LOCATION LOTAWACA CAEstablished Series
TAXONOMIC CLASS: Ashy-skeletal, glassy Humic Xeric Vitricryands
TYPICAL PEDON: Lotawaca very gravelly ashy sandy loam--forestland. (Colors are for dry soil unless otherwise noted).
Oe--0 to 1 inch; dark grayish brown (10YR 4/2), gravelly moderately decomposed organic matter, very dark brown (10YR 2/2), moist; weak fine granular structure; soft, very friable, nonsticky, nonplastic; common very fine roots; many very fine interstitial pores; 25 percent pebbles; slightly acid (pH 6.2); clear smooth boundary. (1 to 4 inches thick)
A--1 to 7 inches; brown (10YR 5/3), very gravelly ashy sandy loam, dark brown (10YR 3/3), moist; weak fine and medium subangular blocky structure; soft, very friable, nonsticky, nonplastic; many very fine to very coarse roots; many very fine interstitial and common very fine tubular pores; 40 percent pebbles, 5 percent cobbles; slightly acid (pH 6.1); clear wavy boundary. (4 to 10 inches thick)
Bt1--7 to 20 inches; brown (10YR 5/3), very gravelly ashy loam, dark brown (10YR 3/3), moist; moderate fine and medium subangular blocky structure; slightly hard, very friable, slightly sticky, slightly plastic; many fine to very coarse roots and common very fine roots; common very fine interstitial and tubular pores; 15 percent faint clay bridges between sand grains; 45 percent pebbles, 10 percent cobbles; moderately acid (pH 5.8); clear wavy boundary. (10 to 18 inches thick)
Bt2--20 to 40 inches; light yellowish brown (10YR 6/4), extremely cobbly ashy loam, dark yellowish brown (10YR 4/4), moist; moderate fine and medium subangular blocky structure; slightly hard, very friable, moderately sticky, slightly plastic; many fine to very coarse roots and common very fine roots; common very fine interstitial and tubular pores; 15 percent faint clay films on all faces of peds and 15 percent faint clay films on surfaces along pores; 40 percent pebbles, 30 percent cobbles; moderately acid (pH 5.8); clear irregular boundary. (10 to 30 inches thick)
Cr--40 inches; weathered and highly fractured andesitic tuff.
TYPE LOCATION: Modoc County, California; on the Modoc National Forest in the Warner Mountains; 2,600 feet north and 800 feet east of the southwest corner of section 3, T 44N, R 15E; Payne Peak USGS 7.5 minute topographic quadrangle; 41 degrees 37 minutes 26.6 seconds north latitude and 120 degrees 15 minutes 20.9 seconds west longitude, NAD27.
RANGE IN CHARACTERISTICS:
Soil moisture - These soils are usually moist in winter, spring, and early summer, dry later in summer and fall; xeric soil moisture regime.
Mean annual soil temperature - 41 to 45 degrees F.
Mean summer soil temperature - 44 to 47 degrees F.
Oxalate extractable Al + 1/2 Fe: 0.4 to 1 percent.
Volcanic glass content - 50 to 80 percent in the coarse silt through fine sand fractions.
Umbric epipedon thickness - 14 to 20 inches.
Depth to bedrock - 40 to 60 inches to a paralithic contact. The paralithic materials below the contact are weathered andesite or tuff.
Profile reaction - Moderately acid or slightly acid.
Particle-size control section - Clay content: Averages 18 to 25 percent, (field estimates).
Rock fragments: Average 60 to 80 percent, mainly gravel or cobbles.
A horizons - Hue: 10YR or 7.5YR.
Value: 4 or 5 dry, 2 or 3 moist.
Chroma: 2 or 3, dry or moist.
Rock fragments: Averages 35 to 70 percent, mainly gravel or cobbles.
Organic matter content: 1 to 4 percent.
Bt1 horizon - Hue: 10YR or 7.5YR.
Value: 4 or 5 dry, 2 or 3 moist.
Chroma: 2 or 3, dry or moist.
Clay content: 18 to 25 percent.
Rock fragments: Averages 35 to 70 percent, mainly gravel or cobbles.
Organic matter content: 1 to 2 percent.
Bt2 horizon - Hue: 10YR or 7.5YR.
Texture: Ashy loam or ashy sandy clay loam.
Clay content: 18 to 25 percent.
Rock fragments: 60 to 80 percent.
Structure: Moderate or strong, fine to coarse subangular blocky.
COMPETING SERIES: These are the Bagmont and Longval soils. Begmont soils have bedrock within 20 to 40 inches. Longval soils have a mollic epipedon 20 to 40 inches thick.
GEOGRAPHIC SETTING: Lotawaca soils are on mountains. They formed in volcanic ash and colluvium over residuum derived from andesite or tuff. Slopes are 8 to 50 percent. Elevations range from 6,170 to 8,020 feet. The climate is subhumid with cold, moist winters and warm, dry summers. The mean annual precipitation is 30 to 50 inches, most of which comes as snow. The mean annual temperature is 38 to 44 degrees F. The frost-free period is 30 to 60 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are Gurlidawg, Nowack, and Paynepeak series. Gurlidawg and Nowack soils have bedrock within 40 inches. Paynepeak has a mollic epipedon 30 to 60 inches thick.
DRAINAGE AND PERMEABILITY: Well drained; medium or high surface runoff; moderately rapid permeability.
USE AND VEGETATION: Lotawaca soils are used for timber production, watershed, wildlife habitat, and limited livestock grazing. The vegetation consists of a closed forest canopy of white fir and western white pine with an understory of currant.
DISTRIBUTION AND EXTENT: Northeastern California. These soils are not extensive. MLRA 21.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.
SERIES ESTABLISHED: Surprise Valley-Home Camp Area, California and Nevada, 2005
REMARKS: The name is coined.
Diagnostic horizons and features recognized in this pedon include:
Umbric epipedon - The zone from the mineral soil surface to 20 inches (Oe, A and the Bt1 horizons).
Andic soil properties - The soil material with high volcanic glass content and acid oxalate extractable Al and Fe more than 0.4 extends from the mineral surface to 40 inches (A, Bt1 and Bt2).
Vitrandic intergrade feature -- High volcanic glass content in the .02 to 2mm fraction from the mineral soil surface to 31 inches (Oe, A, Bt1, and the Bt2 horizons).
Argillic horizon - The zone from 7 to 40 inches (Bt1 and Bt2 horizons).
Paralithic contact - The boundary at 40 inches to underlying soft, weathered bedrock (Cr layer).
Particle-size control section - The zone from 7 to 27 inches (Bt1 and part of the Bt2 horizons).