Articles

Salt neoformations in sandy and silty loam soils of the Aral Sea dried bottom in the south-western part were studied by X-ray fluorescence, electron microscopic, sedimentation methods of analysis and laser diffractometry. The surface layers of soils are significantly saline and enriched with CaCO₃. The distribution of CaCO₃ over the area is quite uniform, which indicates relatively close conditions of its formation during desiccation. The salt content varies from 0.4 to 1.2% in sands and from 3.1 to 5.8% in silty loam. The latter are characterized by the highest salinity, when, in addition to gypsum and halite, readily soluble salts are formed: eugsterite (2Na₂SO₄^.CaSO₄.2H₂O), astrakhanite (Na₂SO₄^.MgSO₄^.4H₂O), and mirabilite (Na₂SO₄^.10H₂O). Precipitation of calcite upon drying leads to the formation of CaCO₃-ooids in sands and CaCO₃- microaggregates from clay and silty particle in silty loam. The reason for the increased activity of easily soluble salts in the processes of aeolian transport has been established. This transport and, correspondingly, the salinization of adjacent territories are facilitated by the blocking of adsorption centers in clays by calcite, which prevents the binding of easily soluble salts in clay-salt microaggregates.

We present a review of the literature data and the results of our own studies on the influence of soil invertebrates of the macrofauna size class on the processes of creating and maintaining the heterogeneity of soil properties in the temperate zone. Significant changes in physical, chemical and biological parameters of soils, compared with background indicators, were noted in excrement and associated soil aggregates, as well as substrates — products of vital activity of key groups of large invertebrates, such as earthworms, diplopod millipedes, diptera and coleoptera larvae, woodlice, and ants. Most of the research is related to the impact of earthworms and ants on soils, whereas for other groups few reports exist. The results of the research will be useful for practical purposes, in particular for the development of sustainable anthropogenic ecosystems.

Methodological aspects of identification, accounting, analysis of development and interaction of soil heterogeneities of various genesis are considered. The modern views on their origin are summarized, methodigical approaches and features of the study are shown. Conceptual views in the field of soil science are presented, which allow a deeper and more comprehensive approach to the assessment of such a phenomenon as soil heterogeneity: the hierarchical orga- nization of soil space, historical and modern («soil-memory» and «soil-moment») components of soil heterogeneity, soil succession and their role in understanding the essence of the phenomenon under consideration. The concept of primary and secondary heterogeneities is formulated, which are defined as a universal feature that manifests itself at all levels of the organization of the soil space and is formed, respectively, by paleo- and cenotic mechanisms. It is shown that the primary heterogeneity is the result of the action of pedogenesis factors, which reflects the desire of the soil to find an equilibrium state with the environment. Secondary heterogeneity is a consequence of the action of various natural and anthropogenic factors that bring the soil system out of equilibrium. A scheme of factors and causes of primary and secondary heterogeneities is proposed and formalized, as well as a scheme of modern factors and causes leading to the emergence of secondary heterogeneity of various origins. The priority role of the works of E.A. Dmitriev and his school in the formation of modern views on the heterogeneity of soils, in the development of field and statistical methods for analyzing the assessment of this natural phenomenon, which he put in a number of direct objects of research, is emphasized.

Th e article discusses the current approaches to the assessment of the heterogeneity of soil properties. On the example of the experimental plot (106 ha) of the RUNE “Grodno Zonal Institute of Plant Industry of the National Academy of Sciences of Belarus” it is shown that ignoring the intra-fi eld heterogeneity leads to even more signifi cant diff erences. On the experimental fi eld, using satellite images and multi-temporal indices EVI, microplots with an area of 50 to 200 m2 with а signifi cantly reduced level of eff ective fertility, up to the death of plants, were identifi ed, on the basis of which а sampling grid was developed. During the fi eld work, 214 pHKCl samples were taken with а sampling step of 70 m and 53 additional samples in the “problem areas”. Using geostatistical methods, data on the spatial heterogeneity of pHKCl were obtained, the degree of spatial dependence and the accuracy of the results obtained were estimated for various numbers of samples (107, 216, and 268 points). Further use of stochastic modeling made it possible to construct high-precision cartograms of acidity with а pixel resolution of 4 m and 12 m. We also showed that the use of cell sizes less than the processing device is not useful for solving applied issues of precision farming. Probabilistic-statistical models were obtained, represented by cartograms of mean square errors and the probability of the phenomenon. Th e resulting cartograms showed the presence of ultra-acidic soils in the “problem zones”; such а reaction also determines the presence of toxic aluminum compounds and extremely low calcium and magnesium contents, which jointly lead to the absence of seedlings of cultivated vegetation. А detailed accounting of soil acidity in comparison with а classical agrochemical survey provided savings of $ 2807 by the application of СаС03, which made it possible to fully compensate for the additional costs of taking and analyzing а larger number of samples.

