Babelthraup soil and landscape
Soil profile: Babelthuap soils are characterized by very low fertility and a high level of soluble aluminum, which is toxic to most plants. The surface layer generally is gravelly. This profile is in an area of map unit 614, Babelthuap-Ngardmau-Typic Udorthents undifferentiated group, 12 to 30 percent slopes, in Aimeliik State, Babeldaob Island. (Soil Survey of the Islands of Palau, Republic of Palau; by Jason L. Nemecek and Robert T. Gavenda, Natural Resources Conservation Service)
Landscape: Ngardmau-Babelthuap-Typic Udorthents undifferentiated group, 20 to 50 percent slopes, is characterized by steep slopes that are sparsely vegetated or barren. This site is in Melekeok State, Babeldaob Island.
The Babelthuap series consists of; very deep, well drained, that is shallow to an abrupt textural change. These soils are on erosional crests of hills on volcanic islands. Babelthuap soils formed in saprolite derived from basalt, andesite, dacite volcanic breccias, tuff, and bedded tuff. Slope is 2 to 75 percent. The mean annual rainfall is about 3685 millimeters (145 inches), and the mean annual temperature is about 27 C (81 F.)
TAXONOMIC CLASS: Very-fine, ferruginous, isohyperthermic Typic Kandiperox
Depth to diagnostic feature: kandic horizon: 2 to 15 centimeters (1 to 6 inches)
Control section: 25 to 100 centimeters (10 to 39 inches)
Thickness of solum: 50 to 100 centimeters (20 to 39 inches.)
Depth to diagnostic features::
abrupt textural change: 3 to 20 centimeters (1 to 8 inches
kandic horizon: 3 to 20 centimeters (1 to 8 inches)
Thickness of diagnostic features:
ochric epipedon: 2 to 15 centimeters (1 to 6 inches)
kandic horizon: 11 to 90 centimeters (4 to 35 inches)
Linear extensibility: 3 to 7 percent, weighted average RV is 4.8 percent
Surface Fragments: Rock fragments are vesicular petroferric fragments, ironstone and gibbsite concretions; 20 to 95 percent total rock fragments; 20 to 80 percent gravel; 0 to 15 percent cobbles
Mean annual soil temperature: 28 C (83 F)
USE AND VEGETATION: These soils are in fern-land plant communities and are used only for watershed. A few areas are used as a source for mining bauxite. The vegetation is degraded anthropic savannah consisting of poor stands of Gleichenia linearis, Nepenthea mirabilis, Ectrosia lepornia and Paspalum orbiculare, scattered shrubs and pandanus.
This plant community is commonly dominant with Gleicheinia sp. Other associates that may be found scattered if the ferns are still short and young include Lycopodium cernuum. If the area has not been subjugated to fire for a considerable amount of time then there is often nothing but Gleichienia or at least a considerable lower diversity then areas exposed to occasional fire. It is common to come across small pockets of these areas deep in the hills of the upland forest.
The surface layer becomes dry for short periods particularly during the months of February, March, and April, due to the high coarse fragment content. The soil does not meet the definition of an oxic horizon for the clay content increases by more than 8 percent within 15 centimeters (6 inches.) Gibbsite is aluminum hydroxide and it is the principal component of bauxite. It is the product of intense soil weathering and is very stable in the soil environment. Gibbsite does not contribute to the soluble aluminum in the soil because it is stable.
Some agricultural crops suffer from aluminum toxicity when the Al saturation is only 10%. Aluminum interferes with the photosynthetic cycle by complexing with phosphate, so with high soluble aluminum the plant is starved for phosphate. Al-toxicity also stunts root growth thereby limiting the amount of soil the plant can exploit for nutrients. Stunted roots can also limit water uptake and can cause plants to wilt with only a few days without water. Some plants (e.g. cassava) have high tolerance to high levels of soluble aluminum. On the Babelthuap series, ferns that are highly tolerant to aluminum can make up nearly 100% of the plant community in places. High soluble Al and acidity may adversely affect soil health by inhibiting beneficial organisms. When liming soils with high soluble aluminum the rule of thumb is to add 1.5 tons of CaCO3 per acre for every milliequivalents of soluble aluminum. The pH only needs to be raised to about 5.5 to eliminate the harmful effects of high soluble aluminum.
Apparent field textures vary for tropical soils; therefore, field textures and their mid-point values of texture classes were used rather than laboratory analysis for particle size. Particle size distribution is difficult to determine in tropical soils because of the strong cohesion of aggregates and their tendency to suspend particles. The poor dispersion reflects the water-stable aggregates of clay in silt and sand-sized "particles." Therefore, the soils may have a lot of clay but physically they behave as coarser textures.
DISTRIBUTION AND EXTENT: MLRA 193 Volcanic Islands of Western Micronesia, Republic of Palau. These soils of these series are of small extent; about 9000 acres in size. They are mapped on the islands of island of Babeldaob and to a lesser extent on Koror and Arakabesan.
For additional information about the survey area, visit:
www.nrcs.usda.gov/Internet/FSE_MANUSCRIPTS/pacific_basin/...
