Effect of ravined forest biogeocenoses on soil humus status in a steppe environment

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.