LOCATION DOUBTFUL                WA

Established Series
Rev. TMR/SBC
06/2011

DOUBTFUL SERIES

The Doubtful series consists of moderately deep to bedrock, well drained soils formed in mixed volcanic ash and glacial drift over glacial drift and residuum on ridges, valley walls, and bedrock benches. Slopes are 15 to 90 percent. The mean annual precipitation is about 1,800 millimeters. The mean annual temperature is about 3 degrees C.

TAXONOMIC CLASS: Ashy over sandy or sandy-skeletal, amorphic over isotic Typic Vitricryands

TYPICAL PEDON: Doubtful gravelly ashy sandy loam, on a ridge with a southwest facing slope of 50 percent and an elevation of 1,800 meters. When described on September 27, 2007, the soil was dry throughout. (Colors are for moist soil unless otherwise noted)

Oi--0 to 2 cm; slightly decomposed plant material from forbs and twigs; abrupt smooth boundary.

A--2 to 9 cm; very dark brown (10YR 2/2) gravelly ashy sandy loam, dark grayish brown (10YR 4/2) dry; weak fine subangular blocky structure; soft, very friable, nonsticky, nonplastic; many very fine and fine, and few medium roots; 5 percent fine gravel, 5 percent medium and coarse gravel, and 5 percent cobbles; moderately acid (pH 6.0); abrupt wavy boundary.

Bw1--9 to 27 cm; dark brown (10YR 3/3) gravelly ashy sandy loam, brown (10YR 5/3) dry; weak medium subangular blocky structure; soft, very friable, nonsticky, nonplastic; many very fine and fine, common medium and coarse, and few very coarse roots; 10 percent fine gravel, 10 percent medium and coarse gravel, and 5 percent cobbles; slightly acid (pH 6.4); clear wavy boundary.

Bw2--27 to 58 cm; dark brown (10YR 3/3) gravelly ashy sandy loam, brown (10YR 5/3) dry; weak medium subangular blocky structure; soft, very friable, nonsticky, nonplastic; many very fine to fine roots; 5 percent fine gravel, 20 percent medium to coarse gravel, and 5 percent cobbles; slightly acid (pH 6.2); clear irregular boundary.

2C--58 to 70 cm; very dark brown (10YR 2/2) extremely gravelly loamy coarse sand, dark grayish brown (10YR 4/2) dry; single grain; loose, nonsticky, nonplastic; few very fine roots; 10 percent fine gravel, 60 percent medium and coarse gravel, and 10 percent cobbles; slightly acid (pH 6.1); gradual irregular boundary.

R--70 cm; metasedimentary bedrock.

TYPE LOCATION: Desolation Peak trail, North Cascades National Park, Whatcom County, Washington; approximately 520 meters north and 330 meters east of the SW corner of Section 32, T40N, R14E, Willamette Baseline Meridian; Hozomeen Mountain, Washington USGS quadrangle; 48 degrees, 54 minutes, 20 seconds north latitude and 121 degrees, 0 minutes, 58 seconds west longitude; UTM 645381 meters E, 5418867 meters N, zone 10N NAD83.

RANGE IN CHARACTERISTICS:
Mean annual soil temperature: 4 to 8 degrees C. Cryic soil temperature regime.
Soil moisture control section: dry for less than 45 consecutive days following the summer solstice. Udic soil moisture regime.
Thickness of volcanic ash mantle: 35 to 60 centimeters
Depth to bedrock (lithic contact): 50 to 100 centimeters
The particle-size control section in this soil is contrasting.

A horizon:
Hue - 10YR or 7.5YR
Value - 2 or 3 moist, 3 or 4 dry
Chroma - 1 or 2 moist and dry
Fine earth texture - ashy SL or ashy FSL
Rock fragments - 10 to 35 percent total
10 to 25 percent gravel
0 to 10 percent cobbles
Clay content - 1 to 6 percent
Volcanic glass - 15 to 50 percent
Reaction - moderately acid to strongly acid
Thickness - 2 to 8 centimeters

Bw horizons:
Hue - 10YR or 7.5YR
Value - 3 to 5 moist, 4 or 5 dry
Chroma - 2 to 4 moist or dry
Fine earth texture - ashy SL, ashy FSL, or ashy COSL
Rock fragments - 10 to 35 percent total
10 to 30 percent gravel
0 to 10 percent cobbles
Clay content - 2 to 6 percent
Volcanic glass - 20 to 50 percent
Reaction - slightly acid to moderately acid
Thickness - 20 to 90 centimeters

2C horizon:
Hue - 10YR or 7.5YR
Value - 2 to 4 moist, 4 or 5 dry
Chroma - 2 to 4 moist or dry
Fine earth texture - LCOS, LS, COS
Rock fragments - 30 to 85 percent total
25 to 80 percent gravel
5 to 25 percent cobbles
Clay content - 0 to 4 percent
Volcanic glass - 0 to 5 percent
Reaction - slightly acid to moderately acid
Thickness - 10 to 15 centimeters

COMPETING SERIES: This is the Spickard(T) series. Spickard soils are very deep. Soils with similar classification are the Ashnola and Tusip series. The Ashnola soils are moderately deep to a densic contact and have an ashy over loamy-skeletal particle-size control section. The Tusip series is deep to a lithic contact and has an ashy over loamy particle-size control section.

GEOGRAPHIC SETTING: Doubtful soils are on ridges, valley walls, and bedrock benches at elevations of 900 to 2,000 meters. Slopes are 15 to 90 percent. These soils formed in volcanic ash mixed with reworked glacial drift over glacial drift and residuum. The climate consists of cool, dry summers and cold, wet winters. Mean annual precipitation ranges from 1,600 to 3,000 millimeters, and mean annual air temperature ranges from 2 to 7 degrees C. Frost-free season is 30 to 60 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Forbidden(T), Stetattle(T), and Tepeh(T) soils. Forbidden and Tepeh soils have less than 36 cm of andic soil material and are usually on more active landscape positions of valley walls and debris cones. Forbidden soils also have coarser textures in the upper portion of the soil profile. Stetattle soils have thick A horizons with higher amounts of organic carbon in the upper portion of the soil profile.

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

USE AND VEGETATION: Used for watershed, recreation, woodland and wildlife habitat. Native vegetation is subalpine fir, Pacific silver fir, and minor mountain hemlock with an understory of Cascade huckleberry, pink mountain heath, and pachistima.

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

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

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

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon: 0 to 9 centimeters (Oi and A horizons)
Cambic horizon: 9 to 58 centimeters (Bw1 and Bw2 horizons)
Andic soil properties: 2 to 58 centimeters (A, Bw1, and Bw2 horizons)
Lithic contact: 70 centimeters

ADDITIONAL DATA: Laboratory data is available for this series. National Soil Survey Laboratory Pedon number 06N0803 (User pedon ID S06WA007001).

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National Cooperative Soil Survey
U.S.A.