Hurricane Harvey Impacts on Local and Landscape Scale Salt Marsh Carbon Storage

沿海湿地储存了全球20%以上的碳，据估计，盐沼是所有沿海湿地中碳埋藏率最高的。像大风暴这样的干扰有可能减少盐沼中的碳储存，降低它们对全球碳循环的总体影响。先前的研究表明，在2005年卡特里娜飓风和丽塔飓风之后，路易斯安那州的盐沼上沉积了大量的沉积物，但对这些影响之前的沼泽状况知之甚少。因此，我们只能推测这些风暴对沉积物碳储存的真正影响。比较风暴前的碳储存和风暴后的储存，使我们能够量化风暴的影响，并在库存信号丢失到下一个事件之前捕获关键数据。该项目将利用调查人员最近（2014年）在2017年8月飓风哈维登陆的两个地点附近对盐沼进行采样的事实。他们将收集新的盐沼沉积物样本，并将其数据与2014年的数据进行比较，以研究风暴通道对这些重要系统的影响。飓风哈维于2017年8月25日以四级风暴强度在德克萨斯州罗克波特登陆，然后向内陆移动并盘旋返回，并于2017年8月30日以热带风暴强度在德克萨斯州亚瑟港以东第二次登陆。这两个主要的风暴登陆与该研究小组于2014年在阿兰萨斯国家野生动物保护区（NWR）和阿纳瓦克NWR进行的盐沼碳埋葬研究的地点相吻合。这些数据提供了一个基线，用以评估最近的大风暴登陆对沼泽增生和碳埋藏的影响。必须尽快返回这些研究地点，以确保这场风暴对这些沼泽地的影响所产生的易腐数据不会因其他气象事件或人为干扰而改变。研究人员假设飓风将沉积物从近海和边缘盐沼重新分布到沼泽平台上，增加了沼泽的海拔，并将有机物作为储存的碳掩埋。本研究的目标是：1）使用2014年基线数据，在局部尺度上量化热带风暴沉积物堆积对两个盐沼碳储量的影响; 2）使用风暴前和风暴后的激光雷达和卫星图像，将这些局部风暴引起的碳变化扩展到景观尺度。为了实现这些目标并保护易腐烂的数据，将于2017年10月16日在阿兰萨斯和阿纳瓦克NWR进行实地工作。将根据地层变化采集四个50 cm岩心（每个地点两个）并进行切片。沉积物的总有机碳、碳-14、铅-210和沉积物的物理性质将被分析（目标1）。将使用麦考利螺旋钻获得整个沼泽的地面实况测量结果，并用于验证飓风后的激光雷达测量结果，这些测量结果将与2014年飓风前的测量结果进行比较（物镜，12）。免费提供的存档和新卫星图像和激光雷达将用于测量沼泽高度和面积的变化（目标2）。该项目将成为一名研究生博士研究的一部分，并将支持一名高年级本科生。

Coastal wetlands store more than 20% of global carbon, and salt marshes are estimated to have the highest carbon burial rates of all coastal wetlands. Disturbances, like large storms, have the potential to reduce the storage of carbon in salt marshes and lower their overall impact on the global carbon cycle. Previous studies have shown that large quantities of sediment were deposited on salt marshes in Louisiana after Hurricanes Katrina and Rita in 2005, but little was known about the state of the marshes before these impacts. Consequently, we can only speculate about the true impact of those storms on sediment carbon storage. Comparing pre-storm carbon storage to post-storm storage immediately (weeks to months) following landfall allows us to quantify the storm impacts and capture critical data before inventory signals are lost to the next event. This project will take advantage of the fact that the investigators have recently (2014) sampled salt marshes near both of the locations where Hurricane Harvey made landfall in August, 2017. They will collect new salt marsh sediment samples and compare their data to 2014 data in order to study the impact of storm passage on these important systems. Hurricane Harvey made landfall as a Category 4 storm at Rockport, TX, on 25 Aug 2017, moved inland, circled back, and made a second landfall as a tropical storm east of Port Arthur, TX, on 30 Aug 2017. These two major storm landfalls coincide with locations of salt marsh carbon burial studies performed in 2014 by this research group at the Aransas National Wildlife Refuge (NWR) and the Anahuac NWR. These data provide a baseline against which to assess the impacts of recent major storm landfalls on marsh accretion and carbon burial. It is imperative to return to these study sites as soon as possible to ensure that the perishable data resulting from the impacts of this storm on these marshes are not altered by other meteorological events or human disturbances. The investigators hypothesize hurricanes redistributed sediments from offshore and within the fringing salt marsh onto the marsh platform, increasing the elevation of the marsh and burying organic matter as stored carbon. The objectives of this research are 1) to quantify the impact of extratropical storm sediment accretion on carbon storage in two salt marshes at the local scale using 2014 baseline data; and 2) to extend these local storm-induced carbon changes to the landscape scale using pre- and post-storm LiDAR and satellite imagery. To address these objectives and preserve the perishable data, field work will take place at the Aransas and Anahuac NWRs during the week of 16 Oct 2017. Four 50 cm cores, two from each site, will be collected and sectioned based on stratigraphic changes. Sediment will be analyzed for total organic carbon, carbon-14, lead-210, and sediment physical properties (Obj. 1). Ground-truth measurements across the marsh will be obtained using a Macaulay auger and used to validate post- hurricane LiDAR measurements, which will be compared to pre-hurricane measurements from 2014 (Obj. 1 & 2). Freely available archived and new satellite imagery and LiDAR will be used to measure changes in marsh height and area (Obj. 2). The project will form part of the doctoral research of a graduate student, and will also support a senior undergraduate student.