LOCATION TAHOMA CA NVEstablished Series
TAXONOMIC CLASS: Fine-loamy, isotic, frigid Ultic Haploxeralfs
TYPICAL PEDON: Tahoma very cobbly sandy loam - forested on a southeast facing convex slope of 10 percent under a cover of red fir at 7100 feet elevation. (Colors are for dry soil unless otherwise noted.)
Oi--0 to 8 cm; red fir litter.
A1--8 to 36 cm; brown (7.5YR 5/4) very cobbly sandy loam, brown (7.5YR 4/4) moist; strong fine granular structure; soft, friable, nonsticky and nonplastic; many very fine, fine and medium roots; few very fine tubular and interstitial pores; 30 percent gravel, 15 percent cobbles and 5 percent stones; moderately acid (pH 6.0); clear wavy boundary. (10 to 28 thick)
A2--36 to 56 cm; brown (7.5YR 5/4) very cobbly sandy loam, brown (7.5YR 4/4) moist; moderate medium granular structure; slightly hard, friable, slightly sticky and nonplastic; many very fine, fine, medium and coarse roots; many very fine interstitial and common very fine tubular pores; 30 percent gravel and 15 percent cobbles; strongly acid (pH 5.5); clear wavy boundary. (15 to 25 cm thick)
BAt--56 to 97 cm; brown (7.5YR 5/4) gravelly loam, brown (7.5YR 4/4) moist; weak medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine and fine tubular pores; common thin clay films line pores and coating sand grains; 20 percent gravel and 10 percent cobbles; very strongly acid (pH 5.0); clear wavy boundary. (13 to 41 cm thick)
Bt1--97 to 150 cm; brown (7.5YR 5/4) gravelly clay loam, brown (7.5YR 4/4) moist; weak fine subangular blocky structure; hard, firm, sticky and slightly plastic; few very fine, fine, medium and coarse roots; common very fine tubular pores; thin clay films line pores and on ped faces; 15 percent gravel and 5 percent cobbles; very strongly acid (pH 5.0); gradual wavy boundary. (33 to 53 cm thick)
Bt2--150 to 180 cm; brown (7.5YR 5/4) clay loam, dark brown (7.5YR 3/4) moist; moderate medium subangular blocky structure; hard, firm, sticky and slightly plastic; few very fine, fine, medium and coarse roots; common very fine and fine tubular pores; many thin clay films line pores and on ped faces; 5 percent gravel; very strongly acid (pH 4.7); gradual wavy boundary. (30 to 60 cm thick)
R--180 cm; coarse vesicular olivine latite.
TYPE LOCATION: Placer County, California; 1.5 miles north of Tahoe City; about 20 feet south of old road; 300 feet south and 700 feet east of W1/4 corner section 36, T.16 N., R.16 E., MDB&M.
RANGE IN CHARACTERISTICS:
Depth to bedrock: depth to weathered bedrock ismore than 100 cm
Mineralogy is influenced by vitric pyroclastic material.
Soil moiosture: usually moist between depths of 38 to 91 cm and are only dry in all parts from early August until early October. The soils have a typic xeric moisture regime.
Soil Temperature: mean annual soil temperature is 4 to 8 degrees C. and the mean summer soil temperature is 10 to 13 degrees C.
Base saturation: ranges from 25 to 35 percent
Reaction: slightly through very strongly acid
Surface rock fragments: Stones cover from 1 to 25 percent
Oi horizons are 3 to 8 cm thick
The A horizon:
Hue: 10YR, 7.5YR or 5YR
Value: 2 through 5 dry or moist (Moist values of 2 or 3 occur only in the upper 8 to 13 centimeters)
Chroma: 2 through 6 dry or moist
Texture of the fine earth: sandy loam or loam
Rock fragments: 15 to 60 percent
Structure: weak to strong granular
Organic Matter: 5 to 7 percent
Bt horizon:
Hue: 10YR, 7.5YR, 5YR or 2.5YR
Value: 4 through 6 dry, 2 through 6 moist
Chroma: 2 through 6 dry or moist
Texture of the fine earth: loam, clay loam or sandy clay loam
Rock fragments: upper 20 inches ranges from 5 to 35 percent gravel and 0 to 15 percent cobbles; the lower part ranges from 5 to 50 percent gravel and 0 to 20 percent cobbles and stones. Rock fragments average less than 35 percent.
COMPETING SERIES: This is the Parrego series. Parrego soils are 50 to 100 cm deep to weathered bedrock.
GEOGRAPHIC SETTING: Tahoma soils are on gently sloping to strongly sloping plateaus and moderately steep to steep mountains at elevations between 1400 and 2505. Slope gradient range from 2 to 50 percent. These soils formed in colluvium over residuum from volcanic flow rock, latite, and andesite. The mean annual precipitation ranges from about 640 to 1525 mm and the mean annual air temperature is 4 to 8 degrees C., mean January temperature is -4 degrees C., and mean July temperature is 15 degrees C. The average frost-free season is 25 to 90 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Jorge and Inville soils. Jorge and Inville soils are skeletal. Jorge is on similar landforms and Inville is found on outwash and alluvial terraces.
DRAINAGE AND PERMEABILITY: Well drained; low to medium runoff; moderate permeability.
USE AND VEGETATION: Timber and watershed; native vegetation is mixed conifers and shrubs where the principal species are red fir, white fir, Jeffrey pine, lodgepole pine, mountain whitethorn, greenleaf manzanita, prostrate manzanita, and mahal mat.
DISTRIBUTION AND EXTENT: The higher elevations of the Sierra Nevada and Southern Cascade Mountains of California. The soils of this series are moderately extensive. MLRA 22A
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Placer County, Tahoe Basin Area, California, 1970.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric Epipedon: The zone from the mineral surface to 56 cm (A1 and A2 horizons).
Argillic Horizon: The zone from 56 to 180 cm (BAt, Bt1 and Bt2 horizons).