Dynamics of grass stand formation in poplar plantations on different types of reclamations of disturbed lands of Western Donbass

The purpose of our research was to study the long-term dynamics of the herbage cover at different stages of growth and development of poplar plantations on the types of artificial soils of the forest reclamation area. The object of research is flora phytotoxic dumps of «Blagodatna» coal mine, where imported substrates such as sand-clay, clay loam, red-brown earth and humic soil in various combination were applied to create reclamations layer on the surface of the mine dumps (Dnipropetrovsk region, Pavlograd region).  Type 1: 30 cm of soil mass of typical chernozem (SMTC), 50 cm of red-brown earth, 80 cm of alluvial sand-clay and sand, and deeper there is the coal mine  solid; type 2: 30 cm of SMTC, 80 cm of sand, and mine solid deeper; type 3: 30 cm of SMTC, 60 cm of alluvial sand-clay, 60 cm of clay, and deeper there is mine solid; type 4: 40 cm of SMTC, 30 cm of red-brown earth, 40 cm of sand and mine solid deeper; type 5: 55 cm of alluvial sand-clay, deeper there is mine solid. Stationary observations were carried out in poplar plantations of 8-, 16-, 27- and 34-year-old age on permanent trial plots. They were presented with a black poplar and seven hybrid poplars. The research has established that climatic conditions, influence of surrounding phytocenoses of undisturbed lands, inheritance by pedozems of seed material of grass plants with a fertile layer of the soil set the direction of succession on the way of formation of zonal herbal group. The long-term growth of the role of the arid element indicates the formation of a structure close to the zonal flora. The formation of the flora of technical soils in poplar plantations occurs in four stages: the first is pioneer plant communities, which begins with the completion of the technical phase of reclamation and confined to the stages of forest formation; the second is a simple grouping that is associated with the development of the stand until the closure of canopy and inter-row soil cultivation; the third is a complex grouping that is fraught with pole wood stage of stand development and partial getting sparse; the fourth in our studies, is partially closed when gradually tree plants disappear and their influence disappears. In addition to the influence of tree vegetation, its age and stage of development, the formation of lower layers of biogeocenoses is significantly influenced by the conditions stipulated by the stratigraphy and the power of artificial substrates, as well as the elements of the landscape, both created initially and formed as a result of the fragmentary subsidence of the dump territory. These factors, depending on their dynamic changes, regulate correlation between various groups of biomorphs, climamorphs, trofomorphs, hygromorphs, heliomorph and zenomorphs in the grass cover. Created forest vegetation conditions on the plateau and the upper third of the dump do not meet the needs of hybrid poplars under conditions of acute shortage of moisture, which are characteristic of the steppe zone. Fast-growing poplar hybrids can be used as a pioneer culture up to 15–20 years of age.