Matanuska-Susitna Wetland Mapping

Cook Inlet Wetlands


RELICT GLACIAL LAKEBED ECOSYSTEM Wetlands

A patterened Relict Glacial Lakebed Ecosystem wetland north of Beaver Lakes. The patterning consists of low-lying pools and mud-bottoms with intervening shrubby strings and tree islands.

These extensive peatlands occur on expansive flat surfaces, which were formerly occupied by large proglacial lakes. Peatlands develop on these surfaces through a process known as "primary peat formation". In contrast to lake infilling, the classical model of peatland formation, typical of ice-block depressions (Kettle, Depression and Spring Fen Ecocsystem wetlands), primary peat formation is the process responsible for most of the peatlands on Earth. Primary peat formation is where a wide, shallow, marshy area gradually fills with peat. The third peat-forming process is paludification, where accumulating sphagnum peat invades upland surfaces.

Relict Lakebed peatlands are mostly fens, often with patterning. The patterns consist of low-lying pools, which can dry up seasonally to form mud-bottoms (flarks), and intervening strangs (low shrubby ridges). Tree islands often form. The tree islands are areas where bog peat is forming on top of the fen peat. Initial comparisons with 1960 aerial photography appear to indicate that bogs and fens are in stable equilibrium: neither appears to be expanding or contracting. This could be because relict lakebeds support a drainage network sufficient to prevent bog mounds from forming. Mound formation is limited by distance to streams, and mounds typically develop on broad interfluves.

Relict Glacial Lakebed Ecosystem peatlands are larger than Kettle Ecosystem wetlands, which also form on abandoned lakebeds. The centers of large Lakebed peatlands are far removed from uplands, so surface water runoff originating from mineral sources appears distant. However, remember that the mineral soil is never more than several meters away, beneath the peatland. Many fens receive shallow groundwater discharge from beneath through sandy underlying sediments.


 

Table 1. Wetland Indicators in Relict Glacial Lakebed 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

LB1

       
6.1(4)
55.1 (4)

LB2

156(61)

7 (63)

  0.1 (19) 5.3(25) 69.6 (20) 1.52 (50)

LB3

174 (25) 10 (22)   5.2 (10) 4.3(10) 58.7 (10) 1.83 (14)

LB4

121 (58) 21 (55)   12 (10) 5.4(16) 83.2 (10)

2.09 (47)

LB5

54 (4) 44 (4)   13 (3) 4.9 (3) 86.1 (2)

2.45 (2)

LB6

94 (80) 31 (67) 49 (22) 11 (23) 4.8 (20) 71.9 (12)

2.42 (60)

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 Relict Glacial Lakebed Ecosystem wetlands.

Map Component

COMMON SOILS COMMON PLANT COMMUNITIES

LB2

STARICHKOF

HISTOSOLS

DOROSHIN

SALAMATOF

Trichophorum caespitosum - Myrica gale

Myrica gale - Carex livida

Trichophorum caespitosum - Eriophorum angustifolium

LB3

STARICHKOF

HISTOSOLS

DOROSHIN

SALAMATOF

Sphagnum spp. - Ericaceae

Sphagnum spp. - Carex rotundata

LB4

STARICHKOF

HISTOSOLS

DOROSHIN

SALAMATOF

Myrica gale - Dasiphora floribunda

Sphagnum spp. - Ericaceae

Trichophorum caespitosum - Myrica gale

Empetrum nigrum - Ledum palustre ssp. decumbens

LB5

STARICHKOF

HISTOSOLS

DOROSHIN

SALAMATOF

Calamagrostis canadensis / Betula nana

Black spruce / Dwarf birch

LB6

STARICHKOF

HISTOSOLS

DOROSHIN

SALAMATOF

Picea mariana / Ledum palustre ssp. decumbens

Picea mariana / Equisetum sylvaticum - Ledum palustre ssp. decumbens

Picea x lutzii / Salix barclayi / Equisetum arvense / Empetrum nigrum

HISTOSOLS are any organic soils greater than 40 cm deep.

Relict Glacial Lakebed 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.

