LOCATION WILHOIT OR

Established Series
Rev. AJG/GLG/RWL
06/2011

WILHOIT SERIES

The Wilhoit series consists of deep, well drained soils that formed in colluvium weathered from andesite, breccias, and tuffs mixed with volcanic ash. Wilhoit soils are on mountains and have slopes of 5 to 60 percent. The mean annual precipitation is about 80 inches, and the mean annual temperature is about 43 degrees F.

TAXONOMIC CLASS: Fine-loamy, isotic, frigid Andic Humudepts

TYPICAL PEDON: Wilhoit gravelly medial loam, forested. (Colors are for moist soil unless otherwise noted.)

Oi--0 to1 inch; slightly decomposed litter of needles, leaves, and twigs.

A1--1 to 4 inches; very dark grayish brown (10YR 3/2) gravelly medial loam, dark grayish brown (10YR 4/2) dry; strong fine granular structure; slightly hard, friable, slightly sticky and slightly plastic; weakly smeary; many very fine, fine and medium, and few coarse roots; many fine irregular pores; 15 percent hard gravel; moderately acid (pH 5.6); clear smooth boundary. (4 to 8 inches thick)

A2--4 to 15 inches; very dark grayish brown (10YR 3/2) medial loam, brown (10YR 4/3) dry; strong fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; weakly smeary; many very fine, fine and medium, and few coarse roots; many fine irregular pores; 5 percent gravel; strongly acid (pH 5.4); clear smooth boundary. (5 to 12 inches thick)

BA--15 to 33 inches; dark brown (10YR 3/3) medial loam, brown (10YR 5/3) dry; moderate medium subangular blocky structure; slightly sticky and slightly plastic; weakly smeary; common medium and coarse, and few fine roots; many very fine tubular pores; 10 percent gravel; strongly acid (pH 5.2); gradual smooth boundary. (5 to 20 inches thick)

Bw--33 to 43 inches; brown (10YR 4/3) clay loam, yellowish brown (10 5/4) dry; moderate medium subangular blocky structure; hard, firm, sticky and slightly plastic; few fine and very fine roots; many very fine tubular pores; 10 percent gravel; strongly acid (pH 5.2); gradual smooth boundary. (5 to 15 inches thick)

BC--43 to 52 inches; brown (7.5YR 4/4) gravelly loam, yellowish brown (10YR 5/4) dry; weak medium subangular blocky structure; hard, firm, slightly sticky and slightly plastic; few fine and very fine roots; many very fine tubular pores; 25 percent gravel; strongly acid (pH 5.2). (5 to 10 inches thick)

Cr--52 inches; soft weathered tuff.

TYPE LOCATION: Clackamas County, Oregon; about 1/2 mile SE of the Bee Ranch; in the NW 1/4 NE 1/4 NE 1/4, sec. 23, T, 7 S., R. 3 E.

RANGE IN CHARACTERISTICS: The soil is usually moist but is dry for less than 45 consecutive days in all parts between depths of 4 and 12 inches. The mean annual soil temperature is 43 to 47 degrees F. The depth to a paralithic contact is 40 to 60 inches. The clay content in the particle-size control section is 18 to 30 percent. The umbric epipedon is 20 to 34 inches thick. Moist bulk density is 0.85 to 0.95 grams per cubic centimeter throughout.

The A and BA horizon has hue of 10YR or 7.5YR, value of 2 or 3 moist, 3 through 5 dry, and chroma of 2 or 3 moist and dry. It is gravelly loam in the upper part ranging to silt loam or loam in the lower part. Rock fragments range from 5 to 30 percent gravel and 0 to 15 percent cobbles. Acid oxalate extractable aluminum plus 1/2 the iron of 1. 0 to 2.0 percent and less than 2.0 cmol kg of the fine earth of 1N KCL extractable aluminum.

The Bw horizon has hue of 10YR or 7.5YR, value of 3 or 4 moist, 4 through 6 dry, and chroma of 2 through 4 moist and dry. It is gravelly loam, loam or clay loam. Rock fragments range from 5 to 30 percent gravel and 0 to 15 percent cobbles, but not exceeding 35 percent total.

COMPETING SERIES: There are no competing series.

GEOGRAPHIC SETTING: Wilhoit soils are on mountains and have slopes of 5 to 60 percent. Elevation is 1,800 to 3,000 feet. They formed in colluvium weathered from andesite, tuffs, and breccias, mixed with volcanic ash. The climate is characterized by cool wet winters and warm moist summers. The mean annual precipitation is 70 to 90 inches. The mean annual temperature is 41 to 45 degrees F. The frost-free period is 45 to 110 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Fernwood, Zygore, and Memaloose soils. Fernwood soils are 20 to 40 inches deep to a lithic contact and are loamy-skeletal. Zygore soils are loamy-skeletal. Memaloose soils have an ochric epipedon, are 20 to 40 inches deep to a paralithic contact and have hue of 2.5YR or 5YR.

DRAINAGE AND PERMEABILITY: Well drained; moderate permeability.

USE AND VEGETATION: Wilhoit soils are used for timber production, wildlife habitat, and recreation. Native vegetation is Douglas-fir, western hemlock, vine maple, red alder, Oregon grape, western swordfern and salal.

DISTRIBUTION AND EXTENT: It is along the west slope of the Cascade Mountains in northern Oregon; MLRA 3. The series is inextensive.

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

SERIES ESTABLISHED: Clackamas County, Oregon, 1982.

REMARKS: Diagnostic horizons and features recognized in this pedon:

Umbric epipedon - from 0 to 33 inches (A1, A2, and BA horizons)

Cambic horizon - from 33 to 43 inches (Bw horizon)

Andic feature - from 0 to 33 inches having an estimated acid oxalate extractable aluminum plus one-half iron of 1.0 to 2.0 percent.

Particle-size control section - from 10 to 40 inches

National Cooperative Soil Survey
U.S.A.