LOCATION POIA MT
Tentative Series
Rev. EMR-JMS-RJS
05/2017
POIA SERIES
The Poia series consists of very deep, somewhat poorly drained soils that formed in outwash, till or mass movement deposits derived from metamorphic and sedimentary rock. Poia soils are commonly found on landslides, moraines or depressions on glacial-valley floors. Slopes are 0 to 15 percent. The mean annual precipitation is about 1,000 mm, and the mean annual air temperature is about 4.0 degrees C.
TAXONOMIC CLASS: Fine-loamy, mixed, superactive Oxyaquic Haplocryalfs
TYPICAL PEDON: Poia loam on a 15 percent slope, west aspect at 1,400 meters elevation. (Colors are for dry soil unless otherwise noted.)
Oi--0 to 2 cm; slightly decomposed plant material; abrupt smooth boundary.
A--2 to 14 cm; brown (7.5YR 4/2) loam, very dark gray (7.5YR 3/1) moist; moderate fine and medium granular structure; friable, slightly hard, slightly sticky and slightly plastic; many very fine, and common fine and medium roots; many very fine irregular pores; 5 percent gravel; neutral (pH 7.2); clear smooth boundary.
Bt1--14 to 36 cm; pinkish gray (7.5YR 6/2) gravelly clay loam, brown (7.5YR 5/2) moist; moderate medium angular blocky structure; firm, moderately hard, moderately sticky and moderately plastic; many very fine, and common fine and medium roots; many very fine irregular pores; 25 percent distinct clay films on all faces of peds; 5 percent fine faint yellowish brown (10YR 5/6), moist, masses of oxidized iron on faces of peds; 20 percent gravel; neutral (pH 6.9); clear wavy boundary.
Bt2--36 to 74 cm; light brownish gray (10YR 6/2) clay loam, dark grayish brown (10YR 4/2) moist; moderate medium angular blocky structure; firm, hard, moderately sticky and moderately plastic; common very fine, and common fine and medium roots; common very fine irregular pores; 30 percent distinct clay films on all faces of peds; 20 percent fine faint dark yellowish brown (10YR 4/4), moist, masses of oxidized iron on faces of peds; 10 percent gravel; neutral (pH 6.8); clear wavy boundary.
Bt3--74 to 152 cm; brown (10YR 5/3) gravelly clay loam, brown (10YR 4/3) moist; moderate medium angular blocky structure; firm, moderately hard, very sticky and very plastic; common very fine, and common fine and medium roots; common very fine irregular pores; 20 percent distinct clay films on all faces of peds; 10 percent fine distinct brown (7.5YR 4/4), moist, masses of oxidized iron on faces of peds; 15 percent gravel; neutral (pH 7.2).
TYPE LOCATION: Glacier County, Montana; located about 40 meters south and 310 meters west of the northeast corner of sec. 5, T. 34N., R. 14W; Saint Mary topographic quadrangle; UTM Zone 12, 319148e, 5401459n. NAD 83.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature: 2.5 to 6.5 degrees C
Ochric epipedon thickness: 7 to 22 cm
Depth to argillic horizon: 7 to 22 cm
Depth to a seasonally high water table: 60 to 100 cm
Particle-size control section: averages 25 to 34 percent clay
Note: Some pedons may contain a small amount of volcanic ash in the A horizon.
Oi horizon
Thickness: 0 to 4 cm
A horizon
Hue: 10YR or 7.5YR dry or moist
Value: 4 or 5 dry; 3 or 4 moist
Chroma: 1 to 2 dry or moist
Textures (less than 2 mm fraction): loam or silt loam
Clay content: 12 to 26 percent
Rock fragments: 0 to 15 percent gravel
Reaction: pH 6.2 to 7.2
Thickness: 7 to 18 cm
Bt1, Bt2 horizons
Hue: 10YR or 7.5YR dry or moist
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2 or 4 dry or moist
Textures (less than 2 mm fraction): clay loam or sandy clay loam
Clay content: 25 to 35 percent
Rock fragments: 0 to 35 percent--0 to 30 percent gravel; 0 to 5 percent cobbles; 0 to 3 percent stones; 0 to 3 percent boulders
Reaction: pH 6.2 to 7.3
Thickness (Bt1, Bt2 combined): 60 to 140 cm
Bt3 horizon
Hue: 10YR or 7.5YR dry or moist
Value: 5 or 6 dry; 3 to 5 moist
Chroma: 3 or 4 dry or moist
Textures (less than 2 mm fraction): clay loam or loam
Clay content: 18 to 34 percent
Rock fragments: 0 to 35 percent--0 to 30 percent gravel; 0 to 5 percent cobbles; 0 to 3 percent stones; 0 to 3 percent boulders
Reaction: pH 6.2 to 7.3
COMPETING SERIES :
Lehunt (MT): has secondary carbonates and natric horizon
GEOGRAPHIC SETTING:
Landform: landslides, moraines or depressions on glacial-valley floors
Elevation: 1,000 to 2,000 meters
Slope: 0 to 15 percent
Parent material: outwash, till or mass movement deposits derived from metamorphic and sedimentary rock
Climate: long, cold winters; moist springs; short warm summers with May and June receiving the most precipitation
Mean annual precipitation: 700 to 1,650 mm
Mean annual air temperature: 1.5 to 5.5 degrees C.
Frost-free period: 35 to 70 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained; moderately slow permeability.
USE AND VEGETATION: These soils are in montane meadows that are subirrigated and used mainly for recreation and wildlife. Native vegetation is primarily composed of multilayered grass and forb species including basin wildrye, bluejoint and slimstem reedgrass, prairie cordgrass, slender and bearded wheatgrass, tufted hairgrass, Nebraska sedge, northwest cinquefoil, leafy aster and blue-eyed grass.
DISTRIBUTION AND EXTENT: Poia soils are of limited extent in northern Montana. MLRA 43A and 43B.
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana
SERIES PROPOSED: Glacier County, Montana. This soil is named for a lake in Glacier National Park.
REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon: 0 to 14 cm (Oi, A horizons).
Argillic horizon: 14 to 152 cm (Bt1, Bt2, Bt3 horizons).
Particle-size control section: 14 to 64 cm (Bt1, part of Bt2 horizon).
Poia soils have a cryic temperature regime and an udic moisture regime and an oxyaquic moisture subclass.
Taxonomic version: Keys to Soil Taxonomy, Twelfth Edition, 2014.
National Cooperative Soil Survey
U.S.A.