LOCATION FIRO                    NM+UT

Established Series
Rev. REN/CLC/KLS
08/2022

FIRO SERIES

The Firo series consists of very shallow and shallow, well drained soils that formed in alluvium and colluvium derived from igneous bedrock on mountain slopes. Slopes are 12 to 60 percent. The mean annual precipitation is about 510 mm and the mean annual temperature is about 6 degrees C.

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Lithic Haplustolls

TYPICAL PEDON: Firo very stony loam - rangeland. (Colors are for dry conditions unless otherwise noted.)

Oi--0 to 3 cm; undecomposed to partially decomposed leaves, needles, and woody twigs. (1 to 8 cm thick)

A--3 to 11 cm; very dark grayish brown (10YR 3/2) stony loam, very dark brown (10YR 2/2) moist; weak fine granular structure; slightly hard, very friable, slightly sticky and slightly plastic; many fine roots; common fine interstitial pores; 5 percent gravel, 10 percent cobble, and 10 percent stones; neutral; clear smooth boundary. (5 to 13 cm thick)

Bw--11 to 41 cm; dark grayish brown (10YR 4/2) very cobbly loam, very dark brown (10YR 2/2) moist; weak fine subangular blocky structure parting to weak fine granular; slightly hard, friable, slightly sticky and slightly plastic; common fine and medium roots; common fine interstitial pores; 5 percent gravel, 25 percent cobble and 15 percent stones; neutral; abrupt irregular boundary. (13 to 38 cm thick)

R--41 cm inches; acid igneous bedrock, somewhat weathered in the upper 5 cm

TYPE LOCATION: Otero County, New Mexico; Mescalero-Apache area, about 965 meters up Cienegita Canyon from Maple Dam on south-facing slope about 185 meters north of the road; NE corner of SW 1/4,of NE 1/4, of Sec. 35, T. 11 S., R. 11 E.; Long. 106 degrees, 45 minutes, 48 seconds W; Lat. 33 degrees, 18 minutes, 43 seconds N.

RANGE IN CHARACTERISTICS:
Soil moisture--moist in the control section with the driest period occurring during April, May and June
Mean annual soil temperature--4 to 8 degrees C
Lithic Contact--15 to 50 cm

Particle-size control section:
Total rock fragment content--35 to 85 percent
Organic matter--2 to 4 percent
Reaction--pH 6.1 to 7.8

A horizon
Hue--7.5YR or 10YR
Value--3 through 5 dry and 2 or 3 moist
Chroma--2 or 3
Texture--sandy loam or loam

Bw horizon
Hue--7.5YR or 10YR
Value--3 through 5 dry and 2 or 3 moist
Chroma--2 or 3
Clay content--18 to 35 percent
Texture--loam or clay loam
Some pedons are slightly calcareous in the lower part of the Bw horizon

An AC horizon may be present in some pedons.

COMPETING SERIES: There are the Boriana(AZ), Castner(MT), Cathedral(CO), Celeste(CO), Comodore(CO), Duffymont(CO)(T), Onaqui(UT)(T), Paunsaugunt(UT) and Pendant(CO) soils. Boriana, Cathedral, Comodore and Duffymont soils have fine earth matrix material that is coarse sandy loam, or loam with less than 18 percent clay. Caster, Paunsaugunt and Pendant soils are calcareous throughout. Celeste soils have hue of 5YR or redder. Onaqui soils are moderately alkaline in the lower horizons and do not have O horizons.

GEOGRAPHIC SETTING:
Landform--mountain slopes and summits
Elevations--2075 to 2750 meters
Parent material--mixed fine grained acid igneous formations
Slope--12 to 60 percent
Mean annual precipitation--430 to 580 mm, mostly as winter snows and late summer rains
Mean annual air temperature--3 to 7 degrees C
Thornthwaite P/E Index--30 to 50
In Montana, elevation is as low as 1350 meters and precipitation is as low as 400 mm.

GEOGRAPHICALLY ASSOCIATED SOILS: None listed

DRAINAGE AND PERMEABILITY: Well drained; rapid runoff; moderate permeability.

USE AND VEGETATION: Mostly for wildlife, native range, recreation, watershed and woodland. Principal native vegetation is mountain muhly, mountain brome, blue grama, white and Douglas fir. In Montana, the native plant community consists of rough fescue, Idaho fescue, bluebunch wheatgrass, Columbia needlegrass, penstemon, and bitterbrush.

DISTRIBUTION AND EXTENT: Firo soils are moderately extensive in the mountainous areas of southcentral and northcentral New Mexico and southcentral Utah; MLRAs 39, 48A, and 70B

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana

SERIES ESTABLISHED: Otero County (Mescalero Apache Area), New Mexico, 1970

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon--3 to 41 cm (A and Bw horizons)
Lithic contact--41 cm (R horizon)
Particle-size control section--25 to 41 cm (Bw horizon)

Converted to metric, updated formatting, and O horizons were updated to start at zero. 8/2022

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National Cooperative Soil Survey
U.S.A.