LOCATION LASTSUMMER CA+NV

Established Series
Rev. EWB-JBF-TM-JVC
03/2017

LASTSUMMER SERIES

The Lastsummer series consists of very deep, well drained soils that formed in colluvium and residuum derived from volcanic rocks with surficial additions of eolian volcanic ash. Lastsummer soils are on mountains and hills. Slopes are 2 to 50 percent. The mean annual precipitation is about 430 mm and the mean annual temperature is about 6 degrees C.

TAXONOMIC CLASS: Ashy-skeletal over loamy-skeletal, glassy over mixed, superactive Vitrandic Argicryolls

TYPICAL PEDON: Lastsummer gravelly ashy fine sandy loam--rangeland. (Colors are for dry soil unless otherwise noted.) The soil surface is covered with 20 percent gravel and less than 5 percent cobbles.

A1--0 to 10 cm; grayish brown (10YR 5/2) gravelly ashy fine sandy loam, very dark grayish brown (10YR 3/2) moist; weak fine and medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; many very fine roots; many very fine interstitial pores; 25 percent gravel; slightly acid (pH 6.4); clear wavy boundary. (5 to 15 cm thick)

A2--10 to 18 cm; grayish brown (10YR 5/2) gravelly ashy sandy loam, very dark grayish brown (10YR 3/2) moist; weak fine and medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; many very fine roots; many very fine interstitial pores; 25 percent gravel; neutral (pH 6.8); clear wavy boundary. (0 to 13 cm thick)

Bt1--18 to 41 cm; brown (10YR 5/3) very gravelly ashy fine sandy loam, dark brown (10YR 3/3) moist; moderate fine and medium subangular blocky structure; slightly hard, very friable, slightly sticky and nonplastic; many very fine and fine roots; common very fine interstitial and tubular pores; faint clay bridges between sand grains; 35 percent gravel; neutral (pH 6.8); clear wavy boundary. (18 to 30 cm thick)

Bt2--41 to 84 cm; brown (10YR 5/3) very gravelly ashy sandy loam, dark brown (10YR 3/3) moist; moderate fine and medium subangular blocky structure; slightly hard, very friable, slightly sticky and nonplastic; common very fine and fine roots; common very fine interstitial and tubular pores; faint clay bridges between sand grains; 35 percent gravel; neutral (pH 6.8); abrupt wavy boundary. (20 to 50 cm thick)

2Btq1--84 to 102 cm; pale brown (10YR 6/3) extremely stony sandy loam, brown (10YR 4/3) moist; massive; very hard, firm and brittle, slightly sticky and slightly plastic; common very fine and fine roots; common very fine interstitial and tubular pores; faint clay bridges between sand grains and distinct clay films lining pores; 30 percent weakly cemented silica nodules; 40 percent gravel, 25 percent cobbles, and 20 percent stones; neutral (pH 6.7); clear wavy boundary. (13 to 38 cm thick)

2Btq2--102 to 132 cm; brown (10YR 5/3), extremely cobbly loam, brown (10YR 4/3) moist; massive; hard, firm and brittle, moderately sticky and slightly plastic; few very fine roots; common very fine and fine interstitial and few very fine and fine tubular pores; faint clay bridges between sand grains and distinct clay films on surfaces along pores; 25 percent weakly cemented silica concretions and 20 percent moderately cemented silica concretions; 30 percent gravel, 30 percent cobbles, and 10 percent stones; neutral (pH 6.7); clear wavy boundary. (15 to 38 cm thick)

2Btq3--132 to 155 cm; pale brown (10YR 6/3) extremely cobbly sandy clay loam, brown (10YR 4/3) moist; massive; extremely hard, extremely firm and brittle, moderately sticky and moderately plastic; few very fine roots; common very fine and fine interstitial pores; faint clay bridges between sand grains; 20 percent moderately cemented silica concretions and 20 percent weakly cemented silica concretions; 30 percent gravel, 30 percent cobbles, and 10 percent stones; neutral (pH 6.7).

TYPE LOCATION: Mono County, California; in the Bodie Hills about 1.6 kilometers southwest of the ghost town of Bodie; approximately 640 meters south and 30 meters west of the southeast corner of section 18, T. 4 N., R. 27 E.; USGS Bodie 7.5 minute topographic quadrangle; latitude 38 degrees 12 minutes 24.3 seconds N and longitude 119 degrees 01 minutes 52.1 seconds W; WGS84 38.20674 latitude, -119.03114 longitude.

RANGE IN CHARACTERISTICS:
Soil moisture: Usually moist in the moisture control section during fall, winter, and spring; usually dry July through early October; xeric moisture regime that borders on aridic.
Mean annual soil temperature: 6 to 8 degrees C.
Mean summer soil temperature: 12 to 14 degrees C.
Mollic epipedon thickness: 64 to 90 cm; includes the Bt1 horizon.
Depth to major lithologic discontinuity: 50 to 100 cm.
Depth to secondary silica: 76 to 100 cm.
Depth to bedrock: 150 to 200 cm to a paralithic contact. The paralithic materials below the contact are weathered andesitic rock.

