ping (lower Clear Creek, Blair Lakes Training
grouping of ecosystem components, and (3) clas-
Facilities, and Charlie Battery), polygon bound-
sification and mapping of smaller-scale ecosys-
aries were delineated on acetate overlaying the
tems (ecosections and ecodistricts). Results of the
photographs using a mirror stereoscope. The
classification and mapping of the various ecosys-
boundaries were digitized and geo-rectified using
tem components (geomorphology and vege-
control points obtained from distinct geographic
tation) and ecosystems at the various scales are
features recognizable on both the photographs
described below by providing a tabular descrip-
and Fort Wainwright Military Installation Maps
tion of each map unit, a map, and a tabular sum-
(1:50,000, Defense Mapping Agency Hydro-
mary of spatial extent.
graphic/Topographic Center, 1986). Reservation
boundaries and roads were obtained from the
Ecosystem components
U.S. Army Corps of Engineers. The positions of
Geomorphology. Field surveys identified 52
road corridors were updated using SPOT satellite
geomorphic units within the study area and
imagery. Maps were generated using Atlas GIS
included 43 terrestrial units and 9 water body
and Arc View software (ESRI, Redlands, Califor-
classes (Table 3). During mapping, 47 geomorphic
nia, 1996).
units were used, including 8 complex units (Table
The mapping of vegetation at 1:50,000 scale and
4, Fig. 4 and 5). Five units were not mapped, how-
use of the pre-existing SCS vegetation maps for eco-
ever, because they were either too small in extent
system mapping, which were based on integrated
or could not be differentiated on the aerial pho-
geomorphologyvegetation classes, required
tography. Classification and mapping was based
some compromises. First, the small scale required
on the geomorphic unit at the surface, although
a compromise in our ecosystem classification ap-
stratigraphic units that commonly are associated
proach. A true ecotype map should delineate indi-
with the surface geomorphic unit are included in
vidual vegetation types, while our polygons,
the descriptions.
which relied heavily on the SCS maps, resulted in
Within the Yukon Maneuver Area (YMA), the
numerous large polygons that included several
dominant geomorphic units include Residual Soil,
vegetation types. In our revisions of the SCS
Upland Loess, Lowland Retransported Deposit,
maps, we emphasized reviewing the vegetation
Lowland Loess, Lowland Eolian Complex, and
classification for each polygon and inserting
Headwater Floodplain. These geomorphic units
breaks where polygons crossed geomorphic
reveal the dominance of hill slope and eolian pro-
boundaries. Because of the large effort that would
cesses. Within the Tanana Flats, the dominant geo-
have been required, we decided to accept these
morphic units include Meander Inactive Flood-
inconsistencies related to scale and inclusions and
plain Cover Deposit, Abandoned Floodplain
use the pre-existing maps that covered much of
Cover Deposit, Organic Fen, Organic Bog, Allu-
the area.
vial Fan Abandoned Cover Deposit, Glaciofluvial
Ecosection maps were produced by aggregating
Outwash Abandoned Cover Deposit, and Col-
ecotypes based on geomorphic units. Ecodistricts
lapse Scar Fen. These deposits reveal the Tanana
were delineated by overlaying acetate on a
Flats are dominated by fluvial processes and
1:175,000 false-color composite of 1991 Landsat
organic deposits associated with thermokarst.
TM (thermatic mapper) imagery. The satellite
Much of the area was mapped as complex units
image was georeferenced using USGS (U.S. Geo-
because of the high interspersion of organic
logical Survey) topographic maps.
deposits associated with thermokarst.
The geomorphic units are ecologically impor-
tant because they represent areas with differing
Classification and mapping
The development of an ecological land classifi-
erosional and depositional environments and,
cation at multiple spatial scales involved three
therefore, are affected differentially by natural
phases: (1) classification of ecosystem components
occurring disturbances. For example, Meander
(topography, geomorphology, hydrology, soils,
Active Floodplain Cover Deposits are flooded fre-
and vegetation) from field data using standard
quently, and the frequent sediment deposition
classification systems, (2) derivation of a reduced
prevents development of a moss layer and con-
set of ecotypes (local ecosystems) by identifying
tributes nutrients that presumably contribute to
associations among ecosystem components
the vigorous growth of shrubs and saplings on
through graphical portrayal of spatial relation-
well-drained soils. Abandoned Floodplain Cover
ships along toposequences and hierarchical
Deposits, on the other hand, are rarely flooded
11
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