LOCATION CHELBACHEB PW+ PBEstablished Series
TAXONOMIC CLASS: Euic, isohyperthermic Lithic Udifolists
TYPICAL PEDON: Chelbacheb highly decomposed plant material on a south-by-southwest-facing, linear convex, 150 percent slope under a limestone-forest plant community at an elevation of 61 meters (200 feet.) (Colors are for moist soil unless otherwise noted. All textures are apparent field textures. When described on April 20, 2003, the soil was moist throughout.) The surface is covered by about 50 percent gravel, 10 percent cobbles, and 2 percent stones. The fragments are coralline limestone The average distance between the stones is 5 meters (16 feet.) About 3 percent is bare ground.
Oa--0 to 20 centimeters (0 to 8 inches); reddish black (10R 2/1); highly decomposed plant material, about 15 percent fiber rubbed; structureless massive structure; loose, non sticky and non plastic; many very fine and fine roots throughout; many very fine and fine dendritic tubular pores; 50 percent gravel, 10 percent cobbles, and 2 percent stones; moderately acid (pH 5.6, 1:1 water); Broken irregular. (10 to 40 centimeters thick) Lab sample # 03N0704
2R--20 centimeters (8 inches); fractured at intervals of 10 cm (4 in) or more apart of coralline limestone with crystal structure apparent in freshly exposed face, white (10YR 8/1) interior; indurated; strongly alkaline (pH 8.6, 1:1 water)
TYPE LOCATION: Koror Municipality and Ulebsechel Island, Republic of Palau; from the base of the lagoon proceed east about 34 meters (112 feet) upslope; WGS 84 UTM 443371 meters E, 809283 meters N, zone 53; Lat 7 19' 16.09" N and Long 134 29' 13" E.
RANGE IN CHARACTERISTICS:
Soil moisture:
Soil moisture regime subclass: typic
Soil moisture regime class: perudic
Seasonal pattern: Precipitation falls mostly even during the year with the exception of February to April being the driest months averaging 179 to 229 millimeters (7 to 9 inches) per month.
Mean annual soil temperature: 27 C (81 F)
Depth to lithic contact: 10 to 30 centimeters (4 to 12 inches)
Depth to diagnostic feature: lithic contact: 10 to 40 centimeters (4 to 16 inches)
lithologic discontinuity: 10 to 40 centimeters (4 to 16 inches)
Thickness of diagnostic feature:
fibric, sapric, or hemic soil materials: 10 to 40 centimeters (4 to 16 inches)
folistic epipedon: 10 to 40 centimeters (4 to 16 inches)
Linear extensibility: 0 to 1 percent, weighted average RV is 0.5 percent
Surface Fragments: Rock fragments are strongly cemented angular coralline limestone; 35 to 90 percent total rock fragments; 10 to 50 percent gravel; 10 to 80 percent cobbles; 5 to 15 percent stones; 0 to 10 percent boulders. The average distance between the stones is about 5 meters (16 feet) and boulders are about 15 meters (49 feet.)
Oi, Oe, and Oa horizon(s):
Hue: 10R, 2.5YR, 5YR, 7.5YR, or 10YR
Value: 2 to 3 moist
Chroma: 1 moist
In lieu texture: slightly decomposed plant material, moderately decomposed plant material and is extremely or very cobbly
Fragment size and content: Rock fragments are hard angular coralline limestone; are strongly cemented angular coralline limestone; 35 to 90 percent total rock fragments; 10 to 50 percent gravel; 10 to 80 percent cobbles; 5 to 15 percent stones; 0 to 10 percent boulders.
Calcium carbonate equivalent: 0 to 5 percent
Reaction: pH 5.1 to 7.3
Cation exchange capacity: 135 to 180 meq/100grams
Organic matter content: 16 to 30 percent
COMPETING SERIES: There are no competing series at this time.
GEOGRAPHIC SETTING: Chelbacheb soils are on karrens of; solution, wave-cut, and raised coralline platforms; karrens on cones, valleys, and towers of karst islands. These soils formed in organic material over coralline limestone, and probably additions of volcanic ash and tropospheric dust; bedrock is commonly part of the Peleliu limestone formation and to a lesser extent the Palau limestone formations (Recent to Pleistocene.) They are dominant under Limestone Forest plant communities. Slope is 50 to 150 percent. On the extremely steep slopes of, tower karst islands these soils are below free faces and base slopes in pockets of jagged limestone. Elevation is 1 to 214 meters (3.3 feet to 702 feet.) The climate is tropical and moist. Because of the strong marine influence, the diurnal and annual range of temperature is limited. Rainfall averages about 3685 millimeters (145 inches) per year and ranges from approximately 2900 to 4400 mm (114 to 173 in.) The seasonal wet (May to November) and dry seasons (December to April) with the driest months (February, March, and April) averaging 178 to 229 milliliters (7 to 9 inches) per month. Rainfall is derived from convective uplift, which results in short duration rainstorms of high intensity. Rainfall is irregularly distributed geographically. These soils lie within the latitudinal zone that receives more solar radiation than it re-radiates back to space. This imbalance maintains the atmospheric temperatures in a quasi-steady state. The mean daily temperature throughout the year averages 27 C (81 F) with a mean diurnal range of about 4 C (7 F.) Relative humidity averages about 90 percent at night and 75 to 80 percent during the day.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Majuro, Ngedebus, Ngerungor, Odesangel, and Peleliu soils. Ngedebus and Majuro soils are very deep somewhat excessively drained soils generally adjacent to coastal beaches. These soils formed in water and wind-deposited coral sand. Ngedebus soils are normally found on lagoon sides of island whereas Majuro soils are located on ocean sides of islands have greater than 35 percent rock fragments in the subsoil. These are transitional soils between the upland soils and marshes. Odesangel soils formed in depressional areas that retain fresh or brackish water. The organic layer is moderately deep with depths typically ranging from 0.5 to 1.0 m (1.6 to 3.3 feet), which is shallower than the Ngerungor series. This soil may contain as much as 80 percent organic matter and has neutral soil chemistry (pH 6.6 to 7.3). Coral sand underlies the organic layer. Ngerungor soils have hemic organic deposits greater than 125 centimeters (49 inches), occur in depressional areas, and are saturated throughout the profile. Peleliu soils are clayey and have greater than 35 percent rock fragments in the subsoil.
