LOCATION HOCONUCO PREstablished Series
TAXONOMIC CLASS: Fine, magnesic, isothermic Typic Argiudolls
TYPICAL PEDON: Hoconuco mucky peat--forestland (Colors are for moist soil).
Oi--0 to 3 inches; very dark brown (7.5YR 2.5/2) mucky peat, about 85 percent fiber crushed and rubbed; massive, very friable; nonsticky, nonplastic; many very fine and fine roots, few medium and coarse roots, about 10 percent, by volume, cobbles and about 2 percent, by volume, stones; strongly acid; clear wavy boundary. (2 to 5 inches thick)
A--3 to 7 inches; dark brown (7.5YR 3/2) gravelly clay loam; strong very fine and fine granular structure; slightly hard, firm; slightly sticky and moderately plastic; many very fine and fine roots, few medium and coarse roots; many very fine and fine irregular pores; about 28 percent, by volume, angular pebbles and about 2 percent, by volume, angular cobbles; slightly acid; abrupt wavy boundary. (4 to 6 inches thick)
Bt--7 to 14 inches; dark reddish brown (5YR 3/3) paragravelly clay; moderate very fine and fine subangular blocky structure; hard, firm; slightly sticky and moderately plastic; common very fine and fine roots; common very fine and fine irregular pores, few very fine and fine interstitial pores; common distinct clay films on faces of peds and coarse fragments; about 12 percent, by volume, angular parapebbles, about 6 percent, by volume, angular paracobbles, and about 2 percent, by volume, angular stones; neutral; abrupt irregular boundary. (5 to 13 inches thick)
Cr--14 to 37 inches; hard fractured and moderately weathered serpentinite bedrock. (5 to 25 inches thick)
R--37+ inches; hard fractured consolidated serpentinite bedrock.
TYPE LOCATION: San German, Puerto Rico. Approximately 0.6 mile northwest from the Maricao State Forest headquarters (Campamento Buena Vista); about 200 feet east from El Alto del Descanso Peak on forestland; USGS Maricao topographic quadrangle (1960); lat. 18 degrees 08 minutes 50.4 seconds N. and long. 66 degrees 59 minutes 46.5 seconds W.
RANGE IN CHARACTERISTICS: Depth to fractured and moderately weathered serpentinite rock ranges from 11 to 25 inches. Depth to hard fractured consolidated volcanic bedrock ranges from 20 to 37 inches. Reaction is strongly acid in the Oi horizon and ranges from slightly acid to neutral in the A and Bt horizons. The combined total of rock fragments in the control section is less than 35 percent, by volume.
The Oi horizon has hue of 7.5YR or 10YR, value of 2 to 3, and chroma of 1 or 2. Content of rock fragments range from 2 to less than 15 percent, by volume. Texture is mucky peat.
The A horizon has hue of 7.5YR or 10YR, value of 2 to 3, and chroma of 1 or 2. Content of rock fragments range from 2 to 30 percent, by volume. Texture is clay loam or clay in the fine-earth fraction.
The Bt horizon has hue of 5YR to 10YR, value of 3 or 4, and chroma of 2 to 3. Content of rock fragments range from 2 to 20 percent, by volume. Texture is clay in the fine-earth fraction.
The Cr layer is composed of hard fractured and moderately weathered serpentinite. It can be excavated with difficulty with hand tools, and is rippable by mechanized equipment.
The R layer is composed of hard fractured consolidated serpentinite bedrock.
COMPETING SERIES: These are no known series in the same family.
GEOGRAPHIC SETTING: The Hoconuco soils are on side slopes and summits of mountains on the Humid Mountains and Valleys MLRA. Slopes range from 5 to 90 percent. They formed in residuum that weathered from serpentinite. The climate is humid tropical. The average annual precipitation ranges from 68 to 134 inches and the average annual temperature ranges from 62 to 68 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cerro Gordo (T), El Descanso (T) and Indiera (T) series. Cerro Gordo (T) and Indiera (T) soils have an oxic horizon and have finer textured profiles. El Descanso (T) soils are shallow to bedrock and are coarser textured.
DRAINAGE AND PERMEABILITY: Well drained; slow permeability.
USE AND VEGETATION: Most areas of Hoconuco soils are in forestland and are used for wildlife habitat. The vegetation consists of native and introduced shrubs and trees.
DISTRIBUTION AND EXTENT: Side slopes and summits of serpentinite mountains of southern Puerto Rico. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Raleigh, North Carolina.
SERIES ESTABLISHED: San German Municipality, Puerto Rico; 2007. The name is from Hoconuco ward where it was originally recognized.
REMARKS: Diagnostic horizons and features recognized in this pedon:
Mollic epipedon - the zone from 0 to 7 inches (Oi and A horizon).
Argillic horizon - the zone from 7 to 14 inches (Bt horizon).
Paralithic contact - the zone from 14 to 37 inches (Cr layer).
Lithic contact - the contact at 37 inches (R layer).
Hoconuco soils were formerly included in the Serpentinite outcrop miscellaneous land type. A soil moisture and soil temperature study performed in the San German Area Soil Survey Update recognized the Perudic Soil Moisture Regime in Puerto Rico, recognized the isothermic soil temperature regime at 750 meters above sea level (in Perudic Soil Moisture Regime) and 900 meters above sea level (in Udic Soil Moisture Regime) and adjusted the isothermic-isohyperthermic line.
Hoconuco soils formed in the Serpentinite Formation (Ks).
Hoconuco soils are in MLRA 270.