LOCATION APKUN AK

Established Series
MPS
11/2024

APKUN SERIES

Depth class: moderately deep to lithic bedrock
Drainage class: well drained
Parent material: gravelly loamy colluvium over gravelly residuum weathered from graywacke
Landscape: mountains
Landform: mountains slopes
Slopes: 10 to 55 percent
Mean annual precipitation: about 500 mm (19.7 in)
Mean annual air temperature: about -4 degrees C. (25 degrees F.)
Frost-free period: 70 to 90 days

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, acid, subgelic Typic Humigelepts

TYPICAL PEDON: Apkun very gravelly silt loam in a dwarf ericaceous subalpine community on a southwest facing convex, linear backslope on a slope of 26 percent at an elevation of 452m (1483 ft)

Oe--0 to 4 cm (0 to 2 in); moderately decomposed plant material; very dark brown (7.5YR 2.5/2) broken face moist, brown (7.5YR 4/2) broken face dry; many very fine, fine, and medium roots throughout; very strongly acid (pH 4.6); clear smooth boundary. (3 to 10 cm, 1 to 4 in thick)

A1--4 to 27 cm (2 to 11 in); very gravelly silt loam; black (10YR 2/1) broken face moist, dark gray (10YR 4/1) broken face dry; moderate medium subangular blocky parts to weak fine granular structure; friable, slightly hard, nonsticky, nonplastic; nonsmeary; many very fine, fine and moderately few medium roots throughout; many very fine dendritic tubular pores; 40 percent gravel; noneffervescent; extremely acid (pH 4.0); clear smooth boundary. (10 to 26 cm, 4 to 10 in thick)

A2--27 to 43 cm (11 to 17 in); extremely gravelly silt loam; very dark grayish brown (10YR 3/2) broken face moist, grayish brown (10YR 5/2) broken face dry; weak fine granular structure; friable, slightly hard, nonsticky, nonplastic; nonsmeary; moderately few very fine and fine roots throughout; few very fine and fine dendritic tubular pores; 6 percent cobbles, 55 percent gravel; noneffervescent; very strongly acid (pH 4.9); clear smooth boundary. (8 to 18 cm, 3 to 7 in thick)

C1--43 to 70 cm (17 to 28 in); extremely gravelly silt loam; dark grayish brown (10YR 4/2) moist, light brownish gray (10YR 6/2) dry; massive; friable, slightly hard, nonsticky, nonplastic; nonsmeary; few medium interstitial pores; 5 percent cobbles, 75 percent gravel; noneffervescent; strongly acid (pH 5.2); clear wavy boundary. (14 to 30 cm, 6 to 12 in thick)

2C2--70 to 90 cm (28 to 35 in); gravel; many medium, fine, and coarse interstitial pores; 5 percent cobbles, 90 percent gravel; gradual irregular boundary. (10 to 25 cm, 4 to 10 in thick)

2R--90 to 115 cm (35 to 45 in); indurated graywacke bedrock.

TYPE LOCATION: Nulato Hills - Continental Divide and Blackburn Hills Soil Survey Area, Alaska; latitude 64.5905212, longitude -160.1933790, datum WGS84, UTM north 7163357.69 and UTM east 442866.85, zone 4, datum WGS84.

RANGE IN CHARACTERISTICS:

Soil moisture regime: udic
Soil temperature regime: gelic
Mean annual soil temperature: -1 to 0 degrees C. (30 to 32 degrees F.)
Thickness of organic material: 3 to 10 cm (1 to 4 in)
Thickness of umbric epipedon: 18 to 42 cm (7 to 17 in)
Depth to lithic contact: 50 to 100 cm (20 to 39 in)

Oe horizon:
Hue: 2.5YR, 5YR, 7.5YR, 10YR
Value: 2 or 2.5 moist, 4 dry
Chroma: 1 or 2
Texture: moderately decomposed material
Organic matter: 60 to 90 percent
Reaction class: extremely acid to very strongly acid (pH 3.5 to 5)

A1 horizon:
Hue: 5YR, 7.5YR, 10YR
Value: 2 to 3 moist, 4 to 5 dry
Chroma: 1 to 3
Texture: silt, silt loam or their gravelly analogues
Sand: 5 to 35 percent
Silt: 57 to 92 percent
Clay: 3 to 8 percent
Rock fragments: 15 to 55 percent
Organic matter: 2 to 8 percent
Reaction class: extremely acid to very strongly acid (pH 3.5 to 5)

A2 horizon:
Hue: 5YR, 7.5YR, 10YR
Value: 2 to 3 moist, 4 to 5 dry
Chroma: 1 to 3
Texture: silt loam or its gravelly or cobbly analogues
Sand: 5 to 40 percent
Silt: 50 to 83 percent
Clay: 3 to 12 percent
Rock fragments: 35 to 85 percent
Gravels: 35 to 60 percent
Cobbles: 0 to 35 percent
Organic matter: 2 to 8 percent
Reaction class: extremely acid to strongly acid (pH 3.5 to 5.4)

