LOCATION TOP                     OR

Established Series
Rev. ED/AON/RWL
04/2019

TOP SERIES

The Top series consists of deep and very deep, well drained soils that formed in colluvium derived from basalt with an influence of loess in the upper part. Top soils are on mountains and have slopes of 2 to 75 percent. The mean annual precipitation is about 20 inches, and the mean annual temperature is about 42 degrees F.

TAXONOMIC CLASS: Fine, smectitic, frigid Vertic Argixerolls

TYPICAL PEDON: Top ashy clay loam - woodland on a 27 percent northeast-facing slope at an elevation of 3,500 feet. (When described on September 4, 2003, the soil was dry throughout. The colors are for moist soils unless otherwise noted.)

Oi--0 to 1/2 inch; slightly decomposed needles, twigs, grass.

Oe--1/2 to 1 inch; moderately decomposed needles and grass.

A1--1 to 6 inches; very dark brown (10YR 2/2) ashy clay loam, dark grayish brown (10YR 4/2) dry; weak medium subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; few fine and common very fine roots; few fine and many very fine tubular pores; neutral (pH 7.0); abrupt smooth boundary.

A2--6 to 13 inches; very dark grayish brown (10YR 3/2) ashy clay loam, dark grayish brown (10YR 4/2) dry; moderate medium subangular blocky structure; hard, firm, moderately sticky and very plastic; few medium and fine and common very fine roots; few medium, fine, and very fine tubular pores; common faint clay films on ped faces; neutral (pH 7.0); clear smooth boundary (Combined thickness of the A horizon is 7 to 16 inches.)

2Bt1--13 to 22 inches; dark brown (10YR 3/3) clay, brown (10YR 5/3) dry; moderate medium and coarse subangular blocky structure; hard, firm, very sticky and very plastic; few coarse, medium, and fine and common very fine roots; few coarse, medium, and fine and common very fine tubular pores; many distinct clay films on ped faces and in pores; neutral (pH 7.1); gradual wavy boundary. (4 to 20 inches thick)

2Bt2--22 to 34 inches; brown (10YR 4/3) clay, pale brown (10YR 6/3) dry; moderate medium and coarse subangular blocky structure; very hard, very firm, very sticky and very plastic; few medium and fine and common very fine roots; few me3dium, fine, and very fine tubular pores; common distinct clay films on ped faces and in pores; neutral (pH 7.1); clear wavy boundary. (6 to 12 inches thick)

2Bt3--34 to 42 inches; very dark grayish brown (10YR 3/2) clay, grayish brown (10YR 5/2) dry; moderate fine and medium subangular blocky structure; hard, firm, very sticky and very plastic; common very fine roots; common very fine tubular pores; many faint clay films on ped faces neutral (pH 7.2); clear wavy boundary. (5 to 15 inches thick)

2Bt4--42 to 61 inches; brown (10YR 4/3) clay, brown (10YR 5/3) dry; moderate medium subangular blocky structure; hard, firm, very sticky and very plastic; few very fine roots; few very fine tubular pores; common faint6 clay films on ped faces; neutral (pH 7.3).

TYPE LOCATION: Grant County, Oregon; located about 5 miles north of the town of Monument on the west side of the Top Road; 1,100 feet south and 1,300 feet east of the northwest corner of section 11, T.8S., R.27E. (Latitude 44 degrees, 53 minutes, and 37.03 seconds North and Longitude 119 degrees, 28 minutes, and 01.85 seconds West.)

RANGE IN CHARACTERISTICS: The mean annual soil temperature is 42 to 47 degrees F, and the mean summer temperature is 59 to 65 degrees F. Top soils are dry between depths of 4 and 12 inches for 45 to 60 consecutive days during the four months following the summer solstice. Depth to lithic contact is 40 to over 60 inches. The mollic epipedon is 20 to 35 inches thick. Stones on the surface range from 0 to 3 percent of surface covered. The base saturation is less than 75 percent in some part of the upper 30 inches of the profile.

The A horizon has hue of 10YR or 7.5YR, value of 4 or 5 dry, 2 or 3 moist and chroma of 2 in the upper part and is 2 or 3 in the lower part of the horizon. It has 15 to 30 percent glass and acid oxalate extractable aluminum plus one-half the iron is 0.2 to 0.5 percent. It has 27 to 35 percent clay.

The 2Bt horizon has hue of 5YR to 10YR, value of 2 or 3 moist and 4 or 5 dry to depth of 20 inches or more and may range to 4 moist and 6 dry below a depth of 20 inches. The chroma is 2 or 3 to a depth of 20 inches or more and may range to 4 below a depth of 20 inches. It is silty clay loam, silty clay or clay and has 35 to 45 percent clay. It has 0 to 25 percent gravel, 0 to 15 percent cobble, and 0 to 5 percent stones.

Some pedons have a 2Bct horizon. When present, it has weak or moderate medium prismatic and moderate or strong medium or fine blocky or subangular blocky structure.

Some pedons have a 2C horizon. When present, it is loam, silt loam, clay loam, or silty clay and has 0 to 25 percent gravel and 0 to 10 percent cobbles and stones.

COMPETING SERIES: These are the Cleymor, Laplatta, Mondey, Shar, Streek and Wickiser series. All of these soils lack an O horizon except for the Cleymor soil. The Cleymore soils are slightly acid or moderately acid throughout and have slickensides. The LaPlatta and Mondey soils have secondary carbonates in the lower part of their profiles and lack vitrandic features. Shar soils are moderately deep to basalt bedrock. Streek soils are moderately well drained and have slickensides. Wickiser soils have secondary carbonates at a depth of 30 to 44 inches and are slightly or moderately alkaline throughout.

GEOGRAPHIC SETTING: Top soils are on mountains at elevations ranging from 3,000 to 5,400 feet. Slopes are 2 to 75 percent. The soil formed in colluvium derived from basalt with an influence of loess in the upper part. The climate is subhumid and has mean annual precipitation of 17 to 30 inches. Mean annual air temperature is 40 to 45 degrees F; mean July temperature is about 63 degrees F; and mean January temperature is about 29 degrees F. The frost-free period is 30 to 100 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Anatone, Helter, Kahler and McGarr soils. Anatone soils are less than 20 inches deep to bedrock. Helter soils are ashy over loamy. Kahler soils are fine-loamy. McGarr soils are 20 to 40 inches deep to bedrock.

DRAINAGE AND PERMEABILITY: Well drained; moderately slow or slow permeability.

USE AND VEGETATION: These soils are used mainly for timber production and cropland. Most areas with slopes of less than 15 percent have been cleared and are used for production for dryland grain and hay. Native vegetation is ponderosa pine, Douglas fir, white fir, pinegrass and elksedge. This series is in what is called the Douglas-fir forest plant community.

DISTRIBUTION AND EXTENT: East-central Oregon; MLRA 10. The series is of moderate extent.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon

SERIES ESTABLISHED: Grant County, Oregon, 1975.

REMARKS: Diagnostic horizons and features recognized in this pedon:

Mollic epipedon (pachic) - from 1 to 22 inches
Argillic horizon - from 15 to 61 inches
Vertic - calculated linear extensibility is greater than 6 cm within the upper 100 cm.
Ultic - based on being in the same plant community as the Larabee series.
Vitrandic subgroup- from 1 to 13 inches; based on data from the similar Hankins series.
Xeric moisture regime; dry 45 to 60 days based on same plant community as the Larabee series.

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National Cooperative Soil Survey
U.S.A.