LOCATION SIXBIT CA

Established Series
CES/TKK/JW
10/2018

SIXBIT SERIES

The Sixbit series consists of shallow, well drained soils formed in colluvium and residuum weathered from serpentinite. Sixbit soils are on hills. Slopes range from 3 to 70 percent. The mean annual precipitation is about 635 mm and the mean annual air temperature is about 16 degrees C.

TAXONOMIC CLASS: Loamy-skeletal, magnesic, thermic Lithic Argixerolls

TYPICAL PEDON: Sixbit gravelly loam on a south-facing, convex, 35 percent slope under a sparse canopy of buckbrush, foothill pine and chamise at an elevation of 389 meters. (Colors are for dry soil unless otherwise noted. When described on April 11, 2007 the soil was slightly moist throughout).

A1--0 to 3 cm; 50 percent very dark grayish brown (10YR 3/2) and 50 percent brown (10YR 4/3) gravelly loam, 50 percent black (10YR 2/1) and 50 percent black (7.5YR 2.5/1) moist; 42 percent sand; 17 percent clay; moderate fine subangular blocky and moderate fine granular structure; slightly hard, friable, nonsticky, slightly plastic; many very fine and fine roots throughout; many very fine and fine irregular, common fine and medium tubular, and few very coarse tubular pores; 15 percent subangular very strongly cemented serpentinite gravel, 2 percent subangular very strongly cemented serpentinite cobbles; neutral (pH 7.1); abrupt smooth boundary.

A2--3 to 12 cm; 50 percent dark grayish brown (10YR 4/2) and 50 percent brown (10YR 4/3) gravelly loam, black (10YR 2/1) moist; 40 percent sand; 18 percent clay; weak fine and medium subangular blocky structure; slightly hard, friable, nonsticky, slightly plastic; common very fine, fine, and medium roots throughout; many very fine and fine irregular, and common fine, medium, and coarse tubular pores; 15 percent subangular very strongly cemented serpentinite gravel and 2 percent subangular very strongly cemented serpentinite cobbles; neutral (pH 7.0); clear wavy boundary. (Combined thickness of the A horizons is 4 to 12 cm)

Bt1--12 to 25 cm; brown (10YR 4/3) gravelly loam, very dark brown (10YR 2/2) moist; 37 percent sand; 21 percent clay; moderate coarse subangular blocky structure; hard, friable, slightly sticky, slightly plastic; common very fine and few fine and medium roots throughout; common very fine and medium tubular pores; 2 percent faint clay films on all faces of peds and 3 percent faint clay films on surfaces along pores; 25 percent subangular very strongly cemented serpentinite gravel and 5 percent subangular very strongly cemented serpentinite cobbles; neutral (pH 7.2); clear wavy boundary.

Bt2--25 to 48 cm; brown (10YR 4/3) very gravelly loam, very dark brown (10YR 2/2) moist; 33 percent sand; 26 percent clay; moderate medium and fine subangular blocky structure; very hard, firm, moderately sticky, slightly plastic; common very fine roots and few fine and medium roots throughout; common very fine and fine dendritic tubular pores; 2 percent distinct clay films on surfaces along pores and 15 percent faint clay films on all faces of peds; 30 percent subangular very strongly cemented serpentinite gravel and 15 percent subangular very strongly cemented serpentinite cobbles; neutral (pH 6.9); abrupt wavy boundary.

R--48 to 200 cm; very strongly cemented serpentinite bedrock, fractured at intervals of 10 to 45 cm.

TYPE LOCATION: Tuolumne County, California, about 1.6 km (1 mile) northeast of the community of Keystone, CA., USGS 7.5 minute topographic quadrangle: Keystone, California; WGS84 37.8621407 latitude and -120.5085297 longitude; UTM Zone 10 719169 meters E 4193445 meters N - U.S.G.S Quad:.

RANGE IN CHARACTERISTICS:

Soil temperature: The mean annual soil temperature at 50 cm is 15 to 17 degrees C and the difference between mean summer and mean winter soil temperature is greater than 6 degrees C. The soils have a thermic temperature regime.

Soil moisture: The soil moisture control section is dry in all parts from about May to October (about 180 days).The soils have a xeric soil moisture regime.

