Classification and floral relationships of seaside salt marsh soils in Accomack and Northampton Counties Virginia

Abstract

Soils in the seaside marshes in Accomack and Northampton Counties were characterized by chemical properties related to salt concentration in order to study the influence of seawater on their properties and the flora they support. These soils have equilibrated to proportions of Na+ and Mg2+ characteristic of seawater and have sums of water soluble cations of Ca2+, Mg2+, K+, and Na+ > 145 mmol (p+) L-1; SARs > 31; and ECs > 29 dS m- 1 in the upper 33 cm.

Soils in marshes flooded by daily tidal action have peraquic moisture regimes and qualify as members of the proposed Almyric subgroups. Soils in marshes flooded by spring and storm tides with subsoil illuvial clay accumulations and aquic moisture regimes qualify as members of Typic Natraqualfs. Soils in these marshes with sandy subsoils that have equilibrated to proportions of Na+ and Mg2+ characteristic of seawater are excluded from Almyric Psammaquents because they have aquic moisture regimes. Therefore, we recommend the peraquic moisture regime requirement be dropped from the definition of Almyric soil properties or both peraquic and aquic moisture regimes be allowed.

Soils in marshes flooded by daily tidal action have developed in fining-upward sediments that are silty in the upper part and vegetated primarily by Spartina alterniflora. pH reductions with moist incubation indicate sulfidic materials and potential acid sulfate soils. Therefore, soils with silty textures that support vegetative communities of S. alterniflora are indicators of potential acid sulfate soils or Sulfaquents in these marshes.

Soils in marshes flooded by spring or storm tides have particle-size distributions that are not significantly different from associated upland soils and are assumed to be submerged uplands. These areas are vegetated primarily by Spartina patens and Distichlis spicata. pH reductions accompanying moist incubation indicate nonsulfidic materials.

Tidal mudflats are not vegetated by vascular plants and not considered to be soils. pH reductions accompanying moist incubation indicate that sediments in these areas are nonsulfidic materials.

Results of this study support the need for the proposed Almyric subgroups for classifying saltmarsh soils since they convey considerably more information than the subgroups currently defined by Soil Taxonomy. Moist incubation for determining sulfidic materials provides a convenient method for analyzing large numbers of samples.

Numerical taxonomic procedures did not separate the soils into families or marsh types. However, Hydraquents and Sulfaquents great groups were generally separated at a similarity index of 1.5.