LOCATION ST. MARTIN WAEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Aquic Hapludolls
TYPICAL PEDON: St. Martin gravelly silty clay loam-forested. (Colors are for moist soil unless otherwise noted.)
0i--2 inches to 0; needles, leaves and twigs.
A--0 to 4 inches; black (10YR 2/1) gravelly silty clay loam, dark grayish brown (10YR 4/2) dry; moderate medium granular structure; soft, friable, slightly sticky and plastic; many very fine, many fine, and few medium roots; common fine irregular pores; 20 percent pebbles; neutral (pH 6.7); clear smooth boundary. (4 to 10 inches thick)
BAt--4 to 11 inches; very dark grayish brown (10YR 3/2) silty clay loam, grayish brown (10YR 5/2) dry; moderate fine subangular blocky structure; slightly hard, friable, sticky and plastic; common very fine, common fine, and common medium roots; many very fine irregular pores; 20 percent soft saprolitic andesite; slightly acid (pH 6.4); clear smooth boundary. (6 to 7 inches thick)
Bt1--11 to 25 inches; light olive brown (2.5Y 5/4) clay, light yellowish brown (10YR 6/4) dry; few fine faint dark grayish brown (2.5Y 4/2) moist, light olive brown (2.5Y 5/4) dry mottles; moderate fine and medium subangular blocky structure; hard, friable, sticky and plastic; common fine and medium roots; common very fine irregular and fine tubular pores; 35 percent soft saprolitic andesite; slightly acid (pH 6.2); gradual smooth boundary. (14 to 17 inches thick)
Bt2--25 to 60 inches; light yellowish brown (2.5Y 6/4) clay, light yellowish brown (10Y 6/4) dry; few fine faint dark grayish brown (2.5Y 4/2) moist, light olive brown (2.5Y 5/4) dry mottles; moderate medium subangular blocky structure; hard, friable, sticky and plastic; few fine roots; common fine irregular and common fine tubular pores; 45 percent soft saprolitic andesite; moderately acid (pH 5.9).
TYPE LOCATION: Skamania County, Washington; about 1/4 mile northwest of Collins; 2,500 feet south and 900 feet west of the northeast corner of sec. 36, T. 3N., R. 8 E.
RANGE IN CHARACTERISTICS: Mean annual soil temperature is 47 to 51 degrees F. The mollic epipedon is 10 to 17 inches thick. Hard rock fragments in the control section average 0 to 15 percent and soft weathered rock fragments average 10 to 35 percent. The clay content in the control section is 40 to 60 percent.
The A horizon has hue of 10YR or 2.5Y, value of 2 or 3 moist, 4 or 5 dry, and chroma of 1 or 2 moist. It contains 15 to 25 percent pebbles. Reaction is slightly acid or neutral.
The BAt horizon has hue of 10YR or 2.5Y, chroma of 2 or 3 dry. It is clay, silty clay loam, or heavy clay loam. Pebbles range from 0 to 15 percent and cobbles from 0 to 5 percent. Reaction is moderately acid to slightly acid.
The Bt horizon has value of 4 through 6 moist and 5 or 6 dry, and chroma of 3 or 4 moist or dry. Soft rock fragments average from 15 to 45 percent. Reaction is moderately acid to slightly acid.
COMPETING SERIES: These are the Collinwood, Guckeen, and Lakeport series. These soils lack soft weathered rock fragments. In addition, Collinwood and Guckeen soils have free lime at 24 to 40 inches.
GEOGRAPHIC SETTING: St. Martin soils are on backslopes and toe slopes of mountains at elevations of 300 to 2,000 feet. They are subject to mass movement. Slopes are 2 to 65 percent. These soils formed in colluvium from andesite. Summers are warm and dry. Winters are cool and wet with intermittent snow cover. Mean annual precipitation is 45 to 65 inches. Mean July temperature is 65 degrees F. Mean January temperature is 26 degrees F, mean annual temperature is about 47 degrees F. Frost-free season is 100 to 150 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the McElroy, Stevenson and Timberhead soils. McElroy soils are medial-skeletal. Stevenson soils are fine-loamy. Timberhead soils are medial.
DRAINAGE AND PERMEABILITY: Moderately well drained; slow to rapid runoff; slow permeability and a perched high water table at 1 to 2 feet from December to April.
USE AND VEGETATION: Used for timber production, some homesites, wildlife habitat and grazable woodland. Vegetation is Douglas-fir, red alder, grand fir, and western redcedar, with an understory of vine maple, bigleaf maple, common snowberry, salal, dwarf rose, Oregongrape, trailing blackberry, creambush oceanspray, western hazel, honeysuckle, inside-out flower, deerfoot vanillaleaf, Oregon fairybells, western swordfern, false-Solomons-seal, and American trailplant.
DISTRIBUTION AND EXTENT: Southeastern Skamania County, Washington. The series is moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Skamania County, Washington, 1947.
REMARKS: Diagnostic horizons and features recognized in this pedon are a mollic epipedon from the mineral surface to 11 inches, an argillic horizon from 11 to 60 inches, and grayish mottles from 11 to 60 inches.