Abstract
In coastal marsh ecosystems, porewater salinity strongly affects vegetation distribution and productivity. To simulate marsh porewater salinity, an integrated, spatially explicit model was developed, accounting for tidal inundation, evaporation, and precipitation, as well as lateral and vertical exchanges in both surface waters and the subsurface. It was applied to the Duplin River marsh, Sapelo Island, USA, over a 3-year period, which covered both drought and wet conditions. Simulated porewater salinity in the low and high marsh correlated with Duplin River salinity, with evapotranspiration and precipitation leading to substantial variations in porewater salinities across seasons, in particular in the high marsh. The model revealed substantial interannual variability in marsh soil conditions, and—due to its process-based approach linked to external forcings—can be used to explore effects of sea level rise and changes in hydrological forcings on marsh soil conditions.
Highlights
Salt marshes experience regular tidal inundation with brackish or oceanic water
Model simulations were compared to porewater salinities measured in 2012–2014 in four different vegetation plots, representing short, medium, and tall Spartina alterniflora, and J. roemerianus (Fig. 2)
The model accurately reproduces field observations, which allows for the exploration of temporal and spatial variability in marsh porewater salinity
Summary
Salt marshes experience regular tidal inundation with brackish or oceanic water. They are prevalent in low-energy wave environments typical of regions between barrier islands and the coast (Wiegert & Freeman, 1990). Intertidal salt marshes are some of the most productive ecosystems on Earth, providing many important ecosystem services, which include: carbon and nitrogen sequestration and transformations, the provision of habitats, reduction of erosion, and mitigation of hurricane impacts on coastal infrastructure (Craft, Broome & Seneca, 1988; Loomis & Craft, 2010; Barbier et al, 2011; Fagherazzi et al, 2013; Kirwan & Megonigal, 2013). In the Southeastern United States, salt marshes are dominated by Spartina alterniflora, with growth forms varying with elevation (Wiegert & Freeman, 1990). The Spartina alterniflora-dominated low marsh, several other plant species can be found, including Juncus roemerianus, Sarcocornia spp. Several studies have focused on the interplay between soil conditions, water
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