LOCATION CHIA FM+ PW PBEstablished Series
TAXONOMIC CLASS: Sandy or sandy-skeletal, carbonatic, euic, isohyperthermic Terric Sulfihemists
TYPICAL PEDON: Chia mucky peat in a level area under coralline mangrove forest, plant community, at an elevation of 0.5 meters (1.6 feet.) (Colors are for moist soil unless otherwise noted. All textures are apparent field textures. When described on September 15, 1980, the soil was wet throughout and the water table, due to fluctuating tide, was at 20 centimeters (8 inches.))
Oi1--0 to 23 centimeters (0 to 9 inches); black (5YR 2.5/1) peat; about 65 percent fiber, 45 percent rubbed; structureless massive; firm; common medium roots and few coarse roots; color in pyrophosphate solution is very pale brown (10YR 8/2); slight odor of sulfur; slightly acid (pH 6.5 in situ in H2O); clear smooth boundary.
Oi2--23 to 51 centimeters (9 to 20 inches); dark reddish brown (5YR 2.5/2) peat; about 70 percent fiber; 60 percent rubbed; structureless massive; firm; common medium, and few coarse roots; pyrophosphate solution is very pale brown (10YR 8/2); moderate odor of sulfur; neutral (pH 7.0, 1:1 water in place); clear smooth boundary.
Oi3--51 to 74 centimeters (20 to 29 inches); very dark grayish brown (10YR 3/2) peat with about 20 percent very pale brown (10YR 8/3) uncoated sand grains; about 80 percent fiber, 70 percent rubbed; structureless massive; friable; few medium roots; color in pyrophosphate solution is very pale brown (10YR 8/2); strong odor of sulfur; about 20 percent mineral material; neutral (pH 7.1, 1:1 water in place); abrupt smooth boundary. (Combined thickness of the Oi horizons is 50 to 129 centimeters)
2C1--74 to 94 centimeters (29 to 37 inches); dark grayish brown (10YR 4/2) gravelly loamy sand with very pale brown (10YR 8/3) uncoated sand grains; structureless single grain; friable; many very fine interstitial pores; moderate odor of sulfur; rock fragments are coral limestone, 20 gravel; neutral (pH 7.2, 1:1 water in place); clear smooth boundary.
2C2--94 to 150 centimeters (37 to 59 inches); dark grayish brown (10YR 4/2) very gravelly loamy sand with very pale brown (10YR 8/3) uncoated sand grains; structureless single grain; friable; many very fine interstitial pores; moderate odor of sulfur; rock fragments are coral limestone, 36 gravel; strongly effervescent; slightly alkaline (pH 7.4 in situ in H2O). (Combined thickness of the 2C horizons is 20 to 100 centimeters)
TYPE LOCATION: Island of Moen (Weno), Chuuk State, Federated States of Micronesia: about 200 meters (656 feet) south of Epinup Village; WGS 84 UTM 2387578 meters E, 858238 meters N, zone 56; Lat 7 25' 55" N and Long 151 51' 50.5" E.
RANGE IN CHARACTERISTICS:
Soil moisture:
Soil moisture regime subclass: oxyaquic
Soil moisture regime class: aquic
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. The soils are flooded semi-diurnally with salt water during periods of high tide.
Depth to diagnostic feature: lithologic discontinuity: 60 to 100 centimeters (24 to 39 inches)
Thickness of diagnostic feature: sulfidic materials: 60 to 100 centimeters (24 to 39 inches)
fibric soil materials: 60 to 100 centimeters (24 to 39 inches)
lithologic discontinuity: 100 to 140 centimeters (39 to 55 inches)
Linear extensibility: 0 to 1 percent, weighted average, RV is 0.5 percent]
Seasonal high water table: All months of the year
Depth to top: 0 to 25 centimeters (0 to 10 inches)
Oi horizon(s):
Hue: 2 or 3 moist
Value: 2 or 3 moist
Chroma: 1 or 2 moist
Texture: peat
Rubbed fiber content: 40 to 85 percent
Clay content: 0 to 15 percent
Sand content: 70 to 100 percent
Silt content: 0 to 25 percent
Fragment size and content: Rock fragments are limestone; 0 to 5 percent total rock fragments; 0 to 5 percent gravel.
Electrical conductivity: 5 to 30 mmhos/cm
Sodium adsorption ratio: 0 to 5
Reaction: pH 3.2 to 5.0
Cation exchange capacity: 75.0 to 110.0 meq/100grams
Effective cation exchange capacity: 100 to 115 meq/100grams
Organic matter content: 70.0 to 90.0 percent
2C horizon(s):
Hue: 10YR
Value: 7 or 8 moist
Chroma: 2 or 3 moist
Texture: loamy sand, sand and may have a gravelly or very gravelly modifier
Fragment size and content: Rock fragments are coralline limestone; 15 to 60 percent total rock fragments; 5 to 50 percent gravel; 0 to 10 percent cobbles
Clay content: 0 to 15 percent
Silt content: 0 to 25 percent
Sand content: 70 to 100 percent
Calcium carbonate equivalent: 70 to 95 percent
Electrical conductivity: 10 to 20 mmhos/cm
Reaction: pH 7.0 to 7.8
Base saturation: 1 to 10 meq/100 grams
Organic matter content: 0.0 to 3.0 percent
COMPETING SERIES: There are no other series in this family at this time.
