LOCATION ORACLEOAK CATentative Series
TAXONOMIC CLASS: Sandy, mixed, mesic Humic Dystroxerepts
TYPICAL PEDON: Oracleoak gravelly loamy sand, on an east facing, linear to convex, 5 percent slope under California buckwheat, grass, annuals, whitethorn ceanothus, and hoary coffeeberry (Rhamnus tomentella) at an elevation of 1,546 meters (5,535 feet). (Colors are for dry soil unless otherwise noted.) The surface is covered by approximately 40% gravel.
A1-- 0 to 6 centimeters, (0 to 2.5 inches); dark grayish brown (10YR 4/2) gravelly loamy sand, black (10YR 2/1) moist; weak fine granular structure; soft, very friable, nonsticky, nonplastic; many very fine roots throughout; common interstitial pores; 15 percent gravel; moderately acid (pH 5.9); clear smooth boundary.
A2-- 6 to 19 centimeters, (2.5 to 7.5 inches); dark grayish brown (2.5Y 4/2) gravelly sandy loam, black (10YR 2/1) moist; moderate medium granular structure; soft, very friable, nonsticky, nonplastic; many very fine roots throughout; common interstitial pores; 25 percent gravel; moderately acid (pH 5.8); clear smooth boundary. (14 to 40 centimeters thick)
Bw-- 19 to 50 centimeters, (7.5 to 20 inches); very dark grayish brown (10YR 3/2) gravelly loamy sand, black (10YR 2/1) moist; weak medium granular; soft, very friable, nonsticky, nonplastic; many very fine roots throughout; common interstitial pores; 15 percent gravel, 5 percent paracobbles and 8 percent parastones; moderately acid (pH 5.8); clear smooth boundary. (10 to 40 centimeters thick)
C-- 50 to 61 centimeters, (20 to 24 inches); brown (10YR 4/3) gravelly loamy coarse sand, very dark grayish brown (10YR 3/2) moist; massive; slightly hard, friable, nonsticky, nonplastic; common very fine roots throughout; 27 percent gravel; neutral (pH 6.6); clear smooth boundary. (5 to 15 centimeters thick)
Cr-- 61 to 141 centimeters, (24 to 56 inches); light gray (10YR 7/2) loamy coarse sand, dark grayish brown (2.5Y 4/2) moist; massive; moderately acid (pH 6.0); clear wavy boundary.
R-- 141 centimeters, (56 inches); granitoid rock.
TYPE LOCATION: Riverside County, California; 60 meters (200 feet) east and 140 meters (450 feet) south of the NW corner of section 7, T. 4 S., R. 2 E.; 33 degrees, 50 minutes and 26.6 seconds north latitude and 116 degrees, 49 minutes and 19.2 seconds west longitude; Lake Fulmor 7.5 minute quadrangle; UTM 11S 0516470e 3744509n (DTM: NAD83).
RANGE IN CHARACTERISTICS: Soil moisture control section: Usually dry in all parts from late May or early June until late November or early December, and usually moist in some or all parts the rest of the year. The soils have a xeric moisture regime.
Mean annual soil temperature: 8 to 14 degrees C. (47 to 57 degrees F.)
Organic matter: 1 to 4 percent
Surface rock fragments: 10 to 40 percent gravel; 0 to 2 percent stones
Control section:
Thickness of umbric epipedon: 35 to 55 centimeters (14 to 22 inches)
Depth to a paralithic contact: 50 to 65 centimeters (20 to 33 inches)
Depth to a lithic material: 80 to 145 centimeters (30 to 57 inches)
Rock fragments: 12 to 40 percent
Clay content: ranges between 3 and 5 percent
A horizon
Hue: 10YR or 2.5Y
Value: 3 or 4 dry; 2 to 3 moist
Chroma: 2 to 3 dry
Texture of the fine earth: fine sandy loam, loamy sand or sandy loam
Clay content: 3 to 8 percent
Rock fragments: 10 to 45 percent
Reaction: moderately to strongly acid
Bw horizon
Hue: 10YR or 2.5Y
Value: 3 to 5 dry; 2 or 3 moist
Chroma: 2 or 3 dry; 1 to 3 moist
Clay content: 3 to 6 percent
Rock fragments: 10 to 40 percent with 10 to
30 percent gravel, 0 to 5 percent cobbles, and 0 to 8 percent stones
Reaction: slightly to moderately acid
COMPETING SERIES: This is the Zayante series. Zayante soils are formed in weakly consolidated marine sediments. They have no Bw horizon, and no R layer within 150 centimeters (60 inches). The mean annual precipitation is about 1,320 millimeters (52 inches) and the mean annual air temperature is about 12 degrees C. (54 degrees F.).
GEOGRAPHIC SETTING: Oracleoak soils are on mountain sideslopes and ridgetops. Slopes range from 4 to 50 percent. These soils formed in residuum or colluvium over residuum from granitoid sources. Elevations range from 1400 to 1550 meters (4600 to 5100 feet). The climate is mesic with warm, dry summers and cool, moist winters with some snow. The mean annual precipitation is 483 to 737 millimeters (19 to 29 inches) and the mean annual air temperature is 7 to 13 degrees C. (45 to 55 degrees F.) The frost-free season is 35 to 178 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Deerbrush (T), Omstott, Lakefulmor (T) soils. Omstott does not have an umbric epipedon. Deerbrush, and Omstott have a loamy particle-size control section. Lakefulmor has neither a paralithic nor a lithic contact within 150 centimeters (60 inches).
DRAINAGE AND PERMEABILITY: Somewhat excessively drained; low to medium runoff; rapid permeability.
USE AND VEGETATION: Oracleoak soils are used for recreation, watershed and wildlife habitat. Some areas are used for homesites. The present vegetation is mainly oracle oak, whitethorn, hoary coffeeberry, grass, annuals, gooseberry, California buckwheat, and live oak.
DISTRIBUTION AND EXTENT: Inland mountain ranges of Riverside county, southern California. MLRA 20. These soils are of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.
SERIES PROPOSED: Riverside County, California, Emergency Watershed Program, Private Land Soil Survey, 2005. The name is from a tree species found in the soil survey area.
REMARKS: Diagnostic horizons and feature recognized in the profile are:
1. Umbric epipedon: 0 to 50 centimeters (A1, A2, and Bw horizons)
2. Paralithic contact: 61 to 141 centimeters (Cr horizon)
3. Lithic contact: the zone beginning at 141 centimeters (R horizon)
4. Particle-size control section: 25 to 61 centimeters (Bw and C horizons)
5. Justification for classification: Base saturation for the A horizons is
43 percent