On some physical and chemical properties of soils of sandy outcrops of the West Siberian northern regions

The ancient aeolian forms of relief, which are mainly covered with pineries and coniferous forests, are widely spread in the territory of Western Siberia. Anthropogenic transformation of these landscapes leads to the formation of technogenic deserts and sandy outcrops on soils of light mechanical structure generally because of the development of oil and gas extraction industry. Such transformed ecosystems are often met in the north of the West Siberian Plain within a subzone of northern taiga of the taiga natural zone and the zone of the forest-tundra. In 2016–2017, we explored three sites of sandy outcrops in the territory of Purovsky District of Yamalo-Nenets Autonomous Okrug (Tyumen region): in 27 km to the south from Muravlenko, in 32 km to the southwest from Gubkinsky and in 23 km to the East-southeast of New Urengoy. The first two sites are located within the northern taiga; the third site is at the southern border of the forest-tundra, in the area of its gradual transition to the northern taiga. Results of the conducted researches show the considerable changes in a number of physical and chemical properties of podsolic sandy soils of technogenic deserts in comparison with soils of undisturbed ecosystems. We have revealed statistically significant decrease in the acidity of the surface soil layer to 5–6 units рН due to the destruction of the top soil horizons and exposure of the illuvial and eluvial horizons having smaller acidity. Our researches show the reduction of maintenance of fine fractions – clay and dusty particles – in the transformed soils and, respectively, increase in content of sand up to 95–100%. Also we have revealed statistically significant reduction of soil moisture content in soils of sandy outcrops.  Thus, the soils of technogenic deserts are characterized by ease, flowability, they are usually not fixed by vegetation and easily are affected by wind. The ecotopes, which are formed on sandy outcrops, differ in extreme conditions. They can be mastered only by a small number of specialized species-erosiophiles, shifting to disturbed felted habitats with similar natural ecotopes with the friable sandy and sabulous sandy soils, often mobile soil typical of marine and lake shallows, river alluvium, taluses, slopes of ravines. On the periphery of sandy outcrops the shafts of falling up to 4,5–5,5 m high are formed. They constitute the real danger to natural undisturbed north taiga and forest-tundra ecosystems, burying them under sandy masses.