LOCATION BROKENHOE               CA

Established Series
Rev. EWB-JVC
02/2017

BROKENHOE SERIES

The Brokenhoe series consists of moderately deep to a duripan, well drained soils that formed in alluvium derived mainly from volcanic rocks with surficial additions of eolian volcanic ash. Brokenhoe soils are on fan remnants. Slopes are 4 to 30 percent. The mean annual precipitation is about 330 mm and the mean annual temperature is about 7 degrees C.

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Vitritorrandic Durixerolls

TYPICAL PEDON: Brokenhoe very cobbly ashy sandy loam--rangeland. (Colors are for dry soil unless otherwise noted.) The soil surface is covered with 25 percent gravel, 10 percent cobbles, 3 percent stones, and 1 percent boulders.

A1--0 to 5 cm; grayish brown (10YR 5/2) very cobbly ashy sandy loam, very dark grayish brown (10YR 3/2) moist; moderate medium platy structure; soft, very friable, nonsticky and nonplastic; many very fine and fine roots; many very fine and fine vesicular pores; 20 percent gravel, 15 percent cobbles, and 5 percent stones; neutral (pH 6.8); clear wavy boundary. (5 to 15 cm thick)

A2--5 to 15 cm; grayish brown (10YR 5/2) very cobbly ashy sandy loam, very dark grayish brown (10YR 3/2) moist; moderate fine and medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; common very fine, fine, medium, and coarse roots; common very fine tubular and interstitial pores; 20 percent gravel, 20 percent cobbles, and 5 percent stones; neutral (pH 6.8); clear wavy boundary. (8 to 18 cm thick)

Bt1--15 to 25 cm; brown (10YR 5/3) very gravelly ashy sandy clay loam, dark brown (10YR 3/3) moist; moderate fine and medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine, fine, medium, and coarse roots; common very fine tubular and interstitial pores; common faint clay bridges between sand grains; 30 percent gravel, 10 percent cobbles, and 5 percent stones; neutral (pH 6.9); clear wavy boundary. (8 to 25 cm thick)

Bt2--25 to 50 cm; yellowish brown (10YR 5/4) very cobbly clay loam, dark yellowish brown (10YR 3/4) moist; strong medium and coarse angular blocky structure; very hard, very firm, moderately sticky and moderately plastic; common very fine, fine, medium, and coarse roots; common very fine tubular and interstitial pores; many distinct and few prominent clay films on faces of peds and lining pores; 30 percent gravel, 20 percent cobbles, and 5 percent stones; neutral (pH 7.0); clear wavy boundary. (25 to 41 cm thick)

Bqm--50 to 94 cm; 60 percent light yellowish brown (10YR 6/4) and 40 percent light brownish gray (10YR 6/2) cemented material, 60 percent dark yellowish brown (10YR 4/4) and 40 percent dark grayish brown (10YR 4/2) moist; weak very thick platy structure; very hard, extremely firm; continuously moderately cemented by opaline silica; very few very fine roots and clay films lining fractures; gradual wavy boundary. (38 to 64 cm thick)

Bq--94 to 152 cm; pale brown (10YR 6/3) cemented extremely stony sandy loam, brown (10YR 4/3) moist; weak coarse subangular blocky structure; very hard, firm, slightly sticky and nonplastic; continuously weakly cemented by opaline silica; very few very fine roots lining fractures; few very fine tubular and interstitial pores; common opal coats on rock fragments; 25 percent gravel, 20 percent cobbles, and 30 percent stones; neutral (pH 7.0).

TYPE LOCATION: Mono County, California; on the Toiyabe National Forest about 1 mile east-southeast of the Bridgeport Reservoir dam; approximately 1,650 feet north and 200 feet east of the southwest corner of section 36, T. 6 N., R. 25 E.; USGS Bridgeport 7.5 minute topographic quadrangle; 38 degrees 19 minutes 20.9 seconds north latitude and 119 degrees 11 minutes 22.9 seconds west longitude; WGS84 Decimal Degrees 38.3224722 latitude, -119.1896944 longitude.

RANGE IN CHARACTERISTICS:
Soil moisture: Usually moist in winter and spring, dry from July through October; aridic soil moisture regime that borders on xeric.
Mean annual soil temperature: 7 to 8 degrees C.
Mollic epipedon thickness: 25 to 48 cm; includes the Bt1 horizon.
Depth to duripan: 50 to 100 cm.
Depth to bedrock: More than 200 cm.

