Information: - The World Reference Base for Soil Resources (WRB) is the international standard taxonomic soil classification system endorsed by the International Union of Soil Sciences (IUSS). It was developed by an international collaboration coordinated by the International Soil Reference and Information Centre (ISRIC) and sponsored by the IUSS and the FAO via its Land & Water Development division. It replaces the previous FAO soil classification. - Central America is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. Central America is bordered by Mexico to the north, Colombia to the southeast, the Caribbean Sea to the east, and the Pacific Ocean to the west. Central America consists of seven countries: Belize, Guatemala, El Salvador, Honduras, Nicaragua, Costa Rica and Panama. The combined population of Central America is between 41,739,000 (2009 estimate) and 42,688,190 (2012 estimate). - The International Union of Soil Sciences (IUSS) founded in 1924, is a Scientific Union member of the International Council for Science (ICSU), which it recognizes as the coordinating body for the international organization of science. - Africa is the world's second-largest and second-most-populous continent. At about 30.3 million km (11.7 million squaremiles) including adjacent islands, it covers 6% of Earth's total surface area and 20.4 % of its total land area. With 1.1 billion people as of 2013, it accounts for about 15% of the world's human population. The continent is surrounded by the Mediterranean Sea to the north, both the Suez Canal and the Red Sea along the Sinai Peninsula to the northeast, the Indian Ocean to the southeast, and the Atlantic Ocean to the west. The continent includes Madagascar and various archipelagos. It contains 54 fully recognized sovereign states (countries), nine territories and two "de facto" independent states with limited or no recognition. - A region is arid when it is characterized by a severe lack of available water, to the extent of hindering or preventing the growth and development of plant and animal life. Environments subject to arid climates tend to lack vegetation and are called xeric or desertic. Most "arid" climates surround the equator; these places include most of Africa and parts of South America, Central America and Australia. - Chalk is a soft, white, porous, sedimentary carbonate rock, a form of limestone composed of the mineral calcite. Calcite is an ionic salt called calcium carbonate or CaCO. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite shells (coccoliths) shed from micro-organisms called coccolithophores. Flint (a type of chert unique to chalk) is very common as bands parallel to the bedding or as nodules embedded in chalk. It is probably derived from sponge spicules or other siliceous organisms as water is expelled upwards during compaction. Flint is often deposited around larger fossils such as Echinoidea which may be silicified (i.e. replaced molecule by molecule by flint). - A Calcisol in the FAO World Reference Base for Soil Resources is a soil with a substantial secondary accumulation of lime . Calcisols are common in calcareous parent materials and widespread in arid and semi-arid environments . Formerly Calcisols were internationally known as Desert soils and Takyrs . Calcisols are developed in mostly alluvial , colluvial and aeolian deposits of base - rich weathering material . They are found on level to hilly land in arid and semi-arid regions . The natural vegetation is sparse and dominated by xerophytic shrubs and trees and / or ephemeral grasses . Dryness , and in places also stoniness and / or the presence of a shallow petrocalcic horizon , limit the suitability of Calcisols for agriculture . If irrigated , drained ( to prevent salinisation ) and fertilised , Calcisols can be highly productive under a wide variety of crops . Hilly areas with Calcisols are predominantly used for low volume grazing of cattle , sheep and goats . Many Calcisols occur together with Solonchaks that are actually salt - affected Calcisols and / or with other soils with secondary accumulation of lime that do not key out as Calcisols . The total Calcisol area may well amount to some 10 million square kilometres , nearly all of it in the arid and semi-arid ( sub ) tropics of both hemispheres . - Calcium carbonate is a chemical compound with the formula CaCO. It is a common substance found in rocks as the minerals calcite and aragonite (most notably as limestone, which contains both of those minerals) and is the main component of pearls and the shells of marine organisms, snails, and eggs. Calcium carbonate is the active ingredient in agricultural lime and is created when calcium ions in hard water react with carbonate ions to create limescale. It is medicinally used as a calcium supplement or as an antacid, but excessive consumption can be hazardous. - A desert is a barren area of land where little precipitation occurs and consequently living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to the processes of denudation. About one third of the land surface of the world is arid or semi-arid. This includes much of the polar regions where little precipitation occurs and which are sometimes called polar deserts or "cold deserts". Deserts can be classified by the amount of precipitation that falls, by the temperature that prevails, by the causes of desertification or by their geographical location. - Mission. ISRIC - World Soil Information is an independent, science-based foundation. The institute was founded in 1966 following a recommendation of the International Society of Soil Science (ISSS, now International Union of Soil Sciences| (IUSS)) and the United Nations Educational, Scientific and Cultural Organization (UNESCO). It has a mission to serve the international community with information about the worlds soil resources to help addressing major global issues. - Calcareous is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines. - Australia, officially the Commonwealth of Australia, is a country comprising the mainland of the Australian continent, the island of Tasmania and numerous smaller islands. It is the world's sixth-largest country by total area. The neighbouring countries are Papua New Guinea, Indonesia and East Timor to the north; the Solomon Islands and Vanuatu to the north-east; and New Zealand to the south-east. Australia's capital is Canberra, and its largest urban area is Sydney. - Soil classification deals with the systematic categorization of soils based on distinguishing characteristics as well as criteria that dictate choices in use. - The Food and Agriculture Organization of the United Nations (FAO) 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 form of the UNESCO Soil Map of the World (1974) (scale 1 : 5 M.). Many of the names offered in that classification are known in many countries and do have similar meanings. - A soil horizon is a layer generally parallel to the soil crust, whose physical characteristics differ from the layers above and beneath. Each soil type usually has three or four horizons. Horizons are defined in most cases by obvious physical features, chiefly colour and texture. These may be described both in absolute terms (particle size distribution for texture, for instance) and in terms relative to the surrounding material (i.e., "coarser" or "sandier" than the horizons above and below). The differentiation of the soil into distinct horizons is largely the result of influences, such as air, water, solar radiation and plant material, originating at the soil-atmosphere interface. Since the weathering of the soil occurs first at the surface and works its way down, the uppermost layers have been changed the most, while the deepest layers are most similar to the original parent material. - Parent material is the underlying geological material (generally bedrock or a superficial or drift deposit) in which soil horizons form. Soils typically inherit a great deal of structure and minerals from their parent material, and, as such, are often classified based upon their contents of consolidated or unconsolidated mineral material that has undergone some degree of physical or chemical weathering and the mode by which the materials were most recently transported. What entity does 'calcisol' has the relation 'instance of' with?
soil type