LOCATION STEVENSON WAEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Humic Dystrudepts
TYPICAL PEDON: Stevenson loam-forested. (Colors are for moist soils unless otherwise noted.)
Oi--1 inch to 0; needles, leaves and twigs.
A1--0 to 4 inches; dark brown (7.5YR 3/2) loam, dark 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; medium acid (pH 5.8); clear wavy boundary. (3 to 6 inches thick)
A2--4 to 11 inches; dark brown (7.5 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; medium acid (pH 5.8); clear wavy boundary. (7 to 9 inches thick)
Bw1--11 to 28 inches; dark 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 soft saprolitic basalt; strongly acid (pH 5.4); clear wavy boundary. (15 to 25 inches thick)
Bw2--28 to 37 inches; dark yellowish brown (10YR 4/4) 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 soft saprolitic basalt material; strongly acid (pH 5.2); abrupt wavy boundary. (8 to 20 inches thick)
C--37 to 60 inches; dark yellowish brown (10YR 4/6) loam, yellowish brown (10Y 5/6) dry; massive; soft, friable, slightly sticky and slightly plastic; few fine roots; few fine irregular pores; 50 percent soft saprolitic basalt; 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. Mean annual soil temperature is 47 to 51 degrees F. The particle-size control section contains from 20 to 35 percent clay. Hard rock fragments in the particle-size control section averages from 0 to 15 percent and soft saprolitic material averages from 15 to 35 percent.
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 hard rock fragments and 35 to 60 percent soft saprolitic material.
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 soft saprolitic rock 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 pebbles 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. Average annual precipitation is 70 to 85 inches. Mean January temperature is about 27 degrees F, mean July temperature is about 65 degrees F. 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 OFFICE RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Skamania County, Washington, 1947.
REMARKS: Diagnostic horizons and features recognized in this pedon are an umbric epipedon from the mineral surface to 11 inches and a cambic horizon from 11 to 37 inches.
Classification changed 6/98 based on 1998 Keys to Soil Taxonomy. The competing series have not been revised.