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Biomes and Regions of Northern Eurasia

Steppe and Forest-steppe

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Environmental Factors Controlling Steppe and Forest-steppe Characteristics

The debate on the origin of steppe and forest-steppe has a long history. Many scientists attempted to explain the main characteristics of these landscapes — the absence or lack of tree vegetation. The first hypothesis dates back to the 18th century when Pallas (1770) suggested that trees were destroyed by man. Later the anthropogenic hypothesis was supported by Palimpsestov (1890) and Taliev (1905). A century ago, the idea of climatic control was put forward by Vysotsky (1905) who suggested that the climate of steppes, with its frequent dry winds and insufficient moisture supply, prevents the development of forests. In the monograph Grasslands of the Northern Hemisphere, Krasnov (1894) explained the lack of tree vegetation by the flat topography of the steppes, which resulted in poor drainage that was unfavourable for tree growth. In his view, climate merely controlled the floristic composition of steppe vegetation. Tanflliev (1894) saw the high salinity of soils as the major factor opposing the development of forests. A prominent soil scientist, Kostychev (1937), advocated the ecological view according to which tree vegetation could not withstand the competition with herbs because their deep and extensive roots form a thick turf layer. All these environmental factors exert control over the characteristics of steppe vegetation, complementing each other's influence. As Milkov (1977) says: 'The treeless character of steppe vegetation is a zonal phenomenon determined in the first place by dry climate. This climate, unfavourable for tree growth, provides a background for the salinization of soils, the domination of herbaceous species and other factors'. Speaking of the treeless character of steppe landscapes it is important to keep in mind that woodlands commonly occur in steppes, including even its southern subzone.

The development of steppe landscape began before the onset of glaciations. In the Neogene, subtropical forests were replaced by grass communities as a result of increasing aridity and the precursors of modern steppes, Neogene savannahs, developed (Neishtadt, 1957; Milkov, 1977). The formation of steppe flora occurred during the glacial periods. The contemporary borders of the Northern Eurasian steppes formed in the early Holocene.

The character of steppe landscapes shaped and strongly influenced the occupations and lifestyle of its nomadic population, Scythians and Sarmatians, until the 4th century AD, and later turcic peoples. Later, however, it was humans who to a great extent controlled the development of steppe and forest-steppe landscapes. In the late Holocene, the areas occupied by woodlands decreased significantly under the human influence and much of the territory was transformed by arable agriculture. Having played an important role in the history of humankind, forest-steppes, and steppes were the first biomes whose original character has been dramatically altered and in the European territory almost completely changed.

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