Common (Translated Scientific) Name: North American Atlantic & Gulf Coastal Salt Marsh Macrogroup
Colloquial Name: North American Atlantic & Gulf Coastal Salt Marsh
Hierarchy Level: Macrogroup
Type Concept: This macrogroup encompasses eastern North American tidal marshes along the Atlantic and Gulf coasts, ranging in halinity from salt to brackish, and in tidal regime from regularly twice-daily flooding on low marshes to irregularly flooded high marshes, as well as hypersaline pannes. It also includes saline inland prairie. Distichlis spicata, Spartina alterniflora, Spartina patens, and species of Salicornia and Sarcocornia are characteristic throughout the range. These species are present but less abundant in brackish marshes that occur along tidal rivershores or in other settings receiving freshwater mixing. Here, additional species include Spartina cynosuroides, Schoenoplectus americanus, Typha angustifolia, and others. Associated species vary across the north-to-south expanse of this macrogroup. Towards the north, common associates include Juncus gerardii, Limonium carolinianum, Plantago maritima var. juncoides, and Triglochin maritima. From the Chesapeake and mid-Atlantic south, Batis maritima, Juncus roemerianus, Monanthochloe littoralis, Sesuvium portulacastrum, Spartina spartinae, and Typha domingensis become increasingly common associates. Salt marshes and pannes are regularly to irregularly flooded by shallow polyhaline waters as a result of lunar, wind and storm tides. Brackish tidal marshes develop along estuaries where freshwater mixes with ocean saltwater moving up the estuary from the tidal force. Waters in brackish marshes are generally in the salinity range of 0.5-18 ppt, and the vegetation is subject to flooding from the twice-daily tides. This macrogroup ranges along the Atlantic Coast and Gulf of Mexico region from the New England states and the southern Maritime Provinces of Canada south to northern Mexico.
Diagnostic Characteristics: Herbaceous vegetation of the Atlantic coast of North America, characterized by halophytic or mesohalophytic species (Spartina alterniflora, Spartina cynosuroides, Spartina patens, Spartina spartinae, Salicornia spp., Sarcocornia spp.) subjected to regular or irregular tidal flooding.
Rationale for Nominal Species or Physiognomic Features:
Classification Comments: Salt marsh zonation has been long recognized and well-studied. The four groups in North American Atlantic & Gulf Coastal Salt Marsh Macrogroup (M079) reflect these common salt marsh zones (low marsh, high marsh, brackish marsh, panne) [see, for example, Adam (1990) and Mendelssohn and McKee (2000)]. Brackish marshes are found within a tidal river, along the upland side of salt marshes where freshwater inputs modify the salinity, or even brackish conditions on tidal streams within a salt marsh. They typically have reduced cover of Spartina patens and increased cover of associated brackish marsh species such as Amaranthus cannabinus, Polygonum spp., Schoenoplectus americanus, and Typha angustifolia.
The Texas Saline Inland Prairie is added to the range of this macrogroup and Atlantic & Gulf Coastal Tidal Flat & Panne Group (G123). There are both southeastern and southwestern warm temperate floristic patterns but the dominants are more southeastern. That is, Borrichia frutescens, Spartina spartinae, and Sporobolus virginicus are Gulf Coast saline. Chloracantha spinosa and Helianthus ciliaris are southwest saline.
Similar NVC Types:
M077 Great Plains Saline Wet Meadow & Marsh, note: "is also characterized by halophytes, but is non-tidal and has no marine influence."
M066 Atlantic & Gulf Coastal Fresh-Oligohaline Tidal Marsh, note: is also tidally flooded but lacks halophytic species.
M735 Tropical Western Atlantic-Caribbean Salt Marsh, note:
Physiognomy and Structure: This macrogroup is characterized by graminoids or forbs, with a notably simple structure, often forming large, even-height monotypic patches, especially where tidal flooding is regular. Marshes of mixed height, comprising graminoids and forbs, are often more characteristic in brackish settings. Shrubs may be interspersed, especially near the transition to upland or non-tidal vegetation, with graminoid cover remaining extensive below. Where present, shrub cover can range widely. Vegetation may also be very sparse on immediate shorelines and tidal flats.
