Table 10 (cont'd). Description of the physiography, geomorphology, hydrology, permafrost and vegetation of
ecodistricts and ecosubdistricts mapped within Fort Wainwright, central Alaska, 1998.
Ecodistrict
Ecosubdistrict
Description
SteeseWhite
Stuart Creek
An association of retransported deposits on lower slopes, meander riverbed deposits, and meander
Mountains
Lowlands
active and inactive floodplain cover deposits. Permafrost is continuous, except under larger streams.
(cont'd.)
Vegetation is dominated by black spruce and birch forests, low shrubland and tussock tundra on fine-
grained, saturated soils. White sprucebalsam poplar forests are found along floodplains.
FrenchMoose
This area has been greatly affected by eolian deposition adjacent to the Tanana River. The low knob
Creek Lowlands
and swale topography has an association of lowland loess, eolian sand, lowland retransported depos-
its, and organic collapse scar and flat bogs. The area generally is above the Tanana Floodplain, but has
numerous small streams originating in the highlands. Permafrost is nearly continuous; it is absent in
collapse scar bogs, thaw ponds, and ridges of well-drained sand dunes. Black spruce and birch forests,
shrub-tussock meadows, sedgemoss bogs, and aquatic vegetation in shallow thaw ponds are common.
Bedrock with an Alpine climate has repeating
its on the flats can occur on Veneer or Flat Bogs
assemblages of Alpine Rocky Dry Dwarf Scrub
overlying the ice-rich Abandoned Floodplain
and Alpine Rocky Moist Tall and Low Scrub,
Cover Deposits, or more recognizably, on Col-
whereas Abandoned Floodplain Cover Deposits
lapse Scar Bogs and Fens that result from paludi-
are dominated by Lowland Wet Needleleaf For-
fication in pits and ponds as a result of thermal
est, Lowland Wet Broadleaf Forest, and Lowland
degradation of ice-rich permafrost.
Wet Low Scrub. In addition, ecosection maps are
Ecodistricts. Ecodistrict maps were created by
produced at a smaller scale (typically 1:100,000 to
a separate delineation on Landsat satellite imag-
1:250,000) with larger minimum mapping size for
ery based on the recurring patterns of geomorphic
patches; thus many tiny patches would be elimi-
classes with distinctive physiographic characteris-
nated.
tics. Three ecodistricts and 21 ecosubdistricts were
Viewing the geomorphic maps (Fig. 4 and 5) as
delineated within Fort Wainwright (Table 10, Fig.
if they were ecosection maps reveals a close asso-
25). Ecodistricts and ecosubdistricts both use geo-
ciation among groups of ecosections that are hy-
morphology and physiography as the differenti-
drologically linked by surface and groundwater
ating characteristics, but differ in that ecosub-
movement. This water movement affects loss and
districts delineate smaller areas with less variation
accumulation of sediments and nutrients and,
in the composition of the geomorphic assemblages.
thus, greatly affects thermal status and ecosystem
The ecodistricts provide a way of stratifying the
productivity. For example, in the White Mountain
distribution of ecotypes that frequently are con-
Ecodistrict, Weathered Bedrock ecosections on
textually related. For example, Lowland Fen
ridges, Residual Soil ecosections on upper slopes,
Meadow, Lowland Scrub Fen, and Lowland Bog
Lowland Retransported ecosections on lower
Meadow were found almost exclusively on the
slopes, and Headwater Stream ecosections in val-
TananaWood River Flats Ecodistrict because of
ley bottoms all are linked by the downslope
the predominance of ice-rich, fine-grained soils.
movement of water and sediments. The accumu-
Similarly, riverine ecotypes were found predomi-
lation of fine-grained sediments and organic
nantly in the Tanana Floodplain Ecodistrict because
material and increased moisture in valley bottoms
they are associated with flooding and sedimenta-
lead to thermal properties that are conducive to
tion. Alpine ecotypes were limited in distribution
permafrost formation. In the EielsonTanana
to the SteeseWhite Mountain Ecodistrict because
Floodplain Ecodistrict, ecosections on Riverbed,
of the higher topographic relief.
Active- and Inactive-Cover Deposits are linked by
This successive partitioning of the landscape is
the flooding regime and sediment transport of the
useful not only for field sampling, but improves
Tanana River. In the Tanana Flats Ecodistrict,
the reliability of conceptual models of ecosystem
ecosections on Abandoned Floodplain Cover
distribution developed from toposequences. In
Deposit, Alluvial Fan Abandoned Floodplain
turn, the ecodistricts are useful for land manage-
Cover Deposit, and Glaciofluvial Abandoned
ment, because management concerns and objec-
Floodplain Cover Deposit are all linked by hydro-
tives will be different, depending on the predomi-
logic changes during deglaciation in the Holo-
nant geomorphic and vegetation characteristics of
cene. Ecosections associated with organic depos-
the area.
46
Go to contents page
Previous Page
