URBANIZED PLANT COMMUNITIES DOMINATED BY INVASIVE ACER NEGUNDO

Abstract

Goal. To compare the α-diversity parameters of plant communities prone and not prone to A. negundo invasion, but aligned with each other according to other characteristics (degree of urbanization, fragmentation, anthropogenic disturbance). Methods. Complex use of field, laboratory, mathematical-statistical, calculationcomparative methods and system analysis. Results. We compared the α-diversity of groups of the grass layer, prone and not prone to Acer negundo invasion, but aligned with each other according to the degree of urbanization, fragmentation, and anthropogenic disturbance. The research was carried out in Odesa on 13 sites with two test sites on each: one – grouping dominated by A. negund; the second is a grouping dominated by other types of trees, i.e. 26 communities in total. It was established that the main reasons for the variation in the characteristics of the grass layer are the dominant tree species (A. negundo or other trees) and the area of plantations. In thickets of A. negundo, the number of grass species per 400 m2 was lower than under the crowns of other trees: 17±3 and 28±3, respectively. However, communities with and without A. negundo did not differ in Shannon index values and degree of dominance, as well as in the ratio of annual/perennial species and graminoids/herbs. The increase in habitat fragmentation was accompanied by an increase in the share of synanthropic species both under the canopy of A. negundo and in groups dominated by other trees. From a methodological point of view, the results showed that when assessing the consequences of plant invasions, it is necessary to take into account the spatial regularities of the determination of the structure of groupings. Conclusions. It was established that the main effect accompanying the dominance of the alien North American tree Acer negundo in urbanized communities is a decrease in the species richness of the grass layer. The change of most other characteristics of the groups under the influence of A. negundo was not confirmed. The effect of A. negundo on grass species is non-selective or slightly selective, but special studies are needed to reliably find out the degree of such selectivity. It was established that the reasons for variation in the composition of urbanized plant communities are the dominant tree species (A. negundo or other trees) and the area of plantations. Thus, from a methodological point of view, the obtained results indicate that when assessing the consequences of plant invasions at the scale of groups, it is necessary to take into account spatial and other regularities of the structure of groups. A clear division of the effects of urbanization, fragmentation, habitat pollution, as well as the consequences of the introduction of alien plants is possible only with special methodological efforts. Otherwise, there is a possibility of misinterpreting the effects of urbanization or fragmentation as the effects of alien species invasions or vice versa.