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F013 Temperate to Polar Freshwater Marsh, Wet Meadow & Shrubland Formation

The U.S. National
Vegetation Classification
Type Concept Sentence: Temperate to Polar Freshwater Marsh, Wet Meadow & Shrubland includes wet riparian and swamp shrublands, wet meadows, wet prairies, and shallow and deep emergent marshes. The vegetation comprises seasonal green emergent, hydrophytic shrubs and herbs with at least 10% cover, on mucky, inundated or saturated soils across the mid-latitudes of the Northern and Southern hemispheres from 23° to 70°.
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Common (Translated Scientific) Name: Temperate to Polar Freshwater Marsh, Wet Meadow & Shrubland Formation
Colloquial Name: Temperate to Polar Freshwater Marsh, Wet Meadow & Shrubland
Hierarchy Level: Formation
Type Concept: Temperate to Polar Freshwater Marsh, Wet Meadow & Shrubland includes wet riparian and swamp shrublands, wet meadows, wet prairies, and shallow and deep emergent marshes on mucky, inundated or saturated soils across the mid-latitudes of the Northern and Southern hemispheres from 23° to 70°. These wetlands have shallow water, with levels that usually fluctuate daily, seasonally or annually due to tides (freshwater tidal), flooding, evapotranspiration, groundwater recharge, or seepage losses. The vegetation comprises seasonal green emergent hydrophytic woody and herbaceous macrophytes with at least 10% cover, including graminoids such as rushes, reeds, grasses and sedges, other herbaceous species such as broad-leaved emergent forbs, and short to tall shrubs (primarily broad-leaved deciduous but some broad-leaved evergreen in warm-temperate regions). Associated with these plants are floating-leaved and submergent species, and nonvascular plants such as brown mosses, liverworts, and macroscopic algae. The vegetation is usually arranged in distinct zones of parallel or concentric patterns in response to gradients of water depth, frequency of drawdown, water chemistry or disturbance. Saline or brackish non-tidal marshes are excluded. Seasonal drawdowns may expose mudflats that are vegetated by pioneering herb and grass species. Plant communities of seasonal marshes are dynamic, shifting spatially with water levels and changing in composition over a short time. Communities of semipermanent marshes usually are more stable, represented by stands of reeds, which may persist for many years in the absence of severe drought.
Diagnostic Characteristics: The vegetation comprises seasonal green emergent hydrophytic macrophytes, chiefly graminoids such as rushes, reeds, grasses and sedges, other herbaceous species such as broad-leaved emergent forbs, and short to tall, primarily broad-leaved deciduous shrubs (some broad-leaved evergreen shrubs in warm-temperate climates), across the mid-latitudes of the Northern and Southern hemispheres from 23° to 70°.
Rationale for Nominal Species or Physiognomic Features:
Classification Comments: Inland salt marshes are currently excluded here and placed with salt marsh. Freshwater tidal marshes are placed here. Further review is needed of the similarities and differences between temperate and tropical freshwater marshes. Subarctic and arctic (polar) marshes belong in this formation.
Similar NVC Types:
F012 Temperate Grassland & Shrubland, note:
F030 Tropical Freshwater Marsh, Wet Meadow & Shrubland, note: 2.C.4 ~Temperate to Polar Freshwater Marsh, Wet Meadow & Shrubland Formation (F013)$$ is more strongly affected by cold climatic conditions, but vegetation criteria that distinguish these two formations need to be described.
F016 Temperate to Polar Bog & Fen, note: Fens and marshes can be similar, especially when fen peat mats are inundated (as with "shore fens").
F026 Temperate Flooded & Swamp Forest, note: 2.C.4 ~Temperate to Polar Freshwater Marsh, Wet Meadow & Shrubland Formation (F013)$$ contains tall-shrub swamps that share many structural and habitat similarities to hardwood tree swamps (F026), especially during the tree regeneration stage.
F035 Salt Marsh, note: Inland salt marshes are non-tidal, but saline (or haline) and may resemble some brackish freshwater marshes.
Physiognomy and Structure: Temperate to Polar Freshwater Marsh, Wet Meadow & Shrubland vegetation predominantly comprises summer green emergent hydrophytic macrophytes, with at least 10% cover, including graminoids such as rushes, reeds, grasses and sedges, other herbaceous species such as broad-leaved emergent forbs, and short to tall shrubs (primarily broad-leaved deciduous, but some broad-leaved evergreen in warm-temperate regions). Associated with these plants are floating-leaved and submergent species, and nonvascular plants such as brown mosses, liverworts, and macroscopic algae. Vegetation is usually arranged in distinct zones of parallel or concentric patterns in response to gradients of water depth, frequency of drawdown, water chemistry or disturbance (National Wetlands Working Group 1997).
Floristics:
Dynamics: Plant communities of seasonal marshes are dynamic. They shift spatially with water levels, and change in composition over a short time, whereas communities of semipermanent marshes usually are more stable, represented by stands of reeds which may persist for many years in the absence of severe drought (National Wetlands Working Group 1997).
Environmental Description: A temperate freshwater marsh is a wetland that has shallow water and levels that usually fluctuate daily, seasonally or annually due to tides (freshwater tidal), flooding, evapotranspiration, groundwater recharge, or seepage losses. Marshes may experience water level drawdowns that will result in portions drying up and exposing the sediments. Marshes receive their water from the surrounding catchment as surface runoff, stream inflow, precipitation, storm surges, groundwater discharge, longshore currents and tidal action. Marshes dependent on surface runoff usually retain less permanent water than sites supplied by groundwater. The water table usually remains at or below the soil surface, but soil water remains within the rooting zone for most of the growing season, except in years of extreme drought. In semi-arid regions, some basin marshes may remain dry for several consecutive years, and consequently may assume some characteristics of terrestrial ecosystems until water levels are restored by above-average precipitation and runoff (National Wetlands Working Group 1997).

