LOCATION ILLAHEE OR

Established Series
Rev. RGC/TDT
06/2011

ILLAHEE SERIES

The Illahee series consists of very deep, well drained soils on mountain side slopes. These soils formed in colluvium and residuum derived dominantly from welded tuffs and flow basalts. Slopes are 3 to 90 percent. The mean annual precipitation is about 70 inches and the mean annual temperature is about 43 degrees F.

TAXONOMIC CLASS: Loamy-skeletal, isotic, frigid Typic Humudepts

TYPICAL PEDON: Illahee very gravelly loam, on a northwest slope of 35 percent under coniferous forest at an elevation of 4245 feet. (Colors are for moist soil unless otherwise stated.)

Oi--0 to 1 inch; slightly decomposed fir needles, twigs, and fern fronds.

A1--1 to 11 inches; black (10YR 2/1) very gravelly loam, dark grayish brown (10YR 4/2) dry; moderate fine granular structure; slightly hard, friable, nonsticky and nonplastic; many very fine, fine, and medium, and common coarse roots; common very fine irregular pores; 35 percent gravel; strongly acid; clear wavy boundary. (8 to 12 inches thick)

A2--11 to 16 inches; very dark brown (10YR 2/2) very gravelly loam, brown (10YR 5/3) dry; moderate fine and medium granular structure; slightly hard, friable, nonsticky and nonplastic; many very fine, fine and medium, and common coarse roots; common very fine irregular pores; 40 percent gravel; very strongly acid; clear wavy boundary. (4 to 6 inches thick)

Bw1--16 to 39 inches; very dark grayish brown (10YR 3/2) very gravelly loam, pale brown (10YR 6/3) dry; weak very fine and fine subangular blocky structure; slightly hard, friable, nonsticky and nonplastic; common very fine, fine, medium and coarse roots; common fine irregular pores; 45 percent gravel and 5 percent cobbles; strongly acid; clear wavy boundary. (20 to 25 inches thick)

Bw2--39 to 48 inches; dark brown (10YR 3/3) very gravelly loam, light yellowish brown (10YR 6/4) dry; weak very fine and fine subangular blocky structure; slightly hard, friable, slightly sticky and nonplastic; common very fine, fine, and medium roots; common fine irregular pores; 40 percent gravel and 10 percent cobbles; strongly acid; clear wavy boundary. (8 to 11 inches thick)

BC--48 to 61 inches; dark yellowish brown (10YR 3/4) very cobbly loam, very pale brown (10YR 7/4) dry; weak very fine and fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine, fine, and medium roots; common fine irregular pores; 30 percent gravel and 25 percent cobbles; very strongly acid.

TYPE LOCATION: Douglas County, Oregon; 2 1/4 miles northwest of Burnt Mtn. in the western Cascade Mtns.; 1155 feet east and 945 feet south of the northwest corner of section 35, T. 25 S., E. 2 W.

RANGE IN CHARACTERISTICS: Solum thickness ranges from 40 to 60 inches or more. The mean annual soil temperature is 42 to 47 degrees F. The soil is usually moist and is dry between 4 and 12 inches for less than 45 consecutive days during the summer. The umbric epipedon is 10 to 20 inches thick. Hue is 10YR or 7.5YR. Rock fragments are of basaltic and welded tuff lithology.

The A horizon has value of 2 or 3 moist, 4 or 5 dry and chroma of 1 or 2 moist and 2 or 3 dry. Rock fragments range from 35 to 60 percent gravel and 0 to 15 percent cobbles. It is very strongly acid to moderately acid. Organic matter is 5 to 9 percent.

The Bw horizon has value of 3 or 4 moist, 5 to 7 dry and chroma of 2 to 6 moist and 3 or 4 dry. It is very gravelly loam, very cobbly loam, or extremely gravely loam with 15 to 25 percent clay. Rock fragments range from 30 to 55 percent gravel and 5 to 20 percent cobbles. It is very strongly acid or strongly acid.

COMPETING SERIES: These are the Balsam, Scaredman and Stackyards series. The Balsam soils contain rock fragments of gneiss or granite origin and few to common mica flakes throughout the particle-size control section. The Scaredman soils are 20 to 40 inches to a lithic contact. Stackyards soils are over 60 inches deep to bedrock and average 25 to 35 percent clay in the particle size control section.

GEOGRAPHIC SETTING: Illahee soils are on mountain side slopes. Elevation is 2800 to 4600 feet. The soils formed in colluvium and residuum derived from welded tuffs and flow basalts. Slopes are 3 to 90 percent. The mean annual temperature is 40 to 45 degrees F. and the mean annual precipitation is 60 to 80 inches. The frost-free season is 50 to 100 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Lempira, Telemon, and Thistleburn soils. Lempira soils are medial. Telemon soils are somewhat poorly and moderately well drained, are fine textured, and have an argillic horizon.

DRAINAGE AND PERMEABILITY: Well drained; moderately rapid permeability.

USE AND VEGETATION: These soils are used for timber production, wildlife habitat, and watershed. The native vegetation includes western hemlock, western white pine and Douglas-fir with an understory of Pacific rhododendron, western swordfern, red huckleberry, cascade Oregongrape, oxalis, salal, vine maple, American twinflower, golden chinkapin, western princes pine and whitevein shinleaf.

DISTRIBUTION AND EXTENT: Cascade Mountain Range, Oregon; MLRA 3. The series is of moderate extent.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon

SERIES ESTABLISHED: Douglas County, Oregon, 1994.

REMARKS: Diagnostic horizons and features recognized in this pedon are:

Umbric epipedon - from 1 to 16 inches (A1 and A2 horizons).

Cambic horizon - from 16 to 48 inches (Bw1 and Bw2 horizons).

Particle-size control section - from 11 to 41 inches (A2, Bw1, and upper Bw2 horizons).

National Cooperative Soil Survey
U.S.A.