GEOGRAPHIC SETTING: The Chia soils are on Coralline Mangrove Forest plant communities in the intertidal zone of mangrove swamps, salt marshes, and tidal marshes adjacent to atolls and karst islands. Slope is 0 to 2 percent. These soils formed in organic deposits derived predominantly from decomposing mangrove roots and litter over water-deposited coralline sand and gravel. Elevation is -1 to 4 meters (-3.3 to 13 feet.) The soils are flooded daily with ocean salt water during periods of high tide; 30 centimeters above (12 inches) to 30 centimeters (12 inches) below the surface. Areas closer to the ocean are submerged longer than areas closer to land. 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 Ilachetomel, Insak, Ngerungor, and Odesangel soils. The Ilachetomel soils are organic throughout with sulfidic materials, flooded semi-diurnally with seawater, and support mangrove vegetation. The Insak soils are moderately deep over coral bedrock. 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.
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Very poorly drained. Negligible runoff, very high-saturated hydraulic conductivity. The soils are flooded very frequently for extremely brief periods, semi-diurnally, by high tides that fluctuate between about 30 centimeters (12 inches) above and 30 centimeters (12 inches) below the soil surface. The soils are ponded frequently for very long periods all months of the year.
USE AND VEGETATION: These soils are in coralline-mangrove forest plant communities and are used for sediment catchment and some timber harvest for local use. The mangroves trap about 30% of sediments in Palau and other coralline islands from entering their coral reefs; it is an important buffer protecting the reefs from excessive sedimentation or eutrophication. Eutrophication will lead to coral reef degradation and stimulate algae growth on corals. These algae communities vigorously strip excess nutrients from the water as they grow much faster than the corals. As the algae blooms get much larger, they trap more sediment in the reefs and ultimately causing coral bleaching. As the old algae decay, they consume the oxygen in the water; the low oxygen then will kill off fish, crabs, shrimp, and the living reef devastating tourism and fishing in these local island economies.
Mangrove Forests are located adjacent to the sea and are affected by the semi-diurnal tidal cycle. The remaining areas of mangrove forest are located inland behind coastal strands, which were probably once open to the sea. Mangrove forests are generally closed-canopied with only a single to few mangrove species of Rhizophora spp., Sonneratia spp. Lumnitzera spp., Xylocarpus spp., and Bruguiera spp. These trees are of medium-size (less than 3 m in height), and less than 8 cm dbh.
The moderate tree sizes and density of trees within the mangrove forest ecological type result in stands containing a relatively high biomass. The species are adapted to reproducing and surviving on the deep soils inundated with brackish seawater. Although the bottomland soils contain large quantities of organic material, the woody biomass above and below ground serves as an important reservoir of nutrients. The mangrove plant communities are efficient in cycling plant nutrients.
DISTRIBUTION AND EXTENT: MLRA 194 Low Limestone Islands of Western Micronesia, Republic of Palau. These soils of these series are of small extent; about 1,100 acres in Palau, and about 1,300 acres in the Federated States of Micronesia. They are mapped in the "rock islands," and the islands of Angaur, Merir, Ngedebus, Ngercheu, Ngermilis, Pulo Ana, and Peleliu in the Republic Palau, island of Kosrae and Chuuk, Federated States of Micronesia, and the islands of Aunu`u, Ofu and Olosega, Territory of American Samoa. .
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Moen (Weno), Chuuk, Federated States of Micronesia, 1981. Local pronunciation of the word Chia is "Chee-a."
REMARKS: Reaction of surface layer decreased to pH 3.5 after exposure to air for a period of 10 days. They are susceptible to subsidence, adverse effects from high salt levels, and have poor engineering properties. Particle-size distribution measurements are usually not reliable for tropical soils; therefore, field textures and the corresponding mid-point values of texture classes were used rather than laboratory analysis for particle sizes. Particle size distribution is difficult to determine in tropical soils because of the tendency to form water-stable aggregates. The poor soil dispersion in laboratory analyses reflects the water-stable aggregates of clay in silt and sand-sized "particles." Therefore, the soils may have large clay content but physically they behave as coarser textures.
Diagnostic horizons and features recognized in this pedon are:
Aquic conditions - Surface to 150 cm (59 inches)
Fibric soil materials - Surface to 74 cm (29 inches) (Oi horizons)
Sulfidic material - Surface to 74 cm (29 inches)
Lithologic discontinuity- 74 cm (29 inches)
Particle-size control section- 0 to 130 cm (0 to 51 in)
ADDITIONAL DATA: University of Hawaii at Manoa - College of Tropical Agriculture and Human Resources # 06-4565 is used to define the series.
Taxonomic Version: Keys to Soil Taxonomy, 10th edition 2006.