Matanuska-Susitna Wetland Mapping

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HEADWATER FEN ECOSYSTEM Wetlands

A stream emerging from under the peat in a Headwater Fen in the Upper Anchor River watershed.

Headwater Fen Ecosystem wetlands are small peatlands occupying the headwaters of first-order streams. They often support diverse plant communities, but a large Headwater Fen on Baldy Ridge had extensive, nearly monospecific areas of Bigelow's sedge (Carex bigelowii). That may be related to the evidence of heavy ATV or snow machine traffic there.

The extensive Carex bigelowii stand in a Headwater Fen on top of Baldy Ridge.

Headwater fens may be particularly important in stream energy cycles. Carbon export from them is important to organisms at the core of the stream's food web. Insects obtain part of their food from carbon processed by micro-organisms. Larger organisms feed on the insects, and the initial carbon source eventually supports larger organisms, such as anadromous fish (Peterson, et.al., 1986).

A Headwater Fen Ecosystem wetland on Baldy Ridge.

Table 1. Wetland Indicators in Headwater Fen 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
H2	147(11)	8 (10)		0 (10)	4.3 (1)		1.76 (11)
H3	135 (18)	11 (18)			5.0(4)	32.2 (4)	2.12 (15)
H4	13 (1)	28 (1)	20 (1)

Explanation:

All data from wetlands throughout the Cook Inlet Lowlands, not just from the Matanuska-Susitna Valley. Headwater fens are realtively uncommon.

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.

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 Headwater Fen Ecosystem wetlands.
Map Component	COMMON SOILS	COMMON PLANT COMMUNITIES
H2	STARICHKOF DOROSHIN SNOWDANCE	Trichophorum caespitosum - Betula nana Sphagnum spp. - Carex aquatilis Carex pauciflora - Betula nana
H3	STARICHKOF DOROSHIN SNOWDANCE	Trichophorum caespitosum - Carex pauciflora Empetrum nigrum - Vaccinium uliginosum Trichophorum caespitosum - Eriophorum angustifolium Vaccinium uliginosum - Betula nana - Deschampsia caespitosa
H4	STARICHKOF DOROSHIN

Headwater Fen Ecosystem Wetland Map Components:

H1: Ponds

H2: Headwater Fens with water table near the surface most of the growing season. Often dominated by sedges.

H3: Headwater Fens with fluctuating water table, often dominated by shrubs.

H4: Headwater fens with deeper, fluctuating water table, forested.

Table 3. Summary of Matantuska-Susitna Valley and Cook Inlet Headwater Fen 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	Mat Su % Area	Cook Inlet % Area
H1	2	10	0.1	8.1	0.03	0.04	0.00	0.00
H12	1	1	30	30	0.02	0.00	0.07	0.02
H13	1	2	0.7	4.1	0.02	0.01	0.00	0.00
H1-3		26		111		0.11		0.06
H2	3	45	30	175	0.05	0.19	0.07	0.09
H21	2	14	10	68	0.03	0.06	0.02	0.04
H23		36		164		0.15		0.09
H2-4	1	7	5	30	0.02	0.03	0.01	0.02
H3	5	77	7.5	186	0.02	0.32	0.08	0.10
H31		1		0.2		0.00		0.00
H32	1	39	2.2	189	0.02	0.16	0.01	0.10
H34		28		101		0.12		0.05
H4		32		102		0.13		0.05
H42		1		0.7		0.00		0.00
H43	1	16	5.2	58	0.02	0.07	0.01	0.03