Impact of aridization on soil cover transformation of the Aral Sea and the modern Syr-Darya Delta

The effects of human activities on the soil cover transformation in the eastern part of Kazakhstan were investigated during the period of 1956-2008. The results of the research for different soil types in Priaralye indicated that there was 643.3x10<'3> hm<'2> solonchaks, accounting for 38.5 % of the total area (1670.5x 10<'3> hm<'2>) in 2008. Vast areas are occupied with dried lakeshore soil (311.1 x 10<'3> hm<'2>), sandysoils (147.6x10<'3> hm<'2>) and grey-brown desert soils and solonetzes (146.7x10<'3> hm<'2>). In 2001 the area of solonchak was 755x10<'3> hm<'2> and decreased to 643.3x10<'3> hm<'2> in 2008, which due to the shrinkage of the Aral Sea, the areas of marsh and lakeshore solonchaks decreased with the increase of dried bottom of the Aral Sea. The level of soil cover transformation in the modern delta of the Syr-Darya River can be seen from the comparison of the results obtained from the different years in the study area. The area of solon-chaks increased by 10x10<'3> hm<'2> and the area of alluvial-meadow salinizied soils increased by 17.9x10<'3> hm<'2>during the period of 1956-1969. It means that many non-salinizied soils were transformed into salinizied ones. Striking changes occurred in the structure of soil cover as a result of aridization. So, the researches in1969 significantly determined the areas of hydromorphic soils subjected to desertification (it was not fixed on the map before 1956). Later, these soils were transformed into takyr-like soils. The area of takyr-like soils increased almost by 3 times for 34 years (from 1956 to 1990). The long-term soil researches on soil cover transformation in Priaralye have shown that the tendencies of negative processes (salinization and deflation) are being kept and lead to further soil and eco-environment degradation in the region.