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In this article we will discuss about:- 1. Location of Steppe Climate 2. Temperature of Steppe Climate 3. Precipitation 4. Characteristics.
Location of Steppe Climate:
The middle latitude steppe climate (BSk) spread over temperate grasslands is located in the interiors of the continents which come in the westerly wind belt but because of their more interior locations they do not get sufficient rainfall and hence the grasslands are practically treeless.
The temperate grassland steppes of the southern hemisphere are located along the southeastern margins of the continents (fig 39.7) and therefore have more moderate climate than their counterparts of the northern hemisphere because of more marine influences as they are closer to marine environments.
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The temperate grasslands of Eurasia, known as steppes, are most extensive as they extend for a distance of more than 3200 km from the shores of the Black Sea across the Great Russian Plain to the foothills of the Altai Moutanins. Their continuity is broken at few places by the highlands.
There are also some isolated patches of steppes e.g., in Hungry (known as Pustaz) and in the plains of Manchuria (Manchurain Grassland). The temperate grasslands in North America (extending in Canada and USA both) are locally known as prairies which extend from the foothills of the Rockies in the west to the temperate deciduous forest biome in the east.
The temperate grasslands of the southern hemisphere include the pampas of Argentina and Uruguay of South America, bush veld and high veld of South Africa, and downs of the Murray-Darling Basins of southeastern Australia and Canterbury grasslands of New Zealand (fig. 39.7).
Temperature of Steppe Climate:
The temperate steppes are characterized by continental climate wherein extremes of summer and winter temperatures are well marked but the temperate grasslands of the southern hemisphere are marked by more moderate climate. Summers are warm with over 20°C temperature in July (Winnipeg, Canada) and over 22°C in January (Petoria, South Africa, January is summer month in the southern hemisphere).
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Winter season becomes very cold in the northern hemisphere because of enormous distances of temperate grasslands from the nearest sea. Winnipeg records -20°C in January. The average temperatures during winter season for Tashkent (Uzbeck Republic) and Semipalatinsk (Kazakh Republic) are 0°C and -12°C respectively.
The steppe climate of the southern hemisphere is never severe rather it is moderate because of nearness to the sea. The average winter temperature ranges between 1°C and 12°C in the southern hemisphere.
The steppe climate is characterized by high annual range of temperature. For example, Winnipeg (Canada) records mean annual range of 40°C. Laramine (Wyoming state in USA) records annual range of 23.4°C (-6.7°C in January and 16.7°C in July).
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Due to marine influences the mean annual range of temperature in the southern hemisphere is much lower than the northern hemisphere as it is around 10°C to 12°C only. Diurnal range of temperature is also very high in the temperate steppe climate.
Precipitation of Steppe Climate:
The mean annual precipitation ranges between 25 cm to 75 cm in different locations of the temperate grassland steppe areas. The winter precipitation in the northern hemisphere is usually received in the form of snowfall and most parts of Eurasian steppes are snow- covered for several months during northern winters. Most of the annual rainfall is received during summer season.
Characteristics of Steppe Climate:
The Eurasian steppe climate covers the largest area in the former Soviet Union (now the Commonwealth of Independent States-CIS and other Republics of former USSR) wherein it extends from Eastern Europe to western Siberia and between temperate coniferous forests in the north and arid regions in the south-west.
The Eurasian steppes are divided into:
(i) Forest steppe, and
(ii) Grass steppe wherein the former receives mean annual precipitation of 50 cm to 60 cm whereas the latter receives 40 cm to 50cm as mean annual precipitation.
The following sequences of vegetation communities are found from north to south:
(1) Forest steppe (consisting of oak, elms, limes, mapple, a few arboreal vegetation of Siberian Steppe such as birch with mixture of aspen and willow).
(2) Meadow steppe (consisting of the species of turf grasses such as stipa and Fescue and numerous herbaceous flowering plants such as numerous herbaceous flower plants such as Trifolium and several types of daisy.
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(3) Grass steppe (consisting of grasses mainly tussock-forming species of Stipa, a few flowering xerophytic shruby species of Artemisia.
(4) Semi-arid xeromorphic steppe dominated by xerophytic grasses such as Fescue and feather grass species, (mean annual precipitation ranging between 30 cm to 35 cm).
The North American Prairie has developed in the USA and Canada between the foothills of the Rockies in the west and temperate deciduous forest biome in the east.
On the basis of decreasing trend of mean annual precipitation from east (105 cm) to west (40 cm) the North American Prairies are divided into 3 sub-regions e.g.:
(1) Tall grass prairie (most dominant species of tallest grass are Bluestem and Switch Grass which attain the height of 1.5m to 2m, few patches of oak and hickory trees are also found),
(2) Mixed prairie (most extensive cover in the Great Plains of the USA, mixture of medium grasses, 0.6 to 1.5m in height, and short grasses such as little bluestem, needle grass- Stipa spartea, June grass and short and bunch grasses such as buffalo grass and blue gramma, and
(3) Short grass prairie (developed over western part of the Great Plains and dominated by short grasses of 60 cm height).
The South American Pampas are developed over 12 per cent area of Argentina and are more humid than Eurasian steppes. The mean annual precipitation decreases from east (coastal land, 90 cm) to west (45 cm).
Thus, the Pampas are divided into two sub-types e.g.:
(1) Humid Pampa, and
(2) Subhumid Peampa.
The humid Pampa, developed in the eastern part of Argentina, is characterized by tall grasses whereas increasing aridity westward results in the growth of short grasses in the western sub-humid Pampa.
The African veld has developed on the high plateau land of varying heights (1500m to 2000 m) in the south-eastern part of South Africa. The African Velds include the temperate grasslands of southern Transwall and Orange Free State of South Africa and some parts of Lisotho. Plant growth is not possible because of uncertainty of rainfall, increasing aridity, severity of frosts during nights and high daily range of temperature during winter season and thus true climax grasslands of African Velds have developed.
The Australian downs have developed in the south-eastern parts of Australia and in the northern part of Tasmania.
The region is characterized by:
(i) Relatively warmer winter season than the temperate grasslands of the northern hemisphere, and
(ii) Mixture of grasses with eucalyptus trees.
The grasslands gradually change from south (Australian coast) to north (interior land) in accordance with the decreasing trend of mean annual precipitation from south (152 cm) to north (63.5 cm).
The region is further divided into distinct 3 sub-regions e.g.:
(1) Temperate tall grasslands,
(2) Temperate short grasslands, and
(3) Xerophytic grasslands.