LOCATION YUNQUE PREstablished Series
TAXONOMIC CLASS: Very-fine, kaolinitic, isothermic Humic Hapludox
TYPICAL PEDON: Yunque silty clay - forest. (Colors are for moist conditions.)
Oi-- 0 to 2 inches; many fine and medium roots, which form a root mat; abrupt smooth boundary.
A-- 2 to 7 inches; dark yellowish brown (10YR 4/6) clay; weak fine subangular blocky structure; firm; sticky, plastic; many fine and medium roots; common large worm casts filled with very dark brown (10YR 2/2) organic matter; extremely acid; clear smooth boundary. (4 to 10 inches thick.)
Bto1-- 7 to 17 inches; yellowish brown (10YR 5/8) clay; weak coarse subangular blocky structure parting to weak medium subangular blocky; firm; sticky, very plastic; common fine and medium roots; common fine interstitial and tubular pores; few faint coatings on vertical and horizontal faces of peds; common large worm casts filled with very dark brown (10YR 2/2) organic material; common distinct red (2.5YR 4/6) pore linings along root channels; few fine distinct strong brown (7.5YR 5/6) and few medium distinct yellowish brown (10YR 5/6) masses of iron accumulation; extremely acid; clear smooth boundary.
Bto2-- 17 to 30 inches; yellowish brown (10YR 5/8) clay; weak medium prismatic structure parting to weak medium subangular blocky; firm; sticky, very plastic; few fine and medium interstitial and tubular pores; common distinct coatings on vertical and horizontal faces of peds; common large worm casts filled with very dark brown (10YR 2/2) organic material; common coarse prominent strong brown (7.5YR 5/6) and few fine distinct yellow (10YR 7/6) masses of iron accumulation; few fine distinct light gray (10YR 7/1) areas of iron depletions; extremely acid; abrupt smooth boundary. (Combined thickness of the Bt horizons ranges from 18 to 35 inches)
Bw1-- 30 to 33 inches; yellowish red (5YR 5/8) silty clay; weak medium platy structure; friable; sticky, plastic; weakly cemented; many coarse prominent strong brown (7.5YR 5/8) masses of iron accumulation; few fine distinct light gray (10YR 7/1) areas of iron depletions; extremely acid; abrupt smooth boundary.
Bw2-- 33 to 51 inches; strong brown (7.5YR 5/8) silty clay loam; massive; friable; sticky, plastic; fracture planes are coated by manganese; common coarse prominent yellowish red (5YR 5/8) masses of iron accumulation; few fine distinct light gray (10YR 7/1) areas of iron depletions; extremely acid; gradual wavy boundary.
Bw3-- 51 to 62 inches; about 60 percent yellowish red (5YR 5/8), about 30 percent strong brown (7.5YR 5/8), and about 10 percent very pale brown (10YR 8/2) silty clay loam; massive; friable, sticky, plastic; fracture planes are coated by manganese; the areas in colors of yellowish red and strong brown are iron accumulations and the areas in white are iron depletions; extremely acid. (Combined thickness of the Bw horizons ranges from 16 to 45 inches.)
TYPE LOCATION: Caribbean National Forest, Aguada Municipio, Noreste SCD, Puerto Rico. Approximately 1.6 miles northwest of Mt. Britton and about 3,000 feet east-southeast of flood monitoring station (estacion fluviometrica) at the termination of P.R. Road 911. Down west fork trail past the creeks and after the trail turns south and levels out on the contour, then upslope. El Yunque topographic quadrangle; lat. 18 degrees 18 minutes 44 seconds N., long. 65 degrees 48 minutes 54 seconds W. PRD 1940.
RANGE IN CHARACTERISTICS: Solum thickness is more than 60 inches. Reaction ranges from extremely acid to strongly acid throughout the profile. Rock fragments range from 0 to 40 percent throughout. Cobbles, stones, and boulders cover from 0 to 60 percent of the soil surface.
The Oi horizon, where present, is composed of roots forming a mat.
The A horizon has hue of 7.5YR or 10YR, value of 2 to 5, and chroma of 1 to 6. Texture is silty clay loam, silty clay, or clay.
The Bto horizon has hue of 7.5YR to 2.5Y, value of 4 or 5, and chroma of 4 to 8. Redoximorphic features in shades of yellow, brown, red, and gray range from few to many. Texture is clay.
The Bo horizon, where present, has colors and texture similar to the Bt horizon.
The Bw horizon has hue of 2.5YR to 7.5YR, value of 4 to 6, and chroma of 4 to 8. Redoximorphic features in shades of yellow, brown, red, and gray range from few to many. In some pedons, the lower part does not have a dominant matrix color and is multicolored in shades of yellow, red, brown, gray, and white. Texture is silty clay loam, silty clay, clay loam, or clay.
The BC horizon, where present, has hue of 2.5YR to 7.5YR, value of 4 to 6, and chroma of 6 or 8; or there is no dominant matrix color and it is multicolored in shades of yellow, red, brown, gray, and white. Redoximorphic features in shades of yellow, brown, red, and gray range from few to many. Texture is silty clay loam, silty clay, clay loam, or clay.
The C horizon, where present, has colors and textures similar to the BC horizon.
COMPETING SERIES: There are no other series in the same family.
GEOGRAPHIC SETTING: Yunque soils are on ridgetops and upper sideslopes of strongly dissected uplands. They formed in material that weathered from volcanic sandstone. The climate is humid tropical. Slopes range from 10 to 90 percent. The average annual temperature ranges from 66 to 72 degrees F., and the average annual precipitation ranges from 150 to 220 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These include the Ciales, Guayabota, Los Guineos, Picacho, and Utuado series. The poorly drained Ciales soils are on similar positions, have fine-loamy control sections, and do not have Oxic horizons. The poorly drained Guayabota soils are on lower sideslope positions and are shallow to bedrock. The somewhat poorly drained Los Guineos soils occur are on lower sideslope positions and have mixed mineralogy. The somewhat poorly drained Picacho soils are on upper sideslopes of lower positions and have fine-loamy control sections. The well drained Utuado soils are on sideslopes of lower positions and have fine-loamy control sections.
DRAINAGE AND PERMEABILITY: Moderately well drained; slow permeability.
USE AND VEGETATION: All areas of Yunque soils are used for recreation, research, wildlife habitat, and watershed protection. Vegetation consists of hardwood forest composed of native and introduced species and tree ferns.
DISTRIBUTION AND EXTENT: Tropical rain forests of Puerto Rico. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Raleigh, North Carolina.
SERIES ESTABLISHED: Noreste SCD, Puerto Rico. 1969.
REMARKS: Diagnostic horizons and features recognized in this pedon:
Ochric epipedon - the zone from 0 to 8 inches (A horizon).
Oxic horizon - the zone from 8 to 28 inches (Bt1 and Bt2 horizons).
Cambic horizon - the zone from 28 to 60 inches (Bw1, Bw2, and Bw3 horizons).
ADDITIONAL DATA: Characterization data - Caribbean National Forest, Puerto Rico. Pedon no. 97P0303 and Soil Survey No. S87PR-003-002. Sample by NSSL, Lincoln, NE. April 1987.