Psamment
Encyclopedia
In USDA soil taxonomy
, a Psamment is defined as an Entisol
which consists basically of unconsolidated sand
deposits, often found in shifting sand dunes but also in areas of very coarse-textured
parent material subject to millions of years of weathering. This latter case is characteristic of the Guiana Highlands of northern South America. A Psamment has no distinct soil horizons, and must consist entirely of material of loamy sand or coarser in texture. In the FAO soil classification
, Psamments are known as Arenosols.
Psamments cover 3.4% of the global land mass. They occur throughout the world, being especially abundant in the deserts of Africa
and Australia
and on the ancient landforms of eastern South America
. Areas dominated by Psamments also occur in other humid regions, notably in Florida
and Nebraska
(the Sand Hills).
Psamments typically have very low water-holding capacities because the sand in the soil is not graded so that sands of varying coarseness are constantly mixed right through the soil. Because most sands are highly siliceous, Psamments are also extremely low in all essential nutrients, most especially phosphorus
and are highly acidic in all except very arid climates. Psamments formed as a result of glacial erosion (common in northern Europe
) are typically of rather higher native fertility because of their youth, but are still much less fertile than most soils in the regions they are located in.
The vegetation on Psamments varies enormously owing to the variety of climates, but in many cases is remarkably well-adapted to the climate, as with the Fynbos
of the Cape region in South Africa
- famous for its remarkable biodiversity
and the equally species-rich Kwongan
of southwestern Western Australia
. The campinas and kerangas are healthy forests typical of psamments in South America and Borneo
.
Few Psamments are farmed, and where they are, the cost is high because of the expense of fertilization. They are always much less productive than other soils in the same region even when fertilized, and require careful management because the sand is very easily eroded.
In USA soil taxonomy, Psamments are divided into:
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...
, a Psamment is defined as an Entisol
Entisol
In USA soil taxonomy, Entisols are defined as soils that do not show any profile development other than an A horizon. An Entisol has no diagnostic horizons, and most are basically unaltered from their parent material, which can be unconsolidated sediment or rock...
which consists basically of unconsolidated sand
Sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...
deposits, often found in shifting sand dunes but also in areas of very coarse-textured
Texture (geology)
Texture in geology refers to the physical appearance or character of a rock, such as grain size, shape, arrangement, and pattern at both the megascopic or microscopic surface feature level. This includes the geometric aspects and relations amongst the component particles or crystals which is called...
parent material subject to millions of years of weathering. This latter case is characteristic of the Guiana Highlands of northern South America. A Psamment has no distinct soil horizons, and must consist entirely of material of loamy sand or coarser in texture. 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...
, Psamments are known as Arenosols.
Psamments cover 3.4% of the global land mass. They occur throughout the world, being especially abundant in the deserts 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...
and 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 on the ancient landforms of eastern South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
. Areas dominated by Psamments also occur in other humid regions, notably in Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
and Nebraska
Nebraska
Nebraska is a state on the Great Plains of the Midwestern United States. The state's capital is Lincoln and its largest city is Omaha, on the Missouri River....
(the Sand Hills).
Psamments typically have very low water-holding capacities because the sand in the soil is not graded so that sands of varying coarseness are constantly mixed right through the soil. Because most sands are highly siliceous, Psamments are also extremely low in all essential nutrients, most especially phosphorus
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
and are highly acidic in all except very arid climates. Psamments formed as a result of glacial erosion (common in northern Europe
Northern Europe
Northern Europe is the northern part or region of Europe. Northern Europe typically refers to the seven countries in the northern part of the European subcontinent which includes Denmark, Estonia, Latvia, Lithuania, Norway, Finland and Sweden...
) are typically of rather higher native fertility because of their youth, but are still much less fertile than most soils in the regions they are located in.
The vegetation on Psamments varies enormously owing to the variety of climates, but in many cases is remarkably well-adapted to the climate, as with the Fynbos
Fynbos
Fynbos is the natural shrubland or heathland vegetation occurring in a small belt of the Western Cape of South Africa, mainly in winter rainfall coastal and mountainous areas with a Mediterranean climate...
of the Cape region in South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
- famous for its remarkable biodiversity
Biodiversity
Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...
and the equally species-rich Kwongan
Kwongan
Kwongan is a type of heathland found on the coastal plains of Western Australia. The name is derived from the language of the Noongar people. Kwongan comprises floristically-rich heath with dense thickets of sclerophyllous shrubs and isolated small trees...
of southwestern Western Australia
Western Australia
Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...
. The campinas and kerangas are healthy forests typical of psamments in South America and Borneo
Borneo
Borneo is the third largest island in the world and is located north of Java Island, Indonesia, at the geographic centre of Maritime Southeast Asia....
.
Few Psamments are farmed, and where they are, the cost is high because of the expense of fertilization. They are always much less productive than other soils in the same region even when fertilized, and require careful management because the sand is very easily eroded.
In USA soil taxonomy, Psamments are divided into:
- Cryopsamments - Psamments that have a cryic soil temperature regime.
- Quartzipsamments - Other Psamments that have, in the 0.02 to 2.0 mm fraction within the particle-size control section, a total of more than 90 percent (by weighted average) resistant minerals.
- Torripsamments - Other Psamments that have an aridic (or torric) moisture regime.
- Ustipsamments - Other Psamments that have an ustic moisture regime.
- Xeropsamments - Other Psamments that have a xeric moisture regime.
- Udipsamments - Other Psamments.
See also
- PedogenesisPedogenesisPedogenesis is the science and study of the processes that lead to the formation of soil ' and first explored by the Russian geologist Vasily Dokuchaev , the so called grandfather of soil science, who determined that soil formed over time as a consequence of...
- Pedology (soil study)Pedology (soil study)Pedology is the study of soils in their natural environment. It is one of two main branches of soil science, the other being edaphology...
- PsammoserePsammosereA psammosere is a seral community, an ecological succession that began life on newly exposed coastal sand. Most common psammoseres are sand dune systems....
- Soil classificationSoil classificationSoil classification deals with the systematic categorization of soils based on distinguishing characteristics as well as criteria that dictate choices in use.- Overview :...
- Soil types