降解碳。为了实现这一目标，将通过将永久冻土移植到土壤中来模拟融化。每年夏季覆盖永久冻土和融化，将在多个时间尺度（周、月和年）采集样本，在移植之前和之后对微生物群落和土壤碳化学进行评估，以确定群落的变化、功能和作用。除了培训研究生和博士后研究员之外，该研究项目将产生的知识对于了解永久冻土融化产生的温室气体如何影响未来的气候变化至关重要。该项目还将实施一项新颖的“采用微生物”计划，作为本科生实验室课程的一部分。据估计，由于全球变暖，永久冻土占全球土壤碳库的 25-50%。到本世纪末，纬度永久冻土可能会因融化而消失，从而释放出先前冻结的碳，使其适合微生物群落的分解。由此产生的全球大量二氧化碳和甲烷可能会导致正反馈循环，从而放大气候变化的影响。这项研究的首要目标是更准确地确定这种微生物介导的反馈的程度。为了解决这个问题，我们将进行一系列不同年龄（全新世和新世）的原位永久冻土实验。更新世）将被移植到活动层（覆盖每年冻结和融化的永久冻土层的土壤）以模拟解冻。在移植之前，土壤将被消毒，然后接种来自活动层、不同年龄的永久冻土层的微生物群落。来自群落的组合，然后在不同的时间间隔采样群落结构、（分类标记基因）、功能潜力（宏基因组）、功能。 （元转录组）和土壤化学（FT-ICR MS，物理化学测量）将得到评估，该研究的结果将是一个综合概念模型，该模型将多个时间尺度的解冻过程中的群落组装和功能与碳周转联系起来。包括本科生、研究生和博士后级别的微生物生态系统生态学研究培训。该奖项反映了 NSF 的法定使命，并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，被认为值得支持。