The authors systematized and comprehensively analyzed the different sources containing the information on surface and underground flooding of soils and lands at the territory of Central Russia. The above processes are observed through their intensive manifestation within the zones of soddy-podzolic, gray forest soils and chernozems in Tver’, Smolensk, Moscow, Ryazan’, Bryansk, Voronezh, Kursk, Tambov, Yaroslavl, Kaluga regions of the studied territory. It is shown that natural events and those induced by human interventions serve as a reason for ccurring and developing these processes in different regions. The soils reveal short-duration flooding and become even waterlogged due to frequent and heavy rainfalls and spring floods taken place almost every year. However, the soils are becoming excessively wet for a long period of time resulted from the groundwater rise due to water engineering constructions and the irrational land use. Being affected by natural and anthropogenic factors, the constant wetting (water-logging and underground flooding) can be also as a consequence of intense urban building accompanying by drainage destruction of the ground water. Special attention is paid to elaborating a complex of measures to prevent the adverse effects of such dangerous natural processes.

The data obtained by GRACE satellite allowed comprehensively analyzing the dynamics of total terrestrial water storage within the period from 2003 to 2012 at the territory of European Russia. Having compared the satellite data and the information on the dynamics of the groundwater level obtained in the course of field survey by using 12 evenly distributed bore holes at the studied territory (Central Federal and North-Caucasian Federal regions), it is worth emphasizing that there is a clearly expressed co-variation between the satellite images and the groundwater depth. The analysis of trend in total water content identified by satellite data showed that it is positive towards the north-western and negative in the south and south-eastern part of European Russia. The total content of terrestrial water storage reveals periodical changes in the range from 3 to 8-9 years. The prolonged periods are observed in central and north-western parts, being shortened towards the north and south-east of the studied territory. The obtained data serve as evidence of periodically changing the total terrestrial water storage but its minimum will be observed in the east of Northern Caucasus, in Vologda, Yaroslavl, Moscow and Kostroma regions in 2016, in central part and Krasnodar region in 2018-2019 and in Kirov and Perm’ regions in 2016-2017. The results of the given studies can find a use in long-term forecasting of crop yields, in soil mapping and cultivation of new fruit plantations.

Under study were the levels of enzymatic (peroxidase, polyphenoloxidase and catalase) activity in air-dry structural particles 1-2 mm thick and water- stable aggregates extracted from the samples of soddy-podzolic soils (under forest and in crop) and typical chernozems used in long-term field experiments including the resting black fallow since 1964, the barren land after the fallowing since 1998 and annually mowed steppe. Peroxodase and polyphenoloxidase activities display approximately similar level being highly changed from 5 to 22 and 2 to 30 mmol/g respectively, whereas the catalase activity seems to be lower from 2 to 7 mmol/g. In the major cases the fermentative activity in water- stable soil aggregates is higher as compared to air-dry structural particles. The peroxidase activity in water- stable aggregates can be considered as an indicator for displacing equilibrium in processes of the organic matter turnover in soils. In soddy-podzolic soils the polyphenoloxidase activity is concentrated in water- stable aggregates, in chernozems it is evenly distributed between structural particles. As distinct from the ferments of carbon cycle (peroxidase and polyphenoloxidase) the catalase activity doesn’t depend on the soil type and its peculiar use.

Under study were the soils developed in flat watersheds with suffusion depressions and subjected to excessive seasonal flooding in Kamennaya Steppe, Talov district and Voronezh region of Russia. Among them are migrational-mycellary chernozem (Haplic Chernozem (Clavic, Pachic) on convex microrelief elements, the clay-illuvial eluvial weakly gleyic chernozem (Luvic Stagnic Phaeozem (Clayic, Pachic) in shallow depressions with seasonal flooding for two weeks in a year and the clay-illuvial quasigley eluvial vertic chernozem (Luvic Vertic Stagnic Phaeozem (Epiloamic, Endoclayic, Pachic) in deep depressions with seasonal flooding in the period from one to three months. A complex of ecological-trophical groups of microorganisms (amilolytics, actinomyces, micromyces, denitrifiers and aerobic azotobacters) along the soil profile has been studied; soil sampling was taken at the end of the summer (in August). It is shown that the excessive surface flooding has a great influence on the following groups of microorganisms: microscopic fungi (dried aerobic microorganisms), actinomyces (continental branch of prokariot with wide ecological amplitude) and denitrifiers (typical anaerobic forms). The population of micromyces is decreasing from 5.6 to 3.5 lg KOE/g with increasing the anaerobic conditions, whereas actinomyces are increased reaching 4.2 lg KOE/g in moist horizons of hydromorphic chernozems; denitrifiers are rather active (2.5-3.6 lg КОЕ/g soil) only in soil of depressions with traces of seasonal flooding. The duration of seasonal flooding is a factor changing the structure of the microbial community in which the dominants are alternated in groups of microorganisms. The ratio between these groups of microorganisms can be used for assessing the aerobic/anaerobic conditions for their habitat in soils of the steppe zone.

