LOCATION HELLMAN CAEstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, thermic Mollic Palexeralfs
TYPICAL PEDON: Hellman loam - on a northwest-facing concave slope of 41 percent under wild oats, medusahead and soft chess at 720 feet elevation. (Colors are for dry soil unless otherwise stated. When described June 3, 1977, the soil was dry throughout.)
A--0 to 7 inches; brown (7.5YR 4/4) loam, dark yellowish brown (10YR 3/4) moist; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine and fine roots; common very fine and fine tubular pores; 10 percent 2 to 15 mm pebbles; slightly acid (pH 6.1); clear wavy boundary. (4 to 10 inches thick)
AB--7 to 14 inches; strong brown (7.5YR 5/6) loam, brown (7.5YR 4/4) moist; moderate medium through very coarse subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; few very fine roots; many very fine and common fine and medium tubular pores; 10 percent 2 to 25 mm pebbles; slightly acid (pH 6.3); clear wavy boundary. (5 to 10 inches thick)
Bt1--14 to 26 inches; brown (7.5YR 5/4) gravelly clay loam, yellowish red (5YR 4/6) moist; weak very coarse prismatic structure parting to moderate coarse subangular blocky; hard, friable, sticky and plastic; few very fine roots; many very fine and common fine and medium tubular pores; few thin clay films on peds and in pores; 15 percent 2 to 20 mm pebbles; slightly acid (pH 6.5); gradual wavy boundary. (10 to 14 inches thick)
Bt2--26 to 40 inches; variegated reddish yellow and yellowish red (5YR 6/6, 5/8) gravelly clay loam, yellowish red (5YR 4/6) moist; weak medium subangular blocky structure; hard, friable, sticky and plastic; few very fine and fine roots; many very fine and fine tubular pores; common moderately thick clay films on peds and in pores; 15 percent 2 to 75 mm pebbles; slightly acid (pH 6.5); clear wavy boundary. (12 to 16 inches thick)
Bt3--40 to 51 inches; strong brown (7.5YR 5/6) gravelly clay loam; variegated yellowish red and brown (5YR 5/6, 7.5YR 5/4) moist; massive; hard, friable, sticky and plastic; few very fine roots; few very fine and fine tubular pores; many moderately thick clay films in pores; 15 percent 2 to 75 mm pebbles; slightly acid (pH 6.3); gradual wavy boundary. (9 to 13 inches thick)
Bt4--51 to 72 inches; variegated reddish yellow and strong brown (7.5YR 6/8, 5/8) clay, strong brown (7.5YR 5/8) moist; massive; extremely hard, firm, sticky and plastic; few very fine and fine tubular pores; continuous thick clay films in pores; slickensides present; extremely acid (pH 4.3). (20 to 23 inches thick)
Cr---72 inches; soft weathered sandstone and fractures about 6 inches apart.
TYPE LOCATION: Near Hopland, Mendocino County, California; one mile south on old Yorkville-Hopland Road from intersection of Hellman Ranch road, 1,500 feet west on farm road to a north-facing roadcut about 300 feet southwest of barn, about 1,770 feet east and 1,560 feet south of the northwest corner of sec. 26, T. 13 N., R. 12 W., MDBM, Hopland NW Quadrangle.
RANGE IN CHARACTERISTICS: Thickness of the solum is 40 inches or more. The soil is more than 60 inches deep to a paralithic cntact. The soil is dry throughout between a depth of 7 to 21 inches from June to October in most years, and is moist throughout from December to May. The mean annual soil temperature is 59 to 62 degrees F. Clay content of the argillic horizon increases with depth an is greater than 35 percent throughout. The soil has 0 to 20 percent gravel throughout. Base saturation is more than 75 percent (sum) in some part of the argillic horizon.
The A horizon is 10YR 6/3; 7.5YR 4/4, 5/4, 5/6, 6/4; 5YR 5/4, or 6/4. Moist colors are 10YR 3/3, 3/4; 7.5YR 3/4, 4/4; 5YR 3/3, or 3/4. The upper part has moist value of 3. It has 20 to 25 percent clay content. It is slightly or moderately acid. Organic matter content is 1 to 3 percent.
The Bt horizon is 7.5YR 4/4, 5/4, 5/6, 5/8, 6/8; 5YR 5/8, or 6/6. Moist colors are 10YR 4/3, 4/4, 4/6, 5/4, 5/6; 7.5YR 3/4, 4/4, 4/6, 5/4, 5/6, 5/8; 5YR 3/4, 4/4, 4/6, or 5/6. It is clay loam or clay or their gravelly equivalents with 35 to 55 percent clay content. It is slightly acid to extremely acid, becoming more acid with depth.
Some pedons have a C horizon. It has dry colors 7.5YR 4/4, 5/4, 5/6, or 6/4. It has moist colors 10YR 4/4, 4/6, 5/4, 5/6, 6/4; 7.5YR 4/4, 4/6, 5/4, or 5/6. It is clay or gravelly clay with 40 to 55 percent clay and 10 to 20 percent gravel. Reaction is strongly acid to extremely acid.
COMPETING SERIES: These are the Bapos (T), Benridge and Honker series. Bapos soils have slightly to strongly alkaline Bt horizons with 5 to 10 percent calcium carbonate. Benridge soils are influenced by amorphous material and are weakly or moderately smeary in the Bt horizon. Honker soils are 20 to 40 inches deep to a lithic contact and have an abrupt A/Bt boundary.
GEOGRAPHIC SETTING: Hellman soils are on sideslopes and concave areas on hills and mountains and have slopes of 9 to 50 percent. They formed in material weathered from sandstone or shale at elevations of 500 to 3,000 feet. The climate is subhumid with hot dry summers and cool moist winters. Mean annual precipitation is 35 to 60 inches. Mean January temperature is about 44 degrees F; mean July temperature is 72 degrees F; man annual temperature is 53 tp 59 degrees F. Frost-free season ranges from 150 to 250 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bearwallow and Witherell soils. Bearwallow soils have fine-loamy control sections. Witherell soils are less than 20 inches deep. Bearwallow and Witherell soils are on ridge tops, shoulders, and convex sideslopes.
DRAINAGE AND PERMEABILITY: Well drained; medium to rapid runoff; slow permeability.
USE AND VEGETATION: Used as rangeland for grazing sheep and cattle, and for wildlife habitat, recreation and watershed. Vegetation is wild oats, soft chess, ripgut brome, foxtail fescue, filaree and other annual grasses and forbs with scattered oaks.
DISTRIBUTION AND EXTENT: Coastal Mountains of Northern California. The soils are moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Mendocino County, Eastern Part, California 1985.
REMARKS: The activity class was added to the classification in February of 2003. Competing series were not checked at that time. - ET
ADDITIONAL DATA: Grab samples (A, AB, Bt2) sent to NSSL for organic carbon and base saturation. Pedon number is S77CA-145-16. Sample numbers are 837003, 837013, 837014. Unpublished.