LOCATION FORTLEWIS CO+NM
Established Series
Rev. JPP/TWH/KLS
03/2018
FORTLEWIS SERIES
The Fortlewis series consists of moderately deep, well drained soils that formed in slope alluvium or colluvium derived from sandstone and shale. Fortlewis soils are on mountain slopes and hillslopes. Slopes range from 3 to 25 percent. Mean annual precipitation is about 508 mm and the mean annual temperature is about 6.1 degrees C.
TAXONOMIC CLASS: Fine, mixed, superactive, frigid Typic Haplustalfs
TYPICAL PEDON: Fortlewis stony fine sandy loam, on a south facing, simple, 15 percent slope in ponderosa pine woodland at an elevation of 2,500 feet. (Colors are for dry soil unless otherwise noted.) Described on October 18, 1988.
Oi--0 to 3 cm; organic layer of partly decayed needles, leaves and roots. (0 to 8 cm thick)
A--3 to 10 cm; brown (7.5YR 5/2) stony fine sandy loam, dark brown (7.5YR 3/2) moist; weak fine granular structure; soft, very friable, nonsticky and nonplastic; 5 percent gravel, 10 percent cobble, 15 percent stones; slightly acid (pH 6.3); clear smooth boundary. (3 to 10 cm thick)
E--10 to 30 cm; pinkish gray (7.5YR 7/2) stony fine sandy loam, brown (7.5YR 5/2) moist; weak fine granular structure; soft, very friable, nonsticky and nonplastic; 5 percent gravel, 10 percent cobble, 15 percent stones; slightly acid (pH 6.2); clear wavy boundary. (5 to 30 cm thick)
B/E--30 to 43 cm; (70 percent B) reddish brown (5YR 5/4) clay loam, reddish brown (5YR 4/4) moist, and (30 percent E) light brown (7.5YR 6/4) sandy clay loam, brown (7.5YR 5/4) moist; moderate medium subangular blocky structure; hard, firm, moderately sticky and moderately plastic; few faint clay films on faces of peds of the B part; 5 percent gravel, 5 percent cobble, 3 percent stones; slightly acid (pH 6.2); gradual wavy boundary. (3 to 15 cm thick)
Bt1--43 to 69 cm; light reddish brown (5YR 6/4) clay, reddish brown (5YR 4/4) moist; moderate medium subangular blocky and angular blocky structure; very hard, very firm, very sticky and very plastic; many prominent clay films on faces of peds; 5 percent gravel, 5 percent cobble, 2 percent stone; slightly acid (pH 6.3); gradual wavy boundary. (15 to 51 cm thick)
Bt2--69 to 99 cm; reddish yellow (5YR 6/6) clay, yellowish red (5YR 4/6) moist; strong medium subangular blocky and angular blocky structure; very hard, very firm, very sticky and very plastic; many prominent clay films on faces of peds; 5 percent gravel, 5 percent cobble; slightly acid (pH 6.3); abrupt wavy boundary.
R--99 cm; sandstone bedrock, fractured in the upper few centimeters.
TYPE LOCATION: LaPlata County, Colorado; about 11 kilometers northwest of Durango; located about 671 meters south and 396 meters east of the northwest corner of Sec. 25, T. 36 N., R. 10 W.; Durango West USGS quad; Lat. 37 degrees, 21 minutes, 04 seconds N. and Long. 107 degrees, 54 minutes, 55 seconds W., NAD 27.
RANGE IN CHARACTERISTICS:
Soil moisture: Soil is the driest in May and June; wettest in July and August.
Mean annual soil temperature: 1.7 to 8.3 degrees C.
Mean summer soil temperature: 15.0 to 17.2 degrees C.
Depth to lithic contact: 50 to 100 cm to sandstone bedrock
Particle-size control section (weighted average):
Clay content: 35 to 45 percent
Rock fragments: 5 to 35 percent sandstone fragments
A horizon:
Hue: 5YR or 7.5YR
Value: 5 or 6 dry, 2 or 3 moist
Chroma: 2 or 3, dry and moist
Reaction (pH): 6.1 to 7.3
E horizon:
Hue: 5YR or 7.5YR
Value: 5 to 7 dry, 4 or 5 moist
Chroma: 2 to 4, dry and moist
Clay content: 5 to 20 percent
Rock fragment content: 15 to 35 percent
Reaction (pH): 6.1 to 7.3
B/E horizon:
B part
Hue: 2.5YR or 5YR
Value: 4 to 6 dry, 4 or 5 moist
Chroma: 3 to 6, dry and moist
Texture: SCL, CL
Clay content: 25 to 40 percent
Rock fragment content: 10 to 30 percent
Reaction (pH): 6.1 to 7.3
E part
Hue: 5YR or 7.5YR
Value: 5 to 7 dry, 4 or 5 moist
Chroma: 2 to 4, dry and moist
Texture: FSL, SCL
Clay content: 15 to 30 percent
Rock fragment content: 10 to 30 percent
Reaction (pH): 6.1 to 7.3
Bt horizon
Hue: 2.5YR or 5YR
Value: 4 to 6 dry, 4 or 5 moist
Chroma: 3 to 6, dry and moist
Texture: SC, C, CL
Clay content: averages 35 to 45 percent
Rock fragment content: 5 to 35 percent
Reaction (pH): 6.1 to 7.3
COMPETING SERIES:
Crow (MT) - do not have a lithic contact
Dargol (NM) - are the driest from December to February
Echolake (CO) - are moderately deep to paralithic contact
Heckly (NM) - do not have an albic horizon
Ligocki (NM) - do not have a lithic contact
Lubrecht (MT) - are moderately deep to paralithic contact
Ordnance (NM) - have horizons of secondary carbonate accumulation
Rittel (MT) - are moderately deep to paralithic contact
Valnor (NM) - are moderately deep to paralithic contact
Zuni (NM) - have rock fragments of granitic lithology
GEOGRAPHIC SETTING:
Landform - mountain slopes, hillslopes
Elevation - 2,130 to 2,950 meters
Slopes - 3 to 25 percent
Parent material - slope alluvium or colluvium derived from sandstone and shale
Precipitation pattern - wettest precipitation months are July and August; the driest months are May and June.
Mean annual temperature - 5.0 to 7.2 degrees C.
Mean annual precipitation - 460 to 560 cm
Frost-free period - 90 to 110 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well drained, medium runoff, slow permeability.
USE AND VEGETATION: These soils are used for timber production, livestock grazing and wildlife habitat. Native vegetation consists mainly of ponderosa pine, Gambel's oak, Arizona fescue, prairie Junegrass, mountain muhly, and mountain brome.
DISTRIBUTION AND EXTENT: Southwestern Colorado and northern New Mexico; LRR D and E; MLRA 36 and 48A. The series is of moderate extent.
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: LaPlata County, Colorado, Animas-Dolores soil survey area, 2001. The name is taken from Fort Lewis College located in Durango.
REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Albic horizon: 10 to 30 cm (E horizon)
Argillic horizon: 30 to 99 cm (B/E and Bt horizons)
Lithic contact: 99 cm to hard sandstone bedrock (R horizon)
Particle-size control section: 30 to 80 cm (B/E, Bt1, and part of the Bt2 horizon)
Series control section: 0 to 99 cm
Fortlewis soils have a frigid temperature regime and are in an ustic soil moisture regime with a typic subclass.
National Cooperative Soil Survey
U.S.A.