Discharge Slope wetlands occur over hydric mineral soils where shallow groundwater discharges at or near the surface. These wetlands often support only seasonally high water tables, and therefore can be difficult to identify. Shallow groundwater wells indicate that sites with late season water tables at least as deep as 100 cm support growing season hydric conditions sufficient to meet wetland criteria (Clark, 1995).

Wetlands in this ecosystem are named after dominant plant species. In the area between Palmer and Houston, Discharge Slopes are frequently forested with paper birch (Betula papyrifera) and/or white spruce (Picea glauca) with an understory of field horsetail (Equisetum arvense). Both of the trees are listed as facultative upland plants, as is the horsetail on the 1988 list of plant indicator status, further complicating wetland determinations. Good local knowledge, consideration of the surrounding landscape and redox features, and auguring to depth is sometimes required.

Explanation:

Peat depth is a minimum, because some sites had thicker peat deposits than the length of the auger used (usually 493 cm).

Water table depth is a one time measurement. At sites with seasonally variable water tables this measurement reflects both the conditions that year, and the time of year.

Redox features with low n and deep depths typically indicate deeper peat deposits, which mask redox indicators.

pH and specific conductance measured in surface water or a shallow pit with a YSI 63 meter calibrated each sample.

Plant Prevalence Index calculated based on Alaska indicator status downloaded from the USDA PLANTS database, which may use different values than the 1988 list.

Explanation:

Soils from 1998 Soil Survey of the Matanuska-SusitnaValley Area, Alaska, available online, follow the link in the table heading.

Plant communities based on Kenai Peninsula wetland mapping and soil survey, or other published accounts, especially Viereck, et.al., 1992.

Discharge Slope Ecosystem Wetland Map Components:

SA: Alder (Alnus incana ssp. tenuifolia) dominated.

SB: Birch (Betula papyrifera) dominated.

SC:Bluejoint reedgrass (Calamagrostis canadensis) dominated.

SG: White spruce (Picea glauca) dominated.

SL: Lutz spruce (Picea X lutzii) dominated

SM: Black spruce (Picea mariana) dominated.

SS: Willow, usually Barclay willow (Salix barclayii), dominated. A single unvisited wetland in the Matanuska Valley Moose Range.

SZ: High elevation diverse meadows. These wetlands occupy the upper slopes of Baldy Ridge, where late snowmelt feeds shallow groundwater for much of the growing season.

Map Units currently in use: SA, SAB, SAC, SB, SBA, SBG, SBd, SBM, SC, SCG, SG, SGA, SGB, SGC, SGM, SGS, SL, SLM, SM, SMB, SMC, SMd, SMG, SML, SS, SZ

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2 April, 2009