Orthent
Encyclopedia
In USDA soil taxonomy
, Orthents are defined as Entisols that lack horizon development due to either steep slopes or parent materials that contain no permanent weatherable minerals (such as ironstone
). Typically, Orthents are exceedingly shallow soils. They are often referred to as "skeletal soils" or, in the FAO soil classification
, as Lithosols. The basic requirement for recognition of an orthent is that any former soil
has been either completely removed or so truncated that the diagnostic horizons typical of all orders other than Entisols are absent.
Most Orthents are found in very steep, mountainous regions where erodible material is so rapidly removed by erosion that a permanent covering of deep soil cannot establish itself. Such conditions occur in almost all regions of the world where steep slopes are prevalent. In Australia
and a few regions of Africa
, Orthents occur in flat terrain because the parent rock contains absolutely no weatherable minerals except short-lived additions from rainfall, so that there is no breaking down of the minerals (chiefly iron
oxides) in the rock.
The steepness of most Orthents causes the flora on them to be sparse shrubs or grassland
. In those on ancient, flat terrain, dry grassland, savanna
, or, very rarely, rainforest
can prevail.
Because of their extreme shallowness and, usually, steepness and consequent high erosion hazard, Orthents are not suitable for arable farming. The flora typically supported on them is generally of very poor nutritive value for grazing, so that typically only low stocking rates are practicable. Many Orthents are very important as habitat for wildlife.
USDA soil taxonomy
USDA Soil Taxonomy developed by United States Department of Agriculture and the National Cooperative Soil Survey provides an elaborate classification of soil types according to several parameters and in several levels: Order, Suborder, Great Group, Subgroup, Family, and Series.- Example of...
, Orthents are defined as Entisols that lack horizon development due to either steep slopes or parent materials that contain no permanent weatherable minerals (such as ironstone
Ironstone
Ironstone is a sedimentary rock, either deposited directly as a ferruginous sediment or created by chemical repacement, that contains a substantial proportion of an iron compound from which iron either can be or once was smelted commercially. This term is customarily restricted to hard coarsely...
). Typically, Orthents are exceedingly shallow soils. They are often referred to as "skeletal soils" or, in the FAO soil classification
FAO soil classification
The Food and Agriculture Organization of the United Nations developed a supra-national classification, also called World Soil Classification, which offers useful generalizations about soils pedogenesis in relation to the interactions with the main soil-forming factors. It was first published in...
, as Lithosols. The basic requirement for recognition of an orthent is that any former soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
has been either completely removed or so truncated that the diagnostic horizons typical of all orders other than Entisols are absent.
Most Orthents are found in very steep, mountainous regions where erodible material is so rapidly removed by erosion that a permanent covering of deep soil cannot establish itself. Such conditions occur in almost all regions of the world where steep slopes are prevalent. In Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
and a few regions of Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
, Orthents occur in flat terrain because the parent rock contains absolutely no weatherable minerals except short-lived additions from rainfall, so that there is no breaking down of the minerals (chiefly iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
oxides) in the rock.
The steepness of most Orthents causes the flora on them to be sparse shrubs or grassland
Grassland
Grasslands are areas where the vegetation is dominated by grasses and other herbaceous plants . However, sedge and rush families can also be found. Grasslands occur naturally on all continents except Antarctica...
. In those on ancient, flat terrain, dry grassland, savanna
Savanna
A savanna, or savannah, is a grassland ecosystem characterized by the trees being sufficiently small or widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of C4 grasses.Some...
, or, very rarely, rainforest
Rainforest
Rainforests are forests characterized by high rainfall, with definitions based on a minimum normal annual rainfall of 1750-2000 mm...
can prevail.
Because of their extreme shallowness and, usually, steepness and consequent high erosion hazard, Orthents are not suitable for arable farming. The flora typically supported on them is generally of very poor nutritive value for grazing, so that typically only low stocking rates are practicable. Many Orthents are very important as habitat for wildlife.