LOCATION MOJO CAEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, frigid Ultic Argixerolls
TYPICAL PEDON: Mojo stony loam - on a 10 percent southwest facing slope under ponderosa pine, Douglas-fir, snowberry and squawcarpet at 5,300 feet elevation. (When described on September 30, 1982, the soil was dry throughout. Colors are for dry soil unless otherwise stated.)
0--2 to 0 inches; new and partially decomposed needles, bark, grass blades, and other organic debris.
A1--0 to 3 inches; brown (10YR 4/3) stony loam, very dark brown (10YR 2/2) moist; weak fine subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; common very fine roots; common very fine interstitial pores; 6 percent stones, 2 percent cobbles and 7 percent pebbles; slightly acid (pH 6.5); clear smooth boundary.
A2--3 to 9 inches; brown (7.5YR 5/4) stony loam, dark brown (7.5YR 3/2) moist; weak medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and fine, few medium and coarse roots; common very fine interstitial and tubular pores; 4 percent stones, 5 percent cobbles and 7 percent pebbles; slightly acid (pH 6.5); gradual wavy boundary. (The combined thickness of the Al and A2 is 9 to 10 inches thick)
Bt1--9 to 17 inches; brown (7.5YR 5/4) clay loam, dark reddish brown (5YR 3/3) moist; moderate medium subangular blocky structure; slightly hard, friable, sticky and plastic; few very fine, fine, medium and coarse roots; few very fine interstitial pores; few thin clay films on ped faces; 2 percent stones, 5 percent cobbles and 7 percent pebbles; slightly acid (pH 6.5); gradual wavy boundary. (7 to 9 inches thick)
Bt2--17 to 27 inches; light brown (7.5YR 6/4) clay loam, dark brown (7.5YR 3/4) moist; strong medium subangular blocky structure; hard, firm, sticky and plastic; few very fine, fine medium and coarse roots; few very fine and fine tubular pores; common thin clay films on ped faces and lining pores; 2 percent stones, 5 percent cobbles and 7 percent pebbles; slightly acid (pH 6.5); gradual wavy boundary. (6 to 11 inches thick)
Bt3--27 to 36 inches; reddish yellow (7.5YR 6/6), very gravelly clay loam, brown (7.5YR 4/4) moist; moderate medium subangular blocky structure; hard, firm, sticky and plastic; few very fine, fine, medium and coarse roots; few very fine and fine tubular pores; common thin clay films on ped faces and lining tubular pores; 10 percent cobbles, 35 percent pebbles; slightly acid (pH 6.5); arupt wavy boundary. (8 to 10 inches thick)
R--36 inches; hard extrusive igneous rock.
TYPE LOCATION: Siskiyou County, California; about 8 miles south of Macdoel, 50 feet east of dirt road; about 750 feet south and 375 feet east of the northwest corner of section 19, T. 45 N., R. 2 W.
RANGE IN CHARACTERISTICS: Depth to hard extrusive igneous rock ranges from 30 to 40 inches. Reaction of the solum is medium acid or slightly acid. The mean annual soil temperature ranges from 44 degrees to 47 degrees F. The soil temperature at a depth of 20 inches is above 41 degrees F from about April 15 to November 10 (205 days) and is above 47 degrees F from about May 15 to October 20 (155 days). The soil between depths of 8 to 20 inches is dry from about July 15 to October 15 (90 days). The mollic epipedon is 16 to 19 inches thick. The base saturation (by sum of cations) ranges from 60 to 75 percent.
The A horizon has dry color of 10YR 5/3, 4/3; 7.5YR 5/4, 5/2, 4/4 or 4/2 and moist color of 10YR 2/2, 3/3; 7.5YR 3/3, 3/2 or 5YR 3/3. It has 20 to 25 percent clay and 10 to 22 percent rock fragments. Stones range from 3 to 7 percent. Cobbles range from 2 to 5 percent. Pebbles range from 5 to 10 percent. Thickness ranges from 9 to 10 inches.
The Bt1 has dry color of 7.5YR 5/2 or 5/4 and moist color of 7.5YR 3/2 or 5YR 3/3. It averages 27 to 35 percent clay with 5 to 15 percent more clay content than the A horizon. The rock fragments range from 7 to 15 percent. Cobbles range from 2 to 5 percent. Stones range from 2 to 5 percent. Pebbles range from 3 to 5 percent.
The Bt2 has dry color of 7.5YR 6/6, 6/4 or 6/2 and moist color of 7.5YR 4/4, 3/4 or 5YR 3/4. The rock fragments range from 7 to 15 percent. Stones range from 2 to 5 percent. Cobbles range from 2 to 5 percent. Pebbles range from 3 to 7 percent.
The Bt3 has rock fragments that range from 35 to 50 percent. Cobbles range from 10 to 15 percent. pebbles range from 25 to 35 percent.
COMPETING SERIES: These are the Carmack, Elkcreek, Johnson, Molyneux (T), Simonton, Suloaf and Trojan series. The Carmack, Johnson, Molyneux, Simonton, Suloaf and Trojan soils are greater than 40 inches to bedrock. The Elkcreek soils lack very gravelly textures in the lower part of B horizon, the mollic epipedon is 16 inches or less thick and lack 0 horizons.
GEOGRAPHIC SETTING: Mojo soils are on mountains. Slopes are 5 to 30 percent. The soils formed in material weathered from extrusive igneous rock. Elevation is 4,400 to 6,500 feet. The climate is continental with warm dry summers and cold moist winters. The mean annual precipitation is 16 to 30 inches. Snowfall is 20 to 40 inches. The mean January temperature is about 25 degrees F; mean July temperature is about 61 degrees F; and mean annual temperature is about 44 degrees F. Frost-free season is about 50 to 80 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Esro, Kalo (T), Orset, Pinehurst and Snell soils. Esro, Orset and Pinehurst soils are deeper than 40 inches. Kalo soils are skeletal. Snell soils have clayey-skeletal particle-size control sections.
DRAINAGE AND PERMEABILITY: Well drained; medium or rapid runoff; moderately slow permeability.
USE AND VEGETATION: Mojo soils are used for woodland and limited livestock grazing. Vegetation is ponderosa pine, Douglas-fir, incense-cedar, antelope bitterbrush,Idaho fescue and squawcarpet.
DISTRIBUTION AND EXTENT: North-central California. These soils are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES PROPOSED: Siskiyou County, California; Butte Valley-Tule Lake Soil Survey 1984. The name is coined.
REMARKS: Diagnostic horizons and features recognized in the pedon are:
Mollic epipedon - The zone from the surface of the soil to a depth of 17 inches (A1, A2, Bt1 horizons).
Argillic horizon - The zone from about 9 to 36 inches (Bt1, Bt2, Bt3 horizons).
Fine-loamy family - The particle-size control section (9 to 29 inches) weighted average clay content is 31 percent.