LOCATION DESCENT                 CA

Established Series
Rev: PBF/CAH/ET
04/2015

DESCENT SERIES

The Descent series consists of very deep, somewhat excessively drained soils that formed in alluvium from granitoid and gneiss. Descent soils are on ballenas and fan remnants. Slopes range from 2 to 50 percent. The mean annual precipitation is about 100 millimeters (4 inches) and the mean annual air temperature is about 21.5 degrees C (71 degrees F).

TAXONOMIC CLASS: Sandy-skeletal, mixed, hyperthermic Typic Torriorthents

TYPICAL PEDON: Descent channery loamy fine sand, on an east-facing, linear, 37 percent slope under sparse desert shrubs at an elevation of 200 meters (656 feet). (Colors are for dry soil unless otherwise noted.)

C -- 0 to 4 centimeters (0 to 1.5 inches) channers; approximately 10 percent fine channers, 68 percent medium and coarse channers, and 7 percent flagstones; abrupt smooth boundary. (0 to 8 centimeters thick)

Akq -- 4 to 5 centimeters (1.5 to 2 inches); pale brown (10YR 6/3) channery loamy fine sand, brown (10YR 5/3) moist; moderate fine subangular blocky structure; slightly hard, very friable, nonsticky and nonplastic; 5 percent fine, light gray (10YR 7/2), weakly cemented durinodes within the matrix; very few very fine roots; 10 percent fine channers and 5 percent medium and coarse channers; slightly effervescent (8 percent calcium carbonate equivalent in the fine earth fraction); moderately alkaline (pH 8.1); clear wavy boundary. (1 to 5 centimeters thick)

Bkq1 -- 5 to 19 centimeters (2 to 7.5 inches); pale brown (10YR 6/3) extremely channery fine sandy loam, brown (10YR 5/3) moist; weak medium subangular blocky structure; slightly hard, very friable, nonsticky and nonplastic; 3 percent fine, light gray (10YR 7/2), weakly cemented durinodes within the matrix; 3 percent fine silica masses on the bottom of rock fragments; few very fine and very few fine roots; 20 percent fine channers and 50 percent medium and coarse channers; violently effervescent (10 percent calcium carbonate equivalent in the fine earth fraction); moderately alkaline (pH 8.1); clear wavy boundary.

Bkq2 -- 19 to 42 centimeters (7.5 to 16.5 inches); very pale brown (10YR 7/3) very channery loamy sand, pale brown (10YR 6/3) moist; massive; slightly hard, very friable, nonsticky and nonplastic; 3 percent fine silica masses on the bottom of rock fragments; common very fine and few fine roots; 15 percent fine channers, 30 percent medium and coarse channers and 5 percent flagstones; violently effervescent (13 percent calcium carbonate equivalent in the fine earth fraction); moderately alkaline (pH 8.2); gradual wavy boundary.

Bkq3 -- 42 to 69 centimeters (16.5 to 27 inches); pale brown (10YR 6/3) extremely channery sand, brown (10YR 5/3) moist; massive; soft, very friable, nonsticky and nonplastic; 3 percent fine silica masses on the bottom of rock fragments; few very fine and very few fine roots; 10 percent fine channers and 65 percent medium and coarse channers; violently effervescent (9 percent calcium carbonate equivalent in the fine earth fraction); moderately alkaline (pH 8.3); gradual wavy boundary.

Bkq4 -- 69 to 152 centimeters (27 to 60 inches); very pale brown (10YR 7/3) extremely channery sand, pale brown (10YR 6/3) moist; single grain; loose, nonsticky and nonplastic; 1 percent fine silica masses on the bottom of rock fragments; 40 percent fine channers, 15 percent medium and coarse channers and 5 percent flagstones; violently effervescent (9 percent calcium carbonate equivalent in the fine earth fraction); moderately alkaline (pH 8.3).

TYPE LOCATION: Riverside County, California; approximately 1.8 kilometers (1.1 miles) north of the junction of California Highway 177 and MWD Aqueduct Road, north of Desert Center; 110 meters (361 feet) south and 306 meters (1,003 feet) east of the NW corner of section 22, T. 4 S., R. 16 E., San Bernardino Base and Meridian; USGS East of Victory Pass 7.5 minute topographic quadrangle; 33 degrees, 48 minutes and 55.9 seconds north latitude, and 115 degrees, 17 minutes and 42.7 seconds west longitude, UTM 11S 0657783e 3743009n (DTM: NAD83).

RANGE IN CHARACTERISTICS:

Soil moisture control section: usually dry, moist in some parts for short
periods during winter and early spring and for 10 to 20 days cumulative
between July and September following convection storms. The soils have
a typic-aridic soil moisture regime.

Soil temperature: 22 to 25 degrees C (72 to 77 F).