For a detailed soil description, visit:
soilseries.sc.egov.usda.gov/OSD_Docs/B/BABELTHUAP.html
For acreage and geographic distribution, visit:
Babelthraup soil and landscape
Soil profile: Babelthuap soils are characterized by very low fertility and a high level of soluble aluminum, which is toxic to most plants. The surface layer generally is gravelly. This profile is in an area of map unit 614, Babelthuap-Ngardmau-Typic Udorthents undifferentiated group, 12 to 30 percent slopes, in Aimeliik State, Babeldaob Island. (Soil Survey of the Islands of Palau, Republic of Palau; by Jason L. Nemecek and Robert T. Gavenda, Natural Resources Conservation Service)
Landscape: Ngardmau-Babelthuap-Typic Udorthents undifferentiated group, 20 to 50 percent slopes, is characterized by steep slopes that are sparsely vegetated or barren. This site is in Melekeok State, Babeldaob Island.
The Babelthuap series consists of; very deep, well drained, that is shallow to an abrupt textural change. These soils are on erosional crests of hills on volcanic islands. Babelthuap soils formed in saprolite derived from basalt, andesite, dacite volcanic breccias, tuff, and bedded tuff. Slope is 2 to 75 percent. The mean annual rainfall is about 3685 millimeters (145 inches), and the mean annual temperature is about 27 C (81 F.)
TAXONOMIC CLASS: Very-fine, ferruginous, isohyperthermic Typic Kandiperox
Depth to diagnostic feature: kandic horizon: 2 to 15 centimeters (1 to 6 inches)
Control section: 25 to 100 centimeters (10 to 39 inches)
Thickness of solum: 50 to 100 centimeters (20 to 39 inches.)
Depth to diagnostic features::
abrupt textural change: 3 to 20 centimeters (1 to 8 inches
kandic horizon: 3 to 20 centimeters (1 to 8 inches)
Thickness of diagnostic features:
ochric epipedon: 2 to 15 centimeters (1 to 6 inches)
kandic horizon: 11 to 90 centimeters (4 to 35 inches)
Linear extensibility: 3 to 7 percent, weighted average RV is 4.8 percent
Surface Fragments: Rock fragments are vesicular petroferric fragments, ironstone and gibbsite concretions; 20 to 95 percent total rock fragments; 20 to 80 percent gravel; 0 to 15 percent cobbles
Mean annual soil temperature: 28 C (83 F)
USE AND VEGETATION: These soils are in fern-land plant communities and are used only for watershed. A few areas are used as a source for mining bauxite. The vegetation is degraded anthropic savannah consisting of poor stands of Gleichenia linearis, Nepenthea mirabilis, Ectrosia lepornia and Paspalum orbiculare, scattered shrubs and pandanus.
This plant community is commonly dominant with Gleicheinia sp. Other associates that may be found scattered if the ferns are still short and young include Lycopodium cernuum. If the area has not been subjugated to fire for a considerable amount of time then there is often nothing but Gleichienia or at least a considerable lower diversity then areas exposed to occasional fire. It is common to come across small pockets of these areas deep in the hills of the upland forest.
The surface layer becomes dry for short periods particularly during the months of February, March, and April, due to the high coarse fragment content. The soil does not meet the definition of an oxic horizon for the clay content increases by more than 8 percent within 15 centimeters (6 inches.) Gibbsite is aluminum hydroxide and it is the principal component of bauxite. It is the product of intense soil weathering and is very stable in the soil environment. Gibbsite does not contribute to the soluble aluminum in the soil because it is stable.
Some agricultural crops suffer from aluminum toxicity when the Al saturation is only 10%. Aluminum interferes with the photosynthetic cycle by complexing with phosphate, so with high soluble aluminum the plant is starved for phosphate. Al-toxicity also stunts root growth thereby limiting the amount of soil the plant can exploit for nutrients. Stunted roots can also limit water uptake and can cause plants to wilt with only a few days without water. Some plants (e.g. cassava) have high tolerance to high levels of soluble aluminum. On the Babelthuap series, ferns that are highly tolerant to aluminum can make up nearly 100% of the plant community in places. High soluble Al and acidity may adversely affect soil health by inhibiting beneficial organisms. When liming soils with high soluble aluminum the rule of thumb is to add 1.5 tons of CaCO3 per acre for every milliequivalents of soluble aluminum. The pH only needs to be raised to about 5.5 to eliminate the harmful effects of high soluble aluminum.
Apparent field textures vary for tropical soils; therefore, field textures and their mid-point values of texture classes were used rather than laboratory analysis for particle size. Particle size distribution is difficult to determine in tropical soils because of the strong cohesion of aggregates and their tendency to suspend particles. The poor dispersion reflects the water-stable aggregates of clay in silt and sand-sized "particles." Therefore, the soils may have a lot of clay but physically they behave as coarser textures.
DISTRIBUTION AND EXTENT: MLRA 193 Volcanic Islands of Western Micronesia, Republic of Palau. These soils of these series are of small extent; about 9000 acres in size. They are mapped on the islands of island of Babeldaob and to a lesser extent on Koror and Arakabesan.
For additional information about the survey area, visit:
www.nrcs.usda.gov/Internet/FSE_MANUSCRIPTS/pacific_basin/...
For a detailed soil description, visit:
soilseries.sc.egov.usda.gov/OSD_Docs/B/BABELTHUAP.html
For acreage and geographic distribution, visit: