LOCATION YACOLT WAEstablished Series
TAXONOMIC CLASS: Medial, ferrihydritic, mesic Pachic Fulvudands
TYPICAL PEDON: Yacolt loam, woodland. (Colors are for moist soil unless otherwise stated.)
A1--0 to 6 inches; very dark brown (10YR 2/2) loam, brown (10YR 4/3) when dry; moderate fine and very fine granular structure; slightly hard, very friable, nonsticky, nonplastic; abundant fine, medium and large roots; about 20 percent shot; moderately acid; clear smooth boundary. (4 to 7 inches thick)
A2--6 to 15 inches; very dark brown (10YR 2/2) loam, brown (10YR
4/3) when dry; moderate fine and medium granular structure; soft, friable, nonsticky, nonplastic; abundant fine, medium, and large roots; about 20 percent shot; moderately acid; gradual wavy boundary. (5 to 11 inches thick)
A3--15 to 23 inches; very dark brown (10YR 2/2) gravelly loam, brown (10YR 4/3) when dry; moderate medium granular structure; slightly hard, very friable, nonsticky, nonplastic; abundant fine, medium, and large roots; moderately acid; clear wavy boundary. (5 to 10 inches thick)
AB--23 to 30 inches; dark brown (10YR 3/3) gravelly loam, yellowish brown (10YR 5/4) when dry; moderate fine subangular blocky structure; slightly hard, firm, slightly sticky, slightly plastic; plentiful fine and medium roots; common very fine tubular pores; moderately acid; clear wavy boundary. (0 to 9 inches thick)
BW--30 to 39 inches; dark yellowish brown (10YR 4/4) gravelly loam, pale brown (109YR 6/3) when dry; moderate fine subangular blocky structure; slightly hard, friable, slightly sticky, slightly plastic; few fine fibrous roots; common very fine tubular pores; few fine prominent black (N2/) manganese stains; moderately acid; gradual wavy boundary. (7 to 12 inches thick)
C--39 to 61 inches; dark brown (7.5YR 4/4) stony loam, light brown (10YR 6/4) when dry; common medium faint strong brown (7.5YR 5/6) mottles; massive; slightly hard, friable, slightly sticky, slightly plastic; few fine fibrous roots; few very fine tubular pores; moderately acid.
TYPE LOCATION: Clark County, Washington. Near Rock Creek, 150 feet north of State Department of Natural Resources gravel storage; 2,000 feet north and 550 feet west of the southeast corner of sec. 5, T. 3 N., R. 4 E.
RANGE IN CHARACTERISTICS: The average annual soil temperature at 20 inches ranges from 47 to 52 degrees F. The umbric epipedon is 20 to 35 inches thick. The particle-size control section averages 15 to 35 percent rock fragments.
The A horizons range from very dark brown to black, and from loam to gravelly loam.
The AB and Bw horizons range in moist value from 3 to 4 and in moist chroma from 3 to 6 in 210YR or 7.5YR hues, and are gravelly loam, stony loam, or cobbly loam.
The C horizon ranges in moist value and chroma from 3 to 6, and is stony loam, cobbly loam, or gravelly loam. Soil reaction ranges from moderately acid to strongly acid.
COMPETING SERIES: These are the Bull Run and Parkdale series. Bull Run and Parkdale soils have an umbric epipedon less than 20 inches thick and less than 15 percent coarse fragments in the particle-size control section.
GEOGRAPHIC SETTING: These soils are terraces at elevations of 400 to 1,100 feet. Slopes are 0 to 15 percent. The regolith consists of volcanic ash and pumice mixed with glacial colluvium and alluvium from andesite and basalt. These soils occur in a hum,id climate having an average annual precipitation of about 85 inches with relatively cool, dry summers and mild, wet winters; with an average January temperature of about 32 degrees F, an average July temperature of about 65 degrees F, a mean annual temperature of about 49 degrees F, and a growing season of about 137 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These include the Cinebar and Olympic soils. Olympic soils have less than 60 percent pyroclastic material.
DRAINAGE AND PERMEABILITY: Well drained; moderate permeability; slow to medium runoff depending on slope.
USE AND VEGETATION: Woodland, hay and pasture; Douglas-fir, vine maple, and brackenfern.
DISTRIBUTION AND EXTENT: Southwestern Washington and northwestern Oregon. Series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Clark County, Washington, 1967.
REMARKS: Diagnostic horizon and feature recognized in this pedon ae an umbric epipedon from the surface to 30 inches and a cambic horizon from 30 to 36 inches.