Surface rock fragments: 80 to 100 percent; with 10 to 25 percent fine
channers, 45 to 70 percent medium and coarse channers, 0 to 25 percent
flagstones, 0 to 5 percent stones and 0 to 1 percent boulders.

Control section -
Rock fragments: averages 40 to 70 percent.
Clay content: ranges from 1 to 8 percent, averages 2 to 6 percent.
Calcium carbonate equivalent: 5 to 16 percent.
Organic matter: 0 to 0.25 percent.

C horizon (when present)
80 to 100 percent rock fragments; channers, flagstones, stones and
boulders.

Akq horizon
Value: 6 to 8 dry, 4 to 7 moist.
Chroma: 3 or 4 dry, 2 to 6 moist.
Texture of the fine earth: loamy sand, loamy fine sand or fine sandy
loam. Clay content: 3 to 12 percent.
Rock fragments: 10 to 25 percent; with 10 to 25 percent channers and 0
to 5 percent flagstones.
Calcium carbonate equivalent: 1 to 10 percent.
Effervescence: slightly to violently effervescent.
Silica: 0 to 10 percent durinodes and 1 to 15 percent silica films on
bottom of rock fragments.

Bkq horizon
Hue: 7.5YR or 10YR.
Value: 6 or 7 dry, 4 to 6 moist.
Chroma: 3 or 4 dry, 3 to 6 moist.
Texture of the fine earth: sandy loam or fine sandy loam in the upper
part and sand or loamy sand in the lower part. Clay content: 6 to 12 percent in the upper part and 2 to 8 percent in
the lower part.
Rock fragments: 50 to 75 percent; with 45 to 75 percent channers, 0 to
10 percent flagstones and 0 to 1 stones. Effervescence: strongly or violently effervescent.
Calcium carbonate equivalent: 5 to 16 percent.
Reaction: moderately or strongly alkaline.
Silica: 0 to 10 percent durinodes, 1 to 5 percent silica masses and 1
to 75 percent silica coats on bottom of rock fragments.
Note: There are no visible or identifiable secondary carbonates within
these horizons.

COMPETING SERIES: These are the Carrwash (NV), Carrizo (CA+AZ) and Rizzo (CA) series. All of these soils have calcium carbonate equivalents (CCE) of less than 5 percent in the control section and do not have rock fragments which are dominantly channers and flagstones. In addition, Carrwash soils have more than 50 percent of the rock fragments in the particle-size control section in the 2 to 5 millimeter range and Rizzo soils have a dryer climate, typical of the Lower Colorado Desert, with a moisture control section that is usually dry, and only moist in some part for short periods during winter and early spring.

GEOGRAPHIC SETTING: Descent soils are on ballenas and fan remnants. Slopes range from 2 to 50 percent. These soils formed in alluvium from granitoid and gneiss. Elevations range from 150 to 660 meters (492 to 2,165 feet). The climate is arid, with hot, dry summers and warm, moist winters. The mean annual precipitation is 75 to 125 millimeters (3 to 5 inches) and the mean annual air temperature is 20 to 23 degrees C (68 to 73.5 degrees F). The frost-free season is 300 to 340 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Blackeagle, Carrizo, Deprave, Oldale, Rizzo and Roostertail soils. Blackeagle soils are on adjacent mountain backslopes, have a cambic horizon and are shallow to bedrock. Carrizo, Deprave, Oldale, Rizzo and Roostertail soils are on adjacent fan aprons and fan remnants. Carrizo and Rizzo are competing soils but have a calcium carbonate equivalent of less than 5 percent in the particle-size control section. Deprave, Oldale and Roostertail soils have loamy-skeletal particle-size control sections and an argillic horizon. In addition, Deprave soils have a duripan within 50 centimeters of the surface and Roostertail soils have a duripan below 100 centimeters.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Excessively drained; very low to medium runoff; high saturated hydraulic conductivity.

USE AND VEGETATION: Descent soils are used for recreation and wildlife habitat. The present vegetation is sparse creosote bush.

DISTRIBUTION AND EXTENT: Southern Mojave Desert of southeastern California. MLRA 30. These soils are of small extent.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: PHOENIX, ARIZONA

SERIES ESTABLISHED: Riverside County, California, Joshua Tree National Park Soil Survey, 2012. The name is coined.

REMARKS: Diagnostic horizons and features in this pedon include:

C horizon - from a depth of 0 to 4 centimeters.
Ochric epipedon - from a depth of 4 to 5 centimeters (A horizon).
Particle-size control section - from a depth of 25 to 100 centimeters
(part of the Bkq2, the Bkq3, and part of the Bkq4 horizons).
ADDITIONAL DATA: NASIS User Pedon ID: EOVP09.

Responsibility for this series was transferred from Davis to Phoenix 4/2015. The last revision to the series was 4/2012. ET

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National Cooperative Soil Survey
U.S.A.