LOCATION FORBIDDEN               WA

Established Series
Rev. CAB/SBC
06/2011

FORBIDDEN SERIES

The Forbidden series consists of very deep, well drained soils formed in volcanic ash, colluvium, and glacial drift on valley walls, debris cones, and terraces. Slopes are 0 to 35 percent on debris cones and terraces and 35 to 90 percent on valley walls. The mean annual precipitation is about 1,800 millimeters. The mean annual temperature is about 6 degrees C.

TAXONOMIC CLASS: Sandy-skeletal, isotic Andic Dystrocryepts

TYPICAL PEDON: Forbidden ashy sandy loam, on a valley wall landform with a north facing slope of 37 percent at 975 meters elevation under coniferous forest vegetation. When described on August 27, 2005 the soil was dry throughout. (Colors are for moist soil unless otherwise noted.)

Oi--0 to 4 centimeters; slightly decomposed plant material; few fine roots throughout; abrupt smooth boundary.

Oe--4 to 14 centimeters; moderately decomposed plant material; common very fine, fine, and medium roots throughout; abrupt wavy boundary.

E--14 to 16 centimeters; dark grayish brown (10YR 4/2) ashy sandy loam, light brownish gray (10YR 6/2), dry; weak medium granular structure; very friable, soft, nonsticky, nonplastic; common very fine, fine, and medium roots throughout; strongly acid (pH 5.2); abrupt wavy boundary.

Bw--16 to 46 centimeters; dark yellowish brown (10YR 4/4) very gravelly ashy sandy loam, light yellowish brown (10YR 6/4) dry; weak fine subangular blocky structure; very friable, slightly hard, nonsticky, nonplastic; many very fine and fine and common medium and coarse roots throughout; 10 percent fine gravel, 20 percent medium and coarse gravel, and 10 percent cobbles; slightly acid (pH 6.5); clear wavy boundary.

2BC1--46 to 68 centimeters; light olive brown (2.5Y 5/4) extremely gravelly loamy sand, light yellowish brown (2.5Y 6/4) dry; single grain; loose, nonsticky, nonplastic; many very fine, common fine, and few medium and coarse roots throughout; 20 percent fine gravel, 30 percent medium and coarse gravel, 15 percent cobbles, and 10 percent stones; moderately acid (pH 6.0); abrupt smooth boundary.

2BC2--68 to 90 centimeters; olive brown (2.5Y 4/3) extremely gravelly loamy sand, light olive brown (2.5Y 5/4) dry; single grain; loose, nonsticky, nonplastic; common very fine and fine and few medium and coarse roots throughout; 20 percent fine gravel, 35 percent medium and coarse gravel, 20 percent cobbles, and 10 percent stones; moderately acid (pH 6.0); abrupt smooth boundary.

2C--90 to 152 centimeters; variegated extremely gravelly coarse sand; single grain; loose, nonsticky, nonplastic; few fine and medium roots throughout; 15 percent fine gravel, 35 percent medium and coarse gravel, 20 percent cobbles, and 5 percent stones; moderately acid (pH 6.0).

TYPE LOCATION: North Cascades National Park, Skagit County, Washington; 306 meters South and 748 meters east of the northwest corner of section 29, T36N, R14E Willamette Meridian; Forbidden Peak, Washington USGS quadrangle; 48 degrees, 34 minutes, 54 seconds north latitude and 121 degrees, 0 minutes, 52 seconds west longitude; NAD83; UTM 646433 meters E, 5382845 meters N, zone 10N.