The regularities of the spatial distribution of ¹³⁷Cs in forest soil at the microlandscape level in semiromophic and hydromorphic conditions in the Bryansk region at different measurement steps with the KORAD radiometer (10, 2 and 0,5 m) are investigated. The variability of the ¹³⁷Cs stock obtained by two devices differing in the size of the sampling area (RPO) is compared: 1) CORAD radiometer 2) sampler D=14 cm. The ratio of the variability of the ¹³⁷Cs distribution obtained by field radiometry to the sampling data (CVcorad/CV sample) for the entire site is 0,63; for the hydromorphic part, B1-1 is 0,87. For the entire site (size 50x80 m), a weak spatial correlation was revealed (the effect of a "chessboard"), for a local hydromorphic site, a strong correlation with a rank of 1,4 m.

The aim is to present statistical portrait of soil cover pattern for farm as series of cumulative statistical distributions of soil horizon’s depth and thickness. The object is soil combinations of Haplic or Luvic Protosodic Kastanozems and Solonetzs at the experimental station “Irrigated” localized in southern-western end of the Volga Upland near the Volga-Don Channel. Majority of empirical statistical distributions of soil horizon’s depth for general data fetch (182 profiles) cannot be approximated by normal one. Nonparametric indices are used. Separation of soil groups using substantial properties does not guarantee data fetches with normal distribution for all morphometric properties. Soil types and subtypes according to Russian soil classification system have different complex of statistical distributions of soil horizon’s depth. Many differences are related to changes of carbonate profile, development of secondary solonetzicity, crust formation, local surface washout and accumulation of upper part of arable horizon.

Soil respiration, which is one of the main fluxes in the global carbon cycle, is characterized by high temporal and spatial variability. Based on the year-round continuous 21-year monitoring of the respiration of soddy weakly-podzolic soil in the forest and meadow coenoses of the southern taiga zone, an assessment of the temporal variability of CO₂ fluxes from soils was made at different time levels: monthly, seasonal, and annual. The values of total respiration of soddy weakly-podzolic soil varied most significantly at the monthly averaging level (coefficient of variation, CV=25–56%), while the variability of the annual respiration of soils was 20–22%. At the seasonal averaging level, the highest variability (CV=39–44%) was noted for winter CO₂ fluxes from soils, whereas the variability of total soil respiration in the other calendar seasons was close and amounted to 26–29%. The effect of the type of cenosis on the total CO₂ fluxes from the soddy weakly-podzolic soil was statistically significant both at the annual averaging level and in all calendar seasons of the year, except for winter. The most stable indicator characterizing the seasonal distribution of CO₂ fluxes within a year is the contribution of the warm period (May–October) to the total annual CO₂ flux from soils, which averages 73–77%. Its variability over 21 years of observation in both coenoses was 8%. It can be recommended to use this indicator to obtain estimates of annual CO₂ fluxes from soils based on field measurements carried out only within the growing season. The numerical experiments performed have shown that continuous measurements of CO₂ emission from soils for five consecutive years reduces the variability of annual and seasonal CO₂ fluxes from soils by more than 2 times compared to a one- or two-year measurement period. This makes it possible to recommend a five-year observation period as the optimal required for obtaining adequate values of annual and seasonal CO₂ fluxes from the soils of the southern taiga zone.