RESULTS AND DISCUSSION

RESULTS AND DISCUSSION

on toe slopes were fine-grained with abundant rocks,

poorly drained, and had thick organic matter accumu-

Hierarchical organization of ecosystem

lations. Vegetation (Alaska Vegetation Classification)

components

ranged from partially vegetated on steep, exposed ridges

Toposequences

to open low shrub birchwillow scrub on moist upper

slopes to open black spruce dwarf tree scrub on lower

The principal foundation for ecosystem classifica-

slopes. Headwater floodplains supported open and

tion was the survey of ecosystem components (e.g.,

closed tall alder scrub.

topography, geomorphology, soil, hydrology, perma-

Within the Hayes Highland Plateau (Transect 3), the

frost, and vegetation) along seven toposequences.

geomorphology was dominated by old glacial moraines,

Cross-sectional profiles were constructed to illustrate

with minor amounts of headwater floodplain and or-

relationships among ecosystem components of the

ganic deposits (Fig. 7b). Permafrost usually was present.

seven toposequences (Fig. 6 and 7). The toposequences

The steeper, exposed slopes had well-drained, gravelly

are two-dimensional views of the structure of the

soils that supported open tall alder and open low shrub

lithofacies that we used as the basis for classifying and

birchericaceous scrub. Gentle upper and lower slopes

mapping geomorphic units. Examples from various

had saturated soils with thick organic matter accumu-

ecosubdistricts within the four ecodistricts (Hayes

Mountains, Delta Highlands, Delta Lowlands, and

lations and supported tussock tundra and open low shrub

birchericaceous scrub. Small headwater streams had

Middle Tanana Floodplain, see section on Ecodistricts)

fluvial deposits with interbedded silts, sands, and or-

are described below to illustrate some of the main eco-

ganics and the saturated soils supported closed shrub

logical relationships within Fort Greely.

birch scrub and wet sedge tundra.

Within the Molybdenum Ridge Mountains (Transect

5), geomorphology is dominated by weathered bedrock

Within the Little Delta River Glaciated Highlands

(Transect 2), the geomorphology was dominated by

and talus on steep slopes, and colluvium and

glacial moraines, with glaciofluvial deposits near the

retransported deposits on toe slopes (Fig. 7a). We as-

moraine terminus (Fig. 7c). The soils on the moraines

sumed that permafrost generally was present, although

were highly variable, ranging from massive gravel on

rocky soils prevented positive determination. The soils

ridges to fines with trace gravel where eolian silt has

on upper slopes were rocky, excessively drained, and

accumulated, to stratified silt and sandy material in

lacked organic matter accumulations, whereas the soils

Organic, massive

Fines, layered (Fl)

(Om)

Sands, massive

Organic, layered

(Sm)

(Ol)

Fines, massive (Fm)

Gravel, massive

(Gm)

Gravel with fines,

Fines with organics,

massive (Gfm)

massive (Fom)

(matrix-supported

gravel)

Fines with organic

Rubble, massive

inclusions, massive

(Rm)

(Fomt)

Rubble w fines,

Fines with trace

massive (Rfm)

gravel (Fgm)

Rubble (angular

Fines with trace

channels, flag-

gravel, turbated

stones, 2-380 mm),

(Fgmt)

(R)

Figure 6. Soil patterns used for lithofacies encountered along

toposequences on Fort Greely.