Book Description

Forested wetlands are ubiquitous throughout New England providing critical ecosystem services however; road deicing salt use (NaCl) threaten their ecosystem structure and function. To investigate impacts, we employed a seed bank study and a multi-site field survey of forested wetlands. We collected soils and conducted a full factorial seed bank experiment to test how road salt concentration (0, 0.5, 1, 2, 4, 8 ppt), frequency of salt exposure (pulse, constant) and water level (surface, 2 cm below surface) affected seedling responses. We identified a salinity threshold of 1-4 ppt that reduced seed bank responses. We surveyed nine road-adjacent red maple dominated wetlands in eastern Connecticut to quantify soil (Na+, K+, Mg2+, Ca2+, pH, electrical conductivity (EC), heavy metals, total N, soil moisture) and water salinity. With increasing distance from roads, soil salinity (EC, Na+) decreased, while soil base cation concentrations increased, potentially due to cation exchange (Na+ displacing other base cations) and after 14 months of water monitoring, surface- and ground- water salinity were well below 1 ppt. We characterized the vegetation (ground, shrub, tree layers) along transects 165 meters into each wetland, but we did not observe strong vegetation spatial patterns with distance from road. However, chronic exposure to road salt may alter plant health and community composition, as we observed elevated Na+ and reduced Mg2+ of dominant species leaf tissue near roads. Our study highlights that managers should consider constructed-roadside wetlands as a tool to filter out road salt pollution, as to reduce degradation to naturally occurring wetlands.