LOCATION BONTA CAEstablished Series
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, frigid Typic Haploxeralfs
TYPICAL PEDON: Bonta loamy coarse sand--on a 26 percent southeast-facing slope under Jeffrey pine, black oak, perennial grasses, and shrubs at about 5,800 feet elevation--forestland. (Colors are for dry soil unless otherwise noted.) The soil surface has a discontinuous cover of about 3 inches of undecomposed and slightly decomposed pine needles, twigs, and leaves.
A1--0 to 4 inches; pale brown (10YR 6/3) loamy coarse sand, brown (10YR 4/3) moist; moderate fine granular structure; slightly hard, friable, nonsticky and nonplastic; many very fine and common fine roots; many very fine interstitial and common very fine and fine tubular pores; slightly acid (pH 6.5); gradual smooth boundary.
A2--4 to 12 inches; pale brown (10YR 6/3) loamy coarse sand, brown (10YR 4/3) moist; weak fine subangular blocky structure; slightly hard, friable, slightly sticky and nonplastic; common very fine and fine roots; many very fine interstitial, common very fine and fine tubular pores; slightly acid (pH 6.2); gradual smooth boundary. (Combined thickness of the A horizons is 9 to 20 inches)
BA--12 to 20 inches; very pale brown (10YR 7/3) coarse sandy loam, brown (10YR 5/3) moist; moderate fine subangular blocky structure; hard, friable, slightly sticky and nonplastic; common very fine and fine, many medium and coarse roots; common very fine and fine tubular and interstitial pores; few faint clay colloid coats on mineral grains; moderately acid (pH 5.8); clear smooth boundary. (6 to 8 inches thick)
Bt--20 to 31 inches; very pale brown (10YR 7/4) sandy loam, yellowish brown (10YR 5/4) moist; moderate medium subangular blocky structure; very hard, firm, slightly sticky and slightly plastic; common fine and medium roots; common very fine and fine tubular and interstitial pores; common faint clay films lining pores and on faces of peds; strongly acid (pH 5.5); abrupt wavy boundary. (5 to 13 inches thick)
Crt--31 to 40 inches; very pale brown (10YR 8/4) soft, weathered quartz diorite that crushes to gravelly loamy coarse sand, light yellowish brown (10YR 6/4) moist; very few fine and medium roots in fractures; few faint clay films line fracture planes; very strongly acid (pH 5.0).
TYPE LOCATION: Plumas County, California; on the Plumas National Forest about 2.75 miles north of Vinton and 0.75 mile west of Little Last Chance Creek; approximately 1,950 feet west and 1,350 feet north of the southeast corner of section 15, T. 23 N., R. 16 E.; USGS Chilcoot 7.5 minute topographic quadrangle; 39 degrees 50 minutes 54 seconds north latitude and 120 degrees 10 minutes 31 seconds west longitude, NAD27.
RANGE IN CHARACTERISTICS:
Soil moisture - The soil moisture control section (8 to 26 inches or bedrock) is dry from July 15 to November 1 and is moist in some or all parts the rest of the year; The soil temperature exceeds 41 degrees F from April 1 to November 1 and exceeds 47 degrees F from about May 1 to November 15; Xeric moisture regime.
Mean annual soil temperature - 43 to 47 degrees F.
Depth to bedrock - 20 to 40 inches to a paralithic contact. The paralithic materials below the contact are weathered granitic rock such as granodiorite.
Base saturation - 75 to 85 percent to a depth of 30 inches or to the paralithic contact when shallower than 30 inches.
Particle-size control section - Clay content: 12 to 18 percent; Rock fragments: 5 to 30 percent, mainly fine and medium (2 to 20 mm diameter) gravel. Lithology of fragments are granitic rocks such as granodiorite, granite, or quartz diorite.
A horizon - Dry color: 10YR 4/3, 5/2, 5/3, 6/2, 6/3, 6/4, 7/3, or 7/4.
Moist color: 10YR 3/3, 4/3 or 4/4. Colors with moist value of 3 are confined to the upper 5 inches or less of this horizon and are lacking in some pedons.
Texture: Coarse sandy loam, loamy coarse sand, or gravelly sandy loam.
Clay content: 2 to 10 percent.
Rock fragments: 5 to 30 percent gravel.
Reaction: Slightly acid or neutral.
Bt horizon - Dry color: 10YR 5/4, 6/3, 6/4, 7/3; 7.5YR 7/4 or 7/6.
Moist color: 10YR 5/4; 7.5YR 5/4 or 5/6.
Texture: Sandy loam, coarse sandy loam, gravelly sandy loam, or gravelly coarse sandy loam.
Clay content: 12 to 18 percent.
Rock fragments: 5 to 30 percent gravel.
Structure: Weak or moderate subangular blocky.
Reaction: Strongly acid through slightly acid.
COMPETING SERIES: There are currently no other series in this family.
GEOGRAPHIC SETTING: Bonta soils are on mountains. They typically occur on footslope and backslope positions. These soils formed in colluvium and residuum derived from granitic rocks such as granodiorite, granite, or quartz diorite. Slopes are 2 to 75 percent. Elevations range from 4,800 to 6,000 feet. The climate is subhumid with cold, moist winters and warm, dry summers. The mean annual precipitation is 16 to 30 inches. The mean annual temperature is 45 to 47 degrees F., the mean January temperature is about 28 degrees F., and the mean July temperature is about 68 degrees F. The frost-free period is 30 to 80 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Haypress, Lasco, Mottsville, and Toiyabe soils. Haypress soils are sandy, deep to paralithic contacts, and have mollic epipedons. Lasco soils are deep to paralithic contacts and have lower base saturation. Mottsville soils are sandy, very deep, and have mollic epipedons. Toiyabe soils are sandy and are shallow to paralithic contacts.
DRAINAGE AND PERMEABILITY: Well drained; high surface runoff; moderately rapid permeability.
USE AND VEGETATION: Bonta soils are used for livestock grazing and timber production. The vegetation is a forest canopy of Jeffrey pine, black oak, and western juniper with an understory of curlleaf mountainmahogany, antelope bitterbrush, mountain big sagebrush, mule'sear wyethia, squawcarpet, and perennial grasses.
DISTRIBUTION AND EXTENT: Northeastern California. These soils are not extensive with about 2,500 acres of the series mapped to date. MLRA 22A.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.
SERIES ESTABLISHED: Plumas County (Sierra Valley Area), California, 1973.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the soil surface to 12 inches (A1 and A2 horizons).
Argillic horizon - The zone from 20 to 31 inches (Bt horizon).
Paralithic contact - The boundary at 31 inches to underlying soft, weathered bedrock (Crt layer).
ADDITIONAL DATA: Samples from the four horizons of the typical pedon had a base saturation of about 80 percent.