Vegetation Composition

Vegetation patterns in New England coastal marshes reflect changes in salinity and tidal innundation. Along the coast, marsh vegetation typically exhibits a banding pattern. Spartina alterniflora dominates low marsh areas while Spartina patens typically dominates the high marsh. Often, small embankments of accumulating sediment and peat form at the water/marsh boundary, where other species, such as Iva frutescens, are established. This pattern is observed in sections of the Quinnipiac River marsh closest to the river's mouth at New Haven Harbor. Upstream, some brackish areas of the marsh are dominated by Typha augustifolia, with small patches of Pluchea purpurascens. However, much of the vegetation in both the more saline and the more brackish areas have given way to vast monocultures of Phragmites australis.

Much of the lower Quinnipiac River marshes are dominated by Phragmites australis, or Common Reed. An upland border species, native Phragmites australis was not typically found in the low and high marsh areas of New England coastal marshes until recently. It is believed that the widespread colonization of Phragmites australis into tidal areas is taking place by a non-native variety of this species, which is considered invasive in several states throughout the US. This variety of Phragmites australis is an early colonizer of recently disturbed sites, spreading rapidly into the surrounding area. Reproducing primarily by vegetative growth, Phragmites australis crowds out native species and often develops vast, dense monocultures.

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