Sediment Accretion in Tidal Freshwater Forests and Oligohaline Marshes of the Waccamaw and Savannah Rivers, USA

• Published in: Estuaries and coasts 2014-09, Vol.37 (5), p.1107-1119
• Main Authors: Ensign, Scott H, Hupp, Cliff R, Noe, Gregory B, Krauss, Ken W, Stagg, Camille L
• Format: Article
• Language: English
• Subjects: Accretion; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Brackish water ecosystems; canopy; Coastal plains; Coastal Sciences; Earth and Environmental Science; Ecology; Environment; Environmental Management; Forestry; Forests; Fresh water; Fresh water ecosystems; freshwater; Freshwater & Marine Ecology; Freshwater resources; Fundamental and applied biological sciences. Psychology; General forest ecology; Generalities. Production, biomass. Quality of wood and forest products. General forest ecology; habitats; herbaceous plants; Inorganic chemistry; Litter; Marine; Marshes; Organic sediments; piedmont; Plant production; pollution load; Rivers; Salts; sea level; Sea level rise; sediment deposition; Sediments; soil; Synecology; Tidal waves; Water and Health; Watersheds
• ISSN: 1559-2723; 1559-2731
• DOI: 10.1007/s12237-013-9744-7

Sediment accretion was measured at four sites in varying stages of forest-to-marsh succession along a fresh-to-oligohaline gradient on the Waccamaw River and its tributary Turkey Creek (Coastal Plain watersheds, South Carolina) and the Savannah River (Piedmont watershed, South Carolina and Georgia). Sites included tidal freshwater forests, moderately salt-impacted forests at the freshwater–oligohaline transition, highly salt-impacted forests, and oligohaline marshes. Sediment accretion was measured by use of feldspar marker pads for 2.5 year; accessory information on wetland inundation, canopy litterfall, herbaceous production, and soil characteristics were also collected. Sediment accretion ranged from 4.5 mm year⁻¹ at moderately salt-impacted forest on the Savannah River to 19.1 mm year⁻¹ at its relict, highly salt-impacted forest downstream. Oligohaline marsh sediment accretion was 1.5–2.5 times greater than in tidal freshwater forests. Overall, there was no significant difference in accretion rate between rivers with contrasting sediment loads. Accretion was significantly higher in hollows than on hummocks in tidal freshwater forests. Organic sediment accretion was similar to autochthonous litter production at all sites, but inorganic sediment constituted the majority of accretion at both marshes and the Savannah River highly salt-impacted forest. A strong correlation between inorganic sediment accumulation and autochthonous litter production indicated a positive feedback between herbaceous plant production and allochthonous sediment deposition. The similarity in rates of sediment accretion and sea level rise in tidal freshwater forests indicates that these habitats may become permanently inundated if the rate of sea level rise increases.