LOCATION BACKDOOR CAEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, active, thermic Typic Argixerolls
TYPICAL PEDON: Backdoor loam on a west facing hill with 38 percent slope under a cover of chamise and wedgeleaf ceanothus at an elevation of 1,936 feet (590 meters). When described on 06/07/2006 the soil was slightly moist from 10 to 31 inches (26 to 78 centimeters). Colors are for dry soils unless otherwise noted.
A1--0 to 5 inches (0 to 12 centimeters); dark grayish brown (10YR 4/2) loam, very dark brown (10YR 2/2) moist; weak fine and medium subangular blocky structure; slightly hard, very friable, slightly sticky, slightly plastic; many very fine roots; many fine interstitial pores; 1 percent gravel; very strongly acid (pH 5.0); clear smooth boundary. (2 to 10 inches, 6 to 25 centimeters thick)
A2--5 to 10 inches (12 to 26 centimeters); grayish brown (10YR 5/2) gravelly loam, very dark grayish brown (10YR 3/2) moist; weak medium subangular blocky structure; slightly hard, very friable, moderately sticky, very plastic; common very fine roots; common fine tubular and common very fine interstitial pores; 15 percent gravel; strongly acid; clear smooth boundary. (0 to 8 inches, 0 to 21 centimeters thick)
Bt1--10 to 15 inches (26 to 39 centimeters); pale brown (10YR 6/3) gravelly clay loam, brown (10YR 4/3) moist; moderate medium angular blocky structure; hard, very friable, moderately sticky, very plastic; common fine and very fine roots; common fine and very fine tubular pores; many faint clay films on surfaces of pores and on all faces of peds; 15 percent gravel; strongly acid (pH 5.5); clear wavy boundary.
Bt2--15 to 27 inches (39 to 68 centimeters); light yellowish brown (10YR 6/4) very paragravelly sandy clay loam, dark yellowish brown (10YR 4/4) moist; moderate coarse angular blocky structure; hard, very friable, moderately sticky, moderately plastic; common very fine, fine and medium tubular pores; many faint clay films on all faces of peds, on surfaces of pores and on rock fragments; 50 gravel; strongly acid (pH 5.3); gradual wavy boundary. (Combined thicknesses of the Bt horizons is 20 to 55 inches, 52 to 140 centimeters thick)
Crt--27 to 60 inches (68 to 153 centimeters); very pale brown (10YR 7/4) extremely paragravelly loamy coarse sand, yellowish brown (10YR 5/4), moist; massive; hard, friable, nonsticky, nonplastic; 10 percent discontinuous faint clay films on rock fragments; 80 percent paragravels; strongly acid (pH 5.3).
TYPE LOCATION: San Benito County, California; about 0.9 miles (1.4 kilometers) along Highway 146 north of the west entrance to Pinnacles National Monument to the east side of Highway 146; 1,958 feet south and 1,333 east of northwest of the corner of section 5, T 17S, R 7E; USGS North Chalone Peak, California topographic quadrangle; 36 degrees 28 minutes 58.20 seconds north latitude and 121 degrees 13 minutes 43.30 seconds west longitude; UTM 658661 meters E, 4038958 meters N, zone 10.
RANGE IN CHARACTERISTICS:
Depth to bedrock: more than 60 inches (150 centimeters).
Mean annual soil temperature: 61 to 53 degrees F (16 to 17 degrees C).
Soil moisture control section: dry in all parts from May 15 to November 15 (180 days), and moist in all parts from about January 15 to April 15 (90 days).
Particle size control section: 25 to 30 percent clay, 5 to 25 percent rock fragments mostly gravel from granite.
