Intensity and periodicity of eolian processes in agrolandscapes of sub-boreal forest in the Tom River lower basin
Eolian processes connected with erosion, disposal and alluviation of sedimentary rocks are usually developed in the natural zones as well as in the arable areas. They are known to be the most developed ones in deserts and semideserts where they draw attention of many scientists. In the forest area of the West Siberian Plain, these processes have been understudied so far. The taiga and sub-boreal forest in the Ob and Irtysh basins are referred to either as a deflation free zone or the zone of accumulation of eolian material. Deforestation, tilting wildlands, public utilities construction contribute to the development of eolian processes. On farm lands, especially on the croplands, where deflation sites occur, eolian erosion causes the decrease in humus layer thickness, loss of nutrients and fertilizers, change of the soil texture. At the sites of accumulation, there might be crop covering up and the textual and chemical composition of soils changes as well. Besides, the relief of croplands is gradually changing: windward slopes are becoming steeper, whereas at the sites of accumulation either surface smoothing is observed or nanorelief is formed. In general, the sustainability of geosystems and the process of soil self-restoring are destroyed, erosion develops. In the course of our 25 year-observations it was found out that the wind velocity in the basin of the Tom River is significant and it can cause soil deflation in agrolandscapes; a high dust mulch is typical for the regional soils. Also, they are attacked by strong winds since their antideflation resistance is not high. The mid depth of soil retirement during our observations at different periods of time varied from 0 to 0.4 mm caused by the deflation size; the intensity of eolian material accumulation during the cold period of the year (October - April) during the 1989-2014 period varied from 1 g/m <sup>2 </sup>(2013) to more than 1000 g/m2 (2012). Dust fractions predominate in the eolian deposits, humus content reaching 4-5 % in some samples. Eolian sediments have a close genetic link with regional soils. Eolian processes by the area of development pertain to local ones; periodicity in processes is clearly expressed: from 1 to 5-6 years, suggesting some peculiarities of global atmospheric circulation as seen in different meteorological characteristics as well as in regional synoptic processes.