The article is devoted to the study of woody plants communities, that spontaneously form in the abandoned areas of Kryvyi Rih Area as a result of spontaneous-invasive settling of species in previously established plantations. For the study, we laid 16 trial plots in 5 growth sites of such communities. We determined the species composition and biometric characteristics of primary woody plants and those, that formed these communities due to the invasion. In the first such community, which was formed due to the settling of other species in a 40-year-old plantation of Salix alba L., we found on 3 plots with an area of 625 m2 94 medium-sized trees Acer negundo L. having height (h) 11.8–13.6 m, trunk diameter (D) 16.8–17.3 cm and crown projection area (S) 9.5–10.4 m2, as well as 210 young generative trees, their height varies between 6.5–7.3 m, trunk diameter 5.0–5.4 cm, and the projection of the crown 2.5–6.3 m2. In this community also grow young and medium-generative trees of Robinia pseudoacacia L. – respectively 7 individuals – h = 7.2–11.7 m, D = 8.1–10.7 cm, S = 6.1–6.5 m2 and 7 ones – h = 13.5–14.0 m, D = 18.1–27.0 cm, S = 14.0–38.5 m2. Among self-seeding plants, such species predominate: Acer platanoides L. – 3905 specimens and Acer negundo – 1823 specimens. Three species dominate in the three dense forestation massive near the highway, which occupy an area of 250 m2: Robinia pseudoacacia, Ulmus pumila L., Fraxinus excelsior L. and Cerasus avium (L.) Moench. Robinia pseudoacacia is the most common among medium-generative plants, and Acer negundo, A. platanoides, A. tataricum L. – among young generative plants. Self-seeding of Robinia pseudoacacia, Acer platanoides, Fraxinus excelsior and Acer negundo is dominated in this area. In the abandoned Ulmus pumila plantation near the iron ore mine in three areas with an area of 625 m2, 12 to 33 specimens of medium-generative trees of this species with a height of 12.2–13.1 m with a trunk diameter of 14.7–16.0 cm and a crown projection of 25, 5–27.3 m2. Its self-seeding is quite active in all areas. Self-seeding plants of Acer negundo are also present here – 51 specimens and Acer platanoides – 35 ones. Self-seeding plants of A. platanoides – 9837 specimens, A. pseudoplatanus – 2111 specimens, Ailanthus altissima (Mill.) Swingle – 396 specimens dominate in the neglected park on the territory of 500 m2, where Acer pseudoplatanus, Acer platanoides, Robinia pseudoacacia grow. A study was also carried out on the example of the Zelena gully in order to determine how invasive species spontaneously penetrate into the formed steppe feathergrass-fescue phytocenoses. In the upper part of the Zelena gully, located outside of Kryvyi Rih, more than 40 years ago, forest belts were created from many species of shrubs, which have already been listed. Crataegus fallacina Klokov and Rhamnus cathartica L. diffusely inhabit and clearly predominate in the 6 trial plots that were laid on the slopes of the south-eastern and north-western exposures. In the presence of a large number of seed donors from the previously mentioned species on the slopes of the gully firstly Crataegus fallacina settles. Morphometric parameters of shrubs of these species were slightly larger on the north-western slope than on the south-eastern: the height of Crataegus fallacina – 2.5–2.9 m, and the diameter of the crown – 3.5–4.3 m, while in Rhamnus cathartica – the height of the bush was 0.7–0.8 m, and the diameter of the crown – 0.5–1.1 m. Thus, invasive species of Ulmus pumila, Acer negundo, Robinia pseudoacacia and Ailanthus altissima, which are the main in spontaneous communities in abandoned anthropogenically disturbed areas of the city, do not penetrate into stable phytocenoses. Most of these species of woody plants show low invasive activity and do not form multispecies communities in weakly disturbed feather-fescue phytocenoses.
Expansion of tree and shrub plant species into undisturbed steppe phytocenoses
