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How do winter frost and summer drought help form chernozem soil?

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Map showing the extent of the Eurasian steppes, highlighted in green, stretching from eastern Europe through Ukraine and southern Russia, across Kazakhstan, and into Mongolia and northern China. The map labels the Western Steppe and Eastern Steppe regions and includes major geographic features, countries, and ancient sites within the steppe zone. — the Steppe Extent of the Eurasian steppes.

The formation of chernozem (black earth) in the steppe is driven by a unique climatic balance that facilitates the accumulation of organic matter.

Winter frost and summer drought play critical roles by inhibiting the decomposition of organic material, which allows humus to build up in the soil profile. Furthermore, high evaporation rates during the warmer months prevent the leaching of nutrients, ensuring the soil remains rich and fertile.1

This process is further defined by the movement of soil solutions:
* Spring: Snowmelt causes calcium compounds to leach downward.1
* Summer: As the soil dries, these solutions are drawn upward, concentrating lime in a horizon beneath the humus layer.21

This cycle, combined with the dense grass cover typical of the Eurasian steppe, creates the dark, thick, and highly productive soil characteristic of the region.31