OPUS:CRS: Synthesis of decadal changes in controls, trajectories, & tipping points in vegetation cover, spatial structure, & marsh platform elevation in Great Sippewissett Marsh

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Salt marshes are common features of coastal environments. They provide fundamental services, such as maintaining water quality, stabilizing shorelines, and providing choice habitats for important fisheries. Across the world, salt marshes are under threat from the long-term effects of human activities. These include increased nutrient loading, accelerating sea level rise, and increased temperature and precipitation. These changes may be reaching tipping points beyond which these services may cease. This project uses a 49-year dataset on salt marsh responses to nitrogen addition and other external drivers to increase understanding of salt marsh structure and function. Knowledge about the response of salt marshes to such changes is necessary for better management of these critical ecosystems. Results from this research will lead to substantial contributions to basic questions about ecology of salt marshes and will be useful to stakeholders responsible for wetland management. The full database generated from this research will be made freely available to any future users through DataONE (Data Observation Network for Earth).The project proposes a synthesis of a rich database derived from long-term research in the Great Sippewissett Marsh, a representative New England salt marshes in Cape Cod, MA. The core database includes a) a high-definition (10x10 cm) record of a mosaic of vegetation, and b) a high-definition (±1-3 mm) spatial distribution of micro-elevations, both measured within replicated experimental 10-m radius plots established 49 years ago. These plots have been subject to chronic treatments, including four different levels of nutrient inputs, comparable to ranges of eutrophication found in the worlds’ estuaries. The enrichments continued while conditions changed substantially: this work therefore will assess how salt marshes exposed to a wide range of eutrophication will respond to interactive and parallel changes in sea level rise, temperatures, and precipitation. Synthesis of this one-of-a-kind database will allow definition of interactive effects of major driving variables, advance understanding of salt marsh responses and decadal trajectories under changing conditions, and develop theoretical understanding of external vs internal controls, stable states, tipping points, and variability of decadal vegetation trajectories.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.