LTREB: Thirty-Four Years of Tidal Marsh Response to Environmental Change

沿海湿地是地球上生产力最高的生态系统之一，是陆地和海洋栖息地之间的关键过渡地带。盐沼是生物活动的热点，它们具有非凡的自我维持能力，这在很大程度上要归功于它们的植被，并在海平面变化时保持海岸线。然而，每年数千公顷的低洼沿海湿地因开阔水域而丧失，威胁到渔业、野生动物栖息地、水质、土壤碳储量和邻近的人类基础设施。该项目的目标是了解沿海湿地，特别是盐沼，将如何应对日益加剧的环境变化。该项目计划扩大实验范围，考察大气中二氧化碳浓度上升、营养物质污染、入侵物种和海平面上升对盐沼植被结构和持久性的影响。它的目标是利用34年来无与伦比的植物、微生物和土壤对全球变化的响应记录，确定对沼泽生存最重要的因素。这些结果应该与其他沿海生态系统相关，并可能改善对未来湿地损失的预测，并为维护湿地的管理战略提供参考。该项目的数据将被纳入两个机构的本科课程，本科生将协助收集数据并使用该项目的数据用于高级论文，普通公众将有机会参观研究现场，并有机会参与公民科学倡议。该项目包括三个相辅相成的长期野外实验，这些实验操纵不同植物群落中的大气二氧化碳和氮浓缩，利用其他关键因素的年际变化，如海平面、盐度和降水量。该团队计划测试一种假设，即海平面上升作为沿海湿地变化的最终驱动力，将导致两种耐洪能力最强的植物(本地莎草和入侵芦荟)在未来十年取代耐洪能力较低的植物(C4草)。由于莎草和芦荟对二氧化碳浓度升高的反应也很强烈，该研究小组预测，植物群落组成最初将发生变化，并增加生态系统规模的二氧化碳反应，但由于洪涝压力增加，最终将下降。随着相对海平面上升的速度加快，由于生产力下降，沼泽变得不稳定，预计沼泽将在未来十年跨过一个门槛。然而，芦荟占主导地位的地区，特别是添加了氮的地块，在沼泽上产生的生产力最高，也最有可能跟上不断上升的海平面。最后，研究小组假设，随着洪水的增加，预计甲烷排放量的增加将最初被耐洪水莎草根际甲烷氧化的更高速率所抵消。这项实验的结果可以继续为模型和全球变化综合提供信息。该网站和广泛的数据集被用作维拉诺瓦大学和布林·莫尔学院生态学课程的动手案例研究。该项目计划培训各级研究人员，让公众参与LTREB遗址产生的长期和前瞻性的科学，并促进这一基础科学的应用，以支持海岸湿地的保护、养护和恢复。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Coastal wetlands are some of the most productive ecosystems on Earth, and are critical transition zones between terrestrial and marine habitats. Salt marshes, hotspots of biological activity, have a remarkable ability to sustain themselves, largely due to their vegetation, and maintain coastlines as sea level changes. However, the annual loss of thousands of hectares of low-lying coastal wetlands to open water each year threatens fisheries, wildlife habitat, water quality, soil carbon stocks, and adjacent human infrastructure. The objective of this project is to learn how coastal wetlands, salt marshes in particular, will respond to intensifying environmental change. This project plans to extend experiments examining the influence of rising atmospheric CO2, nutrient pollution, invasive species, and sea level rise on the structure and persistence of salt marsh vegetation. It aims to take advantage of an unparalleled thirty-four year record of plant, microbe and soil responses to global change to identify the most important factors for marsh survival. These results should be relatable to other coastal ecosystems, and are likely to improve predictions of future marsh loss as well as inform management strategies for maintaining wetlands. Data from the project will be incorporated into undergraduate classes at two institutions, undergraduates will assist with data collection and use data from the project for senior theses, and the general public will be given tours of research site and given the opportunity to participate in citizen science initiatives.This project includes three complementary, long-term field experiments that manipulateatmospheric CO2 and N enrichment in different plant communities, that leverage the inter-annual variability in other critical factors such as sea level, salinity and precipitation. The team plans to test the hypothesis that sea level rise, as the ultimate driver of change in coastal wetlands, will cause the two plant species with the highest flood tolerance (native sedge and invasive Phragmites australis) to replace those with lower flood tolerance (C4 grasses) over the next decade. Because the sedge and Phragmites also respond strongly to elevated CO2, the team predicts that plant community composition will initially shift and increase the ecosystem-scale CO2 response, but it will ultimately decline due to increasing flooding stress. The marsh is expected to cross a threshold in the next decade as rates of relative sea level rise accelerate to the point that the marsh becomes unstable due to declining productivity. However, the areas dominated by Phragmites, particularly plots with added N, yield the greatest productivity on the marsh, and have the best chance to keep up with accelerating sea level. Finally, the team hypothesizes that an increase in methane emissions expected with increased flooding will be offset initially by higher rates of rhizosphere methane oxidation from the flood-tolerant sedge. The results from this experiment can continue to inform models and global change syntheses. The site and extensive dataset are used as a hands-on case study in ecology courses at Villanova University and Bryn Mawr College. This project plans to train researchers at all levels, to engage the public in the long-term and forward-looking science that arises from this LTREB site, and to promote the application of this basic science to support coastal wetland protection, conservation, and restoration.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.