Collaborative Research: How does the deep critical zone (CZ) structure impact the hydrology and coupled carbon cycling of northern peatlands?

北部泥炭地是一种独特的湿地类型，发现于美国北部，是高纬度地区的主要地貌，包括加拿大，斯堪的纳维亚半岛北部和俄罗斯。工业发展导致一些泥炭地被排干或焚烧，以促进农业、建筑或用作燃料。今天，泥炭地被认为是一种独特的生态系统，它支持着其他地方没有的各种植物。此外，它们是全球碳循环的重要组成部分，将二氧化碳捕获在有机质中，并储存了土壤中约33%的总碳。泥炭地将其中一些碳以甲烷的形式释放到大气中，甲烷是一种强有力的温室气体。虽然泥炭地的生态学已经得到了很好的研究，但泥炭地发展的地质控制和泥炭地水的渗透模式尚未完全了解。在缅因州（美国），泥炭地开始形成大约1万年前，在最后一个冰河时代结束时，随着冰盖和冰川的消退。它们形成于洼地，通常以湖泊开始，在冰川雕刻的景观中，覆盖着沉积物。这些地形埋在泥炭地之下，但可能在调节水文和向大气中释放甲烷气体方面发挥关键作用。该项目将使用地下地球物理传感方法对这一隐藏的冰川后景观进行成像，以了解它如何调节泥炭地的地下水流动以及甲烷排放的地点/时间。水文观测和深层地下水和泥炭孔隙水流的计算机模拟将与泥炭地甲烷气体排放的直接测量进行比较，以寻找泥炭地水文和碳循环受这一隐藏景观调节的证据。除了促进对北部泥炭地深层临界带水文过程与大气碳通量之间联系的科学认识外，该项目还将为社会带来独特的效益。它将促进多元化劳动力的发展，让代表性不足的学生积极参与，为研究生和本科生提供支持，并与森林管理行业建立协作互动。该项目的目标是评估深层临界带如何在区域尺度上调节泥炭地地貌的水-碳耦合过程。地球物理成像、水文观测和地下水流动和运输的计算模型将在10个泥炭地进行，以探索三种假设（此处简称）：[1]未识别的esker（冰川衍生的沙子和砾石）山脊埋在缅因州众多泥炭地之下；这些（或类似的）渗透性沉积物通过水力将泥炭地孔隙水与下面的地下水含水层连接起来；这种水力连接导致甲烷释放的热点集中在埋藏的渗透性矿床上。探地雷达和频域电磁学将用于阐明这些泥炭地下面的地质框架，并定位埋藏的esker矿床。取心和渗透率测试将约束流量和输送模型，这些模型是在[1]液压头上校准的，用连接到数据记录器的压力传感器记录，并在水样中测量[2]的特定电导。将使用低维护方法（气体圈闭、水分探针阵列）在预测的甲烷热点处估计沸腾通量。来自城市地区的代表性不足的少数民族学生将从事荒野研究经验，重点关注数据采集的各个方面。与林业管理公司的合作确保了进入私人拥有的泥炭地进行研究。将针对当地社区和缅因州编写描述本项目所调查泥炭地过程的信息手册。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。

Northern peatlands are a unique type of wetland found in the northern United States and a dominant landform at higher latitudes, including Canada, northern Scandinavia and Russia. Industrial development has led to some peatlands being drained or burned to promote agriculture, construction or use for fuel. Today, peatlands are recognized as unique ecosystems that support a diverse range of plants not found elsewhere. Furthermore, they are an important part of a global carbon cycle trapping carbon dioxide in organic matter and storing approximately 33% of the total carbon found in soils. Peatlands release some of this carbon to the atmosphere as methane, a potent greenhouse gas. Although the ecology of peatlands is well studied, the geological controls on peatland development and the percolation patterns of peatland water are not completely understood. In Maine (USA), peatlands began forming about 10,000 years ago following the retreat of the ice sheets and glaciers at the end of the last ice age. They formed in depressions, often starting as lakes, within the landscape carved by glaciers and draped with sediments. These landforms lie buried beneath peatlands but may play a key role in regulating both the hydrology and release of methane gasses into the atmosphere. This project will use subsurface geophysical sensing methods to image this hidden post-glacial landscape in order to understand how it regulates groundwater flow in peatlands and where/when methane emissions occur. Hydrological observations and computer simulations of deeper groundwater and peat porewater flow will be compared to direct measurements of methane gas emissions from peatlands in the search for evidence that peatland hydrology and carbon cycling are regulated by this hidden landscape. In addition to advancing scientific understanding of the link between hydrologic processes in the deep critical zone of northern peatlands and carbon fluxes to the atmosphere, this project will bring unique elements of benefit to society. It will contribute to the development of a diverse workforce with a strong engagement of underrepresented students, support graduate and undergraduate students, and build collaborative interactions with the forest management industry.The goal of this project is to evaluate how the deep critical zone regulates coupled water-carbon processes across peatland landforms at a regional scale. Geophysical imaging, hydrological observations and computational modeling of groundwater flow and transport will be performed across 10 peatlands to explore three hypotheses (abbreviated here): [1] Unidentified esker (glacially derived sand and gravel) ridges lie buried beneath numerous Maine peatlands; [2] These (or similar) permeable deposits hydraulically connect peatland pore waters to the underlying groundwater aquifer; and [3] This hydraulic connection results in hotspots of methane release centered on buried permeable mineral deposits. Ground penetrating radar and frequency domain electromagnetics will be used to illuminate the geological framework beneath these peatlands and to locate buried esker deposits. Coring and permeability tests will constrain flow and transport models calibrated on [1] hydraulic heads recorded with pressure transducers connected to data loggers, and [2] specific conductance measured in water samples. Ebullition fluxes will be estimated at predicted methane hotspots using low maintenance methods (gas traps, moisture probe arrays). Underrepresented minority students from urban areas will engage in wilderness research experiences focusing on all aspects of data acquisition. A collaboration with a forestry management company secures access to privately owned peatlands for research. Informational brochures describing peatland processes investigated in this project will be developed targeting the local community and the State of Maine.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.