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained. Runoff is medium on the gentle slopes and high on the steeper slopes. Saturated hydraulic conductivity is very high in the organic material and moderately low in the bedrock material.
USE AND VEGETATION: These soils are in broadleaf evergreen limestone-forests, plant communities and are used for watershed, fuelwood, recreation, phosphate mining, and limited amounts of timber harvesting for village use. A few areas have been cleared and developed for small garden plots. The potential to develop agricultural in the limestone forest areas is limited. Many of the sites supporting Limestone Forest plant communities have very rocky, shallow soils that are less suitable for agriculture. These areas are susceptible to drought and constraints on both macro- and micro nutrient availability. Fuelwood can be collected from the limestone forests. The forests do provide wildlife habitat and serve as efficient reservoirs for nutrients. Some areas within the limestone forest could be used for agroforestry land-use systems, but may require outside input of plant nutrients to maintain productivity if relatively large amounts of biomass are removed during harvest.
Native vegetation includes; Calophyllum inophyllum, Hernandia sonora, Guettarda speciosa, Pandanus spp. Neisosperma oppositifolia, Hibiscus tiliaceus, Ficus spp., Premna obtusifolia, Psychotria spp., Casuarina equisetifolia, Artocarpus mariannensis and Clerodendrum inerme. Many plant communities include large trees (greater than 1 m in diameter). Many of the forest trees supported lianas and ferns.
DISTRIBUTION AND EXTENT: MLRA 194 Low Limestone Islands of Western Micronesia, Republic of Palau. These soils of these series are of large extent; about 16,500 acres in Palau in size. The soils of this series are of small extent; 400 acres in Yap, Federated States of Micronesia. They are mapped in the "Rock Islands," Peleliu and Angaur in the Republic of Palau, and on the island of Fais, Yap State, Federated States of Micronesia.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Ulebsechel Island, Republic of Palau, 2008. Local pronunciation of the word Chelbacheb is "El-bah-eb." It means "rock islands" in Palauan.
REMARKS: The limestone parent material is 97 percent calcium carbonate, which limits the amounts of available essential nutrients. The source of plant nutrients is the biocycling of organic matter. The limestone bedrock is typically porous and fractured, allowing roots to penetrate into the rock. The mineral soils that are found on limestone are the insoluble residue left after the calcium carbonate dissolves. For this reason, "limestone soils" is technically a misnomer but a convenient way of referring to soils developed on limestone. There are only three percent impurities in the average Peleliu or Angaur limestone from which to form soil (US DOD, 1956). Even "insoluble" residue dissolves over time with the less soluble components remaining in solution to precipitate and form soil minerals. Additions of volcanic ash and long-range transported dust that blows in from the continents may also contribute to soil volume. The dust may also provide needed nutrients, such as potassium, that are generally deficient in soils formed from limestone. The karst topography contains common features including pits and pinnacles, caves, depressions, and sinkholes. The limestone forming was initially underwater as a coral reef that accumulated coral debris on its surface. Tectonic uplift raised the islands to theirs present positions. After uplifting, the exposed limestone was subject to erosive processes. Rainfall eroded the high limestone deposits leaving pitted and pinnacled limestone topography.
The phosphate for mining is believed to have derived from guano, and is found in four-ore types: nodular, oolitic, rock phosphate, and earthy ore. The majority of the mined phosphate is of the first three types; however, the earthy ore is considered the most desirable. The chemical analysis of the dried phosphate ore averaged 33.04 percent P2O5 by weight after ignition.
Diagnostic horizons and features recognized in this pedon are:
Folistic Epipedon - Surface to 20 cm (8 inches)
Sapric soil materials - Surface to 20 cm (8 inches)
Lithic contact - 20 cm (8 inches)
Lithologic discontinuity - 20 cm (8 inches)
Particle-size control section - 0 to 20 cm (8 inches)
ADDITIONAL DATA: National Soil Survey Laboratory Data # 03PW150001 and Military Geology of Palau Islands, 1956, are used to define the series.
Taxonomic Version: Keys to Soil Taxonomy, 10th edition 2006.