Introduction: Temperate grasslands are composed of a rich mix of grasses and forbs and underlain by some of the world’s most fertile soils. Since the development of the steel plow most have been converted to agricultural lands.
Climate: Semiarid, continental climates of the middle latitudes (Koeppen’s BSk climate type) typically have between 10 and 20 inches of precipitation a year. Much of this falls as snow, serving as reservoir of moisture for the beginning of the growing season. Warm to hot summers are experienced, depending on latitude.
Vegetation: Perennial grasses and perennial forbs [especially Compositae (or Asteraceae, depending on the taxonomic system used) and Leguminosae--the sunflower and pea families, respectively] are dominant growthforms. Two or more strata of grasses (erect grasses and recumbent species) are recognized in the more humid expressions of the biome.
Grasses. Perennial grasses, with their growth buds at or just below the surface, are well-adapted to drought, fire, and cold. The tiller or narrow, upright stem reduces heat-gain in the hot summers; the intricate root systems trap moisture and nutrients. Two basic types are:
-
Turf- or sod-forming grasses, with rhizomes or underground stems from which new plants spring forth; associated with the more humid grasslands
-
Bunch grasses, without rhizomes, that reproduce by seed; associated with the drier parts of the biome.
Major regional expressions:
North America: the prairies of the Central Lowlands and High Plains of the US and Canada. The Palouse Prairie of eastern Washington state, the California grasslands, and the desert grasslands of the Southwest are also temperate grasslands.
Eurasia: the steppes from Ukraine eastward through Russia and Mongolia.
South America: the pampas of Argentina, Uruguay, and southeastern Brazil; the Patagonian steppe of Argentina and Chile.
Africa: the veld in the Republic of South Africa.
Soils: Calcification is the dominant soil-forming process in semiarid regions. Mild leaching, high organic content, and concentration of calcium carbonate in the B horizon typifies the dark brown mollisols developed under the temperate grasslands. When this process works on a loess that itself is rich in calcium, the world’s most fertile soils are created, the chernozems (A Russian term meaning black soil). Loess and hence chernozem underlie the eastern prairies of the US, the pampas of South America, and the steppes of Ukraine and Russia.
Fauna: The temperate grassland fauna is very low in diversity, especially in comparison with the tropical grasslands or savannas of Africa. In North America the dominant herbivores are bison Bison bison) and pronghorn (the sole member of the Nearctic endemic family, Antilocapridae). Rodent herbivores include the pocket gopher (another Nearctic endemic), ground squirrels, and the prairie dog. Carnivores include coyote (actually an omnivore), badger, and the federally endangered black-footed ferret, the last two members of the weasel family.
On the Russian steppes the fauna formerly included wisent (Bison bonasus), tarpan or wild horse, and saiga antelope, among others. Mole rats, fossorial members of one of the two mammal families endemic to the Palearctic, are conspicuous by virtue their many mounds. Polecats and other members of the weasel family are among the larger, extant carnivores.
