The dissertation is devoted to the complex analysis of viability of Populus L. species on iron ore dumps of Kryvyi Rih – Pervomaisky and Hannivsky dumps of the Pervomaisky quarry of PrAT «Northern GOK» and Petrovsky dump of PrAT «Central GOK». Representatives of the genus Populus were also studied in the park plantations of Kryvyi Rih. To compare the vitality of poplars in different edaphotopes, the area of conditional control was the park «Vesely Terny», the soils of which are represented by chernozem. The review and analysis of works on forest reclamation of waste heaps is carried out in the work; it is shown that the dumps are characterized by the predominance of substrates of mixed particle size distribution, extreme rigidity of the thermal regime and lack of moisture. The ecological aspects of self-overgrowth of man-caused disturbed lands, as well as the influence of artificial plantations adjacent to dumps on the processes of natural distribution of plants on man-caused lands are highlighted.
It is shown that the basis of park plantations in Kryvyi Rih is made up of poplar massifs as the most durable tree species. The most common in park plantations are P. bolleana, P. italica and P. nigra. It is established that according to the scale of V. Alekseev (1989) the living condition of poplars in parks decreases with increasing their absolute age. In addition, trees in the city often suffer from mechanical damage and disease, which accelerates the aging and extinction. Among the 6 species and 1 hybrid of the genus Populus found on the dumps, the most common are P. italica, P. deltoides and P. alba, which have anemochoric origin.
The root system of poplars in edaphotopes of dumps changes its morphostructure, as a result of which the processes of formation change in poplars and the variety of life forms increases. P. italica, P. alba, and P. tremula form life forms of a single-stemmed tree, a small- and multi-stemmed tree or a bush, a curtain-forming, or a long-oxyloric tree. Single-stemmed trees of these species of poplars make up only 10-15% of the total number of studied individuals. In most cases, these are trees of seed origin on the rocky slopes of dumps in places of soil erosion or on sloping areas in depressions. Such individuals have a lower height, crown habit compared to plants of urban plantations, as well as more significant damage to the leaf apparatus. Small-stemmed and multi-stemmed trees are formed due to the formation of orthotropic shoots from dormant buds at the base of the main trunk.
There are three main zones in the cross section of the poplar root: the rhizoderm, the primary bark and the central axial cylinder. The rhizoderm of P. alba is represented by one layer of epiblem cells. The most developed is the primary bark of the root, which consists of the exoderm, mesoderm, parenchyma of the primary bark and endoderm. Exoderm cells are polygonal, close to each other, are arranged in several rows. Their cell walls are impregnated with suberin and lignin. In the anatomical structure of the poplar root there is a transition from the primary root structure to the secondary. The process of secondary changes begins with the appearance of layers of cambium from the poorly differentiated parenchyma of the central cylinder.
The transition form between the root and the trunk is xylorization - an adaptively important formation in P. alba and P. italica on the iron ore dumps of Kryvyi Rih. In the course of studies of the anatomical structure of the xylorizoma of P. italica it was found that additional buds are formed in the pericycle of the root. Xylorizom has an area of meristematic activity, where the formation of vegetative shoots. In case of damage or death of some shoots, apical buds on the thickening of xylorizomes that occur at the sites of rupture of the primary bark under the action of mechanical damage, are able to actively restore and grow vegetative shoots.
In the apical area of xylorizoma there is an increase in the number of cells in the collenchyma and core rays and the formation of a zone of meristematic activity, which contributes to the laying of additional buds and increase the regenerative capacity of the studied species of the genus Populus L. in iron ore dumps Kryvyi Rih. It is this feature of the woody rhizome that can be used to promote the self-healing processes of man-made disturbed lands. The established pattern of reducing the amount of chlorophyll a and b and increasing the number of carotenoids indicates the activation of adaptive responses of the plant organism to growth in difficult environmental conditions of dumps and the implementation of protective and protective functions of carotenoids.
A method of using white poplar for reclamation of iron ore dumps in Kryvyi Rih has been patented, which significantly reduces the cost and accelerates the processes of afforestation of iron ore dump surfaces.
