LOCATION SIGBIRD MT
Established Series
Rev. DES-JAL-EMM
04/2014
SIGBIRD SERIES
The Sigbird series consists of shallow, somewhat excessively drained soils that formed in colluvium, slope alluvium and residuum derived from hard shale, sandstone, siltstone or argillite. These soils are on escarpments, ridges and sideslopes of mountains. Slopes are 25 to 70 percent. Mean annual precipitation is about 17 inches, and mean annual air temperature is about 38 degrees F.
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive Lithic Haplocryepts
TYPICAL PEDON: Sigbird very channery loam, very bouldery in forest (colors are for dry soil unless otherwise noted).
A--0 to 5 inches; brown (10YR 5/3) very channery loam, dark brown (10YR 3/3) moist; moderate medium granular structure; slightly hard, very friable, slightly sticky and slightly plastic; many fine and very fine roots; many fine and very fine interstitial pores; 10 percent flagstone, 50 percent channers; neutral (pH 7.2); clear wavy boundary. (3 to 6 inches thick)
Bw--5 to 14 inches; pale brown (10YR 6/3) extremely channery loam, brown (10YR 5/3) moist; weak medium subangular blocky structure; slightly hard, very friable, slightly sticky and nonplastic; common very fine and fine roots; common fine and very fine interstitial and tubular pores; 15 percent flagstones, 60 percent channers; slightly alkaline (pH 7.4); clear smooth boundary. (7 to 17 inches thick)
R--14 inches; gray (10YR 5/1) fractured hard shale.
TYPE LOCATION: Jefferson County, Montana; 700 feet south and 350 feet west of the NE corner of sec. 12, T. 5 N., R. 2 W.
RANGE IN CHARACTERISTICS:
Soil temperature - 38 to 42 degrees F.
Moisture control section - between 4 and 12 inches.
Base saturation - greater than 60 percent throughout.
Depth to bedrock - 10 to 20 inches.
Surface stones or boulders - 0 to 3 percent
The soil surface mixed to a depth of 7 inches will not meet the color requirements for a mollic epipedon.
A horizon
Hue: 10YR or 2.5Y
Value: 5 or 6 dry; 3 or 4 moist
Chroma: 2 or 3, dry or moist
Clay content: 18 to 27 percent
Rock fragments: 25 to 60 percent--0 to 10 percent flagstone; 20 to 60 percent channers
Reaction: pH 6.1 to 7.3
Bw horizon
Hue: 10YR, 2.5Y, or 5Y
Value: 5, 6, or 7
Chroma: 2 or 3, dry or moist
Texture: loam or sandy loam, sandy loam textures are due in part to small shale chips that are less than 2mm in size.
Clay content: 15 to 27 percent
Rock fragments: 35 to 80 percent--0 to 20 percent flagstone; 35 to 60 percent channers
Reaction: pH 6.6 to 7.8
COMPETING SERIES:
Caseypeak (MT) - has a paralithic contact of grus over a lithic contact of granite; has O horizons; rock fragments are pebbles.
Cobblank (AK) - has a subarctic climate
Cowood (MT) - slightly to strongly acid throughout; has a udic moisture regime
Hechtman (WY) - slightly to strongly acid throughout; has a udic moisture regime
Hotter (CO) - has a udic soil moisture regime
Jarbidge (NV) - has a xeric moisture regime
Merino (CO) - has a paralithic contact above a lithic contact
Pendergrass (CO) - Has hues of 2.5UR or 5YR
GEOGRAPHIC SETTING:
Landform - escarpments, ridges and sideslopes of mountains.
Elevation - 5,500 to 8,000 feet.
Slope - 25 to 70 percent.
Parent material - colluvium, slope alluvium and residuum derived from hard shale, sandstone, siltstone or argillite.
Climate - long, cold winters; cool, moist springs; short, cool summers.
Mean annual precipitation - 15 to 24 inches.
Mean annual air temperature - 36 to 40 degrees F.
Frost-free period - 50 to 70 days.
GEOGRAPHICALLY ASSOCIATED SOILS: None listed
DRAINAGE AND PERMEABILITY: Somewhat excessively drained, moderately rapid permeability.
USE AND VEGETATION: Sigbird soils are primarily used for woodland and wildlife habitat. The potential native vegetation is mainly Douglas fir, limber pine, Idaho fescue, bluebunch wheatgrass, common juniper, fringed sagewort, and sedges.
DISTRIBUTION AND EXTENT: Sigbird soils are of small extent in southwestern Montana. MLRA 43B.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Jefferson County, Montana, 1998.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - from the surface to 5 inches (mixed) (A horizon)
Cambic horizon - from 5 to 14 inches (Bw horizon)
Particle-size control section from the mineral soil surface to 14 inches (A and Bw horizons)
Lithic contact - hard shale bedrock at 14 inches (R horizon).
Soil interpretation record: MT3085.
Sigbird soils have a cryic temperature regime and an ustic moisture regime.
The 3/2008 description reflected a change in classification from Loamy-skeletal, mixed, superactive Lithic Eutrocryepts to Loamy-skeletal, mixed, superactive Lithic Haplocryepts due to revision of the cryepts great groups and subgroups.
National Cooperative Soil Survey
U.S.A.