LOCATION FORTIRWIN CA

Established Series
REV: PBF/ET
04/2015

FORTIRWIN SERIES

The Fortirwin series consists of very shallow and shallow, well drained soils that formed in mixed alluvium. Fortirwin soils are on fan remnants. Slope ranges from 2 to 15 percent. The mean annual precipitation is about 5 inches and the mean annual air temperature is about 66 degrees F.

TAXONOMIC CLASS: Loamy, mixed, superactive, thermic, shallow Typic Argidurids

TYPICAL PEDON: On Arizo-Tenwell-Fortirwin association, 2 to 8 percent slopes at an elevation of 2,920 feet. (Colors are for dry soil unless otherwise noted.) The surface is covered by approximately 50 percent gravel, 25 percent cobbles, and trace of stones.

A1 -- 0 to 1 inch; light yellowish brown (10YR 6/4) extremely cobbly sandy loam, brown (10YR 5/3) moist; weak thin platy structure; soft, very friable, nonsticky and nonplastic; common very fine and fine roots; common fine interstitial pores; 50 percent gravel, 25 percent cobbles, and trace of stones; strongly effervescent; moderately alkaline (pH 8.0); abrupt smooth boundary.

A2 -- 1 to 3 inches; light yellowish brown (10YR 6/4) gravelly loam, yellowish brown (10YR 5/4) moist; massive parting to weak medium subangular blocky structure; slightly hard, friable, nonsticky and slightly plastic; common very fine and fine, few medium roots; 20 percent gravel, and 5 percent cobbles; strongly effervescent; moderately alkaline (pH 8.0); clear smooth boundary. (Combined thickness of the A horizon is 1 to 5 inches.)

Bt -- 3 to 11 inches; yellowish brown (10YR 5/4) clay loam, dark yellowish brown (10YR 4/4) moist; moderate, fine and medium subangular blocky structure; hard, firm, slightly sticky and moderately plastic; common very fine and fine, few medium roots; 60 percent distinct, discontinuous clay films on faces of peds; 5 percent gravel; very slightly effervescent; moderately alkaline (pH 8.0); abrupt wavy boundary. (4 to 12 inches thick)

Bkqm -- 11 to 60 inches; very pale brown (10YR 8/3 and 10YR 7/4) duripan with 1 mm thick discontinuous laminar cap, very pale brown (10YR 7/4) moist; extremely hard, extremely firm; very strongly cemented to indurated.

TYPE LOCATION: San Bernardino County, California; about 2,100 feet east and 1,600 feet south of the northwest corner of section 4 , T. 14 N., R. 3 E., 35 degrees, 20 minutes, 27 seconds north latitude and 116 degrees, 40 minutes, 11 seconds west longitude; Fort Irwin 7.5 minute quadrangle; UTM 11S, 0530009e 3910708n (DTM=NAS-C)

RANGE IN CHARACTERISTICS:

Soil moisture control section - usually dry, moist in some part for short periods during winter and early spring and for 10 to 20 days cumulative between July and October following convection storms. The soils have a Typic-Aridic moisture regime.

Soil temperature: 63 to 72 degrees F.

Surface rock fragments: 35 to 80 percent gravel, 5 to 25 percent cobbles, and 0 to 3 percent stones.

Control section -

Rock fragments: 5 to 35 percent

Clay content: 15 to 30 percent

Depth to duripan: 7 to 14 inches

Organic matter: 0 to 0.5 percent

A horizon
Value: 4 to 7 dry, 4 to 6 moist

Chroma: 3 or 4, dry or moist

Texture of the fine earth: sandy loam or loam

Clay content: 10 to 15 percent

Rock fragments: 65 to 85 percent in the upper part and 20
to 45 percent in the lower part; with 10 to 75 percent
gravel, 5 to 25 percent cobbles, and 0 to 3 percent
stones

Calcium carbonate equivalent: 0 to 5 percent

Effervescence: noneffervescent to strongly effervescent

Other features: Some pedons have 1 or 2 percent pan
fragments or carbonate crusts in the horizon

Reaction: Slightly or moderately alkaline

Bt horizon
Hue: 7.5YR or 10YR

Value: 4 to 7 dry, 4 or 5 moist

Chroma: 3 to 6 dry, 4 to 8 moist

Texture of the fine earth: sandy loam, loam, clay loam,
or sandy clay loam

Clay content: 18 to 30 percent

Rock fragments: 5 to 35 percent; with 5 to 25 percent
gravel, 0 to 10 percent cobbles, and 0 to 1 percent
stones

Calcium carbonate equivalent: 0 to 5 percent

Effervescence: noneffervescent to violently effervescent

Durinodes: 0 to 5 percent

Reaction: slightly or moderately alkaline

Bkqm horizon
Chroma: 2 or 3 dry, 3 or 4 moist

Consistence: very hard or extremely hard, very firm or
extremely firm

Cementation: very strongly cemented or indurated

Other features: A laminar cap is present, 1 to 6 mm
thick, continuous or discontinuous

COMPETING SERIES: This is the Kanesprings (NV) series. Kanesprings soils have a duripan underlain by bedrock. In addition, Kanespring soils are deeper to a duripan, have a cooler soil temperature regime, and are not moist in some part of the moisture control section for as much as 10 to 20 days cumulative between July and October following convection storms.

GEOGRAPHIC SETTING: Fortirwin soils are on fan remnants. Slope ranges from 2 to 15 percent. The soils formed in mixed alluvium. Elevations are 1,600 to 4,200 feet. The climate is arid with hot, dry summers and warm, moist winters. Most precipitation occurs in winter but a significant portion is received between July and September following convection storms. The mean annual precipitation is 3 to 7 inches; mean annual air temperature is 61 to 70 degrees F., and the frost-free season is 240 to 340 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Arizo, Crackerjack, Crosgrain, Fourcorners, Goldivide, and Tenwell soils. Arizo soils are on alluvial fans and inset fans, have a sandy-skeletal particle-size control section and do not have a duripan or an argillic horizon. Crackerjack, Crosgrain, Fourcorners, Goldivide, and Tenwell soils are on similar landscape positions. Crackerjack soils have a loamy particle-size control section, are shallow to a cambidic duripan and do not have an argillic horizon. Crosgrain and Fourcorners soils are both shallow or very shallow to a duripan and have loamy-skeletal particle-size control sections. In addition, Crosgrain does not have an argillic horizon. Goldivide soils have a coarse-loamy particle-size control section and do not have a duripan. Tenwell soils are moderately deep to a duripan and have fine-loamy particle- size control sections.

DRAINAGE AND PERMEABILITY: Well drained; high to very high runoff; moderately rapid permeability in the surface layer, moderate permeability in the next layer, and moderately slow permeability above the duripan.

USE AND VEGETATION: Fortirwin soils are used for military exercises and wildlife habitat. The present vegetation is mainly creosotebush, white bursage, mojave aster, range ratany, white burrobush, and Joshua tree.

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

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

SERIES ESTABLISHED: San Bernardino County, California, Fort Irwin Soil Survey Area, 1997. The name is from the military installation on which the soil survey was conducted.

REMARKS: Diagnostic horizons and features recognized in the profile are:

1. Ochric epipedon -- 0 to 3 inches (A1 and A2 horizons)
2. Argillic horizon -- 3 to 11 inches (Bt horizon)
3. Duripan -- the zone beginning at 11 inches (Bkqm horizon)
4. Particle-size control section -- 0 to 11 inches

Responsibility for this series was transferred from Davis to Phoenix 4/2015. The last revision to the series was 3/2005. ET

National Cooperative Soil Survey
U.S.A.