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Emergent Tidal Marsh (Biotic Subclass)

Component: Biotic

Unique Identifier: 435

Biotic Setting Benthic/Attached Biota
Biotic Class Emergent Wetland
Biotic Subclass Emergent Tidal Marsh
Biotic Group Brackish Marsh
Freshwater Tidal Marsh
High Salt Marsh
Low and Intermediate Salt Marsh


Description
Definition Communities dominated by emergent, halophytic, herbaceous vegetation (with occasional woody forbs or shrubs) along low-wave-energy, intertidal areas of estuaries and rivers.

Biotic communities in this subclass are equivalent to National Vegetation Classification Associations of FGDC-STD-005-2008, and follow their naming conventions (FGDC 2008). However, FGDC-STD-005-2008 does not split marshes into "herbaceous" or "scrub-shrub" at their Group level. As a result, some of the names of FGDC-STD-005-2008 types (which correspond to the CMECS Emergent Wetland class) indicate that the biotic community is a "Dwarf-shrubland." These specific communities are dominated by woody forbs, which—while technically dwarf-shrubs—function more like herbaceous vegetation. These types were included in Emergent Tidal Marsh, because their total floristics and physiognomy indicate an herbaceous marsh setting.

Vegetation in this subclass is composed of emergent aquatic macrophytes, especially halophytic species—chiefly graminoids (such as rushes, reeds, grasses and sedges), shrubs, and other herbaceous species (such as broad-leaved emergent macrophytes, rooted floating-leaved and submergent species [aquatic vegetation], and macroscopic algae). The vegetation is usually arranged in distinct zones of parallel patterns, which occur in response to gradients of tidal flooding frequency and duration, water chemistry, or other disturbances.

Tides may expose mudflats that contain a sparse mix of pioneering forb and graminoid species. Salinity levels (which control many aspects of salt-marsh chemistry) vary depending on a complexity of factors, including frequency of inundation, rainfall, soil texture, freshwater influence, fossil salt deposits, and more. Salt marshes often grade into (or are intermixed with) scrub-shrub wetlands in higher areas. See Figure 8.16 for an example of an emergent tidal marsh.