During the summer of 2011, researchers at the Jackson Estuarine Laboratory of the University of New Hampshire (UNH) conducted an investigation of the factors that control or contribute to the unusual and unpredictable pattern of Phragmites invasion in portions of the Great Marsh on the Upper North Shore of Massachusetts. An exotic invasive plant, Phragmites threatens the integrity of the Great Marsh by spreading rapidly, displacing native plants, and impacting the ecosystem services provided by salt marsh habitat. Scientists from UNH collaborated with local managers including the Parker River Wildlife Refuge to conduct a study to identify key factors that may contribute to the proliferation of this plant within one of the most ecologically significant salt marshes in New England.
The team investigated the effects of water and soil chemistry on the growth of Phragmites, the efficacy of current vegetation management practices (e.g. chemical treatment, physical removal), and root and rhizome characteristics that may help Phragmites spread rapidly and gain a foothold in the marsh. Results suggest that salinity is the most significant factor favoring Phragmites expansion in the marsh. Fortunately, the management actions currently in place (i.e. selective herbicide spraying) appear to be working as a short-term approach for control until a more comprehensive method is developed. The study identified a great deal of variability in salinity across the marsh, suggesting that there is a mosaic of salinity, micro-elevation and surficial hydrologic conditions that plays a role in the invasion.
The project recommends continuing with existing management approaches and simultaneously conducting: 1) a detailed salinity and elevation mapping; and 2) a hydrologic model that examines the influence of large scale infrastructure salinity and flooding. Integrating fine scale mapping of salinity, elevation and hydrology would form the groundwork to develop large scale management concepts. Such an approach would be a powerful tool to validate theoretical model output with practical on the ground science to identify, map and quantify those areas most susceptible to colonization and further spread by Phragmites.
Details of the survey and data gathered are provided in the report: Moore, G.E. et al. 2012. Investigating causes of Phragmites australis colonization in Great Marsh, Parker River National Wildlife Refuge. University of New Hampshire.