LOCATION STEVENSON WA

Established Series
Rev. EH/AG/RJE
06/2011

STEVENSON SERIES

The Stevenson series consists of deep, well drained soils that formed in landslide material from basalt, andesite and conglomerate. Stevenson soils are on toe slopes and backslopes of uplands. Slopes range from 2 to 50 percent. The mean annual precipitation is about 80 inches and the mean annual temperature is about 47 degrees F.

TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Typic Humudepts

TYPICAL PEDON: Stevenson loam-forested. (Colors are for moist soils unless otherwise noted.)

Oi--0 to 1 inch; slightly decomposed litter of needles, leaves and twigs.

A1--1 to 5 inches; dark brown (7.5YR 3/2) loam, brown (7.5YR 4/4) dry; weak fine and medium granular structure; soft, very friable, slightly sticky and slightly plastic; many very fine and fine roots; many very fine, fine, and medium irregular pores; 5 percent concretions; moderately acid (pH 5.8); clear wavy boundary. (3 to 6 inches thick)

A2--5 to 12 inches; dark brown (7.5YR 3/3) loam, brown (7.5YR 5/4) dry; weak medium granular structure; soft, friable, slightly sticky and slightly plastic; many very fine, fine and few medium roots; many very fine, fine, and medium irregular pores; 5 percent concretions; moderately acid (pH 5.8); clear wavy boundary. (7 to 9 inches thick)

Bw1--12 to 29 inches; brown (7.5YR 4/4) loam, brown (7.5YR 5/4) dry; weak medium subangular blocky structure; soft, friable, slightly sticky and slightly plastic; common very fine and fine and few medium and coarse roots; common fine and medium irregular pores; 5 percent basaltic paragravel; strongly acid (pH 5.4); clear wavy boundary. (15 to 25 inches thick)

Bw2--29 to 38 inches; dark yellowish brown (10YR 4/4) very paragravelly loam, yellowish brown (10YR 5/4) dry; weak fine and medium subangular blocky structure; soft, friable, slightly sticky and slightly plastic; few very fine, fine, and medium roots; many fine and medium irregular and common medium tubular pores; 40 percent basaltic paragravel; strongly acid (pH 5.2); abrupt wavy boundary. (8 to 20 inches thick)

C--38 to 61 inches; dark yellowish brown (10YR 4/6) very paragravelly loam, yellowish brown (10YR 5/6) dry; massive; soft, friable, slightly sticky and slightly plastic; few fine roots; few fine irregular pores; 50 percent basaltic paragravel; strongly acid (pH 5.2).

TYPE LOCATION: Skamania County, Washington, about 300 feet north and 1,750 feet west of the SE corner, sec. 13 T. 3 N., R. 7 E.

RANGE IN CHARACTERISTICS: The solum is 35 to 55 inches thick. The mean annual soil temperature is 47 to 51 degrees F. The particle-size control section contains from 20 to 35 percent clay. Rock fragments in the particle-size control section average 0 to 15 percent and paragravels average 15 to 35 percent. The umbric epipedon is 10 to 15 inches thick.

The A horizon has hue of 7.5YR or 10YR, value of 4 or 5 dry, chroma of 2 or 3 moist, and 2 to 4 dry.

The Bw horizon has hue of 7.5YR or 10YR, value of 5 through 7 dry, and chroma of 4 through 6 moist and dry. It is clay loam, loam, or silt loam. Soil reaction is strongly acid or moderately acid in the B and C horizons.

The C horizon has hue of 10YR or 7.5YR, value of 4 or 5 moist, 5 through 7 dry, and chroma of 4 to 6 moist and dry. It is clay loam or loam. It has 0 to 35 percent rock fragments and 35 to 60 percent pararock fragments.

COMPETING SERIES: These are the Barbourville, Bohannon, Buckshot, Cutshin, Hembre, Horeb, Meda, Molalla, Preacher, and Wadell series. Barbourville, Buckshot, Cutshin, Horeb, Preacher, and Wadell soils lack pararock fragments in the control section. Bohannon soils have a paralithic contact at depths of 20 to 40 inches. Hembre soils have hue of 5YR in the B horizon within the control section. Meda soils are gravelly in the control section and have a sola 20 to 30 inches thick. Molalla soils have 5 to 25 percent very soft weathered gravel in the Bw horizon.

GEOGRAPHIC SETTING: Stevenson soils are on toe slopes and backslopes of old landslide areas, at elevations of 100 to 1,200 feet and the relief in general is hummocky. They formed in colluvial material from basalt, andesite and conglomerate. Slopes are 2 to 50 percent. Summers are warm and dry and winters are cool and wet. The mean annual precipitation is 70 to 85 inches. Mean January temperature is about 27 degrees F, mean July temperature is about 65 degrees F. The mean annual temperature is 46 to 48 degrees F. The frost-free season is 110 to 150 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the St. Martin and Steever soils. St. Martin soils are in the fine family. Steever soils are loamy-skeletal.

DRAINAGE AND PERMEABILITY: Well drained; slow to rapid runoff; moderate permeability.

USE AND VEGETATION: Used mainly for timber production, watershed and recreation. Small areas are cultivated or used as pasture. The town of Stevenson, Washington is located on this soil. Vegetation is mainly Douglas-fir, western hemlock, grand fir, western red cedar, bigleaf maple, and red alder, with an understory of vine maple, Pacific dogwood, creambush oceanspray, common snowberry, red huckleberry, dwarf rose, honeysuckle, bitter cherry, trailing blackberry, western brackenfern, deerfoot vanillaleaf, Oregongrape, insideout flower, and violet.

DISTRIBUTION AND EXTENT: Southern Skamania County. The series is of small extent.

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

SERIES ESTABLISHED: Skamania County, Washington, 1947.

REMARKS: Diagnostic horizons and features recognized in this pedon are;
umbric epipedon from 1 to to 12 inches
cambic horizon from 12 to 38 inches.

National Cooperative Soil Survey
U.S.A.