AbstractThe soil aggregation and structure, water stability of aggregates, and peculiarities of microstructure formation of the ravine forest soils in Dnipropetrovsk region on the example of the northern variant of the ravine forest “Kapitanivskiy” have been identified. The soil properties of southern and northern ravine exposures have been compared. The soil structure, aggregate composition, water stability of aggregates as well as soil-forming processes of the ravine ecosystem have been analyzed. Micro-morphological studies have shown a high degree of aggregation of the upper (0–60 cm) horizons of the soil profile. The structure-forming process is of a zoogenic origin. Aggregates of coprolite nature contain well-disintegrated plant remains. Dark gray, almost black color along the entire area of the micromorphological slide is due to a large amount of organic compounds, which indicates active processes of humification. Fine-dispersed humus consists of a large number of evenly spaced humus clusters. The type of humus is mull. The skeleton consists of minerals of various sizes, dominated by quartz and feldspars. Plasma is humus-clay, homogeneous throughout the entire slide, anisotropic with speckled glowing. Microstructure is mainly aggregated and, in some places, spongy, depending on a microzone of the soil slide. Elemental microstructure is of plasma-silty type. The area of the visible surface of the pores in the upper horizons of the soil profile is fairly large (40%). Pores are round and elongated, of regular shape, here and there with remains of small invertebrates. The deeper the soil slide is, the smaller the area of visible pores along with aggregation becomes. Correlating with micromorphological characteristics, water resistance of structural aggregates reaches very high (90.01% ± 3.07) values in the upper horizons of the soil slide, decreasing at depths. The coefficient of pedality is rather high (7.83 ± 0.81) in the upper horizons, decreasing at depths.

The article contains the results of determination of physical and micromorphological properties of soils under natural ravine vegetation in the southern part of Dnipropetrovsk region. The value of ravine forests for the steppe zone of Ukraine is analyzed, and the methods of investigation are shown. Forest typology characteristics of the vegetation stationary test areas, as well as macro- and micromorphological characteristic of the soil profile, structural condition of the soil, its aggregate composition, and water stability of aggregates, are determined. Soil-forming processes in ravine ecosystems of the southern variant in Dnipropetrovsk region are diagnosed. Micromorphological studies of soil in the intact state, as well as analysis of produced thin sections, revealed the high degree of aggregation of the upper (0–60 cm) soil horizons. Structure formation is of zoogenic origin. Large amount of soil aggregates of coprolite structure is clearly seen under the microscope. Well decomposed plant residues are visible in the aggregates. Soil over the entire area of the section is of dark brown, almost black color. This is due to the large amount (80%) of organic substances indicating the active processes of humification. Fine grained humus is represented by plenty of equally spaced bunches of humones. Humus is in mull form. Skeleton is composed of different sized minerals, with quartz and feldspars dominating in its structure. Plasma is of humus-clay type, uniform over the entire area of the section and anisotropic with point illumination. Visible pore surface area is significant (65%) in the upper layers of the soil profile. Pores feature round and oblong regular shape. Often (on 50% of the pore area) the outbreaks of small invertebrates are found. With the depth of the soil profile, visible pore area decreases, as well as the aggregation. While correlating with the micromorphological characteristics, water stability of the soil structural aggregates reaches very high (80%) indices in the upper horizons of the soil profile and gradually decreases with the soil profile depth. Active biogenic microstructure formation, defining significant aggregation and looseness of microstructure, was diagnosed.

A detailed study of the relationships between all components of each biogeocenosis is needed for its in-depth investigation. According to the concept of biogeocenoses developed by V. M. Sukachev, soil is one of the five components of biogeocenosis being its resulting unit. Soil is a bioinert component body of biogeocenosis. Playing the role of a subsystem, it is characterized by self-regulation, stability, direct and feedback mechanisms, self-restoring fertility, a specific biological cycle of substances and energy flow against the background of a specific natural geographical area. When the soil testing, its chemical, physical, water, micromorphological properties should be determined, and, above all, a total humus content and quality. Humus affects all important soil properties. In fertility, its essential role consists in a nutrient source as a factor that has a physiological effect on plants. A role of humus in improving the physical, thermal and water properties of soils is well-known. The total content and group composition of humus are also determined during the diagnosis and classification of soils. For a more detailed description of humus, Grishina and Orlov proposed a system of indicators of soils humus condition. This is a level of humus content and reserves, its profile distribution, type of humus, degree of humification, etc. In this work, we made an attempt to diagnose the soils of ravined biogeocenoses and steppe virgin lands in Dnipropetrovsk region on the basis of a number of the above parameters. To compare, the common steppe virgin chernozem and forest chernozems of the northern and southern variants of the ravines were used. The study was carried out in the fresh linden-ash oakery (the Kapitanovsky Bayrak) and in the fresh maple oakery (the Viyskovoy Bayrak) occured in the middle part of the slopes of the northern exposition. The paper presents data on the study of the ravined forest biogeocenoses influence on the total content and qualitative composition of soil humus in the northern and southern variants of Dnipropetrovsk region in comparison with the steppe virgin soil. It was established that the total humus content and reserves in the layer of 0–20 cm increased and varied from moderate to high under the influence of ravined forest vegetation; the type of humus turns from humate to fulvate-humate, which has a positive effect on plant growth and development, as it makes nutrients more mobile and available to plants. Under the influence of forest vegetation in the ravines, the soil humus condition improved, namely, the total humus content and reserves in the 20 cm layer varied from moderate to high, and the type of humus turned from humate to fulvate-humate. Our data confirmed  O. L. Belgard and A. P. Travleev provisions that forests in the steppe zone effect positively on soil properties, in particular their humus condition, in contrast to the forest zone.

Наведено матеріали біогеоценотичних досліджень байрачних лісів північного варіанта. Подано детальний геоботанічний опис і біоекологічну паспортизацію травостою пробних площ. Встановлено залежність видового складу травостою пробних ділянок північного варіанта байрачних лісів від світової структури.