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New Hampshire Department of Environmental Services

Monitoring Vegetative Communities

vegetativePlants are the primary food source for salt marsh ecosystems. Most plant material is consumed after it dies as detritus by microbial decomposers and invertebrate consumers. A salt marsh is physically dependent on its plants - plant roots and stems anchor the substratum and enable the gradual build up of peat. Plant communities, along with variation in tidal exchange, geology, and chemical parameters such as salinity, shape salt marsh habitat and help determine which species of invertebrates, fish, birds and other animals will be found there.

Salt marshes are an extremely dynamic habitat for plant species because of wide daily and seasonal fluctuations in surface water and root-zone salinity, temperature, and dissolved oxygen. For this reason, the few plants species which are found in salt marshes fill extremely specialized ecological niches. Plant zonation results from species-specific adaptations to physical and chemical conditions.

Salt Marsh Plants & Zones

goldenrodSalt marshes can be extremely difficult places to live because of wide daily fluctuations in salinity, water, temperature, and oxygen. Few plants have evolved adaptations to cope with the extreme conditions of salt marshes. Plant zonation in a salt marsh results from species-specific adaptations to physical and chemical conditions. Looking out on a healthy salt marsh in full summer growth, one can observe distinct zones of plant growth. Bands of tall grasses inhabit the saturated banks of creeks and bays, and this zone is bordered by a flat "meadow" of grasses and sedges that may extend landward for a great distance before transitioning into upland habitats where there is a greater diversity of shrubs, flowering plants, and grasses.

Marsh Border: The marsh border is located at the salt marsh's upland edge and other isolated areas on the marsh where elevations are slightly above the high marsh. The marsh border is usually only flooded at extreme astronomical tides and under irregular conditions such as storm surges or wind-driven tidal inundations, and does not experience waterlogged conditions or severe salt stress. A high diversity of herbs, shrubs, and even trees exists in the marsh border. Iva frutescens (high tide bush), Baccharis halimifolia (sea myrtle), Agropyren pungens (stiff-leaved quackgrass), Solidago sempirvirens (seaside goldenrod), and Panicum virgatum (switchgrass) are just some of the many marsh border plants.

High Marsh: The high marsh lies between the low marsh and the marsh's upland border. The high marsh can be very expansive in some areas, sometimes extending hundreds of yards inland from the low marsh area. Soils in the high marsh are mostly saturated, and the high marsh is generally flooded only during higher than average high tides. Plant diversity is low (usually less than 25 species), with the dominant species being the grasses and rushes such as Spartina patens (salt hay grass), Distichlis spicata (spike grass), Juncus geradii (black grass), and the short form of S. alterniflora. Other plant species commonly found in the high marsh are Aster tenufolius (perennial salt marsh aster), and Limonium nashii (sea lavender).

Pools: Pannes are located within depressions in the high marsh. There have irregular shallower sloped edges and deeper sections. Pools are generally permanent water holding features in the high marsh that can be vegetated with submerged aquatic species such as Ruppia maritima (widgeon grass).

pannePannes: Pannes are located interspersed with pools within the high marsh. They are shallower than pools, hold standing water but dry out during extended dry periods. Salinity can reach extremely high concentrations in pannes and only the most salt-tolerant species can exist at panne edges, including Salicornia spp. (glassworts), Plantago maritima (seaside plantain), and the short form of Spartina alterniflora, as well as some blue-green algae.

Low Marsh: The low marsh is located along the seaward edge of the salt marsh. The low marsh is usually flooded at every tide and exposed during low tide. It tends to occur as a narrow band along creeks and ditches, whereas the high marsh is more expansive and is flooded less frequently. The predominant plant species found in the low marsh is the tall form of Spartina alterniflora (smooth cordgrass). This species can reach a height of six feet and is very tolerant of daily flooding and exposure.



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