LB1: Open water

LB2: Water table near the surface most of the growing season, often dominated by sedges.

LB3: Bogs, often dominated by sphagnum moss and shrubs. May or may not be forested.

LB4: Dominated by shrubs, especially Labrador tea, leatherleaf and dwarf birch

LB5: Dominated by bluejoint reedgrass, often over relatively shallow peat in areas with large amounts of local groundwater discharge.

LB6: Forested, typically by black spruce.

LBSF: A complex of patterned fen with small high ridges (strangs) alternating with low pools or hollows (flarks) and bog islands which may or may not be forested..

Table 3.Summary of Matantuska-Susitna Valley and Cook Inlet Relict Glacial Lakebed 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
LB1 55 88 139 649 0.83 0.37 0.33 0.35
LB12 2 32 1.5 216 0.03 0.13 0.00 0.12
LB13 2 2 5.3 5.3 0.03 0.01 0.01 0.00
LB1-3 12 141 101 2268 0.18 0.59 0.24 1.21
LB14   1   1.2   0.00   0.00
LB1-4 12 40 73 1361 0.18 0.17 0.17 0.72
LB1-5   1   9.8   0.00   0.01
LB2 41 82 136 1849 0.62 0.76 0.32 0.98
LB21 3 71 16 1055 0.05 0.30 0.04 0.56
LB23 20 126 86 1496 0.30 0.52 0.20 0.80
LB23d 1 1 2.7 2.7 0.02 0.00 0.01 0.00
LB24 18 142 135 1613 0.27 0.59 0.32 0.86
LB2-4 26 114 152 1817 0.39 0.47 0.36 0.97
LB2-4d 1 1 1.6 1.6 0.02 0.00 0.00 0.00
LB25   3   2.6   0.01   0.00
LB2-5   4   46   0.02   0.02
LB26 8 36 37 361 0.12 0.15 0.09 0.19
LB2-6 1 9 2.8 150 0.02 0.04 0.01 0.08
LB26d 1 1 3.0 3.0 0.02 0.00 0.01 0.00
LB2d 4 4 7.4 7.4 0.06 0.02 0.02 0.00
LB3 30 114 107 593 0.45 0.47 0.25 0.32
LB31 1 5 0.5 14 0.02 0.02 0.00 0.01
LB32 28 96 90 541 0.42 0.40 0.21 0.29
LB34 30 126 134 673 0.45 0.52 0.31 0.36
LB34d 1 1 0.9 0.9 0.02 0.00 0.00 0.00
LB36 24 60 74 450 0.36 0.25 0.17 0.24
LB3-6 1 12 3.5 291 0.02 0.05 0.01 0.15
LB3d 1 1 3.5 3.5 0.02 0.00 0.01 0.00
LB4 62 372 207 2194 0.93 1.55 0.49 1.17
LB41 1 3 2.5 5.5 0.02 0.01 0.01 0.00
LB42 17 95 253 1093 0.26 0.39 0.59 0.58
LB43 27 122 234 1338 0.41 0.51 0.55 0.71
LB45   6   65   0.02   0.00
LB46 53 353 462 3428 0.80 1.47 1.08 1.83
LB4-6 1 12 0.5 117 0.02 0.05 0.00 0.06
LB5 1 7 1.3 16 0.02 0.03 0.00 0.01
LB54   3   11   0.01   0.01
LB56 1 3 4.0 17 0.02 0.01 0.01 0.01
LB6 276 829 1720 7348 4.15 3.45 4.03 3.91
LB62 51 87 182 664 0.77 0.36 0.43 0.35
LB63 123 159 242 674 1.85 0.66 0.57 0.36
LB64 81 317 1017 3512 1.22 1.32 2.38 1.87
LB64d 1 1 6.1 6.1 0.02 0.00 0.01 0.00
LB65 1 1 19 19 0.02 0.00 0.05 0.01
LB6d 2 2 1.9 1.9 0.03 0.01 0.00 0.00
LBSF 67 158 1819 5063 1.01 0.66 4.26 2.70

 

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