broken by small, isolated, bedrock knobs that pro-
described many of the vegetation types on FWA.
trude through ancient accumulations of glacial and
The Tanana River Basin Cooperative Study, involv-
fluvial sediments from the Alaska Range (Fig. 6).
ing the USDA Soil Conservation Service, the U.S.
Examples of these features include the Wood River
Fish and Wildlife Service, and the State of Alaska
Buttes and Clear Creek Butte.
Department of Natural Resources, produced de-
Rounded, even-topped ridges or domes with
tailed vegetation maps and resource inventories
gentle to steep side slopes characterize the Yukon
of the Tanana Basin during the 1980s (SCS/DNR
Tanana Upland geographic division north of the
1990). Land-cover mapping was conducted at a
scale of 1:31,680 for over 56,680 km2 (14,000,000
Tanana River (Wahrhaftig 1965) (Fig. 5). The ridges
in the eastern part of the YMA have numerous rock
acres), including all of FWA. These land-cover
outcrops and granite tors. Valley bottoms are gen-
maps were digitized into a GIS for 11 of the 14
erally flat and 0.40.8 km (0.250.5 mi) wide within
USGS 15-minute quadrangles covering FWA. In
a few kilometers of the headwaters. The transi-
this effort, 97 cover types were mapped using an
tion from lowland to hillslope in both geographic
earlier version (198486) of the Viereck vegetation
sections is, in most cases, quite abrupt.
classification system. National Wetland Inventory
Floodplain elevations range from 123 m (370
(NWI) maps (1:63,360 scale) were also derived
ft) at the mouth of the Wood River in the western
from this same mapping effort but have not yet
part of the study area to the domes of the YMA
been digitized into GIS coverages.
that border the floodplain to the east, which at-
In general, the vegetation of Fort Wainwright
tain elevations of 996 m (3265 ft).
is a mosaic of forest, grassland, shrub, bog,
Soils of the Fort Wainwright area have been
fen, and alpine tundra types that have formed
mapped and described in a broad exploratory level
primarily as a result of slope, aspect, elevation,
of survey (Rieger et al. 1979). On south-facing
parent material, permafrost, and succession fol-
slopes, soils are generally well drained and free of
lowing wildfire (Viereck et al. 1986). Because of
permafrost, while poorly drained north-slope soils
the dry continental climate and low sun angle,
are usually underlain by permafrost. South slopes
there is a great contrast in the vegetation of
are occupied by well-drained silt loams that grade
north-facing vs. south-facing slopes. This is par-
from shallow, gravelly silt near ridgetops through
ticularly evident in the forested slopes of the YMA
silt loams of the midslopes to deep, moist silt loams
(Fig. 5) and on the buttes of Tanana Flats. The pres-
ence or absence of permafrost, closely correlated
of the lower slopes. Drainage bottoms and depres-
with slope and aspect, has also been shown to be
sions are occupied by shallow, gravelly silt loam
a dominant factor in the distribution of vegeta-
with a thick overlying peat layer and underlying
tion types (Dyrness and Grigal 1979). Because of a
permafrost. Soils of north-facing slopes are shal-
high frequency of fires in interior Alaska (Gabriel
low, gravelly silt loams with thick cover and per-
and Tande 1983, Viereck 1973), most of FWA tends
mafrost.
to be in successional stages, masking the factors
The greater portion of the YMA is rolling to hilly
that control the distribution of more mature veg-
upland, covered by silt loam soils developed in
etation types. A more detailed description of the
the silt mantle of hills and ridges bordering the
vegetation types is provided in Appendix A of this
Tanana River valley. Stratified, silty to gravelly
report.
stream-deposited materials occupy low terraces
adjoining the Tanana and Chena Rivers. Soils de-
veloped in these materials are well-drained, allu-
vial silty and sandy loams.
METHODS
Wet depressions and much of Tanana Flats and
the Chena River lowlands are covered by thick
Preliminary checklist development
A list of vascular taxa that could potentially
peat deposits presumably underlain by perma-
occur within the study area was compiled from
frost. Polygonal ground, thaw lakes, pingos, and
prior studies in the region (the starred references
other expressions of permanently frozen ground
in the Selected Bibliography). The Northern Plant
were observed in these areas.
Documentation Center (Herbarium, University of
Alaska Museum) also provided a list of collections
Vegetation
for an area centering on FWA (Batten 1995). Inter-
The vegetation of Alaska has been classified by
views were conducted with area and regional ex-
Viereck et al. (1992); they have summarized and
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