Kampoosa Bog in Stockbridge, Massachusetts, USA is a 70-ha wetland comprised of calcareous basin fen and red maple swamp bordered, in part, by roads including the Massachusetts Turnpike. High salt concentrations in the ground water (due to the application of deicing salts on the Turnpike) and Phragmites australis colonies appear to be impacting the native vegetation at this site. Sodium and chloride concentrations at Kampoosa Bog are generally below previously published threshold levels for impacting vegetation, although such levels vary by species and in relation to other environmental stress conditions. Giant reed (Phragmites), a salt-tolerant invasive species, invaded the northern portion of the wetland adjacent to the Turnpike and a gas pipeline sometime after they were built in the 1950s. By 1998, Phragmites had formed dense colonies that continued to spread across the wetland, which supports several state-listed rare plant and animal species. High salt concentrations (Na > 112 mg/L, Cl^- > 54 mg/L) are present up to 300 meters from the Turnpike. Phragmites colonies occur in areas with high and low salt concentrations, and the species abundance is not well-correlated with elevated salt levels. Although high salt concentrations and Phragmites abundance do not seem to produce an interaction effect on the vegetation of the wetland, the graminoid fen community is impacted by both factors separately. We attribute decreases in the abundance of species between invaded and non-invaded areas to the presence of Phragmites. In the graminoid fen, we attribute decreases in both community measures (richness, evenness, and overall cover) and individual species abundances to high salt concentrations.