precipitation, and light surface winds. According
treeless bogs. On the warmest, well-drained sites,
the forests consist of closed spruce-hardwood
to NOAA records, the average annual tempera-
ture is 3.5C, with extremes ranging from 51
stands: white spruce (Picea glauca), paper birch
to 38C. The average annual precipitation is 28 cm
(Betula papyrifera), and quaking aspen (Populus
tremuloides). Productive balsam poplar (Populus
and annual snowfall averages 178 cm.
balsamifera)-white spruce forests form along flood-
The bedrock geology of interior Alaska is domi-
plains. On poorly drained sites, including those
nated by Precambrian micaceous schist of the
underlain by permafrost and on north-facing
Birch Creek formation, also including metamor-
slopes, the dominant forest species is black spruce
phic, sedimentary, and volcanic rocks of Paleo-
(Picea mariana). Bogs vary from rich sedge types
zoic age (Pw et al. 1966). Upland areas adja-
to oligotrophic sphagnum bogs. Sedge-tussock
cent to the Tanana River usually are covered with
meadows are prevalent. The Tanana Flats are
Pleistocene loess deposits varying from a few
noted particularly for the abundance of fens
centimeters on hilltops to over 60 m in low-lying
related to groundwater discharge from the Alaska
areas. Some loess has been retransported from
Range (Racine and Walters 1994).
hills to the valley bottoms where it forms laminar
Fires occur frequently during the summer, can
to massive silt-rich deposits in organic debris
be widespread in occurrence, and have large eco-
(Pw 1975). Fluvial sediments of the Tanana
logical effects (Viereck 1973, Viereck and Schan-
River occupy a large portion of the study area
delmeier 1980, Yarie 1981, Foote 1983). Before fire
(Collins 1990, Mason and Beget 1991, Mann et al.
suppression, an estimated 0.610.0 million hect-
1995). Glaciofluvial sediments from both the
ares had burned per year. Fires in interior Alaska
Healy and Riley Creek glaciations are evident in
primarily occur on tundra, bogs, and noncommer-
the southern portion of the study area (Pw et
cial forest lands.
al. 1966, Pw 1975, Pw and Reger 1983).
Soils of the study area tend to be poorly devel-
oped Inceptisols, undeveloped Entisols, or
METHODS
Histosols (Reiger et al. 1963, 1979, Swanson and
Field survey
M u n g o v e n 1998). Ochrepts (well-drained
Inceptisols that have only small amounts of
Field surveys on Fort Wainwright were con-
organic matter at the surface) occur on hills where
ducted at 240 plots during September 1994, July
permafrost generally is absent. Aquepts (wet
S e p t e m b e r 1995, and September 1998, and
Inceptisols with thin to thick layers of poorly
included two levels of sampling effort. First, the
decomposed organic matter) occur in poorly
main sampling effort was directed toward
drained areas and are commonly associated with
detailed descriptions of ecological characteristics
ice-rich permafrost. Aquents or Fluvents (wet min-
along toposequences (transects) to help identify
eral Entisols associated with shallow or deep
relationships among ecosystems. Second, less
water tables) occur on floodplains and seepage ar-
extensive sampling was done at sites represent-
eas. Histol soils, such as Fibrists (deep organic soils
ing areas not well documented by the transects to
composed mostly of undecomposed sedges or
provide additional ground reference information
mosses), occur in depressions or wet areas that
for photointerpretation.
undergo long periods of soil saturation. Perma-
For the toposequences, 11 sites were selected in
frost may or may not be present in these organic
ecosubdistricts representing the range of geomor-
soils. Overall, permafrost tends to occur on north-
phic types throughout the study area; these types
facing slopes and valley bottoms and is absent on
included areas of active paludification (collapse-
south-facing slopes, coarse-grained sediments,
scar fen formation), thaw settlement (thaw ponds
and areas of groundwater movement (Viereck et
and thermokarst terrain), fluvial processes (flood-
al. 1986, Williams 1970).
plains), glaciofluvial outwash, floodplain terraces,
Within interior Alaska, the interrelationships
lowland eolian and retransported materials
among geomorphology, slope, aspect, hydrology,
(lower slopes), upland slopes, and alpine tundra.
permafrost, and fire result in a complex pattern of
Transects were located in areas that maximized
vegetation types (Johnson and Vogel 1966, Nieland
the range of possible vegetation types over a short
distance (∼1 km). Sampling points for ecosystem
1975, Van Cleve et al. 1983, 1986; Viereck et al. 1983,
1993). Taiga ecosystems are dominated by open,
descriptions (812 per transect) were located in
slowly growing spruce, interspersed with occa-
distinct vegetation types (identifiable on aerial
sional dense, well-developed forest stands and
photographs) or vegetation types within geomor-
5
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