LTREB Renewal: Long-term Experimental Manipulation of a Tidal Marsh

Tidal marshes have a remarkable ability to sustain themselves and maintain the many economic services they provide, including shoreline stabilization and flood protection. However, current trends show thousands of hectares of low-lying coastal wetlands are lost to open water each year, with impacts on fisheries, wildlife habitat, water quality, and adjacent human infrastructure. The ability of a coastal marsh to self-sustain depends largely on the highly productive vegetation generating new organic matter. The objective of this project is to learn how tidal marshes respond to changing coastal conditions. This project examines the influence of atmospheric carbon dioxide, nutrients, plant traits, and water level on the structure and persistence of tidal marsh vegetation. It aims to take advantage of an unparalleled forty-year record of plant, microbe, and soil responses to environmental fluctuations and fertilization to identify the most important factors for marsh survival and coastline integrity. This project will extend a globally unique, AI-ready dataset of plant growth, leaf chemistry, soil chemistry and soil elevation change. It also extends an equally unique archive of genetic samples of plants that enable assessment of the most valuable genotypes for sustaining marshes under variable conditions. These samples and data are a resource for developing biotechnological solutions to marsh restoration and coastal protection. This LTREB project includes three complementary, long-term field experiments that manipulate atmospheric carbon dioxide and nitrogen enrichment in different plant communities, leveraging the inter-annual variability in other critical factors such as water level, salinity, and precipitation. The team will test the hypothesis that changes in water level are the ultimate driver of resilience in coastal wetlands and will cause the two plant species with the highest flood tolerance (native sedge and invasive Phragmites australis) to replace the species with lower flood tolerance (C4 grasses) over the next decade. Because both the sedge and Phragmites respond positively to carbon dioxide, the team predicts that these species will initially be favored by carbon dioxide but will ultimately decline as rising water level reduces productivity. However, the areas dominated by Phragmites, particularly plots with added nitrogen, yield the greatest productivity on the marsh, and have the best chance to expand and prevent marsh collapse. The routinely-updated datasets resulting from these long-term experiments are machine-readable and will continue to inform models and AI-based syntheses. The research site and extensive datasets are used as a hands-on case study in ecology courses at Villanova University and Bryn Mawr College. This project trains researchers at all levels, engages the public in experimental field science, and promotes the application of scientific discoveries 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. NSF Award ID: 2530657 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Jonathan Langley | Institution: Smithsonian Institution, WASHINGTON, DC | Award Amount: $600,000 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2530657 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2530657.html