LOCATION HOLOHAN CAEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic Ultic Haploxeralfs
TYPICAL PEDON: Holohan extremely gravelly sandy loam - on a northwest facing, convex slope of 22 percent under tanoak, madrone, Douglas-fir and evergreen huckleberry at 2,000 feet elevation. (Colors are for dry soil unless otherwise noted. When described (April 1, 1981) the soil was moist throughout).
Oi--4 inches to 0; partially decomposed and decomposed tanoak litter with 40 percent subangular pebbles (2-50 mm).
A--0 to 4 inches; light gray (10YR 7/2) extremely gravelly sandy loam, yellowish brown (10YR 5/4) moist; moderate fine and medium subangular blocky structure; slightly hard, friable, nonsticky and slightly plastic; many very fine and fine and common medium roots; many very fine, fine, medium and coarse interstitial and few very fine tubular pores; 65 percent hard angular and subrounded pebbles (2-75 mm); strongly acid (pH 5.5); clear smooth boundary. (2 to 8 inches thick)
Bt1--4 to 12 inches; very pale brown (10YR 7/3) very gravelly loam, brown (7.5YR 5/4) moist; moderate fine and medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; common very fine and fine, and few medium and coarse roots; many very fine tubular and interstitial and few medium and coarse interstitial pores; common thin clay films and silt coatings on faces of peds and lining pores; 45 percent hard angular and subrounded pebbles (2-75 mm); strongly acid (pH 5.5); clear wavy boundary. (6 to 10 inches thick)
Bt2--12 to 17 inches; very pale brown (10YR 7/3) extremely gravelly loam, yellowish brown (10YR 5/6) moist; weak fine subangular blocky and angular blocky structure; hard, very friable, slightly sticky and slightly plastic; many very fine and common fine roots; many very fine tubular and interstitial and few medium and coarse interstitial pores; common thin clay films and silt coatings on faces of peds and lining pores; 65 percent hard angular and subrounded pebbles (2 to 75 mm); strongly acid (pH 5.5); clear wavy boundary. (3 to 10 inches thick)
2Bt3--17 to 37 inches; very pale brown (10YR 7/3) extremely gravelly loamy sand, yellowish brown (10YR 5/6) moist; weak fine and medium granular structure; hard, very friable, nonsticky and nonplastic; many very fine, common fine and medium and few coarse roots; many very fine, fine, medium and coarse interstitial pores; many thin clay films and silt coatings on rock faces; 80 percent hard angular and subangular pebbles (2 to 75 mm); 50 percent of volume between pebbles is void space; moderately acid (pH 6.0); gradual wavy boundary. (0 to 30 inches thick)
2Bt4--37 to 74 inches; very pale brown (10YR 7/3) extremely gravelly loamy sand, brownish yellow (10YR 6/6) moist; weak fine granular and subangular blocky structure; hard, very friable, nonsticky and nonplastic; common very fine roots; many very fine, fine, medium and coarse interstitial pores; many thin clay films and silt coatings on rock faces; 80 percent hard angular pebbles (2 to 7 mm) 20 percent of volume between pebbles is void space; moderately acid (pH 6.0).
TYPE LOCATION: Mendocino County, California; on the northwest side of Oil Drum Rd., at a point 0.2 miles from its intersection with Red Mountain access road; about 2,000 feet north and 300 feet east of the SW corner of section 2, T.24 N., R.17 W., Noble Butte Quadrangle.
RANGE IN CHARACTERISTICS: Depth to a lithic contact is greater than 60 inches. The mean annual soil temperature ranges from 55 to 59 degrees F. The soil between depths of 16 inches and the lithic contact is moist in all parts from November 1 through June 1 and is dry in all parts from July 15 to October 1 in most years.
