Matanuska-Susitna Wetland Mapping

Cook Inlet Wetlands


DISCHARGE SLOPE  ECOSYSTEM Wetlands

A 2004 satellite photo showing Discharge Slope wetlands (outlined in blue) between Wasilla and Knk Arm. These wetlands frequently lie along toesloes at the base of valley walls.

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 deeper than 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.

A forested Discharge Slope with an alder understory near Moonlight Lake.


 

Table 1. Wetland Indicators in Discharge Slope Ecosystem map components throughout the Cook Inlet Lowlands.

Map Component

Peat Depth (cm)

Water Table (cm)

Redox features (cm) Saturation (cm) pH Specific Conductance µS/cm Plant Prevalence Index

SA

107 (11)
34 (10)
23 (6)
0 (2)
6.2(4)
118.7 (1)
2.85 (10)

SB

83(18)

56(18)

29(15) 45 (17) 6.5(9) 191.3 (8) 3.39 (20)

SC

57 (7) 71(5) 24 (6)   7.0(1)   2.89 (6)

SG

20 (5) 52 (5) 14(4) 47(4) 5.7(4) 74.8(4)

3.34 (5)

SL

31(128) 38(108) 26 (82)   5.4(9) 48.9 (2)

2.56 (120)

SM

44(34) 39 (26) 33 (14) 29 (18) 5.1(9) 89.6 (6)

2.52 (28)

SS

46 (18) 30(15) 26 (8)   6.4(1) 86.6 (1) 2.63(19)

SZ

23 (1) 1 (1)   1 (1) 6.0(1) 18.4 (1) 2.35 (1)

Explanation:

All data from wetlands throughout the Cook Inlet Lowlands, not just from the Matanuska-Susitna Valley.

Numbers in paraentheses indicate number of samples.

Peat depth is a minimum, because some sites had thicker peat deposits than the length of the auger used (between 160 - 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. If no water table was encountered, no value was recorded; use number of samples to aid interpretation. Deeper average water tables idicate higher variability.

Redox features with deep depths typically indicate deeper peat deposits, which mask redox indicators so the depth corresponds to the peat thickness.

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.


Table 2. Common soils and plant communities found in Discharge Slope Ecosystem wetlands.

Map Component

COMMON SOILS COMMON PLANT COMMUNITIES

SA

Typic Cryorthents

BELUGA

Alnus viridis ssp. sinuata / Equisetum arvense

Alnus viridis ssp. sinuata / Equisetum palustre

Alnus incana ssp. tenuifolia / Calamagrostis

Paper birch - White spruce / Thinleaf alder

SB

TYPIC CRYAQUENTS

ESTELLE

KICHATNA

Paper birch - White spruce / Thinleaf alder

Paper birch - Black spruce / Thinleaf alder

SC

BELUGA

Typic Cryorthents

Calamagrostis canadensis - Equisetum arvense

SG

STARICHKOF

HISTOSOLS

CRYAQUEPTS

SOLDOTNA

Paper birch - White spruce / Thinleaf alder

Picea x lutzii / Salix barclayi / Calamagrostis canadensis

SL

STARICHKOF

KILLEY

DOROSHIN

MUTNALA

Picea x lutzii / Salix barclayi / Calamagrostis canadensis

Picea x lutzii / Equisetum arvense - Calamagrostis canadensis

Picea x lutzii / Menziesia ferruginea / Equisetum arvense

SM

HISTOSOLS

CRYAQUEPTS

STARICHKOF

Picea mariana / Equisetum sylvaticum - Ledum palustre ssp. decumbens

Picea mariana / Equisetum arvense - Betula nana

SS

KILLEY

STARICHKOF

DOROSHIN

Salix barclayi / Rich

Salix barclayi / Calamagrostis canadensis - Equisetum arvense

Picea x lutzii / Salix barclayi / Calamagrostis canadensis

SZ

CRYAQUEPTS

UNDEFINED
HISTOSOLS are any organic soils greater than 40 cm deep.

Discharge Slope Ecosystem Wetland Map Components:

Map unit names are made of combinations of map components. A suffix 'c' idicates a created wetland, and a 'd' indicates a highly disturbed wetland.

SA: Dominated by alder, usually Alnus incana ssp. tenuifolia

SB: Dominated by birch. Taxonomy of local birches is problematic; tree biches in this project have been designated Betula payrifera, realizing that B. Kenaica is widespread, and other taxa are porbably present.