Diagnostic Feature(s)
Mollic epipedon thickness: 17 to 50 cm
Argillic horizon thickness: 10 to 40 cm
Depth to lithic contact: 20 to 50 cm
Paralithic materials are present above the lithic contact in some pedons.

Organic carbon in the epipedon: 0.5 to 5 percent

Reaction: moderately acid to neutral

Base saturation: Greater than 50 percent in the epipedon (by ammonium acetate).

Particle size control section weighted average:
Rock fragments: 35 to 80 percent, with 5 to 45 percent gravel, 0 to 50 percent cobbles, and 0 to 10 percent stones
Clay content: averages 18 to 35 percent clay
Base saturation: greater than 75 percent in all horizons between the mineral soil surface and the lithic contact (by sum of cations).

A horizon
Hue: 2.5YR, 10YR
Value: 4 or 5, 2 or 3 moist
Chroma: 2 to 4, 1 or 2 moist
Texture: silt loam, loam
Clay content: 12 to 27 percent
Rock fragments: 15 to 45 percent
10 to 25 percent indurated serpentinite gravel
0 to 25 percent indurated serpentinite cobbles
0 to 5 percent indurated serpentinite stones

Bt horizon
Hue: 2.5YR, 10YR
Value: 4 or 5, 2 to 4 moist
Chroma: 2 to 6, 2 to 4 moist
Texture: loam, silty clay loam, clay loam
Clay content: 18 to 40 percent
Rock fragments: 35 to 80 percent
5 to 45 percent indurated serpentinite gravel
0 to 50 percent indurated serpentinite cobbles
0 to 10 percent indurated serpentinite stones

COMPETING SERIES: These are the Hentine soils. Hentine soils do not have hues of 2.5YR, and have a frost-free season of 150 to 240 days and receive 254 to 508 mm of precipitation annually.

GEOGRAPHIC SETTING: The Sixbit soils are on hills in the Sierra Nevada foothills. Slopes range from 3 to 70 percent. These soils formed in colluvium and residuum weathered from serpentinite. Elevation is 170 to 670 meters. The climate is Mediterranean with warm, dry summers and cool, moist winters. The mean annual precipitation is 550 to 800 mm and the mean annual air temperature is 15 to 17 degrees C. The frost free season is 235 to 330 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Crimeahouse and Fancher soils. The Crimeahouse and Fancher soils are 50 to 100 cm to a lithic contact. The Fancher soils have greater than 35 percent clay and less than 35 percent rock fragments in the particle size control section. These soils are found on similar hillslope positions to the Sixbit soils.

DRAINAGE AND PERMEABILITY: Well drained, moderately high saturated hydraulic conductivity in the A horizons and moderately low to moderately high saturated hydraulic conductivity in the Bt horizons.

USE AND VEGETATION: This soil is used for rangeland, recreation, wildlife habitat, and watershed. Vegetation is buckbrush, foothill pine, chamise, and serpentine-endemic forbs such as bitter root and birds-eye gilia.

DISTRIBUTION AND EXTENT: Sierra Nevada Foothills in California; MLRA 18. The series is not extensive.

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Davis, California

SERIES PROPOSED: Tuolumne County, California. Source of name is from Six Bit Gulch in the Red Hills Area of Critical Environmental Concern.

REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Mollic Epipedon - 0 to 48 cm
Argillic Horizon - 12 to 48 cm
Lithic Contact - 48 cm
Particle Size Control Section for this pedon: 12 to 48 cm
Lithic contact is dominantly less than 50 cm but may range up to 70 cm in fractures of bedrock.

Magnesic minerology: The fraction of Mg silicate minerals is inferred to be greater than 40% by mass in the control section fine earth fraction based on laboratory data collected from geographically-associated serpentine soils. Chlorite, talc and serpentine-subgroup clays (e.g. chrysotile, antigorite, lizardite) are strongly represented in the clay fractions. Sand fractions have substantial amounts of serpentine or mafic minerals (pyroxene, hornblende, and iron oxides) that are associated with the serpentinization process. KSSL certified lab pedons: S09CA109001, S09CA109002, S09CA109004, S2007CA109002.

ADDITIONAL DATA:
NASIS User Pedon ID: S2007CA109002
Lab Pedon #: 07N0471

National Cooperative Soil Survey
U.S.A.