Base Saturation by sum of cations: 87 to 100 %
A horizon(s):
Hue: 10YR, 7.5YR
Value: 4, 5 dry; 3, 4 moist
Chroma: 2, 3 dry; 2, 3 moist
Texture of the fine earth fraction: Sandy loam, loam
Clay content: 8 to 25 percent
Rock fragments: 5 to 15 percent gravel
Reaction: very strongly acid to slightly alkaline
Bt horizons:
Hue: 7.5YR, 10YR
Value: 5, 6, 7 dry; 3, 4, 5 moist
Chroma: 3, 4, 6 dry; 2, 3, 4, 6 moist
Texture of the fine earth fraction: Sandy clay loam, clay loam
Clay content: 20 to 35 percent
Rock fragments: 5 to 50 percent paragravel
Reaction: very strongly acid to neutral
C horizon(s):
Hue: 7.5YR, 10YR
Value: 5, 6, 7 dry; 3, 4, 5 moist
Chroma: 4, 6 dry; 4, 6 moist
Texture of the fine earth fraction: Loamy sand, loamy coarse sand, sandy loam
Clay content: 5 to 20 percent
Rock fragments: 60 to 80 percent paragravel
Reaction: strongly acid to neutral
COMPETING SERIES: These are the Ballard, Bohna, Bootling, Chualar, Chuloak, Feethill, Franciscan, Gilroy, Pinole, Pinto, Shimmon, Soper, Tajea and Tehachapi soils. Ballard soils have gravel from siliceous shale rather than paragravel from granite. Bohna soils are 40 to 73 inches deep to a paralithic contact and lack gravel and paragravel. Boontling soils have base saturation of 50 to 75 percent in the A horizon, and low chroma mottles in the lower Bt horizon. Chualar soils have a gravelly C horizon, but no paragravel. Chuloak soils have less than 15 percent gravel throughout and have mottles in the C horizon. Feethill soils are 20 to 40 inches deep to weathered rock. Franciscan, Gilroy and Tajea soils are 20 to 40 inches deep to a lithic contact. Pinole soils have base saturation of 50 to 75 percent throughout, and variegated colors and manganese stains in the lower Bt horizon. Pinto soils have less than 15 percent rock fragments throughout and have sandy clay loam or clay loam C horizons with black manganses stains. Shimmon and Soper soils are 20 to 40 inches deep to a paralithic contact. Tehachapi soils have a weakly cemented, moderately alkaline C horizon.
GEOGRAPHIC SETTING: The Backdoor soils are on backslopes of hills. Slopes range from 9 to 70 percent. These soils formed in residuum weathered from granite. Elevation is 984 to 2,789 feet (300 to 850 meters). The climate is characterized by warm, dry summers and cool, moist winters. The mean annual precipitation is 17 to 19 inches (432 to 483 millimeters) and the mean annual air temperature is about 59 to 63 degrees F (15 to 17 degrees C). The frost free season is 190 to 210 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Rimtrail and Tuborcio soils. Tuborcio soils are in the fine particle size family and are on north facing sideslopes of hills under blue oak savannah. Rimtrail soils have a Pachic epipedon, have no root limiting layer within a depth of 60 inches (150 centimeters), and are on basin floors under annual grasses.
DRAINAGE AND PERMEABILITY: Well drained, moderately slow permeability, medium to very high runoff. They do not flood or pond.
USE AND VEGETATION: This soil is used for watershed, wildlife habitat and recreation. Vegetation is Chamise chaparral or mixed chaparral.
DISTRIBUTION AND EXTENT: San Benito and Monterey Counties, California in MLRA 15 -- Central California Coast Range. These soils are of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: San Benito County, California. Source of name: rock formation in Pinnacles National Monument. This series was established based on limited acreage observed within the National Park Service Pinnacles National Monument boundary.
REMARKS:
Particle Size Control Section for this pedon: 10 to 27 inches (26 to 68 centimeters)
Diagnostic horizons and features recognized in this pedon are:
Mollic Epipedon: the zone from 0 to 10 inches (0 to 26 centimeters) (A1 and A2 horizons)
Argillic Horizon: the zone from 10 to 27 inches (26 to 68 centimeters) (Bt1 and Bt2 horizons)
ADDITIONAL DATA: