Soils+Desert

Introduction In order to truly understand the soils in a desert, we should first refute a common misconception. While there are many sandy deserts in the world, a desert does NOT have to contain sand to be classified as a desert, nor does it have to be located in a hot region of the world. What is a desert, then? A desert is simply a region of the world with very little rainfall. Specifically, the evaporation rate is higher than the precipitation rate (G1). Soil in deserts are therefore very dry. Most soils in deserts are known as Aridisols (literally meaning "dry soil"). In exceptionally arid regions of the Sahara and Australian outback, there is another order of soil known as Entisols. Entisols are soils such as sand dunes which do not contain enough moisture to support any major soil horizon development (G2). (G3) Aridisols The first of the two major types of soils found in the desert are known as Aridisols. The term Aridisol can be used to refer to any one of 12 soil orders according to the US Soil Taxonomy (G4). Aridisols are characterized by their low humus (organic content) and sparse drought- and/or salt-tolerant vegetation (G4). On the surface, most Aridisols have a layer of either clay, sodium, or soluble salts. Beneath the surface, calcium carbonate, hydrate calcium carbonate, and cemented silica is present. Technically, this subterranean layer is all an aridisol needs to be classified as such (G4, G5). (G6) Entisols The second type of desert soil is known as an Entisol. Entisols are perhaps the most boring soils on the plant. That is because these soils exhibit an identifiable topsoil horizon, but contain little or no development beyond that (G7). In Entisols, the rate of deposition (of sediments and other matter) often meets or exceeds the rate of soil formation (G7), thus preventing extensive soil development from taking place. In the desert, this type of soil can most clearly be seen in the form of sand dunes (G7). (G7)

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