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steppe

(stĕp), temperate grassland of Eurasia, consisting of level, generally treeless plains. It extends over the lower regions of the Danube and in a broad belt over S and SE European and Central Asian Russia, stretching E to the Altai and S to the Transbaykal and Manchurian plains. The term is sometimes applied to the corresponding temperate grasslands of Hungary (PusztaPuszta
, arid grasslands that once covered a large part of the Alföld, E Hungary. They were used for extensive cattle raising. With the irrigation and drainage projects of the late 19th cent., the Puszta disappeared except in the small Hortobagy region (c.
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), the prairiesprairies,
generally level, originally grass-covered and treeless plains of North America, stretching from W Ohio through Indiana, Illinois, and Iowa to the Great Plains region.
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 of the United States, the pampaspampas
, wide, flat, grassy plains of temperate S South America, c.300,000 sq mi (777,000 sq km), particularly in Argentina and extending into Uruguay. Although the region gradually rises to the west, it appears mostly level. Precipitation decreases from east to west.
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 of South America, and the highveld (see veldveld
or veldt
[Du.,=field], term applied to the grassy undulating plateaus of the Republic of South Africa and of Zimbabwe. The veld comprises territory of varying elevation—the highveld (4,000–6,000 ft/1,220–1,830 m), the middleveld
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) of South Africa; it is sometimes also applied to the semiarid regions on the fringe of the hot deserts. The steppe consists of three vegetation zones with significant differences in climate—the wooded, or forest, steppe; the tillable steppe, or prairie; and the nontillable steppe. The wooded steppe has deciduous trees and the heaviest annual rainfall, over 16 in. (41 cm). The tillable steppe has black earth and an annual rainfall of between 10 and 15 in. (25–38 cm). The nontillable steppe is a semidesert, found especially around the Caspian Sea, with an annual rainfall of less than 10 in. (25 cm). There is some grazing, and its soils are relatively fertile under irrigation. Although the tillable steppe was originally grassland used almost exclusively for grazing, it is now almost entirely under cultivation. Some of the world's most productive agricultural areas, such as Ukraine and the U.S. wheat belt, are situated on the tillable steppe.

Steppe

 

(in North America, prairie; in South America, pampa), a type of vegetation represented by communities of drought- and frost-resistant perennial herbs, with a predominance of sod grasses or, less frequently, sedges and onions. Steppes occur primarily on chernozems and brown soils in regions having an arid climate with the maximum precipitation in the summer. They occupy the greatest areas within the inner-continental temperate regions of the northern hemisphere, extending from east to west in Europe and Asia and from north to south in North America. Steppes are also found in South America. Significant portions of steppes are under cultivation (however, the steppes of Europe are mainly in preserves).

In the USSR, virgin steppes are found in the northern part of the Kazakh Melkosopochnik and in southern Transbaikalia. Large steppe “islands” surrounded by mountainous taiga are found’ in the Minusinsk and Tuva river basins. Small steppe areas, primarily on southern slopes, extend far into Northeastern Siberia. Steppes also occur in the mountains of Transbaikalia, Southwest Asia, Middle Asia, and Central Asia, where they reach high elevations.

The natural vegetative cover of steppes in Europe and Asia (including the USSR) are characterized by a predominance of feather grasses, fescue, Koeleria, Avenastrum, bluegrass, and caespitose species of sedge and onion. The prairies of North America are covered with caespitose species of feather grass endemic to the continent. Various species of broom sedge are common in the less arid prairies, whereas species of the genus Bouteloua are common in the more arid ones.

Steppes are also characterized by many forb species from different families of dicotyledonous and monocotyledonous plants related to various biomorphs and several subshrub species (primarily species of Artemisia) and steppe shrubs (in Europe and Asia, species of Caragana, Spiraea, and Amygdalus). In the northernmost steppes a mossy cover of Thuidium and Tortula is common, whereas in the southernmost steppes lichens of the genera Parmelia, Cladonia, and Cornicularia are encountered with sparse grassy covers.

The vegetative cover of steppes varies greatly, as a result of the alternation of years with light and heavy precipitation and the presence of rodents (mostly murids—in particular, herbivorous and burrowing species), which in years of peak population almost completely destroy the grassy cover of steppes and bring a tremendous quantity of earth to the soil surface, creating natural wastelands over broad regions in which steppe vegetation gradually returns.

The greatest expanses of steppes are found in Eurasia, extending from west to east from the lower course of the Danube to Inner Manchuria. Three major zonal types of steppes are distinguished: (1) grassy steppes with a predominance of sod grasses and some forbs, (2) forest steppes consisting of forbs and, often, a continuous cover of mosses, and (3) desert steppes with a predominance of steppe sod grasses and large amounts of xerophytes (primarily Artemisia). Desert steppes are sometimes regarded as semideserts.

The geobotanical division of the steppe region of Eurasia distinguishes two subregions: the Black Sea-Kazakhstan subregion and the Central Asiatic subregion. The latter subregion includes the steppe and forest-steppe regions of Mongolia, southern Transbaikalia, and central Manchuria. The Black Sea-Kazakhstan subregion is characterized by a predominance of pinnate large-bench feather grass (Stipa pennata), whereas in the Central Asiatic subregion there is a predominance of endemic species of capillary feather grass (Stipa capillata). Central Asiatic varieties of small-bench and low-growing feather grasses predominate in desert steppes.

The Black Sea-Kazakhstan subregion has a relatively warm and humid spring; similar climatic conditions prevail to some extent in the autumn. During the spring and early summer, shortlived annuals (ephemerals) and perennials predominate. Annual spring plants include species of Ceratocephalus, Alyssum, and Androsace; perennials include Gagea, Hyacinthus, Tulipa, Geranium, Ferula, and bulbous bluegrass (Poa bulbosa).

The Central Asiatic subregion has a cold, dry, and windy spring. Annual and perennial ephemerals are practically absent. However, in years with a great deal of precipitation annuals and biennials with long vegetation periods (several species of Artemisia) frequently form a continuous cover until autumn.

REFERENCES

Dokuchaev, V. V. Nashi stepiprezhde i teper’. St. Petersburg, 1892.
Alekhin, V. V. “Rastitel’nost’ SSSR v ee osnovnykh zonakh.” In G. Val’ter and V. Alekhin, Osnovy botanicheskoi geografii. Moscow-Leningrad, 1936.
Lavrenko, E. M. “Stepi i sel’skokhoziaistvennye zemli na meste stepei.” Rastitel’nyipokrov SSSR. Moscow-Leningrad, 1956.
Weaver, J. E. North American Prairie. Lincoln, Neb. 1954.
Weaver, J. E. and F. W. Albertson. Grasslands of the Great Plains. Lincoln, Neb. 1956.

E. M. LAVRENKO

steppe

[step]
(geography)
An extensive grassland in the semiarid climates of southeastern Europe and Asia; it is similar to but more arid than the prairie of the United States.
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