LOCATION YOLLABOLLY CAEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, active, acid, frigid Lithic Xerorthents
TYPICAL PEDON: Yollabolly gravelly loam--very open stand of pine trees and shrubs. (Colors are for dry soil unless otherwise noted.)
0--1/2 to 0 inch; loose litter of pine needles and twigs. (1/2 to 3 inches thick)
A--0 to 4 inches; light brownish gray (10YR 6/2) gravelly loam, dark grayish brown (10YR 4/2) moist; weak thin platy structure that parts to fine granular structure; slightly hard, friable; common very fine roots and pores; surface half inch is covered with a continuous pavement of gravel; about 30 percent of horizon is gravel; strongly acid; gradual irregular boundary. (1 to 5 inches thick)
C--4 to 10 inches; light brownish gray (10YR 6/2) very gravelly loam, dark grayish brown (10YR 4/2) moist; massive; slightly hard, friable; few very fine roots; very porous; mica lines pores and coats some pebbles; about 45 percent gravel; strongly acid; abrupt irregular boundary. (5 to 15 inches thick)
R--10 to 14 inches; fractured schist.
TYPE LOCATION: Tehama County, California; 1 mile east of south Yollabolly Mountain in the SE portion of the NE 1/4 of section 11, T.25 N., R.9 W.
RANGE IN CHARACTERISTICS: Depth to a lithic contact is 10 to 20 inches. Changes in depth occur erratically over a span of less than 2 feet. The mean annual soil temperature is about 44 degrees to 47 degrees F. Soil just above the bedrock is usually moist all the time from October until June or mid-July and is usually dry all the rest of the year. Angular and subangular rock fragments of various sizes and amounts form a surface layer. On the average, rock fragments make up 35 to 75 percent of the soil profile. The soils are sandy loam or loam throughout.
The A horizon is 10YR or 2.5 4/2, 4/3, 5/2, 5/3, 5/4, 6/2, 6/4, 7/4, or 7/2 or 7.5YR 6/4.. Reaction is moderately to very strongly acid.
The C horizon is similar to the A horizon and differs mostly by being lighter color in all pedons. It is 10YR or 2.5Y 5/6, 6/2, 6/3, 6/4, 6/6, 7/3, 7/4. Moist colors in the A horizon and C horizon are 1 or 2 units darker. Except for mica or silt coats, horizon features such as clay films are lacking. Soil structure is lacking in most pedons or is weak where present. The C horizon is strongly or very strongly acid. No pedons are very strongly acid throughout.
COMPETING SERIES: There are no competing series in the same family. Similar series are the Goulding, Maymen, Sheetiron, Waca, and Weitchpec in other families. Goulding and Maymen soils have a mean annual soil temperature above 47 degrees F. Sheetiron and Waca soils have a lithic contact at depths of 20 to 40 inches. Waca soils also have umbric epipedons. Weitchpec soils have magnesic mineralogy.
GEOGRAPHIC SETTING: Yollabolly soils are near mountain crests at elevations of 6,000 to 8,000 and down to 5,000 feet on north slopes in Lake and Colusa County. They formed in material weathered from sedimentary and metasedimentary rocks. The climate is subhumid with cold wet winters and cool dry summers. Mean annual precipitation is 40 to 70 inches, with a cover of snow from about November to March. The average annual temperature is about 43 to 48 degrees F, the average July temperature is about 62 degrees F, the average January temperature is about 30 degrees F. The frost-free season is about 80 to 130 days.
GEOGRAPHICALLY ASSOCIATED SOILS: Sheetiron, Masterson and Snag soils that have umbric and mollic epipedons.
DRAINAGE AND PERMEABILITY: Excessively drained; rapid and very rapid runoff; moderate permeability.
USE AND VEGETATION: Used mainly for watershed and a small amount of incidental timber production. Vegetation is a sparse stand of Jeffrey and ponderosa pine, red fir, white fir and shrubs.
DISTRIBUTION AND EXTENT: Higher elevations in the north part of the Coast Range Mountains in California and possibly Oregon. The soils are moderately extensive. MLRA 5 and 15.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Tehama County, California, 1961.
REMARKS: As formerly mapped the series contained pedons thought to have cambic horizons. The horizon was usually absent and recognition questionable. As now defined, the series excludes soils with cambic horizons. Tyson series in the Mendocino National Forest Interim Report is a taxadjunct.
Diagnostic horizons and features recognized in this pedon are: Ochric epipedon - 0 to 4 inches.
Lithic contact - 0 to 10 inches.
Particle-size control section - the entire soil.
Acid class: pH(1:1 water) is 5.5 or less.