A marsh is a minerotrophic and usually eutrophic wetland. Nutrients are derived from the substrate through periodic aeration. High nutrient levels give rise to the characteristic high productivity of vascular plants and high decomposition rates of the plant material at the end of the growing season. Such high rates of decomposition give rise to marshes producing significant quantities of gases such as methane and carbon dioxide. Freshwater marshes are usually circumneutral to highly alkaline owing to the presence of dissolved minerals such as calcium, potassium carbonate, or potassium bicarbonate.

Soils and substrates encountered in marsh wetlands typically range from mineral soils such as Humic and Rego Gleysols to organic soils such as Humisols and Mesisols in the Canadian soil classification system [see Brady and Weil (2002) for comparison of Canadian soil orders with U.S. and FAO systems]. Normally, marsh sediment is a mixture of unconsolidated organic and inorganic material. Clumps, hummocks, or tussocks of live and dead herbaceous vegetation may exist in standing water. Those marshes that are seasonally dry or exposed to high energy currents usually accumulate little organic matter, in contrast to hydrologically more stable and permanently saturated marshes. In the latter case, such as in lakeshore or delta marshes, Humisols develop; this organic material can accumulate but seldom is more than 40 to 50 cm deep. Under persistent conditions of stable water, sedges and aquatic mosses create floating mats of vegetation. This is characteristic of marsh stages transitional to rich fens (National Wetlands Working Group 1997).

Marshes occur in many geomorphological settings which include low-lying areas adjacent to rivers, lakes, the sea, and any other position on the land surface where groundwater may discharge. In northern regions, marshes are common in nutrient-rich sites associated with rivers either in the floodplains or at their mouth on alluvial fans and deltas (National Wetlands Working Group 1997).
Geographic Range: This formation is found on mucky, inundated or saturated soils across the mid-latitudes of the Northern and Southern hemispheres from 23° to 70°.
Nations: CA, MX, US
States/Provinces:
Omernik Ecoregions:
Plot Analysis Summary:
Confidence Level: High
Confidence Level Comments:
Grank: GNR
Greasons:
Concept Lineage: Split between 4.B.2 (F031) and 2.B.6 (F013) (DFL 7-12).
Predecessors:
Obsolete Names:
Obsolete Parents:
Synonomy: < Freshwater Marshes (Mitsch and Gosselink 2000) [Both tropical and temperate marshes are treated together.]
< Nontidal Freshwater Marshes (Roth 2009) [It is not clear whether nontidal salt marshes are included here. Both tropical and temperate marshes are treated together.]
< Tidal Freshwater Marshes (Roth 2009) [Both tropical and temperate marshes are treated together.]
< Tidal Freshwater Marshes (Mitsch and Gosselink 2000) [Both tropical and temperate marshes are treated together.]
Concept Author(s): Hierarchy Revisions Working Group, Federal Geographic Data Committee (Faber-Langendoen et al. 2014)
Author of Description: D. Faber-Langendoen, after National Wetlands Working Group (1997)
Acknowledgements:
Version Date: 17Oct2014
References:
  • Brady, N. C., and R. R. Weil. 2002. The nature and properties of soils. Thirteenth edition. Prentice Hall, Upper Saddle River, NJ.
  • Faber-Langendoen, D., T. Keeler-Wolf, D. Meidinger, C. Josse, A. Weakley, D. Tart, G. Navarro, B. Hoagland, S. Ponomarenko, J.-P. Saucier, G. Fults, and E. Helmer. 2015c. Classification and description of world formation types. General Technical Report RMRS-GTR-000. USDA Forest Service, Rocky Mountain Research Station, Fort Collins, CO.
  • Mitsch, W. J., and J. G. Gosselink. 2000. Wetlands. Third edition. John Wiley & Sons, Inc., New York. 920 pp.
  • National Wetlands Working Group. 1997. Wetlands of Canada. C. D. A. Rubec, editor. Ecological Land Classification Series No. 24. Environment Canada, Ottawa, and Polyscience Publications, Inc., Montreal. 452 pp.
  • Roth, R. A. 2009. Freshwater aquatic biomes. Greenwood Press, Westport, CT.