MANYCENTURY PERIODICITY OF SOLAR-ACTIVITY AND SOIL FORMATION

A correlation was made between the frequency of changes of soil format ion index and solar activity for the last 5000 years. Soil formation i ndex (SFI) represents the difference between the magnitudes of humus h orizon in the present time points which was divided by these time poin ts. The soil formation index was determined for the intervals of 100 y ears, the value of which is within the range of +1,55 up to -2,00 mm/y ear. It is a resultant between the rate of humus horizon growth during soil formation and its decrease in denudation. It has been establishe d that maxims of SFI values were timed to coincide with minima of sola r activity and vice versa. The periods of minima and high values of SF I are favourable ecological conditions in steppe zone. The date obtain ed can be used to assess the rhythms of biosphere development.