LTREB-Renewal: Twenty-Nine Years of Tidal Marsh Response to Environmental Change

美国正在迅速失去沿海湿地，这是滋养渔业、清洁水和保护我们免受风暴影响的重要生态系统。虽然有些沼泽的丧失是沿海开发造成的，但其他沼泽的丧失尚待充分解释。沼泽地可以垂直地建造土壤，并获得海拔，以跟上缓慢上升的海平面，但当海平面上升过快时，维持这些生态系统的沼泽植物会受到压力。沼泽地所能承受的海平面高度取决于其他也在变化的因素。例如，大气中的二氧化碳含量正在上升。同样，氮等营养物质的污染也比前工业时代急剧增加。增加的二氧化碳和氮都倾向于使沼泽植物生长得更多，这可以帮助沼泽跟上海平面上升的步伐。但它们也改变了生长的植物类型，目前还不知道这将对沼泽地产生什么影响。这个项目的问题是：二氧化碳和氮的上升将如何影响植物和沿海沼泽地的能力，以跟上海平面上升？由于大约一半的美国人口居住在海岸线50英里以内，沿海湿地及其提供的服务面临相当大的压力。低洼沿海湿地每年流失到开阔水域，威胁着渔业、野生动物栖息地、水质和基础设施。该项目还将继续在多个层面上开展公共教育和科学教育项目，研究结果将在史密森学会的公共网站上免费提供。为了解决这个项目的核心问题，这项研究建立在马里兰州的切萨皮克湾沼泽30年的生态观测历史。初级生产和土壤化学的测量将与平行实验相结合，通过向沼泽地添加二氧化碳和氮来模拟未来的环境，并将本地植物与入侵植物进行比较。这个地点的长期记录使科学家能够记录沼泽地上生长的植物物种组成随时间的变化。在这一点上，沼泽土壤的表面高程落后于当地海平面上升，这表明这片沼泽可能正在崩溃。调查人员将继续进行当地的测量，但结果应该普遍适用于各地的沿海湿地。

The United States is rapidly losing coastal wetlands, critical ecosystems that nourish fisheries, clean our water and protect us from storms. While some marsh losses result from coastal development, others losses have yet to be fully explained. Marshes can build soil vertically and gain elevation to keep pace with slowly rising seas, but the marsh plants that sustain these ecosystems get stressed when sea level rises too quickly. The amount of sea level a marsh can tolerate depends on other factors that are also changing. For instance, the amount of carbon dioxide in the atmosphere is rising. Likewise, pollution from nutrients like nitrogen has increased sharply from preindustrial times. Both increased carbon dioxide and nitrogen tend to make marsh plants grow more, which could help marshes keep up with sea level rise. But they also change the types of plants that grow and it is unknown what effects that will have on marshes. This project asks: how will rising carbon dioxide and nitrogen affect plants and the ability of coastal marshes to keep up with sea level rise? Since about half of the U.S. population lives within 50 miles of a coastline, there is considerable pressure on coastal wetlands and the services they provide. The annual loss of low-lying coastal wetlands lost to open water each year threatens fisheries, wildlife habitat, water quality, and infrastructure. The project will also continue public education and science education programs at many levels, and the research results will be made freely available on a public Smithsonian Institution website. To address the central question of this project, the study builds on a thirty-year history of ecological observations at a Chesapeake Bay marsh in Maryland. Measurements of primary production and soil chemistry will be combined with parallel experiments that simulate the future environment by adding carbon dioxide and nitrogen to marsh plots, and comparisons will be made of native to invading plants. The long-term records of this site enable the scientists to document changes in the species composition of plants growing on the marsh over time. At this point, the surface elevation of the soil in the marsh is falling behind local sea level rise, suggesting that this marsh may be in the process of collapsing. The investigators will continue their local measurements, but the results should be generally applicable to coastal wetlands everywhere.