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Biomes and Regions of Northern Eurasia

Steppe and Forest-steppe

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Climate

The location of the Eurasian steppe biome coincides with the zone of high atmospheric pressure and, despite the differences in climates of the landlocked steppes and those located closer to the coast (e.g., southern Moldova receives about 410 mm of precipitation per annum while Tuva has only about 215 mm), moisture supply is insufficient across the biome. Evaporation exceeds precipitation by a factor of 2-3. Typical are the distinct June (July-August in the Dahurian steppes) maximum in precipitation and its high interannual variability. An important climatic feature is the small thickness of snow cover and the redistribution of snow by wind. Snow is often blown off the watersheds and accumulates in topographic depressions, shrublands, and woodlands, which causes strong spatial differences in soil climates. The temperature gradient changes eastwards as a result of increasing continentality. The mean annual temperatures change from approximately 9°C in Moldova to about -6°C in Tuva and the mean annual temperature amplitude increases from 27°C to 53°C. Figure 11.2 illustrates the spatial variations in the mean January temperatures and the duration of the frost-free period in the southern steppes.

Fig. 11.2 Mean January temperatures and average continuation of the frost-free period in the southern steppes

All biotic components of steppes are closely controlled by climate and change from west to east in response to the increasing continentality. This is expressed in both the changing structure and floristic composition of vegetation (the replacement of the European species by the Kazakh and then Mongolian species) and in the changing productivity of ecosystems, the ratio between the above ground and below ground biomass, and the thickness of the humus horizon (Mordkovich, 1982).

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