Specific features of accumulation of humus	in technozems under poplar plantations in the conditions of the Western Donbass
Authors: Masyuk A. N. , Gorban V. A. 
Published: February 2020

One of the consequences of the mining industry’s activity is the removal of various granulometric composition on the daily surface of rocks, differing in water, physical and chemical properties. Subsequently, these rocks become the object of biological reclamation of land. The study of the role of humus in soil-forming processes occurring in reclaimed lands is important for establishing the features of their genesis. The suitability of soils for biological reclamation, taken out during development in dumps, is divided into three groups: suitable (fertile soil, which, as a rule, is separately removed, and potentially fertile rocks), are of little use (they have limited opportunities for growing plants) and are unsuitable phytotoxicity, rocky and others, in which edapho-ecological restrictions approach a minimum and a maximum). Proceeding from this, it is of interest to study: 1) the humus profile in technozems that are formed only from rocks, since from the moment of their emergence on the day surface the counting of the soil-forming process begins; 2) consideration of the behavior of humus in the fertile layer of technozems, consisting only of the mixed horizons H and Hp of zonal soils, because in the process of the technical stage of reclamation, the connections and properties characteristic of their natural historical compilation are lost. Field studies were concentrated on the experimental and experimental site of forest recultivation number 2 of Dniprovsky National University named after Oles Honchar in the Western Donbass, representing various variants of artificially created edaphotopes. Formation of the site lasted for two years and in its final form was a dump made up by a mine rock (carefully planned), on the surface of which there were artificially designed single-, two- and three-tier structures of reclaimed lands. The heap with a total area of 11.4 hectares was located between the mines «Blagodatnaya» and «Pavlogradskaya» (Dnepropetrovsk region, Pavlograd district). Stationary observations were carried out in poplar plantations. Edaphotop constructions were created as a result of the technical stage of reclamation, when the ground mass of ordinary chernozem and overburden rocks in different sequence and thickness fell to the phytotoxic mine rock (the product of the coal mining industry), which was placed on the day surface in the dumps. In the trial plots, soil sections were laid. Sampling was carried out every 10 cm along all the soil profile in 3-fold repetition, including mine rock. For a more complete (objective) characteristic, in some cases, the selection was carried out from the top 0–2 cm layer, as well as at the boundaries of the different-quality reclamation layers. The total content of humus was determined by Tyurin. As control (zero-moment), rocks were used from the sides of the quarry, from which the edaphotops artificially created for reclamation were formed and located in the immediate vicinity of the experimental site. To determine the stage of soil formation in comparison technologies, zonal soils were used (chernozems of ordinary heavy loam on loess) located in the Mavrinsky nursery (Dnipropetrovsk region, Pavlograd district), in which there were plantations of black poplar, the age of which corresponds to the age of plantations in the areas of forest reclamation in the Western Donbass and located 20 km from the experimental site outside the zone of influence of coal industry objects. As a result of the studies carried out, it has been established that the processes of humus accumulation in techno-scales are most active in surface layers (0–2 cm), which are characterized by the maximum content of humus primarily due to the fall of poplar plantations. In the studied techno-scales with depth, a gradual attenuation of the processes of humus accumulation is observed. The main source of organic matter, which eventually turns into soil humus, is the roots and decay of poplar, which under these conditions is the main edificator. The flow of organic matter in the form of leaf litter stimulates the processes of humus accumulation in the surface layers of technozems, and in the form of roots in all layers of the technozems where they are located. The humus content in the fertile soil layer increases, and the profile changes depend on the content of organic matter in the «parent» (zonal) horizons H and Hp involved in the reclamation and their relationships (or their share in the formation of the upper part of the technozem). In the horizons of rocks lying below the fertile soil layer, the humus content was within the limits corresponding to the zero-moment of soil formation. In the composition of ancient alluvial deposits, inclusions of various clays (loess-like, kaolinic, reddish-brown and others) are often found, ground mass of chernozems, sometimes of mine rock, which gives it a new qualitative state and promotes the formation of fertility close to loam. In places of significant impurities of clay (more than 30 %), the fertility of various mixtures can be higher than that of each breed separately – sands, sandy loams, loams, clays. Significant carbon stocks in the mine rock are not a source of organic matter used to feed plants due to the lack of mobile and water-soluble forms of humus nature.