APPLICATION OF ELECTRICAL GEOPHYSICAL METHODS FOR CHARACTERIZATION OF HALOPHYTIC PLANT ZONATION IN SALT MARSHES

Abstract:

Many surface vegetation patterns are partially regulated by subsurface lithology and its impact on water chemistry. In Harrier Meadow, a rehabilitating salt marsh, the native halophytic plant species Salicornia virginica exhibits a spatial patterning that was hypothesized to correlate with high salinity zones. However, measurements of the pore fluid conductivity obtained from lysimeter installations do not appear to correlate with the vegetation patterning. In fine grain sediments, salt may diffuse into small pores or poorly connected pores of the soil matrix and remain in these locations for extended periods of time. Electrical geophysical methods sense an average of the electrical conductivity of the well and poorly connected pores within a soil matrix. Electrical resistivity tomography (ERT) and electromagnetic induction (EMI) methods were used to locate high electrical conductivity regions, assumed to indicate areas of salinity storage in immobile pores. 2D resistivity and 3D electromagnetic inversions reveal a clear spatial correlation between the high electrical conductivity of the soils and the patterns of Salicornia virginica distribution. The study indicates that electrical geophysical methods can be employed to better understand salinity (or contaminant) concentration gradients when mass is stored in the less mobile porosity. This result has important implications for marsh restoration efforts as geophysical methods may assist in selecting plausible habitats to restore halophytic plant populations in salt marshes.