LOCATION STEHEKIN WA

Established Series
Rev. PHR/MPR
08/2011

STEHEKIN SERIES

The Stehekin series consists of very deep, well drained soils formed in mixed volcanic ash, glacial till, and colluvium. Stehekin soils are found on slopes of 0 to 65 percent on debris aprons, debris cones and valley walls of glaciated mountain landscapes. Mean annual precipitation is about 1,500 millimeters and the mean annual air temperature is about 5 degrees C.

TAXONOMIC CLASS: Loamy-skeletal, isotic Vitrixerandic Dystrocryepts

TYPICAL PEDON: Stehekin ashy sandy loam, with approximately 5 percent of the soil surface covered with subangular boulders, located on a non-forested northeast facing debris apron with a slope of 20 percent and an elevation of 1,010 meters. When described on September 6, 2009 the soil was slightly moist throughout. (Colors are for moist soil unless otherwise noted)

A--0 to 18 cm; dark yellowish brown (10YR 3/4) ashy sandy loam, yellowish brown (10YR 5/4) dry; moderate coarse subangular blocky structure; slightly hard, friable, nonsticky, nonplastic; common very fine to fine and few medium roots; common fine to medium irregular pores; 10 percent gravel; very strongly acid (pH 5.0); clear wavy boundary.

Bw--18 to 44 cm; dark yellowish brown (10YR 4/4) very cobbly sandy loam, light yellowish brown (10YR 6/4) dry; moderate fine subangular blocky structure; slightly hard, friable, nonsticky, nonplastic; common very fine to medium roots; common fine to medium irregular pores; 15 percent gravel, 15 percent cobbles, and 10 percent stones; very strongly acid (pH 5.0); gradual wavy boundary.

BC--44 to 109 cm; dark yellowish brown (10YR 4/4) very stony sandy loam, light yellowish brown (10YR 6/4) dry; moderate fine subangular blocky structure; moderately hard, firm, nonsticky, nonplastic; few very fine to medium roots; common fine to medium irregular pores; 20 percent gravel, 10 percent cobbles, and 10 percent stones; strongly acid (pH 5.1); gradual wavy boundary.

C--109 to 152 cm; light olive brown (2.5Y 5/4) very stony sandy loam, light yellowish brown (2.5Y 6/4) dry; weak fine subangular blocky structure; soft, very friable, nonsticky, nonplastic; few fine roots; common fine to medium irregular pores; 20 percent gravel, 20 percent cobbles, and 15 percent stones; strongly acid (pH 5.4).

TYPE LOCATION: Chelan County, Washington; approximately 27 km northwest of the town of Stehekin along the North Fork of Bridge Creek trail, North Cascades National Park Service Complex; 615 m west and 330 m north of the southeast corner of section 29, T. 35 N, R. 16 E, Willamette Meridian; Goode Mountain, Washington USGS quadrangle; 48 degrees, 30 minutes, 4 seconds north latitude and 120 degrees, 53 minutes, 31 seconds west longitude; UTM zone 10N 655726 meters E, 5374168 meters N.

RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 4 to 7 degrees C.
Moisture control section - dry for 45 to 60 consecutive days.
Particle size control section:
Clay content - 0 to 10 percent throughout
Rock fragments - 35 to 75 percent total, 15 to 50 percent gravel, 10 to 40 percent cobbles, and 0 to 30 percent stones

A horizon:
Hue - 10YR or 7.5YR
Value - 2 to 4 moist, 4 to 6 dry
Chroma - 1 to 3 moist or dry
Fine earth texture - ashy SL or ashy FSL
Rock fragments - 10 to 35 percent total, 5 to 25 percent gravel, 0 to 20 percent cobbles
Volcanic glass - 10 to 25 percent
Reaction - very strongly acid to strongly acid
Thickness - 10 to 20 centimeters

E horizons are sometimes present with thickness ranging from 1 to 8 cm, textures of ashy SL or ashy COSL, reaction of very strongly acid or strongly acid, hue of 7.5YR or 10YR, moist value of 4 or 5, and moist chroma of 1 or 2

Bw horizon:
Hue - 10YR or 7.5YR
Value - 3 to 5 moist, 4 to 6 dry
Chroma - 3 to 6 moist or dry
Fine earth texture - SL, FSL or COSL
Rock fragments - 25 to 75 percent total, 10 to 45 percent gravel, 5 to 40 percent cobbles, 0 to 10 percent stones
Volcanic glass - 5 to 15 percent
Reaction - very strongly acid to strongly acid
Thickness - 10 to 40 centimeters

BC horizon:
Hue - 10YR or 2.5Y
Value - 3 to 5 moist, 4 to 6 dry
Chroma - 3 to 4 moist or dry
Fine earth texture - SL, FSL or COSL
Rock fragments - 35 to 75 percent total, 15 to 50 percent gravel, 5 to 40 percent cobbles, 0 to 10 percent stones
Volcanic glass - 5 to 15 percent
Reaction - strongly acid to moderately acid
Thickness - 20 to 70 centimeters

C horizon:
Hue - 2.5Y
Value - 3 to 5 moist, 5 to 7 dry
Chroma - 2 to 6 moist or dry
Fine earth texture -SL, COSL, LS
Rock fragments - 35 to 75 percent total, 10 to 50 percent gravel, 5 to 40 percent cobbles, 0 to 30 percent stones
Reaction - strongly acid to moderately acid

COMPETING SERIES: There are no competing series in this family.

GEOGRAPHIC SETTING: Stehekin soils are found on slopes of 0 to 35 percent on debris aprons, debris cones, and valley walls of glaciated mountain landscapes at elevations from 700 to 1,300 meters. They formed in volcanic ash overlying glacial drift and colluvium from glacial drift. The climate is characterized by cool, dry summers and cold, wet winters. Mean annual precipitation ranges from 1,000 to 1,700 millimeters. Mean annual air temperature ranges from 4 to 6 degrees C. Frost-free season is 40 to 75 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Noca and Primus soils. Noca soils are dry in the moisture control section for less than 30 days from June through October. Noca and Primus soils have andic soil properties to a depth greater than 40 cm and have an ashy over sandy or sandy-skeletal particle size control sections.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained; high to very high saturated hydraulic conductivity.

USE AND VEGETATION: Stehekin soils support wildlife habitat, recreation, and watershed drainage. Native vegetation includes subalpine fir and Douglas-fir. Understory species include fireweed, pachistima, vine maple, thimbleberry and grasses.

DISTRIBUTION AND EXTENT: North Cascade Mountains, Washington. MLRA 3. Series is of small extent.

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

SERIES ESTABLISHED: North Cascades National Park Service Complex, Chelan County, Washington, 2011.

REMARKS: Diagnostic horizons and features recognized in this pedon include:
Cryic soil temperature regime
Xeric soil moisture regime
Particle-size control section - 25 to 100 cm (25 to 100 cm from the mineral surface)
Ochric epipedon
Andic soil properties - the zone from 0 to 18 cm (A horizon)
Cambic horizon - 18 to 44 cm (Bw horizon)

National Cooperative Soil Survey
U.S.A.