Floristics: Distichlis spicata, Spartina alterniflora, Spartina patens, and species of Salicornia and Sarcocornia are characteristic throughout the range. These species are present but less abundant in brackish marshes that occur along tidal rivershores or in other settings receiving freshwater mixing. Here, additional species include Schoenoplectus americanus, Spartina cynosuroides, Typha angustifolia, Typha domingensis, and others. Associated species vary across the north-to-south expanse of this macrogroup. Towards the north, common associates include Juncus arcticus, Juncus gerardii, Limonium carolinianum, Solidago sempervirens, Plantago maritima var. juncoides, and Triglochin maritima. From the Chesapeake and mid-Atlantic south, Batis maritima, Juncus roemerianus, Monanthochloe littoralis, Sesuvium portulacastrum, Spartina spartinae, and Typha domingensis become increasingly common associates. Succulent genera Sarcocornia (e.g., Sarcocornia pacifica) and Salicornia (e.g., Salicornia depressa (= Salicornia virginica), Salicornia bigelovii, Salicornia maritima), as well as several grasses (which may be stunted), including Spartina spartinae, Spartina alterniflora, Sporobolus virginicus, and Distichlis spicata, characterize hypersaline pannes. Macroalgae such as Ascophyllum nodosum may be present (though sparse) particularly in the northern part of the macrogroup's range.
Dynamics: Wave and ice-scour can have a significant influence on the year-to-year appearance of the vegetation, and also influences variations in physiognomy and composition along estuary reaches. High marshes develop in areas above mean high water that still receive tidal influence from lunar spring tides, wind tides, or storm tides. Storm tides often deposit sand on salt marsh surfaces where overwash breaches the barrier dune. Salt pannes are part of the shifting mosaic of plant communities of the salt marsh complex. They tend to occur more frequently on the high marsh, but are present in the low marsh as well. Pannes are variable in shape and likely variable in origin. Formation can result from ice-scouring or rafting flotsam that scrapes away or smothers existing vegetation, or from peat compaction, mosquito ditch levees, or tidal creekbank erosion that blocks or impedes drainage. Lack of vegetation decreases local sedimentation, which also maintains lower micro-relief (Redfield 1972).
Environmental Description: Salt marshes and pannes are regularly to irregularly flooded by shallow polyhaline waters as a result of lunar, wind and storm tides. They generally develop on fine-grained sediments, but can develop over sands as well. Production exceeds decomposition, leading to the buildup of marsh peat. Pannes form in depressions that range from 2-30 cm lower than the elevation of the marsh. The depressions are regularly to irregularly flooded by tides, and as the water evaporates during low tide, the salinity concentration increases, forming "salt pannes." Substrate is soft, silty muck or peat of variable density. Brackish tidal marshes develop along estuaries where freshwater mixes with ocean saltwater moving up the estuary from the tidal force. They also occur near uplands where freshwater inputs reduce the salinity of the salt marsh. Waters in brackish marshes are generally in the salinity range of 0.5-18 ppt, and the vegetation is subject to flooding from the twice-daily tides. This macrogroup ranges along the Atlantic coast and Gulf of Mexico region from the New England states and the southern Maritime Provinces of Canada south to northern Mexico.
Geographic Range: This vegetation is found along the North American Atlantic and Gulf of Mexico coasts from the Bay of Fundy south to Texas and possibly northern Mexico.
Nations: CA, MX, US
States/Provinces: AL, CT, DC, DE, FL, GA, LA, MA, MD, ME, MS, MXTM?, NB, NC, NH, NJ, NS, NY, RI, SC, TX, VA
|US Forest Service Ecoregions (2007)|
Prairie Parkland (Subtropical) Province
Confident or certain
Northern Atlantic Coastal Plain Section
Confident or certain
Omernik Ecoregions: 34:C, 34g:C, 34h:C, 34i:C, 59:C, 59e:C, 59f:C, 59g:C, 63:C, 63b:C, 63c:C, 63d:C, 63e:C, 63g:C, 63n:C, 73:C, 73o:C, 75:C, 75d:C, 75j:C, 75k:C, 75l:C, 82:C, 82f:C, 82g:C, 84:C, 84a:C, 84c:C
Confidence Level: Moderate
Confidence Level Comments:
Synonomy: < Estuarine Persistent Emergent Wetland (Cowardin et al. 1979)
< High Marsh (Adams 1963)
= High Marsh (Mendelssohn and McKee 2000)
? Salt Marsh (Rawinski 1984a) [formerly Southern New England and Gulf of Maine Salt Marshes]
< Salt marsh ecosystem (Odum and Copeland 1974)
Concept Author(s): H.T. Odum and B.J. Copeland (1974)
Author of Description: S.C. Gawler and L.A. Sneddon
Version Date: 20May2015
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