World Congress of Soil Science Logo 18th World Congress of Soil Science
July 9-15, 2006 - Philadelphia, Pennsylvania, USA
International Union of Soil Sciences

Friday, 14 July 2006

This presentation is part of 99: 1.2B Soil System Behavior in Time - Theater

Evolution of Virgin Solonetzic Soil Complexes in the Past 50 Years.

Nikolai B. Khitrov1, Nina M. Novikova2, and Natalia A. Volkova2. (1) V.V. Dokuchaev Soil Science Institute, Pyzhevskii per. 7, Moscow, Russia, (2) Water Problems Institute, Novaya Basmannaya ul. 10, Moscow, Russia

Estimation of modern tendencies of natural processes taking place in the solonetzic soil complexes of virgin dry steppe ecosystems in the northern Caspian region is based on the comparison of detailed maps of microrelief, vegetation, and soils compiled by the authors in 2002-2005 with the analogous maps compiled by Mozeson D.L., Kamenetskaya I.V., Polsky M.N. in 1950-1955 on the same plot located on the territory of the Dzhanybek research station. The following conclusions are made: (1) The microrelief of the plot with solonetzic complex has not changed much during 50 years. It is easy to align with high accuracy two topographic maps. Bottoms of all the depressions with the size of more than 20-30 sq. m fit precisely. The microhighs are also generally preserved. (2) At the same time, differently directed changes in the microrelief can be seen: some parts of the territory have risen, whereas other have lowered. Positive (rising) changes are seen in the following: (a) the extension of higher elements up to 1,5-4 m to the sides and the increase of absolute heights within these elements by 15-25 cm; these changes are caused by the digging activity of susliks with the transfer of soil mass lower horizons to the surface; (b) some rise (by 5-7 cm) of different elements of the microtopography without any signs of the additional input of soil material onto the soil surface. Negative (lowering) changes are more diverse: (a) lowering of flat microslopes of large depressions by 5-7 cm and some enlargement of the depressions (1,5-5 m wider); (b) disappearance or narrowing of saddles in the bottoms of some depressions; (c) lowering of saddles between the adjacent depressions; (d) lowering of ledges and deepening of the bottoms of ex-shallow closed microdepressions on the slopes of larger depressions and the complete transformation of some of these microdepressions into open hollows; (e) appearance of new depressions as a result of lowering of the higher parts (by 15-20 cm) at the expense of surface undermining; and (f) lowering (by 10-15 cm) of the highest parts of the territory with the radial-arched type of the microrelief due to the rise in the groundwater level, wetting of salt-bearing horizons within the capillary fringe zone, and dissolution of salt crystals. (3) Every type of soil (solonetzes proper, solonetzic light chestnut soils, nonsolonetzic light chestnut soils, and meadow-chestnut soils) can be met on different elements of the microrelief and under a wide range of plant communities. Thus, there is no strict correspondence between the soil types and the particular elements of the microtopography and the character of vegetation, though such correspondence was noted by many researchers (Kamenetskaya I.V., Polsky M.N., Rode A.A.) studying soils of the Dzhanybek Research Station in the 1950s-1970s. (4) The observed solonetzic complexes (ecosystems) and natural processes taking place on the virgin lands of the Dzhanybek station are not in the steady state. The most probable reason for this is the ground water level rise to the level of 4,5-5 meters that have taken place since 1980s. The appearance of the ground water at a relatively shallow depth leads to plastic deformation of water-saturated subsoil layers. In turn, this leads to settling of some areas and elevation of other areas. . As a result, stable interdependencies between different components of local ecosystems (relief, soils, and vegetation) become disturbed. This study was supported by the Russian Foundation for Basic Research, project no. 03-04-48299.

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