Pacific Coast Freshwater Marsh

Freshwater marshes are found at all elevations below timberline throughout the temperate Pacific Coast and mountains of western North America. In the Pacific Northwest, they are mostly small-patch, confined to limited areas in suitable floodplain or basin topography. They are mostly semipermanently flooded, but some marshes have seasonal hydrologic flooding. Water is at or above the surface for most of the growing season. Soils are muck or mineral (in Alaska typically muck over a mineral soil), and water is high-nutrient. Occurrences of this system typically are found in a mosaic with other wetland systems. It is often found along the borders of ponds, lakes or reservoirs that have more open basins and a permanent water source throughout all or most of the year. Some of the specific communities will also be found in floodplain systems where more extensive bottomlands remain. By definition, freshwater marshes are dominated by emergent herbaceous species, mostly graminoids (Carex, Scirpus and/or Schoenoplectus, Eleocharis, Juncus, Typha latifolia) but also some forbs. Common emergent and floating vegetation includes species of Scirpus and/or Schoenoplectus, Typha, Eleocharis, Sparganium, Sagittaria, Bidens, Cicuta, Rorippa, Mimulus, and Phalaris. Maritime Alaska freshwater marshes are described as having Carex rostrata, Equisetum fluviatile (often pure stands), Carex aquatilis var. dives, Menyanthes trifoliata, Comarum palustre, Eleocharis palustris, and Schoenoplectus tabernaemontani. In relatively deep water, there may be occurrences of the freshwater aquatic bed system, where there are floating-leaved genera such as Lemna, Potamogeton, Polygonum, Nuphar, Hydrocotyle, and Brasenia. A consistent source of freshwater is essential to the function of these systems.

By definition, freshwater marshes are dominated by emergent herbaceous species, mostly graminoids (Carex, Scirpus and/or Schoenoplectus, Eleocharis, Juncus, Typha latifolia) but also some forbs. Common emergent and floating vegetation includes species of Scirpus and/or Schoenoplectus, Typha, Eleocharis, Sparganium, Sagittaria, Bidens, Cicuta, Rorippa, Mimulus, and Phalaris. Maritime Alaska freshwater marshes are described as having Carex rostrata, Equisetum fluviatile (often pure stands), Carex aquatilis var. dives (= Carex sitchensis), Menyanthes trifoliata, Comarum palustre, Eleocharis palustris, and Schoenoplectus tabernaemontani. In relatively deep water, there may be occurrences of the freshwater aquatic bed system, where there are floating-leaved genera such as Lemna, Potamogeton, Polygonum, Nuphar, Hydrocotyle, and Brasenia. A consistent source of freshwater is essential to the function of these systems.

In Alaska marshes, standing water is usually persistent throughout the growing season and is generally at least 10 cm above the ground surface.

This system occurs throughout the temperate Pacific Coast and coastal mountains of western North America, from southern coastal California north into coastal areas of British Columbia and Alaska.