LOCATION COMO MT+CO
Established Series
Rev. JJU-RJS
02/2011
COMO SERIES
The Como series consists of very deep, somewhat excessively drained soils that formed in colluvium derived from coarse grained igneous and sedimentary rock. These soils occur on mountain slopes. Slopes are 10 to 60 percent. Mean annual precipitation is about 760 mm, and the mean annual air temperature is about 3 degrees C.
TAXONOMIC CLASS: Sandy-skeletal, mixed Typic Haplocryepts
TYPICAL PEDON: Como very gravelly sandy loam, forested. (Colors are for dry soil unless otherwise noted).
Oi--0 to 6 cm; slightly decomposed forest litter; clear smooth boundary. (4 to 10 cm thick)
A--6 to 18 cm; grayish brown (10YR 5/2) very gravelly sandy loam, dark brown (10YR 3/3) moist; moderate fine granular structure; soft, very friable, nonsticky and nonplastic; many very fine, fine, and medium roots; many very fine and fine irregular pores; 40 percent gravel and 5 percent cobbles; moderately acid (pH 6.0); clear smooth boundary. (6 to 15 cm thick)
Bw--18 to 46 cm; light brownish gray (10YR 6/2) very gravelly sandy loam, dark grayish brown (10YR 4/2) moist; moderate fine subangular blocky structure; soft, very friable, nonsticky and nonplastic; common very fine and fine roots; many very fine and fine irregular pores; 50 percent gravel and 5 percent cobbles; moderately acid (pH 5.8); clear wavy boundary. (15 to 30 cm thick)
BC--46 to 72 cm; brown (10YR 5/3) very gravelly loamy sand, grayish brown (10YR 5/2) moist; single grain; loose, nonsticky and nonplastic; few very fine and fine roots; many fine irregular pores; 50 percent gravel and 5 percent cobbles; moderately acid (pH 6.0); clear smooth boundary. (20 to 50 cm thick)
C--72 to 152 cm; light brownish gray (10YR 6/2) extremely gravelly loamy sand, brown (10YR 5/3) moist; single grain; loose, nonsticky and nonplastic; few very fine roots; 65 percent gravel and 5 percent cobbles; moderately acid. (pH 6.0)
TYPE LOCATION: Beaverhead County, Montana; located about 264 meters south and 700 meters east of the northwest corner of sec. 22, T. 14 N., R 2 W; Slide Mountain topographic quadrangle; UTM 12T, 433628e., 4938945n. NAD 83
RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 2 to 5 degrees C.
Thickness of the cambic horizon - 15 to 30 cm
Particle size control section - averages 8 to 14 percent clay
Note: Some pedons may have an E horizon present
A horizon
Value: 4 or 5 dry; 3 or 4 moist
Chroma: 2 or 3; dry or moist
Clay content: 12 to 18 percent
Rock fragments: 35 to 60 percent--35 to 50 percent gravel, 0 to 10 percent cobbles, 0 to 10 percent stones
Reaction: pH 5.6 to 6.5
E horizon (when present)
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2 or 3; dry or moist
Clay content: 8 to 18 percent
Rock fragments: 35 to 60 percent--35 to 50 percent gravel, 0 to 10 percent cobbles, 0 to 10 percent stones
Reaction: pH 5.6 to 6.5
Bw horizon
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2 or 3; dry or moist
Clay content: 8 to 14 percent
Rock fragments: 35 to 60 percent--35 to 50 percent gravel, 0 to 15 percent cobbles, 0 to 15 percent stones
Reaction: pH 5.6 to 6.5
BC horizon
Value: 5 or 6; dry or moist
Chroma: 2 or 3; dry or moist
Clay content: 6 to 12 percent
Rock fragments: 35 to 60 percent--35 to 55 percent gravel, 0 to 15 percent cobbles, 0 to 15 percent stones
Reaction: pH 5.6 to 6.5
C horizon
Value: 5 or 6; dry or moist
Chroma: 2 or 3; dry or moist
Clay content: 4 to 12 percent
Texture: loamy sand or sand
Rock fragments: 45 to 80 percent--45 to 70 percent gravel, 0 to 15 percent cobbles, 0 to 15 percent stones
Reaction: pH 5.6 to 6.5
COMPETING SERIES:
Donnelly (AK) - has a lithologic discontinuity
Pippin (AK) - has a lithologic discontinuity
Sinona (AK) - has a lithologic discontinuity
GEOGRAPHIC SETTING:
Landform - mountain slopes
Elevation - 2000 to 2750 meters
Slope - 10 to 60 percent
Parent material - colluvium derived from coarse grained igneous and sedimentary rock
Climate - long, cold winters; moist springs; short warm summers
Mean annual precipitation - 600 to 900 mm
Mean annual air temperature - 1 to 4 degrees C.
Frost free period - 30 to 70 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Somewhat excessively drained and rapid permeability.
USE AND VEGETATION: Como soils are used mainly for understory grazing and timber. The vegetation is mainly Douglas-fir, subalpine fir, lodgepole pine, huckleberry, grouse whortleberry, snowberry, buffaloberry, heartleaf arnica, western meadowrue, and other miscellaneous grasses and forbs.
DISTRIBUTION AND EXTENT: Como soils are of small extent in southwestern and central Montana. MLRA 43B.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Bitterroot Valley Area, Montana, 1914. Type location moved to Beaverhead County, Montana in 2011.
REMARKS: Diagnostic horizons and features recognized in this pedons are:
Ochric epipedon - from 0 to 18 cm (Oi and A horizons)
Cambic horizon - from 18 to 46 cm (Bw horizon)
Particle size control section - from 31 to 106 cm (part of Bw, BC, and part of C horizons)
Como soils have a cryic temperature regime and an udic moisture regime.
Taxonomic version: Eleventh Edition, 2010.
National Cooperative Soil Survey
U.S.A.