Table 7 (cont'd).
Geomorphic unit
Description
Upper Perennial
Permanently flooded channels of freshwater rivers where the gradient is relatively high, and dis-
River, Glacial
charge and water quality are affected by glacial meltwater. Rivers appear brown from high concentra-
tions of suspended sediments during mid-summer. Rivers experience peak flooding during mid-
summer.
Deep Isolated
Deep (>1.5 m) ponds and lakes that do not freeze to the bottom during winter. These lakes are found
Lakes, Bedrock
in uplands and highlands, do not have distinct outlets and are not connected to rivers. Bottoms are
rocky.
Deep Isolated
Deep (>1.5 m) "kettle" ponds and lakes that do not freeze to the bottom during winter. The lakes do
Lakes, Morainal
not have distinct outlets and are not connected to rivers. The lakes develop from the melting of glacial
ice in moraines and typically have rocky bottoms.
Deep Isolated
Deep (>1.5 m) ponds and lakes that do not freeze to the bottom during winter. The lakes do not
Lakes, Thaw
have distinct outlets and are not connected to rivers. The thaw lakes develop from the melting of ice-
rich permafrost and typically have muddy, organic-rich bottoms.
Shallow Isolated
Shallow (<1.5 m) ponds or small lakes associated with old river channels. Water freezes to the
Pond, Riverine
bottom during winter and thaws by early to mid-June. Sediments are fine-grained silt and clay.
ing and sedimentation. Only a few of these characteris-
Very few climate data are available for evaluating
tics were differentiated in the final ecotypes (see
the climatic differences across the major topoclimatic
Ecotype section) to reduce the number of classes. These
boundaries used in differentiating the ecodistricts.
waterbody types are preserved in the ecosection (geo-
Short-term monitoring at numerous locations by
morphic unit) codes in the map database and can be
Holmes and Benninghoff (1957) found that the mean
monthly air temperature for July 1955 was 13C in the
used for specific analyses, such as habitat use.
Jarvis Creek Lowlands as compared to 10C in the
Ecodistricts
Jarvis Creek Glaciated Highlands.
Classification and mapping
Ecological relationships
Five ecodistricts and 25 ecosubdistricts were delin-
eated within Fort Greely, based on differences in physi-
The ecodistricts provide a way of stratifying the dis-
ography and geomorphology (Table 9, Fig. 18 and 19).
tribution of ecotypes that frequently are contextually
Ecosubdistricts differ from ecodistricts in that
related on the landscape (Fig. 21 and 22). For example,
ecosubdistricts delineate smaller areas with less varia-
rocky alpine ecotypes are found primarily in the Hayes
tion in the composition of the geomorphic units.
and Gakona Mountain ecodistricts because of the high
The two main ecological factors used in differenti-
elevations and rugged topography. Lowland Dwarf
ating ecodistricts and ecosubdistricts were physiogra-
Scrub Bogs, Lacustrine Fen Meadows, and Lowland
phy and climate associated with topography
Wet Mixed Forests were some of the ecotypes found
(topoclimate). The main factors determined by physi-
exclusively in the Delta Lowlands. Riverine ecotypes
ography were elevations and ruggedness, as exempli-
were found primarily in the Middle Tanana Floodplain,
fied by the shaded-relief map of the area (Fig. 20).
although smaller patches were associated with small
Mountains and highland plateaus extended above the
headwater streams within the Delta Lowlands and
treeline at about 900 m. Highland areas typically ranged
nearby highlands
from 600900 m and generally had glacial deposits or
This successive partitioning of the landscape is use-
residual soils formed from bedrock. Lowland areas typi-
ful not only for field sampling, but improves the reli-
cally were below 600 m and generally had old
ability of conceptual models of ecosystem distribution
glaciofluvial deposits, old moraines, retransported de-
developed from toposequences. In turn, the ecodistricts
posits, and lowland loess. Glaciated highlands and low-
are useful for land management, because management
lands were differentiated because of the rugged kame
concerns and objectives will be different, depending
and kettle topography formed by melting out of glacial
on the predominant geomorphic and vegetation char-
ice.
acteristics of the area.
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