Every ecological group of plants including hygrophytes, mesophytes and xerophytes is characterized by a definite narrow interval of the soil water potential, in which the values of relative transpiration cannot be lower than the optimal level (1.0-0.9). These intervals take into account the influence of soil properties (moisture potential) and meteorological conditions (transpiration) and can be used as optimal indices for the water supply of plants. The peculiar soil water uptake by plants has been studied to show that the soil water and its intensive uptake become increasing but its “dead” reserve decreasing from hygrophytes towards mesophytes and then xerophytes. It is worth emphasizing that the decline in the growth and accumulation of useful products by plants occur due to decreasing the content of soil water to the lower boundary of optimal moistening. The further decrease in soil moisture leads to permanent and then ultimate wilting of plants. Under study were also intervals for soil water potential corresponding to the moisture of ultimate wilting of different ecological plant groups. Lettuce (hygrophyte) is becoming dead when the content of soil water is equal to 1.5, oat (mezophyte) - 1.0 and xerophytes - lower than 1.0 of the wilting moisture. The method of “vegetative miniatures” widely adopted now is imperfect and can be performed only for preliminary notions about the lower limit for plant availability of the soil water.

Under consideration are the history and principles of two soil classifications including “Classification and diagnostics of soils of the USSR” published in 1977 and “Russian soil classification system” of 2004. Their advantages and shortcomings are also considered. Special attention is paid to a new classification, in which not only natural but also the soils used in agriculture are classified for the first time. The soil classification published in 1977 elaborated on a basis of ecologic-genetic principles became out of date and was to be updated because of new knowledge on soils gained in the last years. New ideas determined the priority of substantive-genetic principle or more precisely the profile-genetic principles to be of major importance in the new classification system. A comprehensive analysis of ecological conditions for the soil development is absent. However, the agro-soils designed for cultivation of different agricultural crops can be recognized and typified only with account of ecological characteristics. The substantive-genetic approach to classify agricultural soils seems unacceptable because the most important diagnostic horizons become destructed in the course of soil tillage and the identical definitions or names of soils included into different types and even orders (agrozems) don’t provide the information on properties of initial soils. The classification must be elaborated using the principles permitting to determine and diagnose initial natural soils, thus maintaining their name, taxonomic level and indicating that they have been plowed. Not only the analysis of the soil profile but the analysis of soil-forming factors and the comparative-geographical method can be of great importance for these purposes. Only in this case the classification of agro-soils can be more informative to solve problems in agricultural production.

Being grown on soils with different salinity degree, Tamarix ramosissima as the major representative of crinohalophytes reveals its ability to accumulate and removal the soluble salts. This is evidenced by a conjugated analysis to determine the chemical composition of soluble salts in ground waters, salt crusts, plant tissues and the salt excretion covering the Tamarix ramosissima sprigs. In these studies the soils were represented by hydromorphic solonchaks with salt crusts 5 and 0.1 cm thick and the content of toxic salts accounted for 32.4 and 57.6 respectively. The salinity was sulfate-sodium by nature. Based upon a comparative analysis of definite anions and cations in plant tissues and the salt excretion it seemed possible to notice that their content in salt secreted is higher by 3.2-7.7 times as compared to that in plant tissues. There is much in common in the content of cations and anions in the salt excretion of Tamarix ramosissima that can be presented in the following way: Na⁺ > Mg²⁺ > Ca²⁺ > K⁺ и Cl^- > SO₄^2-. It has been also established that the maximal removal of Na⁺ and Cl^- in the salt excretion doesn’t connected with the amount of given ions in ground waters. One should be assumed that the content of Na⁺, Ca²⁺, Mg²⁺ и SO₄^2- is associated with the concentration of these cations in salt crusts of the studied solonchaks. It is worthy of note that the Cl^- exudation is not dependent on its content in the ground water and salt crust being comparable with Na⁺ exudation. Thus, Tamarix ramosissima grown under natural conditions reveals no direct dependence between the ions exudation by plants in the kind of salt excretion, the chemical composition and the amount of salts in soil (salt crust) and the ground water.

The national and foreign literature was reviewed in terms of milestones and prospects of development of soil salinity assessment and mapping in arid regions. The contribution of the department of salt-affected soils of V.V. Dokuchaev Soil Science Institute into the development of methods for assessment and mapping of salt-affected soils in Russia and Central Asia during the second half of the XXth century was illustrated. The analysis of the state of assessment and inventory of salt-affected soils in Russia by the beginning of the XXIst century has shown that the latest data given in the published literature on properties and distribution of salt-affected soils are outdated as they are based on the 30-year-old studies. Undoubtedly, these data should be revised with the use of modern methods and approaches widely adopted worldwide. A uniform guideline for the assessment of salt-affected soils of Russia should be developed with the due account for international approaches. Such a guideline will be necessary for inventory and creation of database of salt-affected soils compatible with international databases. The methodology of mapping and inventory of salt-affected soils based on the uniform approach to the assessment of salt-affected soils and specified methodology of large-scale mapping with the use of remote sensing data and proximal soil sensing should be developed.