Relation of Intertidal Salt Marsh Ecosystem Structure to Surficial Fluid and Solute Exchange

This field study used electromagnetic induction geophysics to map the near-surface bulk soil conductivity (ECa) of a coastal salt marsh. ECa data reflect the effects of multiple edaphic factors of hydroecologic interest, predominantly the soil water, solute, and clay contents. Under a known change in tidal conditions, fluid versus solute exchange-dominated areas of the marsh were inferred from temporal changes in ECa. The spatially-distributed magnitudes of the water and solute exchanges were estimated using Archie's Law and measurements of soil properties. The mapped patterns of exchange were related to marsh channel geometry, microtopography, and vegetation patterns. We suggest a conceptual model of salt marsh vegetation zonation that considers multiple edaphic variables, interspecies competition, and plausible ecohydrologic feedbacks.