LOCATION COMAD MT+CO

Established Series
Rev. LCB-JJU-RJS
03/2011

COMAD SERIES

The Comad series consists of very deep, excessively drained soils that formed in alluvium, alluvium, colluvium or alpine till derived from gneiss, schist, granite and quartzite rock. These soils are on hills, mountains, alluvial fans, stream terraces and moraines. Slopes are 8 to 80 percent. Mean annual precipitation is about 25 inches, and mean annual air temperature is about 38 degrees F.

TAXONOMIC CLASS: Sandy-skeletal, mixed Lamellic Cryorthents

TYPICAL PEDON: Comad extremely stony sandy loam, forested (colors are for dry soil unless otherwise noted).

Oi--0 to 3 inches; undecomposed and slightly decomposed forest litter. (1 to 3 inches thick)

E1--3 to 8 inches; light brownish gray (10YR 6/2) extremely stony sandy loam, brown (10YR 5/3) moist; moderate fine and very fine granular structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine and fine, and few medium and coarse roots; 15 percent gravel, 25 percent cobbles and 30 percent stones; strongly acid (pH 5.4); clear smooth boundary.

E2--8 to 20 inches; very pale brown (10YR 7/3) extremely stony loamy sand, brown (10YR 5/3) moist; weak fine and medium granular structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine, and fine, and few medium roots; many very fine tubular and interstitial pores; 15 percent gravel, 25 percent cobbles and 30 percent stones; strongly acid (pH 5.3); gradual wavy boundary. (combined thickness of E horizons - 5 to 21 inches)

E and Bt1--20 to 33 inches; E part (90 percent) very pale brown (10YR 7/3) extremely stony loamy sand, yellowish brown (10YR 5/4) moist; weak fine granular structure; slightly hard, very friable, nonsticky and nonplastic; Bt part (10 percent) yellowish brown (10YR 5/4) sandy clay loam lamellae; hard, friable, slightly sticky and slightly plastic; lamellae are wavy and discontinuous, 1/8 to 1/2 inch thick and 2 to 6 inches apart; common very fine and fine, and few medium roots; many very fine tubular and interstitial pores; 20 percent gravel, 25 percent cobbles and 30 percent stones; moderately acid (pH 5.7); gradual smooth boundary. (10 to 25 inches thick)

E and Bt2--33 to 60 inches; E part (95 percent) very pale brown (10YR 7/4) extremely stony loamy sand, yellowish brown (10YR 5/6) moist; massive; slightly hard, very friable, slightly sticky and nonplastic; few fine and medium roots; few very fine tubular pores; Bt2 part (5 percent) dark yellowish brown (10YR 4/4) moist sandy loam lamellae; 15 percent gravel, 30 percent cobbles and 35 percent stones; moderately acid (pH 5.7).

TYPE LOCATION: Lewis and Clark County, Montana; 2,200 feet south and 1,200 feet west of the NW corner of Sec. 35, T. 12 N., R. 6 W.

RANGE IN CHARACTERISTICS:
Soil temperature - 36 to 43 degrees F.
Depth to lamellae - 13 to 20 inches

Note: Some pedons may have an A, BC, and/or C horizon.

E1 horizon
Hue: 7.5YR or 10YR; dry or moist
Value: 6 or 7 dry; 3 to 5 moist
Chroma: 2 or 3; dry or moist
Texture: loam, sandy loam or loamy sand
Clay content: 5 to 26 percent
Rock fragments: 35 to 85 percent--10 to 30 percent gravel, 20 to 30 percent cobbles, 0 to 35 percent stones and boulders
Reaction: pH 5.1 to 7.3

E2 horizon
Hue: 7.5YR or 10YR; dry or moist
Value: 6 to 8 dry; 3 to 6 moist
Chroma: 2 or 3; dry or moist
Clay content: 5 to 15 percent
Rock fragments: 35 to 80 percent--10 to 30 percent gravel, 10 to 25 percent cobbles, 0 to 35 percent stones and boulders
Reaction: pH 5.1 to 7.3

E and Bt1 horizon
Hue: 7.5YR or 10YR; dry or moist
Value: E part 6 or 7 dry; 4 to 6 moist
B part 5 or 6 dry; 4 or 5 moist
Chroma: E part 2 or 3; dry or moist
B part 3 to 6; dry or moist
Texture: sand, loamy coarse sand, coarse sand or loamy sand--the lamellae are sandy loam or sandy clay loam
Clay content: 0 to 10 percent
Rock fragments: 40 to 80 percent--10 to 30 percent gravel, 10 to 25 percent cobbles, 15 to 35 percent stones
Reaction: pH 5.1 to 7.3

E and Bt2 horizon
Hue: 7.5YR or 10YR; dry or moist
Value: 5 to 7 dry; 4 to 6 moist
Chroma: 2 to 6; dry or moist
Texture: sand, coarse sand or loamy sand--the lamellae are sandy loam or sandy clay loam
Clay content: 0 to 10 percent
Rock fragments: 45 to 80 percent--10 to 20 percent gravel, 15 to 30 percent cobbles, 20 to 35 percent boulders and stones
Reaction: pH 5.1 to 7.3

COMPETING SERIES:
Nanita (CO) - have an udic moisture regime
Ovando (MT) - have an udic moisture regime
Rusbach (NM) - have Bw horizons

GEOGRAPHIC SETTING:
Landform - hills, mountains, alluvial fans, stream terraces and moraines
Elevation - 4,600 to 9,400 feet
Slope - 8 to 80 percent
Parent material - alluvium, colluvium or alpine till derived from gneiss, schist, granite and quartzite rock
Climate - cool with long, cold winters; cool, moist springs
Mean annual precipitation - 18 to 35 inches
Mean annual air temperature - 34 to 41 degrees F.
Frost-free season - 30 to 70 days

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Garlet and Whitore soils. Garlet soils are loamy-skeletal and have horizons of secondary carbonate accumulation. Whitore soils are loamy-skeletal and have carbonatic mineralogy. These soils are on similar landform positions.

DRAINAGE AND PERMEABILITY: Excessively drained; rapid permeability.

USE AND VEGETATION: Comad soils are used mainly as woodland. The potential native vegetation is mainly Douglas fir and lodgepole pine with an understory of bluebunch wheatgrass, Idaho fescue, elk sedge, snowberry, pinegrass, twinflower, huckleberry, raceme, Oregongrape, kinnikinnick, and heartleaf arnica.

DISTRIBUTION AND EXTENT: Comad soils are of moderate extent in southwestern Montana. MLRA - 43B, 44B, 46.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.

SERIES ESTABLISHED: Madison County, Montana, 1983.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Albic horizon - from 3 to 20 inches (E1 and E2 horizons)
Horizons with lamellae - from 20 to 60 inches (E and Bt1, E and Bt2 horizons);
Particle-size control section - from 13 to 43 inches (part of E2, E and Bt1, and part of E and Bt2 horizons)

Comad soils have a cryic temperature regime and an ustic moisture regime that borders on udic.

ADDITIONAL DATA: Soil interpretation records - MT0371, MT1251.

National Cooperative Soil Survey
U.S.A.