LOCATION UNDERDOWN NV

Tentative Series
Rev. JBF/TM/JVC
07/2016

UNDERDOWN SERIES

The Underdown series consists of moderately deep, somewhat excessively drained soils that formed in residuum and colluvium derived from granitic rocks. Underdown soils are on mountains. Slopes are 50 to 75 percent. The mean annual precipitation is about 760 mm and the mean annual temperature is about 5 degrees C.

TAXONOMIC CLASS: Sandy-skeletal, mixed Xeric Haplocryepts

TYPICAL PEDON: Underdown extremely bouldery loam--forestland. (Colors are for dry soil unless otherwise noted.) The surface is covered with 25 percent boulders, 20 percent cobbles, and 35 percent gravel and also with a discontinuous layer of undecomposed pine needles.

A1--0 to 5 cm; dark gray (7.5YR 4/1) extremely bouldery sandy loam, black (7.5YR 2.5/1) moist; moderate fine subangular blocky structure parting to weak fine granular; soft, very friable, slightly sticky and slightly plastic; common very fine roots; many very fine interstitial pores; 25 percent boulders, 20 percent cobbles, and 25 percent gravel; neutral (pH 6.6); abrupt wavy boundary. (3 to 10 cm thick)

A2--5 to 18 cm; pale brown (10YR 6/3) very gravelly sandy loam, brown (10YR 4/3) moist; moderate fine subangular blocky structure; soft, very friable, slightly sticky and nonplastic; many very fine and fine roots and common medium and coarse; many very fine interstitial and tubular pores; 45 percent gravel and 10 percent cobbles; neutral (pH 6.8); abrupt wavy boundary. (8 to 18 cm thick)

Bw1--18 to 33 cm; light brown (7.5YR 6/3) very gravelly coarse sandy loam, dark brown (7.5YR 3/3) moist; weak fine subangular blocky structure; soft, very friable, nonsticky and nonplastic; many very fine to coarse roots; many very fine interstitial and few tubular pores; 45 percent gravel and 10 percent cobbles; slightly acid (pH 6.4); clear wavy boundary. (15 to 24 cm thick)

Bw2--33 to 53 cm; light brown (7.5YR 6/3) very cobbly loamy sand, dark brown (7.5YR 3/3) moist; weak fine subangular blocky structure; soft, very friable, nonsticky and nonplastic; many very fine and fine roots and common medium and coarse; many very fine interstitial pores; 30 percent gravel and 20 percent cobbles; slightly acid (pH 6.2); abrupt irregular boundary. (20 to 36 cm thick)

Cr--53 to 97 cm; highly weathered granite (grus); 30 percent harder zones which yield cobble-size fragments.

TYPE LOCATION: Nye County, Nevada; about 600 feet west and 2,400 feet north of the southeast corner of section 2, T. 14 N., R. 42 E.; USGS Millett Ranch 7.5 minute topographic quadrangle; latitude 39 degrees 5 minutes 51.1 seconds N and longitude 117 degrees 13 minutes 32.9 seconds W; NAD 83.

RANGE IN CHARACTERISTICS:
Soil moisture: Usually moist from mid-October through June, dry in summer and early fall; xeric soil moisture regime.
Mean annual soil temperature: 4 to 7 degrees C.
Mean summer soil temperature: 7 to 9 degrees C.
Depth to bedrock: 50 to 76 cm to a paralithic contact. The paralithic materials below the contact are weathered granite (grus).
Other features: Thin C horizons are in some pedons.

Particle-size control section - Clay content: Averages 5 to 9 percent;
Rock fragments: Averages 45 to 60 percent, mainly gravel and cobbles. Lithology of fragments is granitic rocks.

A1 horizon
Hue: 7.5YR or 10YR.
Value: 4 through 6 dry, 2 through 4 moist.
Chroma: 1 through 3, dry or moist.
Other features: Layers with value of 4 or 5 dry, 2 or 3 moist are less than 10 cm thick.

A2 horizon
Hue: 7.5YR or 10YR.
Value: 4 through 6 dry, 2 through 4 moist.
Chroma: 1 through 3, dry or moist.
Reaction: Slightly acid or neutral.
Other features: Layers with value of 4 or 5 dry, 2 or 3 moist are less than 10 cm thick.

Bw1 horizon
Value: 3 or 4 moist.
Chroma: 3 or 4, dry or moist.
Texture: Very gravelly coarse sandy loam or very gravelly sandy loam.
Rock fragments: 45 to 60 percent gravel, 0 to 15 percent cobbles.
Clay content: 8 to 15 percent.
Structure: Fine or medium subangular blocky.
Reaction: Slightly acid or neutral.

Bw2 horizon
Value: 3 or 4 moist.
Chroma: 3 or 4, dry or moist.
Texture: Very cobbly loamy sand or very cobbly loamy coarse sand.
Rock fragments: 15 to 25 percent cobbles, 30 to 35 percent gravel.
Clay content: 4 to 12 percent.
Structure: Fine or medium subangular blocky.
Reaction: Moderately acid or slightly acid.

COMPETING SERIES: These are the Pikaden, Pirapeak and Struggle series.

Pikaden, Pirapeak and Struggle soils are very deep.

GEOGRAPHIC SETTING: Underdown soils are on mountains. They typically occur on backslope positions. These soils formed in residuum and colluvium derived from granitic rocks. Slopes are 50 to 75 percent. Elevations range from 2,505 to 3,055 meters. The climate is semiarid with cold, moist winters and cool, dry summers. The mean annual precipitation is 630 to 900 mm, the mean annual temperature is 3 to 6 degrees C., and frost-free period is 20 to 50 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Hiridge and Snopoc soils. Hiridge soils are shallow and have 25 to 35 percent clay. Snopoc soils are very deep.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Somewhat excessively drained; high surface runoff; high saturated hydraulic conductivity .

USE AND VEGETATION: Underdown soils are used for livestock grazing and wildlife habitat. The present vegetation is mainly a forest canopy of limber pine with an understory of mountain brome, mountain big sagebrush, and snowberry.

DISTRIBUTION AND EXTENT: Central Nevada. These soils are not extensive. MLRA 28B.

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

SERIES PROPOSED: Nye County, Nevada (Toiyabe National Forest), 1997.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the soil surface to 18 cm (A1 and A2 horizons).
Cambic horizon - The zone from 18 to 33 cm (Bw1 horizon).
Paralithic contact - The boundary at 53 cm to underlying soft, weathered bedrock (Cr layer).
Particle-size control section - The zone from 25 to 53 cm. (Bw2 horizon and part of the Bw1 horizon).

National Cooperative Soil Survey
U.S.A.