Wetland Classification and Mapping of Seward, Alaska



Map Unit Descriptions


Ecosystem: Tidal


Map Component: T6


Seward Area Extent: 6 wetland polygons; 27.6 acres

T6 is represented by the dense, uniform Lyngbye sedge stand in the foreground of this photo, taken near the mouth of the Resurrection River.

Wetland Indicators

Type: Tidal

Average depth to water table: 8 cm on 20 June 2006 at the one site measured

Organic layer thickness: 9 cm

Average depth to redoximorphic features: 0 cm at the one site measured

Common Soils: Typic Cryaquents at the single site visited, but probably also Oxyaquic Cryofluvents

Common Plant communities:

Lyngbye's sedge (Carex lyngbyei)


T6 wetlands are dominated by Lyngbye's sedge (Carex lyngbyei).  They are found in the upper sedge marsh zone in the upper reaches of estuaries.  Monotypic stands are common.


T6 corresponds with Vince and Snow's (1984) 'Inner Sedge Marsh Zone 7', estimated to be inundated on only the highest spring tides, or an average of 2 times per summer on the Susitna Flats (with a range of 0-5 times per summer), in upper Cook Inlet, Alaska.  Vince and Snow found that water was retained for greater than 5 days per inundation. 


Just below T6, pools containing the Alaska Natural Heritage Program tracked rare plant (S2S3) Kamchatka spikerush (Eleocharis kamchatica), along with common mare's tail (Hippuris vulgairs), and saltmarsh starwort (Stellaria humifusa) are frequently encountered.  Landward, T6 typically borders a beachrye (T7) or mixed forb / grass component (T8).


T6 is typically composed of tall, dense sedges over a thick organic soil, often the hydric, Clunie histosol.  Occasionally, Lyngbye's sedge is found growing inland, in small dense stands far removed from tidal influence.



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Contact: Mike Gracz
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12 February 2007 15:31