Collaborative Research: RUI: Human alteration of sediment delivery to the coast - Legacies of land use, coastal wetland accretion and future vulnerability to sea level rise

合作研究：RUI：人类对海岸沉积物输送的改变——土地利用的遗留问题、沿海湿地增生和未来对海平面上升的脆弱性

• 批准号: 1457435
• 负责人: Scott Neubauer
• 金额: $ 7.09万
• 依托单位: Virginia Commonwealth University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-01 至 2019-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1457435&HistoricalAwards=false
• 关键词: Collaborative; Research; RUI; Human; alteration

Tidal marshes are productive ecosystems that provide key services to society such as storm surge buffering, and water-quality mitigation. The long-term stability of coastal wetlands is explained by interactions between sea level, plant growth, sediment supply, and wetland accretion, but coastal wetland stability is threatened by changes in environmental conditions. Sediment supply has been implicated as the ultimate control on potential vertical accretion rates in many tidal wetlands and, hence, their ability to keep pace with sea level. Human activities in watersheds have significantly altered the delivery of sediment from watersheds to the coast, and indeed there is evidence of past expansion of tidal wetlands in response to increased sediment supply. However, more recent land use change, reforestation, and dam construction have reduced sediment delivery from many watersheds to the coast. The goal of this project is to understand how past and current land use in watersheds that drain to the East Coast of the United States has altered sediment concentrations in rivers, to determine how changes in sediment supply influences sediment accumulation rates in coastal wetlands, and to project future wetland vulnerability along the East Coast under various scenarios of sea level rise and sediment supply. This information is critically needed, and will be of use to researchers, managers, and stakeholders. This collaborative project includes a strong commitment to integrate research and undergraduate education and increase diversity in the sciences. The lead institution on this project serves primarily undergraduate students, and undergraduate student summer interns and academic year thesis research students will be involved in all aspects of the project. This project takes the novel approach of documenting temporally-variable wetland accretion rates over the past century to evaluate changing watershed-derived sediment supply in nine estuaries along the East Coast of the United States. Land use change over the same time period will be examined in these watersheds to determine the major drivers of changing sediment supply. The investigators will test the following hypotheses: H1. Suspended sediment concentrations (SSCs) have decreased in many (but not all) rivers draining to the East Coast in recent decades due to increased population densities, shifts away from agricultural land-use, and dam construction in watersheds, H2. Recent declines in fluvial SSC are reflected in lower wetland mineral accretion rates in many coastal estuarine wetlands. Geographic patterns of recent accretion rates reflect regional patterns of sediment decline, with the greatest reductions in mid-Atlantic wetlands, H3. Sediment deposition and marsh accretion will be greater in the plots with higher SSC availability and with plant trapping of SSCs. Further, due to complex ecogeomorphic feedbacks between marsh elevation, sediment deposition, and plant production, plant productivity will respond to SSC availability, and H4. Coastal wetland vulnerability to current sea level rise follows a regional pattern that reflects both the rate of relative sea level rise (highest in mid-Atlantic) and SSC (lowest in Northeast and Southeast). However, changing SSC and mineral accretion rates (greatest declines in mid-Atlantic) will alter future regional patterns of vulnerability to sea level rise. The researchers will use innovative experiments to manipulate suspended sediment concentrations in water flooding a marsh over several years in a sediment-poor marsh system to directly evaluate rates of sediment deposition, plant growth, and marsh elevation, yielding empirical evidence for the role of sediment availability on ecogeomorphic feedback processes in marshes. These data will be used to validate, parameterize, and expand an existing model (the Marsh Equilibrium Model). The model will then be used to hindcast marsh accretion rates and to forecast marsh stability under various future scenarios of sediment availability and rates of relative sea level rise. The land use change and fluvial sediment supply analyses will be coupled with measurements of temporally-variable marsh accretion rates and modeling to provide a comprehensive examination of estuarine wetland vulnerability to sea level rise. This research will provide integrated assessment of estuarine marsh response to both sea level rise and sediment availability.

潮汐沼泽是富有成效的生态系统，为社会提供关键服务，例如风暴潮缓冲和水质缓解。沿海湿地的长期稳定性可以通过海平面、植物生长、沉积物供应和湿地增生之间的相互作用来解释，但沿海湿地的稳定性受到环境条件变化的威胁。沉积物供应被认为是对许多潮汐湿地潜在垂直吸积率的最终控制，因此也是对它们与海平面保持同步的能力的最终控制。流域中的人类活动显着改变了沉积物从流域到海岸的输送，而且确实有证据表明，潮汐湿地过去因沉积物供应增加而扩大。然而，最近的土地利用变化、重新造林和水坝建设减少了从许多流域到海岸的沉积物输送。该项目的目标是了解流向美国东海岸的流域过去和现在的土地利用如何改变河流中的沉积物浓度，确定沉积物供应的变化如何影响沿海湿地的沉积物积累率，并预测东海岸在各种海平面上升和沉积物供应情况下未来湿地的脆弱性。这些信息是迫切需要的，并且将对研究人员、管理人员和利益相关者有用。该合作项目包括对整合研究和本科教育以及增加科学多样性的坚定承诺。该项目的牵头机构主要服务于本科生，本科生暑期实习生和学年论文研究生将参与该项目的各个方面。该项目采用记录过去一个世纪随时间变化的湿地增生率的新颖方法来评估美国东海岸九个河口流域沉积物供应的变化。将在这些流域检查同一时期的土地利用变化，以确定沉积物供应变化的主要驱动因素。调查人员将检验以下假设：H1。近几十年来，由于人口密度增加、农业用地转移以及流域水坝建设，许多（但不是全部）流向东海岸的河流的悬浮沉积物浓度（SSC）有所下降，H2。最近河流SSC 的下降反映在许多沿海河口湿地湿地矿物沉积率的降低。最近沉积率的地理模式反映了沉积物减少的区域模式，其中大西洋中部湿地（H3）减少幅度最大。在具有较高SSC 可用性和植物捕获SSC 的地块中，沉积物沉积和沼泽增生将会更大。此外，由于沼泽海拔、沉积物沉积和植物生产之间复杂的生态地貌反馈，植物生产力将对 SSC 可用性和 H4 做出反应。沿海湿地对当前海平面上升的脆弱性遵循区域模式，该模式反映了相对海平面上升率（大西洋中部最高）和南海平面上升率（东北部和东南部最低）。然而，变化的南南海和矿物增生率（大西洋中部下降幅度最大）将改变未来区域对海平面上升的脆弱性模式。 研究人员将利用创新实验，在缺乏沉积物的沼泽系统中操纵几年来淹没沼泽的悬浮沉积物浓度，以直接评估沉积物沉积率、植物生长和沼泽海拔，从而为沉积物可用性对沼泽生态地貌反馈过程的作用提供经验证据。这些数据将用于验证、参数化和扩展现有模型（马什均衡模型）。然后，该模型将用于事后预测沼泽增生率，并预测未来各种沉积物可用性和相对海平面上升率情景下的沼泽稳定性。土地利用变化和河流沉积物供应分析将与时变沼泽增生率的测量和建模相结合，以全面检查河口湿地对海平面上升的脆弱性。这项研究将对河口沼泽对海平面上升和沉积物可用性的响应进行综合评估。