Orthents are

soil Soil, also commonly referred to as earth, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from ''soil'' by re ...

s defined in

USDA soil taxonomy USDA soil taxonomy (ST) developed by the United States Department of Agriculture and the National Cooperative Soil Survey provides an elaborate Soil classification, classification of soil types according to several parameters (most commonly their p ...

entisols Entisols are soils, as defined under USDA soil taxonomy, that do not show any profile development other than an A-horizon (or “A” horizon). Entisols have no diagnostic horizons, and are unaltered from their parent material, which could ...

that lack due to either steep slopes or parent materials that contain no permanent weatherable

minerals In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): M ...

(such as

ironstone Ironstone is a sedimentary rock, either deposited directly as a ferruginous sediment or created by chemical replacement, that contains a substantial proportion of an iron ore compound from which iron (Fe) can be smelted commercially. Not to be c ...

). Typically, Orthents are exceedingly shallow soils. They are often referred to as ''skeletal soils'' or, in the United Nations

FAO soil classification The Food and Agriculture Organization of the United Nations (FAO) developed a supra-national classification, which offers useful generalizations about pedogenesis in relation to the interactions between the main soil-forming factors. It was first p ...

, as ''lithosols''. The basic requirement for recognition of an orthent is that any former soil has been either completely removed or so truncated that characteristics typical of all orders other than entisols are absent.

Characteristics

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, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

and a few regions of

Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...

, orthents occur in flat terrain because the

parent rock In the earth sciences, parent rock, also sometimes ''substratum'', is the original rock from which younger rock or soil is formed. In soil formation, the parent rock (or parent material) normally has a large influence on the nature of the resultin ...

contains ''absolutely no weatherable minerals except short-lived additions from rainfall'', so that there is no breaking down of the minerals (chiefly

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

oxides) in the rock. The steepness of most orthents causes the

flora Flora (: floras or florae) is all the plant life present in a particular region or time, generally the naturally occurring (indigenous (ecology), indigenous) native plant, native plants. The corresponding term for animals is ''fauna'', and for f ...

on them to be sparse shrubs or

grassland A grassland is an area where the vegetation is dominance (ecology), dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes such as clover, and other Herbaceo ...

. In those on ancient, flat terrain,

dry grassland The key characteristic of dry grasslands is that they have low-growing plants, causing the area to be quite open. They also have a mottled structure, which leads to a biome with sunny or semi-shaded areas. On top of that, their soil is relatively ...

savanna A savanna or savannah is a mixed woodland-grassland (i.e. grassy woodland) biome and ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach th ...

, or rarely,

rainforest Rainforests are forests characterized by a closed and continuous tree Canopy (biology), canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforests can be generally classified as tropi ...

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

livestock Livestock are the Domestication, domesticated animals that are raised in an Agriculture, agricultural setting to provide labour and produce diversified products for consumption such as meat, Egg as food, eggs, milk, fur, leather, and wool. The t ...

stocking rates are practicable. Many orthents are very important as

habitat In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...

for wildlife.

References

* tp://ftp-fc.sc.egov.usda.gov/NSSC/Soil_Taxonomy/tax.pdfv Soil Taxonomy p420br>New Zealand Journal of ScienceFundamentals of Soils By John Gerrard
Pedology Types of soil {{Soil-sci-stub

Characteristics

See also

References