LOCATION STORNETTA CAEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, nonacid, isomesic Aquic Ustifluvents
TYPICAL PEDON: Stornetta fine sandy loam on a nearly level slope of 1 percent under pasture at 15 feet elevation. (Colors are for dry soil unless otherwise stated. When described October 16, 1986, the soil was moist throughout).
Ap1--0 to 2 inches; light yellowish brown (2.5Y 6/4) fine sandy loam, brown (10YR 4/3) moist; massive; soft, very friable, slightly sticky and nonplastic; many very fine roots; many very fine interstitial and common very fine tubular pores; slightly alkaline (pH 7.8); abrupt smooth boundary. (1 to 6 inches thick)
Ap2--2 to 5 inches; light yellowish brown (2.5Y 6/4) loam, brown (10YR 4/3) moist; common fine distinct light brownish gray (2.5Y 6/2) mottles, grayish brown (2.5Y 5/2) moist, and common fine distinct yellowish brown (10YR 5/6) mottles, yellowish brown (10YR 5/6) moist; massive; hard, friable, slightly sticky and plastic; many very fine roots; common very fine tubular and interstitial pores; slightly acid (pH 6.2); abrupt smooth boundary. (0 to 5 inches thick)
C1--5 to 22 inches; light yellowish brown (2.5Y 6/4) loam, dark brown (10YR 3/3) moist; moderate, fine and medium subangular blocky structure; soft, friable, sticky and plastic; common very fine roots; common very fine tubular and interstitial pores; neutral (pH 6.8); gradual smooth boundary. (10 to 25 inches thick)
C2--22 to 37 inches; brown (10YR 5/3) loam, very dark brown (10YR 2/2) moist; weak fine, medium and coarse subangular blocky structure; slightly hard, friable, slightly sticky and plastic; common very fine roots; common very fine tubular and interstitial pores; slightly acid (pH 6.4); gradual smooth boundary. (10 to 25 inches thick)
C3--37 to 62 inches; brown (10YR 5/3) silt loam, dark brown (10YR 3/3) moist; massive; slightly hard, friable, sticky and slightly plastic; few very fine roots; common very fine tubular and interstitial pores; neutral (pH 6.8).
TYPE LOCATION: Mendocino County, California; about 600 feet north and 300 feet east of the southwest corner section 36, T.13 N., R.17 W., MDBM, Point Arena quadrangle.
RANGE IN CHARACTERISTICS: Soil depth is greater than 60 inches. The mean annual soil temperature ranges from 50 to 56 degrees F. The difference between mean summer and mean winter soil temperature ranges from 6 to 9 degrees F. The soil between the depths of 6 and 18 inches is moist in all parts from November 1 to June 1. It is dry in some or all parts from July 1 to October 1 in most years. The particle-size control section averages 18 to 25 percent clay. Organic carbon decreases irregularly with increasing depth. Reaction is slightly alkaline through slightly acid.
The Ap horizon is 2.5Y 6/4; 10YR 5/3 or 6/4. Moist color is 10YR 3/3 or 4/3. Redox depletions are 2.5Y 6/2, or 2.5Y 5/2 moist; redox concentrations are 10YR 5/6 or 5/8, or 10YR 5/6 moist. Redox features occur between the depths of 2 and 10 inches. It is loam or fine sandy loam.
The C horizon is 2.5Y 6/4 or 10YR 5/3. Moist color is 10YR 2/2 or 3/3. It is stratified fine sandy loam, silt loam and loam. Clay content ranges from 10 to 27 percent.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: The Stornetta soils occur on floodplains. Slopes are 0 to 2 percent. Elevations are 10 to 100 feet. They formed in alluvium derived from mixed rock sources. The climate is humid with cool foggy summers and cool moist winters. A strong marine influence limits the diurnal and annual range of temperature. Mean annual precipitation ranges from 35 to 45 inches. Mean January temperature is 48 degrees F., mean July temperature is 57 degrees F., and the mean annual temperature is 53 degrees F. The frost-free period is 250 to 330 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cabrillo, Crispin, Flumeville, Mallopass, and Windyhollow soils, all of which are on higher landscape positions. Cabrillo soils have mottles between 30 and 50 inches, and have thick umbric epipedons. Crispin soils lack mottling, and are moderately deep to a cemented pan. Flumeville soils have mottles between 10 and 30 inches, have a clayey particle-size class, an argillic horizon and a mollic epipedon. Mallopass soils have mottles between 50 and 70 inches, and have thick mollic epipedons. Windyhollow soils have mottles between 30 and 50 inches, and have mollic epipedons.
DRAINAGE AND PERMEABILITY: Moderately well drained; the soil is saturated with water in the upper 6 inches for extended periods following episodes of heavy rain from December through April. The saturated zone exists above a dense layer caused by grazing. The soils are frequently flooded for brief periods from December through April. Surface runoff under bare soil conditions is ponded through slow; permeability is moderate.
USE AND VEGETATION: This soil is used as pasture. A few areas are used for crop production. Vegetation consists of perennial and annual grasses and forbs.
DISTRIBUTION AND EXTENT: Northern coastal California. The series is not extensive. MLRA 4.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Mendocino County, California, Western Part, 1993.
REMARKS: The activity class was added to the classification in February of 2003. Competing series were not checked at that time. - ET
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from 0 to 5 inches (Ap2, Ap2)
Redox depletions in the upper 6 inches of the soil are a result of a perched water table as a result of compaction by grazing.
Areas mapped as the Stornetta series were mapped as the Loleta series in the Soil Survey of the Mendocino County Bottomlands, 1973.