RANGE IN CHARACTERISTICS:
Mean annual soil temperature: 4 to 8 degrees C. Cryic soil temperature regime.
Soil moisture control section: dry for less than 30 consecutive days from June to October. Udic soil moisture regime.
Thickness of volcanic ash mantle: 18 to 35 centimeters

E horizon:
Hue - 7.5YR or 10YR
Value - 3 to 4 moist, 5 to 6 dry
Chroma - 1 to 3 moist or dry
Fine earth texture - ashy FSL, ashy SL or ashy LS
Rock fragments - 0 to 35 percent total
0 to 35 percent gravel
0 to 25 percent cobbles
0 to 10 percent stones
Clay content - 1 to 8 percent
Volcanic glass - 15 to 50 percent
Reaction - very strongly acid to strongly acid
Thickness - 0 to 4 centimeters

Bw horizon:
Hue - 7.5YR or 10YR
Value - 3 to 4 moist, 4 to 6 dry
Chroma - 2 or 4 moist or dry
Fine earth texture -ashy SL or ashy LS
Rock fragments - 35 to 75 percent total
25 to 65 percent gravel
0 to 30 percent cobbles
0 to 10 percent stones
0 to 5 percent boulders
Clay content - 3 to 8 percent
Volcanic glass - 5 to 50 percent
Reaction - strongly acid to neutral
Thickness - 18 to 35 centimeters

2BC horizons:
Hue -2.5Y or 10YR
Value - 3 to 5 moist, 4 to 6 moist
Chroma - 3 or 4 moist or dry
Fine earth texture -LS or LCOS,
Rock fragments - 35 to 85 percent total
20 to 65 percent gravel
15 to 35 percent cobbles
0 to 15 percent stones
Clay content - 0 to 5 percent
Volcanic glass - 0 to 10 percent
Reaction - strongly acid to slightly acid

2C horizon:
Hue -2.5Y or variegated
Value - 3 to 4 moist, 4 to 5 moist
Chroma - 3 or 4 moist or dry
Fine earth texture -LS, LCOS, COS, or S
Rock fragments - 50 to 90 percent total
25 to 60 percent gravel
20 to 60 percent cobbles
0 to 10 percent stones
Clay content - 0 to 3 percent
Volcanic glass - 0 to 5 percent
Reaction - strongly acid to slightly acid

COMPETING SERIES: These are the Jantill and Maryspeak series. Jantill soils are dry in the moisture control section for 30 to 45 consecutive days. Maryspeak soils are medial and have less than 5 percent volcanic glass in the upper 18 to 23 centimeters of the mineral soil.

GEOGRAPHIC SETTING: The Forbidden soils are on valley walls, debris cones, and terraces at elevations of 975 to 1,890 meters. Slopes are 0 to 35 percent on debris cones and terraces and 35 to 90 percent on valley walls. These soils formed in volcanic ash mixed with reworked glacial drift and colluvium. The climate consists of cool, dry summers and cold, wet winters. Mean annual precipitation ranges from 1,800 to 3,300 millimeters, and mean annual air temperature ranges from 3 to 7 degrees C. Frost-free season is 30 to 60 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Doubtful (T), Spickard (T) and Tepeh (T) series. Doubtful soils form on more stable portions of valley walls, are moderately deep to bedrock, and have andic soils properties to a depth greater than 36 centimeters. Spickard soils form on more stable portions of valley walls and debris aprons and have andic soil properties greater than 36 centimeters. Tepeh soils have finer textures on valley walls and debris aprons.

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

USE AND VEGETATION: Used for watershed, recreation, woodland and wildlife habitat. Native vegetation consists of Pacific silver fir, mountain hemlock, subalpine fir, minor amounts of western redcedar and western hemlock. Understory vegetation consists of Oregon grape, queencup beadlily, dwarf bramble, devil's club, prickly currant, and black huckleberry.

DISTRIBUTION AND EXTENT: Western slopes of the 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 soil survey, 2011.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Particle-size Control Section: 39 to 114 cm. (25 to 100 cm from the mineral surface)
Ochric epipedon: 0 to 18 cm (Oi, Oe, E and upper 2 cm of Bw horizon)
Andic soil properties: 14 to 46 cm (E and Bw horizons)
Albic horizon: 14 to 16 cm. (E horizon)
Cambic horizon: 16 to 68 cm. (Bw horizon)

ADDITIONAL DATA: Laboratory data is available for this series. National Soil Survey Laboratory Pedon number 06N0801 (User Pedon ID 05WA057004).

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National Cooperative Soil Survey
U.S.A.