The A horizon is 10YR 5/2, 5/3, 6/2, 6/3, 6/4, 7/2, 7/3 or 7/4. Moist color is 10YR 2/2, 3/2, 3/3, 4/2, 4/3, 4/4, 5/3, 5/4, 5/6 or 7.5YR 3/4. It is very gravelly sandy loam or extremely gravelly sandy loam. Clay content ranges from 5 to 15 percent. Gravel content ranges from 25 to 70 percent. Cobble content ranges from 0-10 percent. Total coarse fragment content is 35 to 70 percent. Base saturation (sum) ranges from 35 to 75 percent. Reaction is slightly through strongly acid.
The upper Bt horizon is 10YR 5/3, 5/4, 6/2, 6/4, 7/2, 7/3, or 7/4. Moist color is 10YR 3/3, 3/4, 4/3, 4/4, 5/3, 5/4, 5/6; 7.5YR 4/4, 5/4, 5/6 or 5/8. It is very cobbly loam or very gravelly or extremely gravelly loam, sandy loam, sandy clay loam, or clay loam. Clay content ranges from 18 to 30 percent. Gravel content ranges from 35 to 70 percent. Cobble content generally ranges from 0 to 15 percent but may reach 40 percent. Base saturation (sum) ranges from 25 to 50 percent. Reaction is moderately through very strongly acid.
The lower Bt horizon is 10YR 6/3 or 7/3. Moist color is 10YR 5/4, 5/6, 6/6 or 7.5YR 4/6. It is very gravelly or extremely gravelly loamy sand, sandy loam, loam or sandy clay loam. Clay content ranges from 5 to 30 percent. Gravel content ranges from 45 to 80 percent. Cobble content ranges from 0 to 35 percent. Total coarse fragment content ranges from 45 to 90 percent. Base saturation (sum) ranges from 35 to 70 percent. Reaction is moderately through very strongly acid. Some profiles have a C horizon that is similar in color and texture to the lower Bt horizon.
COMPETING SERIES: These are the Abegg (OR), Asabean (T CA), Behemotosh (T CA), Collayomi (CA), Hambone (T CA), Hollowtree (CA), Hoosimbim (CA), Marpa (CA), Pendola (CA), Skalan (ID) and Whispering (CA) series. Abegg soils do not have hues of 10YR or 7.5YR. Asabean soils have moisture control sections that are moist throughout for less than 180 days. Behemotosh, Hollowtree, Marpa, Skalan and Whispering soils are 20 to 40 inches deep. Collayomi soils have mean annual soil temperatures of 51 to 56 degrees F, and Pendola of 50 to 54 degrees F. Hambone and Hoosimbim soils are 40 to 60 inches to bedrock.
GEOGRAPHIC SETTING: The Holohan soils are on mountains. Slopes are 9 to 75 percent. Elevations are 500 to 4,000 feet. The soils formed in material weathered from sandstone. The climate is subhumid with warm dry summers and cool moist winters. Mean annual precipitation is 45 to 130 inches with occasional snowfall above 2,500 feet. Mean January temperature is about 43 degrees F and mean July temperature is about 70 degrees F. The mean annual temperature is about 55 degrees F. The frost-free period is about 150 to 290 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Hollowtree soils and the Casabonne, Dann, Witherell, Wohly, Woodin and Yorkville soils. Casabonne and Wohly soils are non-skeletal. Dann, Witherell, Wohly and Woodin soils are less than 40 inches deep to a lithic or paralithic contact. Yorkville soils have a mollic epipedon.
DRAINAGE AND PERMEABILITY: Well drained; surface runoff under bare soil conditions is medium to very rapid; moderate permeability.
USE AND VEGETATION: This soil is used for timber and firewood production, wildlife habitat and watershed. Vegetation consists of tanoak, madrone, black oak, Douglas-fir, California huckleberry and interior live oak.
DISTRIBUTION AND EXTENT: Northern coastal California. The series is moderately extensive. MLRA 5.
MLRA OFFICE 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
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - surface layer from 0 to 4 inches.
Argillic horizon - the zone from 4 to 74 inches (Bt1, Bt2, 2Bt3, 2Bt4 horizons)
These soils are subject to creep because of hard, highly fractured parent material and their landscape position.