LOCATION COHOE AK

Established Series
Rev. RBH-SR
8/95

COHOE SERIES

The Cohoe series consists of very deep, well drained soils formed in silty
volcanic ash and loess overlying marine sediments and, in places, gravelly
glacial drift. Cohoe soils are on upland slopes. Slopes range from 0 to
60 percent. Mean annual temperature is about 35 degrees F., and the average
annual precipitation is about 24 inches.

TAXONOMIC CLASS: Medial over loamy, mixed Typic Haplocryods

TYPICAL PEDON: Cohoe silt loam - forest (All colors are for moist soil)

Oi--3 to 2 inches; forest litter

Oe--2 inches to 0; dark reddish brown (5YR 2/2) mat of roots, moss, and
decomposing plant parts; charcoal particles; very strongly to strongly acid; abrupt smooth boundary. (2 to 3 inches thick)

E--0 to 1 1/2 inches; gray (10YR 5/1) silt loam, with common small distinct mottles of reddish brown; weak very fine subangular blocky structure; very friable; roots plentiful; very strongly acid; abrupt wavy
boundary. (1 to 2 inches thick)

Bs--1 1/2 to 7 inches; brown (7.5YR 4/4) silt loam, with discontinuous
layer of dark reddish brown (5YR 3/4) at top of horizon; patches of grayish
brown (10YR 5/2) occur throughout horizon; weak medium subangular blocky
structure; very friable; roots plentiful; strongly to medium acid; clear
wavy boundary. (5 to 7 inches thick)

BC--7 to 16 inches; dark yellowish brown (10YR 4/4) silt loam; very weak medium subangular blocky structure; very friable; few roots; medium
acid; gradual boundary. (8 to 12 inches thick)

2C1--16 to 30 inches; olive (5Y 4/3) coarse silt loam, with few streaks
of strong brown at bottom of horizon; weak fine platy structure; very friable; few roots; fine pores common; medium acid; clear wavy boundary.

3C2--30 to 39 inches; olive gray (5Y 4/2) very fine sandy loam; weak to
moderate fine platy structure; very friable; few roots; occasional moderately indurated horizontal bands of strong brown; medium acid.

4C3--39 to 50 inches +; olive gray (5Y 5/2) gravelly clay loam;massive;
fri ble to firm; no roots; contains layers of fine sand and silt loam; medium to slightly acid.

TYPE LOCATION: Kenai-Kasilof Area, Alaska. SE 1/4, SE 1/4, section 18, T.
1N., R. 12W., Seward Meridian. About 4 miles south of Clam Gulch.

RANGE IN CHARACTERISTICS: Thickness of the solum ranges from 10 to 22 inches. Depth to underlying stratified silty and sandy sediments ranges
from 24 to 39 inches. Pebbles and fine gravel may occur below 24 inches;
in places the substratum is gravelly glacial drift. Clay minerals are dominantly allophane. Coarse white grains of sandsize volcanic ash are commonly mixed with the E horizon. The Bs horizon commonly has patchy colors of dark reddish brown and brown with hues of 5YR and 7.5YR and with
values of 3 to 4 and chromas of 2 to 6. The C horizon typically has brown
to olive gray colors in hues from 2.5Y to 10YR with values of 4 to 5 and
chromas of 2 to 3. Mottling may occur below the solum.

COMPETING SERIES: These are the Boulder Point, Darling, Kenai, Kroto, Strandline, and Whitsol series of the same family. Boulder Point soils are
silty throughout the control section. Darling soils have more than 35 percent fine sand or coarser in the control section. Kenai soils have more
than 18 percent clay in the control section. Kroto and Strandline soils
have firm till substratums. Whitsol soils are bisequal.

GEOGRAPHIC SETTING: Cohoe soils occur mostly on nearly level to moderate
slopes of the uplands. Slope gradients are dominantly less than 5 percent
but range from 1/2 percent to 45 percent. The parent material is a mixture
of silty volcanic ash and loess overlying medium and fine textured marine
sediments and, in places, gravelly glacial drift. The climate is maritime
with cool summers and long moderately cold winters. Average annual precipitation is between 20 and 28 inches and the average annual temperature is between 33 and 36 degrees.

GEOGRAPHICALLY ASSOCIATED SOILS: These include the Salamatof, Spenard, and
Island series. Salamatof soils are poorly drained peat soils occupying muskegs. Spenard soils are poorly drained mineral soils in shallow depressions. Island soils are dark colored soils that occupy grass covered
areas surrounded by the forested Cohoe soils.

DRAINAGE AND PERMEABILITY: Well drained. Medium runoff and moderately slow permeability.

USE AND VEGETATION: Some areas have been cleared and used for potatoes,
hardy vegetables, hay, and pasture. The natural vegetation is an open growing white or Sitka spruce forest with an intermingling of paper birch
and balsam poplar. The forest floor commonly supports a growth of bluejoint grass and associated forbs and shrubs.

DISTRIBUTION AND EXTENT: Western Kenai Peninsula, Alaska. The Cohoe series is of moderate extent.

MLRA OFFICE RESPONSIBLE: Anchorage, Alaska

SERIES ESTABLISHED: Kenai-Kasilof Area, Alaska. 1960.

REMARKS: The concept of the Cohoe series is poorly defined, especially in
terms of substratum properties. More field data is needed to firm up the
concept or the series should be inactivated (jpm, 2/87).

National Cooperative Soil Survey
U.S.A.

Contact: Mike Gracz Kenai Watershed Forum  PO Box 15301 Fritz Creek, AK  99603 907-235-2218

04 May 2007 10:19