LOCATION TRICOUNI                WA

Established Series
Rev. TMR/CAB/SBC
06/2011

TRICOUNI SERIES

The Tricouni series consists of very deep, well drained soils formed in mixed volcanic ash and glacial drift over glacial drift on terraces, debris cones, and valley walls. Slopes are 0 to 60 percent. The mean annual precipitation is about 1,800 millimeters. The mean annual temperature is about 7 degrees C.

TAXONOMIC CLASS: Loamy-skeletal, isotic, frigid Andic Dystrudepts

TYPICAL PEDON: Tricouni ashy sandy loam, on a valley wall with a north facing slope of 50 percent and an elevation of 760 meters. When described on July 24, 2008, the soil was slightly moist throughout. (Colors are for moist soil unless otherwise noted)

Oi--0 to 3 cm; slightly decomposed plant material from twigs, needles, and forbs; abrupt wavy boundary.

Oe--3 to 9 cm; moderately decomposed plant material; few fine and medium roots; abrupt irregular boundary.

E--9 to 10 cm; dark grayish brown (10YR 4/2) ashy sandy loam, grayish brown (10YR 5/2) dry; weak fine subangular blocky structure; soft, very friable, nonsticky, nonplastic; few fine and medium roots; many very fine interstitial pores; 5 percent fine gravel; strongly acid (pH 5.4); abrupt irregular boundary.

Bw1--10 to 28 cm; brown (10YR 4/3) gravelly ashy sandy loam, brown (10YR 5/3) dry; weak medium subangular blocky structure; soft, very friable, nonsticky, nonplastic; few very fine and fine, common medium and coarse roots; many very fine interstitial pores; 10 percent fine gravel, 10 percent medium and coarse gravel, and 10 percent cobbles; strongly acid (pH 5.5); gradual wavy boundary.

2Bw2--28 to 60 cm; dark yellowish brown (10YR 4/4) very gravelly sandy loam, yellowish brown (10YR 5/4) dry; weak medium subangular blocky structure; soft, very friable, nonsticky, nonplastic; common very fine, fine and medium, few coarse and very coarse roots; many very fine interstitial pores; 15 percent fine gravel, 10 percent medium and coarse gravel, and 10 percent cobbles; moderately acid (pH 5.6); abrupt wavy boundary.

2BC--60 to 104 cm; light olive brown (2.5Y 5/3) very gravelly sandy loam, light yellowish brown (2.5Y 6/3) dry; weak medium subangular blocky structure; soft, very friable, nonsticky, nonplastic; few very fine, fine, medium and coarse roots; 10 percent fine gravel, 15 percent medium and coarse gravel, and 15 percent cobbles; moderately acid (pH 5.8).

2C--104 to 152 cm; olive brown (2.5Y 4/4) very gravelly loamy sand, light yellowish brown (2.5Y 6/4) dry; single grain; loose, nonsticky, nonplastic; few very fine, fine, and medium roots; 10 percent fine gravel, 40 percent medium and coarse gravel, and 5 percent cobbles; moderately acid (pH 5.9).

TYPE LOCATION: Sourdough Mountain Trail, North Cascades National Park, Whatcom County, Washington; approximately 120 meters west and 360 meters south of the NE corner of Section 25, T38N, R13E, Willamette Baseline Meridian; Pumpkin Mountain, Washington USGS quadrangle; 48 degrees, 45 minutes, 14 seconds north latitude and 121 degrees, 2 minutes, 34 seconds west longitude; UTM 643856 meters E, 5401936 meters N, zone 10N NAD83.

RANGE IN CHARACTERISTICS: Depths to diagnostic horizons and features start from the mineral soil surface.

