Characterizing Vegetative Communities Across the Salt Marsh to Upland Ecotone in Connecticut: Indications of Tidal Inundation Stress in the High Marsh

The viability of Connecticut’s future salt marshes remains uncertain as pressure from multiple anthropogenic stressors and accelerated relative sea level rise continue to undermine the dynamic ecogeomorphic mechanisms that allow these landscapes to persist in times of environmental change. Observed rates of relative sea level rise in the Long Island Sound estuary appear to be accelerating since recording began in the early 1930s. Furthermore, as much as 90% of the land parcels expected to undergo habitat change as marine ecosystems migrate landward are privately owned and managed. This finding suggests that, in addition to these intrinsic ecogeomorphic feedbacks that make salt marshes viable, sociopolitical variables will also play a key role in the sustainability of these ecosystems in the future. This thesis characterized vegetative community structuring at the salt marsh to upland boundary at five different sites along the Connecticut Coast. Nearly 40% of the marshes sampled exhibited manifestations of tidal inundation stress including high relative percentages of the low marsh species Spartina alterniflora (stunted) and deposited tidal wrack mats in the high marsh zone. Common reed, bare areas, and turf lawns had the highest average percent cover type of all the cover types identified within the transition zone. Six of the fourteen transects were observed to have these features prevailing near the apparent salt marsh to upland edge. Despite these apparent disturbances, the transects sampled in this thesis were found to have high variability in plant community assemblages both within and between each study site location. Other than observing species richness to increase from west to east across the state, the presence of tidal restricting structures, adjacent upland cover type, and geographic variables were not found to be good predictors of the variation in vegetative assemblages in the marshes studied in this thesis. This finding suggests that local variations, such as topography, competition, and tidal regimes, are prevailing conditions controlling plant community assemblages across the high marsh to upland ecotone