RELICT GLACIAL DRAINAGEWAY ECOSYSTEM Wetlands

Relict Glacial Drainageway wetlands are peatlands occupying relict, sometimes abandoned, drainageway features. These are linear features which drained once more extensive glaciers. Some may have formed during outburst flooding. Some support modern streams but these streams are underfit. Many are now filled with peat. These peatlands are fens, with a stable high water table supported by ample groundwater throughflow that has had recent contact with mineral substrates.

Table 1. Relict Glacial Drainageway Ecosystem Wetlands
Peat Depth (n=31)	Water Table (n=37)	Redox features (n=1)	Saturation (n=34)	pH (n= 32)	Specific Conductance (25°C; n=32)	Plant Prevalence Index (n=32)
149 cm	2 cm	190 cm	6 cm	5.9	129.2µS	1.73

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.

COMMON SOILS

COMMON PLANT COMMUNITIES

CRYAQUEPTS

KICHATNA

KNIK

KASHWITNA

HISTOSOLS

Sweetgale - dwarf birch / water horsetail

Black spruce / sweetgale - dwarf birch / water horsetail

Water sedge - marsh fivefinger

Sweetgale - bluejoint reedgrass

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.

Relict Glacial Drainageway Ecosystem Wetland Map Components:

DW1: Open water.

DW2: Drainageways with water table near the surface most of the growing season. Often dominated by sedges.

DW3: Shrubby Drainageways, typically dominated by sweetgale (Myrica gale), dwarf birch (Betula nana), and water horsetail (Equisetum fluviatle).

DW4: Drainageways dominated by bluejoint reedgrass (Calamagrostis canadensis).

DW5: Drainageways dominated by forested bog, typically black spruce (Picea mariana) with a Labrador tea (Ledum palustre ssp. decumbens) understory.

DW5A: Forested Drainageway fens, typically dominated by white or Lutz spruce (Picea glauca or P. X Lutzii) with an alder (Alnus incana ssp tenuifolia) or sweetgale (Myrica gale) understory.

DWR: A combination of many components at a scale too fine to map at 1:18,000. These are typically narrow wetlands occupied by a DW1 and/or DW2 center, with DW3 and DW5A edges.