C1 horizon:
Hue: 10YR or 2.5Y
Value: 2 to 4 moist, 4 to 6 dry
Chroma: 1 to 3
Texture: silt loam or its gravelly or cobbly analogues
Sand: 5 to 40 percent
Silt: 50 to 83 percent
Clay: 2 to 12 percent
Rock fragments: 45 to 85 percent
Gravels: 35 to 80 percent
Cobbles: 0 to 40 percent
Organic matter: 0.4 to 3 percent
Reaction class: extremely acid to strongly acid (pH 3.5 to 5.4)

2C2 horizon:
In lieu of texture: gravel, cobbles
Rock fragments: 90 to 100 percent
Gravels: 45 to 100 percent
Cobbles: 0 to 45 percent

2R horizon:
Strongly coherent to indurated graywacke bedrock

COMPETING SERIES: This is the Piksrun (AK) series.
Piksrun soils lack lithic contact within 200 cm (79 in) and lack a fragmental layer

GEOGRAPHIC SETTING:
Elevation: 250 to 700 meters (820 to 2300 feet)
Parent material: gravelly loamy colluvium over gravelly residuum weathered from graywacke
Landform: mountains slopes
Slopes: 10 to 55 percent
Mean annual precipitation: 400 to 600 mm (16 to 24 in)
Mean annual air temperature: -6 to -1 degrees C. (21 to 30 degrees F.)
Frost free period: 70 to 90 days

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Debauch, Ingik, Kikku, Myoukchuk, Niakuk, Nunanjiak, Piksrun, and Ugguktuk soils.
Debauch soils have a paralithic contact at depths between 25 to 50 cm (10 to 20 in), have an ochric epipedon, lack a fragmental layer, have a nonacid reaction class, and occur on ridges
Ingik soils have a paralithic contact at depths between 50 to 100 cm (20 to 40 in), have an ochric epipedon, lack a fragmental layer, have a nonacid reaction class, have a cryic soil temperature regime, and occur on mountainflanks, upper third
Kikku soils have aquic conditions starting between 0 to 25 cm (0 to 10 in), have a reduced matrix starting within 50 cm (20 in), lack a lithic contact within 200 cm (79 in), lack a fragmental layer, have a histic epipedon, have free carbonates below 40 cm (16 in), have a fine-loamy particle size class, have a nonacid reaction class, and occur on shoulders and mountainflanks, upper thirds
Myoukchuk soils have a paralithic contact at depths between 100 to 150 cm (40 to 60 in), have an ochric epipedon, have a fragmental particle size class, have a cryic soil temperature regime, and occur mountainflanks, lower third on valley sides and on mountainflanks, upper third
Niakuk soils have a lithic contact at depths between 100 to 150 cm (39 to 59 in), have an ochric epipedon, have a cambic horizon, have a coarse-loamy over fragmental particle size class, have a cryic soil temperature regime, and occur on similar landforms on mountainflanks, upper and center thirds
Nunanjiak soils have a paralithic contact at depths between 100 to 150 cm (40 to 60 in), lack a fragmental layer, have a folistic epipedon, have andic soil properties, have a cambic horizon, can have spodic materials, have a medial over loamy-skeletal particle size class, have a cryic soil temperature regime, and occur on head slopes and mountainflanks, center third
Piksrun soils lack lithic contact within 200 cm (79 in), lack a fragmental layer, and occur on similar landforms on mountainflanks, upper and center thirds
Ugguktuk soils have aquic conditions starting between 25 to 50 cm (10 to 20 in), have a reduced matrix starting within 50 cm (20 in), lack a lithic contact within 200 cm (79 in), lack a fragmental layer, have an ochric epipedon, have a cambic horizon, have a cryic soil temperature regime, and occur on saddles and broad ridges

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class: well drained
Saturated Hydraulic Conductivity: very high in the Oe and 2C2 horizons and moderately high in the A1, A2, C1 horizons
Permeability: rapid to very rapid in the Oe horizon, moderate to moderately rapid in the A1, A2, and C1 horizons, and very rapid in the 2C2 horizon
Runoff: high

USE AND VEGETATION:
Use: wildlife habitat, recreation, and subsistence
Native vegetation: dwarf birch, marsh Labrador tea, black crowberry, lingonberry, red fescue, smallawned sedge, alpine sweetgrass, arctic willow, Flavocetraria cucullate, beauverd spirea, reindeer lichen, greygreen reindeer lichen, lichen, moss, polytrichum moss, racomitrium moss

DISTRIBUTION AND EXTENT: MLRA 240, Nulato Hills-Southern Seward Peninsula Highlands. The series is of moderate extent.

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Wasilla, Alaska

SERIES ESTABLISHED: Nulato Hills - Continental Divide and Blackburn Hills Soil Survey, Alaska, 2024.

REMARKS: Diagnostic features and horizons recognized in this profile include:

Particle-size control section: 29 to 90 cm (11 to 35 in)

Umbric epipedon: 4 to 43 cm (2 to 17 in) (A1 and A2 horizons)

Lithologic discontinuity: 70 to 115 cm (28 to 45 in) (2C2 and 2R horizons)

Lithic contact: 90 to 115 cm (35 to 45 in) (2R horizon)

ADDITIONAL DATA:

User pedon ID: 2021AK180747

National Cooperative Soil Survey
U.S.A.