Table 5 (cont'd). Description of vegetation types (Level IV, Alaska Vegetation Classification) found on Ft. Wainwright,
central Alaska, 1998. For more complete descriptions see Viereck et al. (1992).
Class
Description
Thermokarst Complex
This vegetation complex is related to collapse scar fen creation and includes Closed Paper Birch Forests, Open Low
(Open Paper Birch
Shrub BirchEricaceous Shrub Bogs, and Subarctic Lowland Herb Bog Meadow.
Shrub BirchFen)
Thermokarst Complex
This complex is similar to the Open Paper Birch Thermokarst Complex above. However, unlike that association,
(Open Paper Birch
Open Tall Shrub Swamp frequently forms a border at the edges of fens in this class where shrubs and forest are
Shrub SwampFen)
actively collapsing into the fens.
Thermokarst Complex
This complex is related to thermokarst processes and is dominated Open Black Spruce Forests with circular
(Black SpruceBog)
thermokarst depressions that support Lowland Subarctic SedgeMoss Bog Meadows.
Thermokarst Complex
This complex is related to thermokarst processes and is dominated Closed Paper Birch Forest and circular
(Closed Paper Birch
thermokarst depressions. Depressions have moats at the periphery (Fresh Herb Marsh), and Lowland Subarctic
Collapse Bog)
Wet Sedge Meadows or Lowland Subarctic SedgeMoss Bog Meadows.
Thermokarst Complex
This complex is similar to the Closed Paper BirchCollapse Bog above, but the forest type is Mixed SprucePaper
(Mixed SprucePaper
Birch.
BirchCollapse Bog)
Thermokarst Complex
This complex mosaic is related to thermokarst processes and is dominated by Open Paper Birch Forest and Closed
(Open Paper Birch
Low Shrub BirchEricaceous Shrub on frozen areas and Lowland Subarctic SedgeMoss Bogs Meadows in circular
Shrub BirchCollapse
thermokarst depressions.
Bog)
Barren
Vegetation covers less than 5% of the soil surface.
Partially Vegetated
Vegetation covers 530% of the soil surface.
gins of active channels, have frequent silt deposi-
from accumulations of birch litter and aquatic
tion due to flooding approximately every 25
species, indicating changing ecological conditions
years, and support tall alder-willow and young
during the evolution of the landscape. Adjacent
balsam poplar communities. In contrast, inactive-
to these elevated birch forests, frequently are
cover deposits have interbedded silt and organic
large, linear collapse-scar fens associated with
layers near the surface, which are indicative of
groundwater discharge that include several stages
infrequent flooding, and they typically support
of paludification. These stages include the "moat"
balsam poplar and white spruce forests.
formed immediately adjacent to the collapsing
Within the White Mountains Ecodistrict, the
banks, large expanses of buckbean and swamp
geomorphology is dominated by residual soils
horsetail, and slightly raised areas with willows,
over weathered bedrock, but also includes smaller
alder, and sweet gale. In contrast, in more stable
areas with a loess cap near the Tanana River,
areas where thermokarst is less prevalent, black
retransported deposits on lower slopes, veneer
spruce forests and low shrub birchericaceous
bogs on retransported deposits, and narrow head-
shrublands are more common (Fig. 10 and 22).
water floodplains (Fig. 1721). Generally, upland
Within the Tanana Floodplain Ecodistrict, the
areas with residual soils have vegetation that fol-
geomorphology is dominated by erosional and
lows a successional sequence after fire evolving
depositional processes associated with braided or
from herb and shrub stages to deciduous forest,
meandering rivers, in contrast to the thermal, per-
mixed forest, and, finally, white spruce and black
mafrost-related processes dominating the Tanana
spruce stages. Retransported deposits are domi-
Flats Ecodistrict. Geomorphic units include
nated by black spruce forest, but have occasional
braided or meandering riverbed deposits and ac-
patches of birch forest, willow and ericaceous
tive- and inactive-cover deposits (Fig. 12). River-
shrub lands, and low shrub-tussock meadows.
bed deposits have gravelly material, are flooded
Smaller headwater streams are dominated by riv-
every year or two, and generally are barren or
erine willow vegetation, but occasionally include
partially vegetated due to the frequent distur-
spruce and birch forest combinations.
bance. Active-cover deposits occur along the mar-
22
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