Mean annual soil temperature: 6 to 8 degrees C. Frigid soil temperature regime.
Soil moisture control section: dry for 30 to 45 consecutive days following the summer solstice. Udic soil moisture regime.
Reaction: moderately acid to strongly acid through the profile
Clay content - 2 to 10 percent through profile
Thickness of volcanic ash mantle: 18 to 35 centimeters

E horizon (absent in some pedons; does not typically meet albic criteria)
Hue - 10YR or 7.5YR
Value - 4 or 5 moist, 5 or 6 dry
Chroma - 2 or 3 moist or dry
Fine earth texture - ashy SL
Rock fragments - 0 to 10 percent fine gravel
Volcanic glass: 15 to 50 percent
Thickness - 0 to 2 centimeters

Bw1 horizon:
Hue - 10YR, 7.5YR, or 2.5Y
Value - 3 or 4 moist, 4 or 5 dry
Chroma - 3 to 6 moist or dry
Fine earth textures - ashy SL or ashy FSL
Rock fragments - 5 to 60 percent
0 to 15 percent fine gravel
5 to 35 percent medium and coarse gravel
0 to 15 percent cobbles
Volcanic glass: 20 to 50 percent
Thickness - 18 to 35 centimeters

2Bw2 horizon:
Hue -10YR, 7.5YR or 2.5Y
Value - 3 or 4 moist, 4 or 5 dry
Chroma - 3 to 6 moist or dry
Fine earth textures - SL, COSL
Rock fragments - 5 to 60 percent
0 to 20 percent fine gravel
5 to 40 percent medium and coarse gravel
0 to 20 percent cobbles
0 to 5 percent stones
Volcanic glass: 0 to 5 percent
Thickness - 30 to 50 centimeters

2BC horizon:
Hue - 2.5Y or 10YR
Value - 3 to 5 moist, 4 to 6 dry
Chroma - 3 to 6 moist or dry
Fine earth textures - SL, COSL, LS
Rock fragments - 20 to 60 percent
10 to 20 percent fine gravel
15 to 50 percent medium and coarse gravel
5 to 20 percent cobbles
0 to 5 percent stones
Volcanic glass: 0 to 5 percent
Thickness - 40 to 60 centimeters

2C horizon:
Hue - 2.5Y, 10YR, or variegated mineral colors
Value - 3 to 5 moist, 4 to 6 dry
Chroma - 3 to 6 moist or dry
Fine earth textures - LS, COSL, SL
Rock fragments - 20 to 60 percent
10 to 20 percent fine gravel
15 to 50 percent gravel
5 to 20 percent cobbles
0 to 5 percent stones

COMPETING SERIES: These are the Dougan, Fernwood, Hoffstadt, Sarazan, and Zygore series. The Dougan and Fernwood soils are moderately deep to a lithic contact. Hoffstadt and Sarazan soils are deep to a lithic contact. Textures in the Dougan, Fernwood, Sarazan, and Zygore soils range from loam to silt loam or have medial modifiers in the upper part of the particle-size control section. The Hoffstadt soils are formed in colluvium or residuum from basic igneous rocks.

GEOGRAPHIC SETTING: The Tricouni soils are on terraces, debris cones, and valley walls at elevations of 300 to 1,200 meters. Slopes are 0 to 60 percent. These soils formed in volcanic ash mixed with glacial drift, over glacial drift. The climate is mild; with warm, dry summers and cool, wet winters. Mean annual precipitation ranges from 1,500 to 2,500 millimeters and mean annual air temperature ranges from 5 to 10 degrees C. Frost-free season is 60 to 90 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Easy, Nohokomeen, and Thorton series. Easy and Thorton soils have an ashy over loamy-skeletal particle-size control section. Easy soils also meet criteria for albic and spodic materials in the upper portion of the soil profile. Nohokomeen soils have a seasonal high water table within 50 centimeters of the soil surface and generally occur in the lower portions of the landscape.

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 western hemlock, Douglas-fir, and western red cedar with an understory including Oregon-grape, vine maple, bunchberry, queen's cup beadlily, prince's pine, red huckleberry, twin flower, 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 in this pedon are:
Albic horizon: 9 to 10 centimeters (E horizon)
Cambic horizon: 10 to 104 centimeters (Bw1, Bw2, and 2BC horizons)
Andic soil properties: 9 to 28 centimeters (E and Bw1 horizons)
Particle-size control section: 25 to 100 centimeters from the mineral surface.
Some pedons do not have albic horizons and have ochric epipedons.

ADDITIONAL DATA: Laboratory will be available for this series. National Soil Survey Laboratory User pedon ID S08WA073003).

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National Cooperative Soil Survey
U.S.A.