LOCATION WRIGHTWOOD CAEstablished Series
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, mesic Typic Haploxeralfs
TYPICAL PEDON: Wrightwood sandy loam on a 2 percent slope under scrub oak and annual grasses at 4,200 feet elevation. (Colors are for dry soil unless otherwise stated. When described the soil was dry throughout.)
A1--0 to 3 inches; brown (10YR 5/3) loamy sand, dark brown (10YR 3/3) moist; weak very thin platy structure; slightly hard, very friable; common very fine roots; few very fine interstitial pores; about 10 percent (1/4 to 3/8 inch) pebbles; neutral (pH 7.0); clear smooth boundary. (1 to 3 inches thick)
B1--3 to 9 inches; brown (10YR 5/3) sandy loam, dark brown (10YR 4/3) moist; weak fine and medium angular blocky structure; slightly hard, very friable, nonsticky and nonplastic; common very fine, few fine roots; few very fine interstitial and fine tubular pores; common thin clay films as bridges between mineral grains and in tubular pores; about 5 percent (1/4 to 3/8 inch) pebbles; neutral (pH 7.0); gradual smooth boundary. (4 to 6 inches thick)
B21t--9 to 22 inches; brown (7.5YR 5/4) sandy loam, dark brown (7.5YR 4/4) moist; moderate medium subangular blocky structure; very hard, friable, slightly sticky and nonplastic; few very fine and fine, few coarse roots; few very fine interstitial and fine tubular pores; few moderately thick clay films on peds, many moderately thick c;clay films as bridges between mineral grains and in tubular pores; about 5 percent (1/4 to 1/2 inch) pebbles; neutral (pH 6.8); gradual smooth boundary. (10 to 13 inches thick)
B22t--22 to 46 inches; brown (7.5YR 5/2) sandy loam, dark brown (7.5YR 4/2) moist; moderate medium and coarse angular blocky structure; very hard, friable, slightly sticky and nonplastic; few very fine and fine roots; few very fine interstitial and fine tubular pores; clay films as in above horizon; has 1 or 2 oblique discontinuous sandy clay loam bands, about 1/2 to 3/4 inch wide; about 5 to 10 percent (1/4 to 1/2 inch) pebbles; neutral (pH 6.6); gradual smooth boundary. (18 to 24 inches thick)
B23t--46 to 60 inches; brown (7.5YR 5/4) gravelly sandy loam, dark brown (7.5YR 4/4) moist; moderate coarse angular blocky structure; very hard, firm, sticky and plastic; few fine roots; few very fine interstitial pores; common moderately thick clay films on peds; many moderately thick clay films in bridges between mineral grains and in tubular pores; about 20 percent (1/2 to 3/4 inch) pebbles; slightly acid (pH 6.5).
TYPE LOCATION: San Bernardino County, California; east of Oak Hill Road, behind the highway at Summit Inn; about 50 feet from the southwest corner of the water tank in the SE1/4 NE1/4 SE1/4 section 5, T.3N., R.5W.
RANGE IN CHARACTERISTICS: The mean annual soil temperature is about 54 to 59 degrees F. The soil is usually moist in some part between depths of 8 and 24 inches from late November to late April or early May and is continuously dry the rest of the time. There is a 3 to 10 percent clay increase from the A to the B horizon. The solum has 5 to 15 percent gravel in the A and Bt horizons and 15 to 25 percent gravel in the B23tb horizon. It is slightly acid or neutral throughout.
The A horizon is brown, dark brown, yellowish brown, or light yellowish brown (10YR 5/3, 4/3, 5/4, 6/4). Organic carbon is 0.4 to 0.6 percent. This horizon is loamy sand or sandy loam.
The Bt horizon is strong brown, brown, light brown, reddish yellow, or yellowish red (7.5YR 5/6, 5/4, 5/2, 6/4, 6/6; 5YR 5/6). Yellowish red colors are usually in the lower part of the Bt horizon. Structure is weak or moderate fine to coarse angular, subangular blocky or prismatic. Depth to the upper boundary of the B23tb horizon is about 40 to 55 inches and lower boundaries are below a depth of 6 or 6 1/2 feet in some pedons. The B23tb horizon is brown, strong brown, reddish brown, or yellowish red (7.5YR 5/2, 5/4, 5/6; 5YR 5/4, 5/6). It is gravelly sandy loam or gravelly sandy clay loam.
COMPETING SERIES: These are the Adelanto, Greenfield and Lucerne series in other families. Adelanto and Lucerne soils have thermic soil temperatures and an aridic moisture regime bordering on xeric. Greenfield soils have soil temperatures of 59 to 65 degrees F.
GEOGRAPHIC SETTING: Wrightwood soils are on terraces and have slopes of 2 to 9 percent. They formed from older, mixed alluvium dominantly from granitic sources. Elevations are 3,900 to 4,300 feet. The climate is subhumid mesothermal having warm, dry summers and cool, moist winters. The mean annual precipitation is 14 to 18 inches of which 1/3 to 1/2 falls as snow of short duration. The average January temperature is 40 to 44 degrees F.; the average July temperature is 68 to 74 degrees F.; and the mean annual temperature is 54 to 58 degrees F. The frost free season is 160 to 190 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bull Trail and Oak Glen soils. Bull Trail soils have a thin dark colored A1 horizon and a sandy clay loam B2t horizon. Oak Glen soils have a mollic epipedon more than 20 inches thick and lack an argillic horizon.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; moderately rapid permeability in the B2t horizon and moderate in the B23tb horizon.
USE AND VEGETATION: Used mainly for wildlife habitat and for dryland pasture. Vegetation is scrub oak, chamise, and grass.
DISTRIBUTION AND EXTENT: Foothills of the San Bernardino Mountains adjacent to the high Mojave Desert near Cajon Pass. The soils are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: San Bernardino County, California, Mojave River Area, 1978.