Biotic homogenization of dendroflora in the conditions of the megapolis (Dnipro, Ukraine)

Purpose. Biodiversity assessment and clarification of the trend towards homogenization of the dendroflora of the Shevchenko Park (Dnipro, Ukraine). Methods. Floristic methods of research are applied - elucidation of the taxonomic composition and selection of the adventitious fraction of dendroflora, methods of species richness assessment (according to the Menkhinik index and Margalef index), determination of floristic commonality (according to the Jaccard index) and floristic homogeneity (according to the Koch index of biotic dispersion), methods of ecological analysis (by biomorphs and ecomorphs), physical, physicochemical, chemical methods of soil analysis, soil biological activity, statistical methods of data processing (descriptive statistics and correlation analysis). Results. It was established that artificial stands of trees in the Shevchenko Park are capable of forming a sufficient amount of viable undergrowth of autochthonous and introduced (adventurous) species, the ratio of which is 37.0% to 63.0%. The amount of tree growth of adventive sites in the areas according to the level of recreational load is distributed as follows: with no load - 38.5% of the number of self-regenerating trees, with moderate - 68.2%, with strong - 80.5%. The indexes of species richness of Margalef and Menkhinik of self-regenerating tree species for the site with a strong recreational load turned out to be the largest (due to adventitious species) compared to the sites with no and moderate recreational load. Koch index of biotic dispersion is 50.0%. Correlation coefficients between the number of allochthonous and autochthonous tree species that have self-regenerated for the studied areas with strong, moderate and no recreational load are statistically significant (0.73, 0.76, 0.77 respectively). Conclusions. On the territory of the investigated areas of the park, there are 14 tree species capable of seed self-regeneration, which taxonomically belong to 12 genera and 10 families. Of them, 9 adventive species were registered, represented by 9 genera and 7 families with the leading family Sapindaceae. The calculated index of biotic dispersion testifies to the presence of a process of floristic homogenization of the forest stand on the territory of the park. As part of the adventitious fraction of the self-regenerating dendroflora, there is an increased invasion of Ailanthus altissima and the occurrence of such neophyte species as Celtis occidentalis and Acer negundo, which indicates the penetration of alien species into the local flora and a potential threat to natural floristic diversity.