LOCATION YORKVILLE CAEstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, thermic Typic Argixerolls
TYPICAL PEDON: Yorkville loam - on a southwest facing concave slope of 20 percent under medusahead, tarweed, filaree, wild oats and soft chess at 1,040 feet elevation. (Colors are for dry soil unless otherwise noted. When described November 19, 1976, the soil was moist throughout.)
A1--0 to 5 inches; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; moderate fine subangular blocky structure; slightly hard, firm, slightly sticky and slightly plastic; many very fine and fine roots; common fine tubular pores; moderately acid (pH 5.8); clear wavy boundary. (3 to 7 inches thick)
A2--5 to 15 inches; grayish brown (10YR 5/2) loam, dark grayish brown (10YR 3/2) moist; moderate medium angular blocky structure; hard, firm, slightly sticky and slightly plastic; many very fine and common fine roots; common very fine and fine tubular pores; moderately acid (pH 5.8); clear wavy boundary. (7 to 12 inches thick)
Bt--15 to 29 inches; light brownish gray (2.5Y 6/2) clay, dark grayish brown (2.5Y 4/2) moist; weak medium prismatic structure breaking to moderate medium angular blocky; very hard, very firm, sticky and plastic; many very fine roots; common very fine tubular pores; few thin clay films on peds and common thin clay films and some pressure faces in pores; 10 percent pebbles; neutral (pH 7.0); gradual wavy boundary. (14 to 21 inches thick)
2Bt--29 to 41 inches gray (N 6/0) clay, dark gray (N 4/0) moist moderate medium subangular blocky structure; very hard, very firm, sticky and plastic; few very fine roots; common very fine tubular pores; many moderately thick clay films and some pressure faces on peds and in pores; 10 inches pebbles; mildly alkaline (pH 7.5); gradual irregular boundary. (10 to 24 inches thick)
2BCt--41 to 60 inches; gray (N 6/0) gravelly clay, dark gray (N 4/0) moist; common medium distinct mottles of light yellowish brown (10YR 6/4); moderate medium subangular blocky structure; very hard, very firm, sticky and plastic; few very fine roots; few very fine tubular pores; many moderately thick clay films on peds and in pores; 25 percent 2 to 75mm pebbles; mildly alkaline (pH 7.5).
2Cr--60 to 72 inches; highly weathered fault gouge material consisting of chloritic schist and graywacke with soil material between rock fragments.
TYPE LOCATION: Mendocino County, California; about 6.4 miles south of Hopland; 150 feet south of the cattle corral and .9 mile east on dirt road from Mountain House Road (at old Rodeo Grounds); 1;200 feet north and 2,600 feet east of southwest corner, section 3, T.12 N., R.11 W., MDBM.
RANGE IN CHARACTERISTICS: The thickness of the solum and depth to bedrock is greater than 60 inches. The soil is dry in all parts between depths of 6 to 19 inches from May to October. It is moist in all parts from December to April. The mean annual soil temperature is 59 degrees to 64 degrees F. The mineralogy is mixed with high amounts of chlorite, vermiculite, and mica. The particle-size control section has 35 to 50 percent clay and 10 to 20 percent coarse fragments.
The A horizon has dry color of 10YR 5/3, 5/2, 4/3, 4/2, 4/1, 3/3, 3/2; 2.5Y 5/2, 4/2 or 3/2 and moist color of 10YR 3/3, 3/2, 3/1, 2/2, 2/1; or 2.5Y 3.2. Particle size is loam or clay loam and averages 20 to 32 percent clay. Reaction is moderately acid to mildly alkaline.
The Bt horizon has dry color of 10YR 5/3, 5/2, 5/1, 4/3, 4/2, 4/1, 3/2; 2.5Y 6/4, 6/2, 5/4, 5/2, 4/4, 4/2; N 6/0, 5/0, 4/0; 5Y 6/3, 6/1, 5/1 or 4/4 and moist color of 10YR 5/6, 5/4, 4/1, 3/4, 3/2, 3/1, 2/1; 2.5Y 4/2, 3/2; N 4/0; 5Y 4/3, 4/2, 4/1 or 3/2. Particle size is clay loam or clay and averages 35 to 50 percent clay and about 9 to 20 percent more clay than the A horizon. Reaction is neutral to moderately alkaline. In the lower part of the Bt horizon there are common faint and few distinct 10YR 6/4/or 7.5YR 6/6 mottles. Also some pedons have a few secondary lime concretions.
The 2BCt horizon has dry color of 10YR 5/3,5/2,4/3,4/2; 2.5Y 6/2,5/4, 5/2, 4/2; N 6/0, 4/0; 5Y 6/3, 6/1, 5/l or 4/1 and moist color of 10YR 5/4,4/2, 3/2; 2.5 Y 4/2, 3/2; N 4/0; 5Y 4/3, 4/2, 4/1 or 3/2. Particle size is clay loam or clay and ranges from 27 to 45 percent clay and has 10 to 30 percent gravel. Reaction is neutral to moderately alkaline. Some pedons have a C horizon with similar colors and textures as the Bt horizon.
COMPETING SERIES: This is the Quiensabe (CA) series. Quiensabe soils are 20 to 40 inches deep to a lithic contact.
GEOGRAPHIC SETTING: The Yorkville soils are on hills and mountains. Slopes are 5 to 75 percent, are unstable, complex, and are characterized by slips, slides, hummocky relief, sag ponds seeps and springs. The soils formed in material weathered from chloritic schist intermixed with other sedimentary and metamorphic rocks. The underlying material is commonly altered from occurring in fault zones and is locally know as "gouge material". Elevations are from 50 to 4,000 feet. The climate is subhumid with hot dry summers and cool moist winters. Mean annual precipitation is 25 to 70 inches. Mean January temperature is about 44 degrees F; mean July temperature is about 72 degrees F; mean annual temperature is 53 degrees to 59 degrees F. Frost-free period is 125 to 270 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Etsel, Henneke, Hopland, Maymen, Montara, Squawrock and Yorktree soils. Etsel, Henneke, Maymen and Montara soils are less than 20 inches deep to fractured rock. Etsel, Hopland, Maymen and Squawrock soils have an ochric epipedon. Hopland soils have a fine-loamy particle-size control section and are 20 to 40 inches deep. Squawrock soils are 20 to 40 inches deep. Henneke and Squawrock soils have more than 35 percent rock fragments in the subsoil. Yorktree soils has a mean annual soil temperature of less than 59 degrees F and base saturation in the upper 75 cm of less than 75 percent.
DRAINAGE AND PERMEABILITY: Moderately well and well drained; medium to rapid runoff; slow and very slow permeability.
USE AND VEGETATION: Used for livestock grazing, watershed, and wildlife habitat. Vegetation is wild oats, soft chess, filaree, dogtail fescue, burclover, medusahead, wildrye, and tarweed.
DISTRIBUTION AND EXTENT: Northern California in the Coast Range. The soils are moderately extensive. MLRA 5,15.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Mendocino County, California, 1952.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - the surface layer from 0 to 15 inches (A1, A2 horizons)
Argillic horizon - the zone from 15 to 40 inches (Bt, 2Bt horizons)
ADDITIONAL DATA: NSSL Pedon S76CA-045-114.(type location) and ref. samples 760938 and numerous pedons from UC-Davis.