LOCATION ISLAND AK

Established Series
Rev. RBH-SR
8/95

ISLAND SERIES

The Island series consists of deep, well drained soils formed in ash influenced loess overlying marine sediments on hillslopes. Slopes range from 0 to 30 percent. Mean annual temperature is about 35 degrees F., and the mean annual precipitation is about 23 inches.

TAXONOMIC CLASS: Medial, mixed Humic Vitricryands

TYPICAL PEDON: Island silt loam - native grass (All colors are for moist soil)

Oi--2 1/2 inches to 0; very dark brown (10YR 2/2) organic mat with silt loam admixture; thin layer of fine sand size volcanic ash at base; abrupt smooth boundary. (1/2 to 4 inches thick)

C--Recent ash; brown (10YR 4/3) silt loam; weak fine granular structure; very friable; many roots; abrupt broken boundary. (0 to 2 inches thick)

Ab1--1 1/2 to 6 inches; very dark brown (10YR 2/2) silt loam; weak very thin platy structure; smeary; many roots; few small fragments of charcoal; clear wavy boundary. (4 to 8 inches thick)

Ab2--6 to 19 1/2 inches; very dark brown (10YR 2/2) silt loam with streaks and patches of brown (10YR 4/3); weak very thin platy structure; smeary; common roots; few small charcoal fragments; patches of brown (10YR 4/3) ash at 16 inches and fine streaks throughout horizon; abrupt wavy boundary. (6 to 14 inches thick)

Bb--19 1/2 to 27 inches; brown (10YR 4/3) silt loam with patches of very dark brown (10YR 3/2); weak very thin platy structure; smeary; few roots; many fine pores; abrupt wavy boundary. (6 to 15 inches thick)

A'b--27 to 30 inches; very dark brown (10YR 3/2) silt loam with streaks of brown (10YR 4/3), dark yellowish brown (10YR 4/4), and olive brown (2.5Y 4/4); weak very thin platy structure; smeary; few roots; many fine vesicles and pores; contains streaks similar to horizon below; abrupt broken boundary. (0 to 3 inches thick)

B'b--30 to 37 inches; brown (10YR 4/3) silt loam; very weak, very thin platy structure; smeary; few roots; many fine vesicles and pores; abrupt smooth boundary. (0 to 10 inches thick)

2C1--37 to 42 inches; olive gray (5Y 5/2) silt loam with common large faint mottles of olive (2.5Y 5/4); weak thin platy structure; very friable; few dead roots; many vesicles and pores; this horizon derived from soft sediments rather than eolian material; abrupt smooth boundary. (0 to 12 inches thick) 3C2--42 to 48 inches +; olive gray (5Y 5/2) fine sand with common medium distinct mottles of dark yellowish brown (10YR 4/4); weak fine platy structure; loose; strong brown (10YR 5/6) stains along pores.

TYPE LOCATION: Homer-Ninilchik Area, Alaska. SW 1/4, SE 1/4 of Section 3, T.2 S., R.14 W. About 2 miles south of Ninilchik.

RANGE IN CHARACTERISTICS: Depth to the stratified sandy and silty substratum ranges from 30 to 60 inches. Layers of pebbles may occur in the substratum or, in places, below 18 inches. The soil surface is commonly irregular, with earth hummocks about 18 inches high and a few feet in diameter. Profile characteristics are essentially the same in hummocks and in low areas between them. Texture of the surface 6 inches is commonly very fine sandy loam in coastal areas. Thin lenses of white sand size volcanic ash may occur in the upper 2 feet of the profile. Total thickness of the A horizon is normally between 16 and 33 inches. The color is typically 10YR hue, but it ranges to 7.5YR. Values range from 2 to 3 and chromas from 2 to 3. The B horizon is typically brown or dark brown in hues of 10YR and 7.5YR, values of 3 to 4, and chromas of 3 to 4.

COMPETING SERIES: These include the Kachemak, Kodiak, and Sharatin series. The Kachemak soils are darker and redder and have incipient albic horizons. The Kachemak soils are also shallower over underlying sediments. The Kodiak and Sharatin soils have about 11 inches of recent volcanic ash overburden, have redder buried sola, and are shallower over underlying materials.

GEOGRAPHIC SETTING: The Island soils occupy natural grass openings in forested uplands. They occur in narrow hilly bands bordering the sea cliffs and in nearly level slight depressions farther inland. Slope gradients are dominantly less than 3 percent, but range to 30 percent in the hilly coastal areas. The Island soils have developed in a mixture of volcanic ash and loess overlying layered silty, sandy, and clayey marine sediments. They are formed under a maritime climate with cool summers and long moderately cold winters. Average annual precipitation is between 18 and 28 inches and average annual air temperature is between 33 and 36 degrees F.

GEOGRAPHICALLY ASSOCIATED SOILS: These include the Cohoe, Mutnala, Soldatna, Salamatof, and Nikolai soils. The Cohoe, Mutnala and Soldatna soils have a thin gray E horizon and a reddish B horizon. The Salamatof and Nikolai soils are peat soils.

DRAINAGE AND PERMEABILITY: Well drained. Surface runoff is medium to slow depending on slope. Permeability is moderate.

USE AND VEGETATION: The native vegetation consists of grasses and associated low growing plants. Sitka or white spruce is invading most areas. A few areas are used for gardens, potatoes, hay, and small grain.

DISTRIBUTION AND EXTENT: Southcentral Alaska. The series is of small extent with about 3000 acres mapped.

MLRA OFFICE RESPONSIBLE: Anchorage, Alaska

SERIES ESTABLISHED: Kenai-Kasilof Area, Alaska. 1960.

REMARKS: The present concept of the Island series is poorly defined and the range in characteristics encompasses more than one family. More data is needed to adequately define the concept or the series should beinactiv ted (jpm 1/87).

National Cooperative Soil Survey
U.S.A.

Contact: Mike Gracz Kenai Watershed Forum  PO Box 15301 Fritz Creek, AK  99603 907-235-2218

04 May 2007 10:20