Inland salt marshes of the northeastern United States: Stress, disturbance and compositional stability

Inland salt marsh (ISM) is a globally endangered, halophytic plant community occurring where groundwater chemistry is influenced by brine. Our goal is to provide the most comprehensive analysis to date of the physiochemical setting and drivers of spatial and temporal variability of this community in the northeastern United States. Non-native Phragmites australis is a significant threat across the range of northeastern ISMs; hence we aim to characterize the conditions associated with the dominance of this species in ISMs. To our knowledge eight naturally-occurring and relatively unimpacted (or restored) ISMs remain in the Northeast. We evaluated the vegetation composition, soils and hydrology of four sites in Michigan and New York. Perennial species dominated the ISM in Michigan while annuals were dominant in New York's ISMs that have not been invaded by P. australis. Native ISM species were restricted to areas of high soil salinity, frequent flooding, and low nutrient levels. Periodic droughts and animal disturbances augment these stresses and function to facilitate ISM stability by inhibiting dominance of robust emergent species. Humans have unintentionally created saline habitats throughout the Northeast; such areas may be restored with ISM species and the data provided herein should assist restoration professionals with this application.