LOCATION PORTOLA CA

Established Series
Rev. JHR/GE/DJE/TDC
12/2022

PORTOLA SERIES

The Portola series consists of moderately deep, well drained soils formed in material weathered from volcanic tuff. They area on convex side slopes of mountains and have slopes of 2 to 75 percent. Mean annual precipitation is 22 inches and mean annual temperature is 45 degrees.

TAXONOMIC CLASS: Medial, mixed, frigid Andic Haploxerepts

TYPICAL PEDON: Portola gravelly fine sandy loam on a NE facing slope of 40 percent at an elevation of 6600 feet. Vegetation is mixed conifers of white fir and Jeffrey pine. (Colors are for dry soils unless otherwise noted.)

01--2 inches to 0; decomposed and partially decomposed fir and pine needles.

A1--0 to 3 inches; brown (10YR 5/3) gravelly loam, very dark grayish brown (10YR 3/2) moist; weak very fine and fine granular structure; soft, very friable, nonsticky and slightly plastic, common very fine, fine and medium roots; many very fine interstitial pores; 30 percent pebbles; strongly acid (pH 5.5); abrupt smooth boundary (3 to 9 inches thick).

B1--3 to 10 inches; light yellowish brown (10YR 6/4) gravelly sandy loam, brown (10YR 4/3) moist; weak very fine and fine granular structure; soft, friable, nonsticky and slightly plastic; many very fine, common medium and coarse roots; many very fine; common fine and few medium interstitial pores; 30 percent pebbles; slightly acid (pH 6.3); clear wavy boundary (5 to 9 inches thick).

B21--10 to 21 inches; pale brown (10YR 6/3) gravelly sandy loam, brown (10YR 5/3) moist; weak fine subangular blocky structure; soft, friable, nonsticky and nonplastic; many fine, common medium, few coarse roots; many very fine interstitial pores; 25 percent pebbles, 3 percent cobbles; moderately acid (pH 6.0); clear wavy boundary (10 to 30 inches thick).

B22--21 to 31 inches; pale brown (10YR 6/3) cobbly sandy loam, brown (10YR 5/3) moist; weak fine subangular blocky structure; soft, non very fine and medium roots; friable, nonsticky and nonplastic; many very fine interstitial pores; 15 percent pebbles, 10 percent cobbles, 5 percent stones; moderately acid (pH 6.0); clear wavy boundary. (0 to 10 inches thick).

B3--31 to 39 inches; pale brown (10YR 6/3) very cobbly sandy loam, brown (10YR 5/3) moist; massive; soft, friable, nonsticky and nonplastic; common very fine and fine, few medium and coarse roots; 20 percent pebbles, 10 percent cobbles, 5 percent stones; moderately acid (pH 6.0); clear irregular boundary. (6 to 16 inches thick).

Cr--39 inches; weathered rhyolite with fractures greater than 5 inches apart, few roots in fractures.

TYPE LOCATION: Sierra county, California; approximately 7 miles south-west of Loyalton, 3 miles south on Alder Creek Road off of Smithneck Road, 100 feet south of road in cutbank on landing site in the NW1/4 of the NW1/4 of Sec. 23, T.23N., R.16E.

RANGE IN CHARACTERISTICS: Depth to a paralithic contact ranges from 20 to 40 inches. The mean annual soil temperature at a depth of 20 inches varies from 42 to 47 degrees. The mean summer soil temperature is 60 to 63 degrees. The soil moisture control section is usually moist in some or all parts from late October to mid July and is dry in all parts the rest of the year. Rock fragments of gravel and cobbles range from 5 to 35 percent throughout the profile. The soil is slightly to medium acid. The soil from a depth of about 10 inches to a paralithic contact is assumed to be dominated by amorphous material based on lab data from similar surrounding soils.

The A horizon has dry colors of N6/; N7/; 10YR 5/2, 6/1, 6/2, 6/3, 7/1 or 7/2. Moist colors are 10YR 3/3, 3/2; 7.5YR 4/2 or 4/3. Where Mollic colors exist the horizon is less than 10 inches thick. It is sandy loam, coarse sandy loam, fine sandy loam or loamy sand and may be gravelly. Bulk density averages about 0.85 to 1.0 g/cc.

The B horizon has dry colors of 7.5YR 6/4; 10YR 6/3, 6/4, 7/3, 7/4, 8/3 or 8/4. Moist colors are 7.5YR 4/2, 4/4, 10YR 4/2, 4/3, or 5/3. It is coarse sandy loam, sandy loam, or fine sandy loam and may be gravelly or cobbly. Bulk density averages from about 0.9 to 1.0. The 15 bar water to clay ratio is about 1 to 1.5.

COMPETING SERIES: These are the Ahart and the Cathcart, Cathlamet, Chelan, Nevat, Ponto, and Sadie soils in other families. Ahart soils have umbric epipedons. The Cathcart, Cathlamet, Chelan, Nevat, Ponto and Sadie soils are all mesic.

GEOGRAPHIC SETTING: The Portola soils are on convex slopes of 2 to 75 percent at elevations of 4,800 to 6,000 feet. They formed in partially consolidated volcanic tuff. The climate is su[humic with warm dry summers and cold moist winters. Mean annual precipitation is 14 to 30 inches. Snowfall averages 24 to 36 inches. Average January temperature is 28 degrees. and average July temperature is 64oF. Mean annual temperature is 44 degrees to 46 degrees. The freeze-free season is 50 to 60 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Delleker, Sierraville and Trojan soils. All three soils have argillic horizons. Delleker soils are in lacustrine modified alluvium.

DRAINAGE AND PERMEABILITY: Well-drained; medium to rapid runoff, rapid permeability.

USE AND VEGETATION: Use for timber production. The vegetation is mainly open stands of ponderosa pine, and jeffrey pine, incense cedar, and white fir with an understory of manzanita, big sagebrush, and prostrate ceanothus.

DISTRIBUTION AND EXTENT: Northeastern California. The soils are extensive.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California

SERIES ESTABLISHED: Plumas County, California, 1973.

REMARKS: The Portola soils were formerly classified as Medial, frigid Typic Vitrandepts.

National Cooperative Soil Survey
U.S.A.