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S44 Shrub & Herb Wetland Subclass

The U.S. National
Vegetation Classification
Type Concept Sentence: Shrub & Herb Wetland includes open bogs, fens, fresh and saltwater marshes, wet meadows and wet shrublands. The vegetation occurs from tropical to polar regions.
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Common (Translated Scientific) Name: Shrub & Herb Wetland Subclass
Colloquial Name: Shrub & Herb Wetland
Hierarchy Level: Subclass
Type Concept: Shrub & Herb Wetland includes open bogs, fens, fresh and saltwater marshes, wet meadows and wet shrublands. The vegetation occurs from tropical to polar regions.
Diagnostic Characteristics: Shrub & Herb Wetland is dominated by grasses and shrubs, with or without scattered trees (which may have up to 10% cover), sometimes with a wet moss layer (bogs and fens), halophytic growth forms (salt marsh), or a mix of emergent and hydromorphic growth forms, with seasonally to annually saturated or flooded soils, or standing water.
Rationale for Nominal Species or Physiognomic Features:
Classification Comments: These wetlands contain vegetation that is hydrophytic, but none-the-less, largely mesomorphic growth forms, not hydromorphic growth forms.
Similar NVC Types:
S13 Freshwater Aquatic Vegetation, note:
S17 Tropical Forest & Woodland, note: This subclass contains flooded and swamp forests (which can transition to open bogs and marshes) and mangroves (which can be similar to salt marshes). Where tree cover exceeds 10%, stands are typically placed in Forest & Woodland subclasses.
Physiognomy and Structure: This type is dominated by grasses and shrubs, with or without scattered trees (but tree cover typically <10%), sometimes with a strong moss (sphagnum or brown moss) component, or with hydromorphic growth forms. A summary of the range of variation for the various wetlands within the subclass is provided in Table 6.
Floristics:
Dynamics: No Data Available
Environmental Description: Stands are found in a variety of wetland settings, including seasonally to annually saturated or flooded soils, or standing water. A summary of the range of variation for the various wetlands within the subclass is provided in Table 1.

Table 1. Major wetland types used to guide formation distinctions. Types and definitions are adapted from the National Wetlands Working Group (1997) and Mackenzie and Moran (2004), but need further review for tropical summaries.
Wetland Type Definition Environmental features Growth forms Mitsch & Gosselink (2000) type
Bog & Fen Bogs are shrubby, nutrient-poor peatlands with distinctive communities of ericaceous shrubs and hummock-forming Sphagnum species, sometimes with sedges, adapted to high acid and oxygen-poor soil conditions. Trees >2 m have <10% cover (rarely, raised bogs may contain some forested stands). Vegetation of bogs and poor fen often overlap and are sometimes treated together as "acid peatland." +/- ombrotrophic
pH <4.5
>40 cm fibric/mesic peat.
Stunted (<2 m tall) needle-leaved tree, stunted broad-leaved tree, low shrub, dwarf-shrub (ericaceous), sphagnum. Peatland
Fens are peatlands where groundwater inflow maintains relatively moderate to high mineral content within the rooting zone. Sites are characterized by non-ericaceous shrubs, sedges, grasses, reeds, and brown mosses (often with sphagnum). Ranges from poor fen to rich fen. Poor fens overlap with bogs and are sometimes treated as "acid peatland" separate from "alkaline peatland." Groundwater-fed
pH >4.5 (approximate ranges include poor fen 4.5-5.5, medium or intermediate fen 5.5-6.5, rich fen 6.5-7.5 and extremely rich fen >7.5).
>40 cm fibric/mesic peat.
Low shrub (often non-ericaceous, but evergreen), sedge (often fine), grass, reed, and brown moss, often with sphagnum. Peatland
Freshwater Marsh, Wet Meadow & Shrubland A marsh-wet meadow is a shallowly flooded or saturated wetland dominated by emergent grass-like vegetation. A fluctuating water table is typical in marshes and wet meadows, with early season high water tables and some flooding dropping through the growing (or dry) season, and exposure of the substrate or drying of the profile possible in late (or high of dry) season or drought years. Shrub wetlands (shrub carrs) occupy similar sites to wet meadows. Mineral soils or well-humified peat. Protracted shallow flooding (0.1 to 2.0 m) or prolonged soil profile saturation. Grass, sedge (often coarse), forb, low shrub, tall shrub. Freshwater marshes
Tidal freshwater marshes
Riparian ecosystem (wetland, herb/shrub)
Salt Marsh Saltwater marshes are intertidal to supratidal ecosystems that are flooded diurnally (or less), sometimes with freshwater inputs, and has communities dominated by salt-tolerant emergent graminoids and succulents. Intertidal and supratidal zones, semi-diurnal to diurnal, flooding by brackish or saltwater [n.b. inland non-tidal saline wet meadows may also be placed here]. Grass, sedge, forb, halophytic (succulent) forb, halophytic shrub. Tidal salt marshes
Wetlands Treated Elsewhere
Flooded & Swamp Forests (I.A.4, I.B.3, I.B.5) A swamp forest is a tree-dominated mineral or peat wetland, on sites with a flowing/flooded or fluctuating semipermanent, near- or at-surface water table. A flooded forest occurs on sites where flooding varies from temporary (<7 days) to semipermanent (>180 days). Mineral soils or well-humified peat, temporary to semipermanent flooding (0.1 to 2 m deep), rarely saline Broad-leaved tree, needle-leaved tree, tall shrub, forb, graminoid, hydromorphic herb (rarely), trees >10% cover. Freshwater swamps
Riparian ecosystems (wetland, tree)
Mangrove (I.A.5) Mangroves occur in the intertidal and brackish backwater of estuarine areas in tropical regions. Intertidal and supratidal zones, semi-diurnal to diurnal, flooding by brackish or saltwater. Mangrove, halophytic shrub, halophytic (succulent) forb, graminoids. Mangrove swamps
Aquatic Vegetation (5.A, 5.B) Aquatic wetlands are shallow waters dominated by rooted, submerged and floating aquatic plants. They are associated with permanent still or slow-moving waters, such as shallow potholes, ponds, rivers and lakes or in oceans. Aquatic plants may occur in mineral or in well-humified sedimentary peat. +/- Permanent deep flooding (0.5-2 m), or deep water lakes and oceans. Hydromorphic (aquatic) herb, emergents <10% cover.
Geographic Range: This subclass is found widely throughout the world in lowland and montane wetland habitats, from the tropics to the poles.
Nations:
States/Provinces:
Omernik Ecoregions:
Plot Analysis Summary:
Confidence Level: Moderate
Confidence Level Comments:
Grank: GNR
Greasons:
Name:Database Code:Classification Code:
Class 2 Shrub & Herb Vegetation C02 2
Subclass 2.C Shrub & Herb Wetland S44 2.C
Formation 2.C.3 Tropical Freshwater Marsh, Wet Meadow & Shrubland F030 2.C.3
Formation 2.C.2 Temperate to Polar Bog & Fen F016 2.C.2
Formation 2.C.4 Temperate to Polar Freshwater Marsh, Wet Meadow & Shrubland F013 2.C.4
Formation 2.C.5 Salt Marsh F035 2.C.5
Formation 2.C.1 Tropical Bog & Fen F002 2.C.1
Concept Lineage:
Predecessors:
Obsolete Names:
Obsolete Parents:
Synonomy:
Concept Author(s): Hierarchy Revisions Working Group, Federal Geographic Data Committee (Faber-Langendoen et al. 2014)
Author of Description: D. Faber-Langendoen
Acknowledgements:
Version Date: 17Oct2014
References:
  • 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.