Natural Communities of NH -- Photo Guide

Low salt marsh  (S3)



Low salt marshes
are dominated by smooth cord-grass (Spartina alterniflora). They form along the coast in protected bays, along rivers, and behind barrier beaches, sand bars, and rocky spits. This community is often restricted to a narrow fringe along ditches, creeks, rivers, and bays where poly- to euhaline conditions limit competition. Sometimes these steeply-sloped fringes occur at the seaward edge of high salt marsh. The smooth cord-grass in these bands can reach heights of 1-2 m (ca. 3-6 ft.). The term “low” refers to the height of the land, not the vegetation. Smooth cord-grass is usually quite tall, though it does have a low form that sometimes grows in pannes. Where slopes are gentler, smooth cord-grass may cover broader areas. 

Elevationally, these marshes occur between mean sea level and mean high tide, in areas protected from high-energy wave action. They are flooded and exposed by the tide twice a day. They grade into intertidal flats and subtidal communities seaward and high salt marshes landward. can occur as patches within this community, but are more common in the high salt marsh. While this is a distinct, narrowly-defined natural community, it does share similarities with the low brackish riverbank marsh.

Salt marsh soil water salinity roughly corresponds to polyhaline levels (18–30 ppt). Many low salt marsh soils are organic materials 16 to 50" thick overlying sandy materials (Terric Sulfihemists over sand). However, most of the low salt marsh soils along stream and river mouths entering Great Bay and the narrow margins around the bay are organic materials overlying silty materials.

Characteristic vegetation: Smooth cord-grass (Spartina alterniflora) dominates. Associated vascular halophytes occur in low abundance and may includecommon glasswort (Salicornia depressa), halberd-leaved orach (Atriplex prostrata), smooth orache (Atriplex glabriuscula), small spike-rush (Eleocharis parvula), sea blites (Suaeda spp.), seabeach sand spurrey (Spergularia salina), and macroalgae (seaweed) such as Ascophyllum nodosum and Fucus spp. (rockweeds). At more brackish sites (i.e. those with lower salinity), stout bulrush (Bolboschoenus robustus) and narrow-leaved cattail (Typha angustifolia) become more prominent and may dominate the low salt marsh (see also: low brackish riverbank marsh).

Variants:
This community occurs in two distinct settings, forming two variants. The typic variant is more common than the mineral soil variant in New Hampshire.

1. Typic variant: As described above. This variant occurs in organic soils, typically as a narrow fringe at the seaward edge of high marsh.

2. Mineral soil variant
: This variant occurs as linear strands of smooth cordgrass (Spartina alterniflora) in moderate to high-energy settings. Mineral soils are coarse (often gravel or cobble) with a shallow (or absent) organic layer. Frequently occurs together with the shallow peat variant of high salt marsh.

Good examples of this community can be seen at Sandy Point on the south shore of Great Bay at the Great Bay Discovery Center (walk to the outer edge of the boardwalk and look north towards the bay) in Greenland/Stratham, the Salt Marsh Trail at the Urban Forestry Center in Portsmouth, Rye Harbor State Park (Rye), Berry Brook at the western entrance of Odiorne Point State Park (Rye), Hampton Marsh (Hampton/Hampton Falls/Seabrook), Lubberland Creek Preserve (Newmarket), Bellamy River Wildlife Sanctuary (Dover), Crommet Creek (Durham), and from the boat launch along the Squamscott River in Stratham.


Low salt marsh usually occurs as part of a larger salt marsh system.


patch of low salt marsh community on the shore of Great Bay (photo by Ben Kimball for the NH Natural Heritage Bureau)
patch of low salt marsh community on the shore of Great Bay (photo by Ben Kimball)

Spartina alteriflora (smooth cord-grass) in low salt marsh at New Castle (photo by Ben Kimball for the NH Natural Heritage Bureau)
Smooth cord-grass (Spartina alteriflora) in low salt marsh at New Castle (photo by Ben Kimball)

Narrow fringe of low salt marsh (the taller grass) between the river and the high salt marsh (upper right) (photo by Ben Kimball for the NH Natural Heritage Bureau)
Narrow fringe of low salt marsh (the taller grass) between the river and the
high salt marsh (upper right) along the Squamscott River (photo by Ben Kimball)

low salt marsh community on the shore of Great Bay (photo by Ben Kimball)
low salt marsh community on the shore of Great Bay (photo by Ben Kimball)

patch of low salt marsh community on the shore of Great Bay (photo by Ben Kimball)
patch of low salt marsh community on the shore of Great Bay (photo by Ben Kimball)

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