Particle-size control section - Clay content: Averages 27 to 35 percent.
Rock fragments: Averages 50 to 80 percent, mainly cobbles and stones. Lithology of fragments is mainly volcanic rocks such as andesite.

A horizons
Value: 4 or 5 dry, 2 or 3 moist.
Chroma: 2 or 3, dry or moist.
Organic matter content: 1 to 3 percent.
Reaction: Slightly acid or neutral.
Volcanic glass content: 30 to 60 percent in coarse silt through fine sand fractions.

Bt1 horizon
Hue: 10YR or 7.5YR.
Texture: Very gravelly ashy sandy clay loam, very cobbly ashy sandy loam, or extremely stony ashy sandy loam.
Clay content: 18 to 25 percent.
Rock fragments: 50 to 80 percent.
Reaction: Slightly acid or neutral.
Organic matter content: 1 to 3 percent.
Volcanic glass content: 15 to 40 percent in coarse silt through fine sand fractions.
Oxalate aluminum plus one-half oxalate iron: 0.2 to 0.4 percent.

Bt2 horizon
Hue: 10YR or 7.5YR.
Texture: Very cobbly clay loam, very cobbly clay, or extremely stony clay loam.
Clay content: 35 to 50 percent.
Rock fragments: 50 to 80 percent.
Reaction: Slightly acid or neutral.

Bq horizon (when present)
Hue: 10YR or 7.5YR.
Texture: Very cobbly clay loam, very cobbly sandy clay loam, or extremely stony clay loam.
Clay content: 25 to 35 percent.
Rock fragments: 50 to 80 percent.
Reaction: Slightly acid or neutral.
Other features: Some pedons have a thin Btq horizon immediately above the duripan.

Bqm1 horizon
Cementation: Continuous moderate cementation by silica.
Rupture resistance: Very hard dry, extremely firm moist.

Bqm2 horizon
Cementation: Continuous weak cementation by silica.
Rupture resistance: Hard or very hard dry, very firm moist.
Texture: Cemented very stony sandy loam, cemented extremely stony sandy loam, or cemented extremely cobbly sandy loam.
Rock fragments: 50 to 80 percent, dominantly cobbles and stones.

COMPETING SERIES: There are currently no other series in this family.

GEOGRAPHIC SETTING: Brokenhoe soils are on fan remnants. They typically occur on summit and shoulder positions. They formed in alluvium derived mainly from volcanic rocks such as andesite with surficial additions of eolian volcanic ash. The probable sources of the volcanic ash are the Mono Craters and Long Valley Caldera in eastern California. Slopes are 4 to 30 percent. Elevations range from 2,015 to 2,260 meters. The climate is semiarid with cool, moist winters and warm, dry summers. The mean annual precipitation is 300 to 360 mm, the mean annual temperature is 6 to 7 degrees C, and the frost-free period is 50 to 70 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Fisherdig, Hardnut, and Ocashe soils. Fisherdig soils are clayey-skeletal and are shallow to a duripan. Hardnut and Ocashe soils are shallow to lithic contacts.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained; very high surface runoff; slow permeability (moderately low saturated hydraulic conductivity) in the upper part and very slow permeability (low saturated hydraulic conductivity) in the duripan.

USE AND VEGETATION: Brokenhoe soils are used for rangeland, recreation, watershed, and wildlife habitat. The native vegetation is mainly mountain big sagebrush, antelope bitterbrush, and Thurber's needlegrass with scattered singleleaf pinyon.

DISTRIBUTION AND EXTENT: Eastern California, in the western part of the Great Basin. These soils are not extensive with about 2,200 acres of the series mapped to date. MLRA 26.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.

SERIES ESTABLISHED: Mono County (Toiyabe National Forest Area), California, 2006.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the soil surface to 25 cm (A1, A2, and Bt1 horizons).
Argillic horizon - The zone from 15 to 50 cm (Bt1 and Bt2 horizons).
Vitrandic intergrade feature - The zone from the soil surface to 25 inches (A1, A2, and Bt1 horizons).
Duripan - The zone from 50 to 152 cm (Bqm1 and Bqm2 horizons).
Particle-size control section - The zone from 15 to 50 cm (Bt1 and Bt2 horizons).

ADDITIONAL DATA: Volcanic glass content determined locally by optical grain count with a polarizing petrographic microscope.

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National Cooperative Soil Survey
U.S.A.