SC: Dominate by bluejoint reedgrss (Calamagrostis canadensis).

SG: Dominated by white spruce (Picea glauca); occurs primarily in the Matanuska Susitna Valley. Much of the spruce that is not black spruce (P. mariana) is Lutz spruce (Picea X Lutzii), a hybrid between the more continental white spruce and coastal Sitka spruce (P. sitchensis).

SL: Dominated by Lutz spruce (Picea X Lutzii), a hybrid between the more continental white spruce (P. glauca) and coastal Sitka spruce (P. sitchensis). Most common on the Kenai Peninsula, especially closer to maritime influence.

SM: Dominated by black spruce (Picea mariana).

SZ: High elevation moutain meadows of various lush forb assembladges. Mapped only along the upper slopes on Baldy Ridge, above Wasilla.

Table 3.Summary of Matantuska-Susitna Valley and Cook Inlet Discharge Slope Map Unit occurrence (percentages of all wetlands).
Map Unit MatSu N Cook Inlet N Mat Su Hectares Cook Inlet Hectares Mat Su % Polygons Cook Inlet % Polygons MatSu % Area Cook Inlet % Area
SA 2 70 1.7 288 0.03 0.25 0.00 0.15
SAB 1 1 0.3 0.3 0.02 0.00 0.00 0.00
SAC 1 20 16 167 0.02 0.08 0.04 0.09
SAG   3   12   0.01   0.01
SAL   50   604   0.21   0.32
SAM   3   20   0.01   0.01
SAS   9   50   0.04   0.03
SB 90 90 991 991 1.35 0.37 2.32 0.53
SBA 4 4 19 19 0.06 0.02 0.05 0.01
SBd 3 3 7 7 0.05 0.01 0.02 0.00
SBG 7 7 14 14 0.11 0.03 0.03 0.01
SBM 10 10 295 295 0.15 0.04 0.69 0.16
SC 6 38 12 206 0.09 0.16 0.03 0.11
SCA   20   114   0.08   0.06
SCAd   5   9   0.02   0.00
SCd   3   0.6   0.01   0.00
SCG 2 2 2.7 2.7 0.03 0.01 0.01 0.00
SCL   10   63   0.04   0.03
SCLd   7   7.9   0.03   0.00
SCS   20   107   0.08   0.06
SCSd   1   24   0.00   0.01
SG 34 59 530 861 0.51 0.25 1.24 0.46
SGA 119 4 20 84 0.02 0.02 0.05 0.04
SGB 19 19 123 123 0.29 0.08 0.07 0.05
SGC 3 3 69 69 0.05 0.01 0.16 0.04
SGM 5 9 22 105 0.08 0.04 0.06 0.05
SGS 1 4 2 15 0.02 0.02 0.00 0.01
SL 7 1463 24 18,715 0.11 6.08 0.06 9.97
SLA   66   635   0.27   0.34
SLC   7   49   0.03   0.03
SLCd   2   2.1   0.01   0.00
SLd   6   37   0.02   0.02
SLM 4 58 16 447 0.06 0.24 0.04 0.24
SLMd   2   2.9   0.01   0.00
SLS   336   3164   3.18   2.53
SLSd   1   0.7   0.00   0.00
SM 475 765 2772 4851 7.15 3.18 6.49 2.53
SMA   5   34   0.02   0.02
SMB 31 31 200 200 0.47 0.13 0.47 0.11
SMC 1 1 1.7 1.7 0.02 0.00 0.00 0.00
SMd 7 7 29 29 0.11 0.03 0.07 0.02
SMG 20 24 94 121 0.30 0.10 0.22 0.06
SML 4 42 37 340 0.06 0.17 0.09 0.18
SMLd   1   5.9   0.00   0.00
SMS   9   55   0.04   0.03
SPS   2   6.7   0.01   0.00
SS 1 315 3.3 1580 0.02 1.31 0.84 0.00
SSA   17   109   0.07   0.06
SSC   29   176   0.12   0.09
SSG   3   15   0.01   0.01
SSL   272   2149   1.13   1.14
SSM   13   63   0.05   0.03
SZ 20 20 214 214 0.30 0.08 0.50 0.11

Do I Need a Permit?

Downloads:

Shapefile

1987 Delineation manual

2007 Regional AK Supplement

Methods, metadata

Maps and posters


Contact:
Mike Gracz
Kenai Watershed Forum 
PO Box 15301
Fritz Creek, AK  99603
13 January, 2010