114 Classification of the Soils – Donegan Series

Classification of the Soils
Donegan Series

 Depth class: Moderately deep to bedrock

Drainage class: Well drained

Permeability: Moderately slow

Position on landscape: Mountainsides

Parent material: Ash mixed with colluvium derived from andesite

Slope range: 30 to 65 percent

Elevation: 4,000 to 5,100 feet

Average annual precipitation: 40 to 50 inches

Average annual air temperature: 41 to 45 degrees F

Frost-free period: 30 to 70 days

 Taxonomic class: Loamy-skeletal, mixed, superactive, frigid Humic Dystroxerepts

 Typical Pedon

Oi—0 to 1 inch; partially decomposed leaves, needles, and twigs.

A—1 inch to 5 inches; dark brown (7.5YR 3/3) very gravelly ashy sandy loam, brown (7.5YR 4/3) dry; weak very fine granular structure; soft, very friable, nonsticky and nonplastic; many very fine and fine roots; many fine interstitial pores; 40 percent gravel and 10 percent cobbles; slightly acid (pH 6.2); clear wavy boundary.

Bw1—5 to 14 inches; dark brown (7.5YR 3/3) very gravelly loam, brown (7.5YR 4/3) dry; weak very fine and fine subangular blocky structure; soft, very friable, nonsticky and nonplastic; many very fine and fine roots and common medium roots; many fine interstitial pores; 40 percent gravel and 15 percent cobbles; moderately acid (pH 6.0); clear wavy boundary.

Bw2—14 to 30 inches; dark brown (7.5YR 3/3) extremely gravelly loam, brown (7.5YR 4/4) dry; weak fine subangular blocky structure; soft, very friable, nonsticky and nonplastic; many fine, medium, and coarse roots; many fine interstitial pores; 60 percent gravel and 10 percent cobbles; moderately acid (pH 6.0); clear wavy boundary.

Bw3—30 to 39 inches; dark brown (7.5YR 3/3) extremely gravelly loam, brown (7.5YR 5/4) dry; weak fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many medium and common coarse roots; many fine and medium interstitial pores; 60 percent gravel and 10 percent cobbles; moderately acid (pH 6.0); clear smooth boundary.

Cr—39 inches; weathered andesite.

 Typical Pedon Location

 Map unit in which located: Donegan very gravelly ashy sandy loam, 30 to 65 percent south slopes

Location in park: Red Blanket Creek Valley, in the southwestern corner of the park; 560375 meters easting and 4739013 meters northing, UTM Zone 10T, NAD 27

 Range in Characteristics

 Profile:

Depth to bedrock—20 to 40 inches

Thickness of umbric epipedon—20 to 40 inches

Content of clay—18 to 35 percent

A horizon:

Hue—5YR or 7.5YR

Value—2 or 3 moist, 3 to 5 dry

Chroma—2 or 3 moist or dry

Texture—very gravelly ashy sandy loam or gravelly ashy loam

Content of gravel—10 to 40 percent

Content of cobbles—5 to 10 percent

B horizon:

Hue—5YR or 7.5YR

Value—3 or 4 moist, 4 or 5 dry

Chroma—2 or 3 moist, 3 or 4 dry

Texture—loam or clay loam

Content of gravel—20 to 60 percent

Content of cobbles—10 to 40 percent

 

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