Particle-size control section - Clay content: Averages 8 to 12 percent in the upper part and 12 to 24 percent in the strongly contrasting lower part.
Rock fragments: Averages 35 to 60 percent, mainly gravel in the upper part and 60 to 85 percent, mainly cobbles and stones in the strongly contrasting lower part. Lithology of rock fragments is volcanic rock such as andesite.

A horizons
Value: 4 or 5 dry, 2 or 3 moist.
Chroma: 2 or 3, dry or moist.
Texture: Gravelly ashy fine sandy loam or gravelly ashy sandy loam.
Reaction: Moderately alkaline through neutral.
Organic matter content: 2 to 4 percent.
Volcanic glass content: 40 to 70 percent in coarse silt through fine sand fractions.

Bt1 horizon
Chroma: 2 or 3, dry or moist.
Texture: Very gravelly ashy fine sandy loam or very gravelly ashy sandy loam.
Clay content: 8 to 12 percent.
Rock fragments: 35 to 60 percent.
Reaction: Slightly acid or neutral.
Organic matter content: 1 to 3 percent.
Volcanic glass content: 30 to 50 percent in very fine sand and fine sand fractions.

Bt2 horizon
Chroma: 2 or 3, dry or moist.
Texture: Very gravelly ashy sandy loam or very gravelly ashy fine sandy loam.
Clay content: 8 to 12 percent.
Rock fragments: 35 to 60 percent.
Reaction: Slightly acid or neutral.
Organic matter content: 0.5 to 1 percent.
Volcanic glass content: 30 to 50 percent in very fine sand and fine sand fractions.
Other features: Some pedons have a Bt3 horizon, which may be extremely cobbly ashy sandy loam.

2Btq horizons
Value: 5 or 6 dry, 4 moist.
Chroma: 2 or 3, dry or moist.
Texture: Extremely cobbly loam, extremely cobbly sandy loam, or extremely stony loam.
Clay content: 12 to 24 percent.
Rock fragments: 60 to 85 percent.
Reaction: Slightly acid or neutral.
Organic matter content: 0.2 to 0.8 percent.
Rupture resistance: Firm to extremely firm when dry with a brittle manner of failure when moist.
Secondary silica: 20 to 70 percent moderately to strongly silica-cemented concretions.

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

GEOGRAPHIC SETTING: Lastsummer soils are on mountains and hills. They typically occur on footslope positions. They formed in colluvium and residuum derived 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 2 to 50 percent. Elevations range from 2,400 to 3,150 meters. The climate is semiarid with cold, moist winters and cool, dry summers. The mean annual precipitation is 400 to 500 mm, the mean annual temperature is 5 to 7 degrees C., and the frost-free period is 30 to 60 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Adamatt, Bodiehill, Hardshoulder, and Roughridge soils. Adamatt soils are ashy-skeletal, shallow to lithic contacts, and have a frigid temperature regime. Bodiehill soils are ashy-skeletal over loamy-skeletal and have a frigid temperature regime. Hardshoulder soils are ashy-skeletal and average 60 to 85 percent rock fragments throughout the particle-size control section. Roughridge soils are ashy-skeletal, have a frigid temperature regime, and have an aridic moisture regime.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained; low or medium surface runoff; moderately rapid permeability; high saturated hydraulic conductivity.

USE AND VEGETATION: Lastsummer soils are used for livestock grazing, recreation, watershed and wildlife habitat. The native vegetation is mainly mountain big sagebrush, western needlegrass, lupine, sedge, prairie junegrass, snowberry, and currant.

DISTRIBUTION AND EXTENT: Eastern California and western Nevada, in the western part of the Great Basin. These soils are not extensive. MLRA 26.

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

SERIES ESTABLISHED: Mono County (Coleville-Bridgeport Area), California, 2010.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the soil surface to 84 cm (A1, A2, Bt1 and Bt2 horizons).
Argillic horizon - The zone from 18 to 155 cm (Bt1, Bt2, 2Btq1, 2Btq2, and 2Btq3 horizons).
Vitrandic intergrade feature - The zone from the soil surface to 75 cm (A1, A2, and Bt1 horizons and part of the Bt2 horizon).
Major lithologic discontinuity - The change to loamy-skeletal material at 84 cm (between the Bt2 and 2Btq1 horizons).
Duric feature - The zone from 84 to 155 cm (2Btq1, 2Btq2, and 2Btq3 horizons).
Particle-size control section - The zone from 18 to 100 cm (Bt1 and Bt2 horizons and part of the 2Btq1 horizon).

ADDITIONAL DATA: The typical pedon at the series type location has full characterization data by the Soil Survey Laboratory (SSL), Lincoln, NE, as user pedon ID S06CA051003 (pedon # 07N0053). Volcanic glass content also determined locally by optical grain counts using a polarizing petrographic microscope.
User Pedon ID: S2007CA686A148amb.

National Cooperative Soil Survey
U.S.A.