LOCATION BIGHILL CAEstablished Series
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, mesic Humic Dystroxerepts
TYPICAL PEDON: Bighill coarse sandy loam; on a 25 percent west-facing slope under bear clover, ponderosa pine, Douglas-fir, incense-cedar, white fir, and black oak at about 3,770 feet. (Colors are for dry soil unless otherwise stated. When described on June 10, 1983, the soil was moist below 15 inches).
0--1 to 0 inches; decomposing conifer needles and hardwood leaves.
A1--0 to 5 inches; dark grayish brown (10YR 4/2) coarse sandy loam, dark brown (10YR 3/3) moist; weak very fine and fine granular structure; soft, very friable, nonsticky and nonplastic; few very fine, fine and medium roots; common very fine interstitial and few fine tubular pores; 2 percent pebbles; slightly acid (pH 6.1); clear smooth boundary.
A2--5 to 17 inches; brown (10YR 5/3) gravelly sandy loam, dark brown (10YR 3/3) moist; weak very fine and fine granular structure; soft, very friable, nonsticky and nonplastic; common very fine and few fine and medium roots; common very fine interstitial and tubular pores; 15 percent pebbles; medium acid (pH 5.8); clear irregular boundary. (Combined thickness of the A horizon is 7 to 19 inches)
Bw--17 to 32 inches; brown (7.5YR 5/4) cobbly sandy loam, dark brown or brown (7.5YR 4/4) moist; weak very fine and fine granular structure; soft, very friable, nonsticky and nonplastic; few very fine, fine, medium and coarse roots; common very fine interstitial and few very, fine and fine tubular pores; 15 percent pebbles and 15 percent cobbles; strongly acid (pH 5.4) abrupt irregular boundary. (10 to 30 inches thick)
Cr--32 to 39 inches; brownish yellow (10YR 6/6) highly weathered granite.
TYPE LOCATION: El Dorado County, California; about 1.3 air miles south southeast of Quintette; about 750 feet southwest from Sand Mountain Boulevard along a dirt road; in the NW 1/4 of the NE 1/4 of the NW 1/4 of Section 18, T. 12 N., R. 12 E., Tunnel Hill Quadrangle.
RANGE IN CHARACTERISTICS: Depth to a paralithic contact of weathered granitic rock is 20 to 40 inches. The soil between the depths of 10 inches and the paralithic contact is usually dry in all parts from mid-July through mid-October and is moist in some or all parts the rest of the year. The mean annual soil temperature is estimated to be 49 to 54 degrees F. Base saturation (ammonium acetate) is 15 to 50 percent throughout and usually decrases with depth. Texture is sandy loam, coarse sandy loam, or their gravelly or cobbly equivalent throughout. Rock fragment content, consisting of gravel and cobbles, ranges from 0 to 35 percent. Total rock fragment content and cobble content (when present) usually increase with depth.
The A horizon is 10YR 4/2, 4/3, 5/2, 5/3. Moist color is 10YR 2/2, 2/3, 3/2, 3/3. It is slightly acid to medium acid. Organic matter content is 2 to 10 percent.
The Bw horizon is 5YR 5/4; 7.5YR 5/4, 5/6, 5/8; 10YR 5/4 or 5/6. Moist color is 5YR 3/4; 7.5YR 3/4, 4/4; 10YR 3/4, 4/3, or 4/4. It is medium acid to strongly acid.
The Cr horizon is strongly weathered granitic rock that is easily dug by hand tools but retains the original rock structure.
COMPETING SERIES: These are the Skamania series in the same family and the Pilliken and Shaver series in other families. All are over 40 inches deep.
GEOGRAPHIC SETTING: Bighill soils are on mountain slopes. Slopes are 5 to 75 percent. The soils formed from granitic rock. Elevations are 3,100 to 5,300 feet. The climate is moist subhumid with warm dry summers and cold moist winters. Mean annual precipitation is 50 to 65 inches, much of which occurs as snow. Mean annual temperature is about 48 to 55 degrees F. Mean January temperature is about 39 degrees F; mean July temperature is about 70 degrees F. Frost-free season is about 100 to 150 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Chaix, Dome, Holland, Musick, and the competing Pilliken soils. Chaix soils have an ochric epipedon. Dome soils have an ochric epipedon and greater than 40 inches deep to a paralithic contact. Holland and Musick soils have argillic horizons and are greater than 40 inches deep to a paralithic contact.
DRAINAGE AND PERMEABILITY: Well drained; slow to very rapid runoff; moderately rapid permeability.
USE AND VEGETATION: Used mainly for timber production, watershed, and wildlife habitat. Native vegetation is ponderosa pine, white fir, sugar pine, incense-cedar, Douglas fir, black oak, and mountain shrubs.
DISTRIBUTION AND EXTENT: The central part of the west slope of the Sierra Nevada of California. The soils are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.
SERIES ESTABLISHED: El Dorado County, California (Eldorado National Forest), 1985.
REMARKS: Lab data for the type location is available from University of California, Davis, Soil Morphology Lab, Sample Number UCD 83-09-8X.