LOCATION JAFA CA

Established Series
DWS/TDC/ET
01/2023

JAFA SERIES

The Jafa series consists of very deep, well drained soils formed in alluvium from mixed rock sources. Jafa soils are on alluvial terraces and fans and have slopes of 2 to 30 percent. The mean annual precipitation is about 40 inches and the mean annual temperature is about 56 degrees F.

TAXONOMIC CLASS: Fine-loamy, mixed, active, mesic Ultic Palexeralfs

TYPICAL PEDON: Jafa loam--on a west facing convex slope of 6 percent under ponderosa pine, Douglas-fir, black oak, and manzanita at an elevation of 1,900 feet. (Colors are for dry soil unles otherwise stated. When described on June 16, 1981, the soil was dry to 25 inches and moist below).

O1 and O2--2 inches to 0; decomposed and partially decomposed conifer litter.

A1--0 to 6 inches; brown (7.5YR 5/4) loam, dark brown (10YR 3/3) moist; moderate fine and medium granular struture; soft, very friable, slightly sticky and nonplastic; many very fine and fine and common medium and coarse roots; many very fine and fine interstitial pores; 10 percent rounded pebbles 2 to 25 mm in diameter; moderately acid (pH 5.8); clear smooth boundary. (5 to 8 inches thick)

A2--6 to 13 inches; light brown (7.5YR 6/4) gravelly loam, brown (7.5YR 4/4) moist; moderate fine and medium granular structure; slightly hard, friable, slightly sticky and slightly plastic; many fine and medium and common very fine and coarse roots; many very fine and fine interstitial pores; 15 percent rounded pebbles 2 to 25 mm in diameter; moderately acid (pH 5.7); gradual wavy boundary. (5 to 8 inches thick)

BAt--13 to 25 inches; reddish yellow (7.5YR 6/6) gravelly heavy loam, strong brown (7.5YR 4/6) moist; moderate fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common fine, medium and coarse roots; many very fine and fine interstitial and common fine tubular pores; few moderately thick clay films on peds and in pores; 20 percent rounded pebbles 2 to 50 mm in diameter; moderately acid (pH 5.7); clear wavy boundary. (10 to 15 inches thick)

Bt1--25 to 40 inches; reddish yellow (5YR 6/6) gravelly clay loam, yellowish red (5YR 4/6) moist; moderate fine, medium and coarse subangular blocky structure; slightly hard, friable sticky and plastic; common fine, medium and coarse roots; many very fine and fine interstitial and common fine tubular pores; common moderately thick clay films on peds and in pores; 20 percent rounded pebbles 2 to 75 mm in diameter; strongly acid (pH 5.5); clear wavy boundary. (12 to 20 inches thick)

Bt2--40 to 63 inches; reddish yellow (5YR 6/6) gravelly clay loam, yellowish red (5YR 5/6) moist; moderate fine, medium and coarse subangular blocky structure; slightly hard, friable, sticky and plastic; few fine, medium and coarse roots; common very fine, fine and medium interstitial and tubular pores; many moderately thick clay films on peds and in pores; 25 percent rounded pebbles 2 to 75 mm in diameter and 2 percent rounded cobbles 75 to 150 mm in diameter; strongly acid (pH 5.3); gradual wavy boundary. (20 to 30 inches thick)

BCt--63 to 85 inches; reddish yellow (5YR 6/8) gravelly clay loam, yellowish red (5YR 5/6) moist; weak fine and medium subangular blocky structure parting to massive; slightly hard, friable, sticky and slightly plastic; few medium and coarse roots; common fine and medium interstitial pores; many moderately thick clay films on peds and in pores; 30 percent rounded pebbles 2 to 75 mm in diameter and 4 percent rounded cobbles 75 to 150 mm in diameter; strongly acid (pH 5.1). (20 to 30 inches thick)

TYPE LOCATION: Lake County, California; about 50 feet southwest of the intersection of forest roads 18N16 and 18N53, on the east side of the Lake Pillsbury, Mendocino National Forest; about 500 feet north and 2,450 feet east of the southwest corner of sec. 1, T. 18 N., R. 10 W.

RANGE IN CHARACTERISTICS: Thickness of the solum and depth to bedrock is greater than 60 inches. The mean annual soil temperature is 54 degrees to 59 degrees F. The soil temperature exceeds 47 degrees F from March 15 to November 30 and exceeds 41 degrees F from February 15 to December 30. The soil between the depths of 7 and 21 inches is dry in all parts from July 1 to October 15 and is moist in all parts from January 1 to April 30. The particle-size control section (25 to 45 inches) averages from 25 to 35 percent clay and from 5 to 35 percent total rock fragments.

The A horizon is 7.5YR 5/4, 5/6, 6/4; 10YR 4/3, 4/4, 5/3, 5/4 or 6/3. Moist color is 7.5YR 3/4, 4/4, 4/6; 10YR 3/3, 3/4 or 4/3. Only the upper 7 inches have moist chromas of 3 or less. It is loam, or gravelly loam with 18 to 25 percent clay. Rock fragment content ranges from 5 to 30 percent and consists of pebbles. It is neutral to strongly acid.

The Bt horizon is 5YR 5/6, 5/8, 6/4, 6/6, 7/6; 7.5YR 4/6, 5/6, 6/4 or 6/6. Moist color is 5YR 4/4, 4/6, 5/6, 5/8; 7.5YR 4/4, 4/6 or 5/6. Chroma is more than 4 in at least the lower part. It is heavy loam, clay loam, sandy clay loam or their gravelly equivalents. Clay content increases with depth or decreases only slightly from its maximum throughout the upper 60 inches of the profile. Rock fragment content ranges from 5 to 35 percent and consists of 5 to 30 percent pebbles and 0 to 10 percent cobbles. It is slightly acid to strongly acid. Base saturation (by sum of cations) ranges from 40 to 70 percent.

Some pedons have a B3t or C horizon below 60 inches. It is gravelly or very gravelly clay loam or sandy clay loam. Rock fragment content ranges from 25 to 50 percent and consists fo 20 to 35 percent pebbles and 4 to 15 percent cobbles.

COMPETING SERIES: These are the Manzanita and Redvine series in another family. Manzanita and Redvine soils are thermic in addition Redvine soils are fine.

GEOGRAPHIC SETTING: Jafa soils are on alluvial terraces and fans. Slopes are 2 to 30 percent. The soils formed in alluvium derived from mixed rock sources dominantly of sedimentary origin. Elevations are 800 to 3,000 feet. The climate is subhumid with warm, dry summers and cool, moist winters. The average annual precipitation is 30 to 55 inches. Light snowfall occurs in some but not all years. Mean January temperature is 41 degrees F; mean July temperature is 68 degrees F; mean annual temperature is 56 degrees F. Frost-free season is 90 to 200 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Sanhedrin and Speaker soils. Sanhedrin and Speaker soils have mean annual soil temperatures of 54 degrees F or less and are in upland positions.

DRAINAGE AND PERMEABILITY: Well drained; slow to rapid runoff; moderately slow permeability.

USE AND VEGETATION: This soil is used mainly for timber production, hay and pastsure, homesite development and wildlife habitat. Natural vegetation is ponderosa pine, Douglas-fir, California black oak, Pacific madrone, manzanita and California-Laurel.

DISTRIBUTION AND EXTENT: Interior part of the Coast Range of northern California. The series is not extensive.

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

SERIES ESTABLISHED: Lake County, California, 1983.

REMARKS: The activity class was added to the classification in February of 2003. Competing series were not checked at that time. - ET

National Cooperative Soil Survey
U.S.A.