Structure of the adventive fraction of the flora of floodplain ecosystems of Lutsk city and its environs.
The problem of urbanization lies in increasing of the number of adventive species, which leads to a decrease of the share of aboriginal ones. The study of alien species is of great practical importance, since most of them are weed crops, poisonous plants and species with high invasive capacity. The study of the flora of floodplain communities was conducted by traditional route and reconnoitring methods. A herbarium collection of vascular plants has been prepared during the field research. According to the obtained results, the share of the adventive flora fraction of Lutsk city comprises 121 species of vascular plants (88,3% of the total number of adventive species of the studied territories), belonging to 3 classes; 26 orders; 33 families and 91 genera. The leading place in the taxonomic hierarchy belongs to the Magnoliosida class (126 taxa or 92,71%). The family Asteraceae is characterized by the richest species diversity 3 - 3 species (26,19%). The second and third places belong to Fabaceae and Lamiaceae respectively (12 species or 9,52% and 11 species, 8,73% respectively). Twenty-three families of Magnoliosida (or 74,19%) in the studied cenoflora are represented by only single species and monotypic genera form 25,25%. The river flood plains of Lutsk city form a powerful center of concentration of adventive plants (45,50% of the total number of species); several families predominate in the systematic structure of the adventive cenoflora of the flood plains, most of which are represented by single species; the prevalence of archeophytes is observed. The structure of the adventive cenoflora is dominated by Eurasian (31 species, 25,6%), Holarctic (23 species, 19%), cosmopolitan (8 species, 6%) and Euro-Asiatic-North African and North American species (6 species each, 4,9% respectively). The most abundant groups according to the moisture regime are xeromesophytes - 49 species (40,5%) and mesophytes - 43 species (35,5%). As for the light regime the most numerous are heliophytes - 59 species (48,7%) and scioheliophytes 45 species (37,1%). The ratio of trees to herbaceous plants is 1: 13.7. Regarding the ways of seed dispersal the most numerous groups in the adventive fraction are: anemochores, endozoochores, barochores and zoochores. The alien species are intensively introduced and naturalized into the regional flora and are becoming its integral component. Knowledge of the species composition of the adventive fraction of the flood plain flora of Lutsk city and its suburbs, biological and cenotic features of these species, their migratory opportunities and naturalization ability will help to clarify the trends in the development of flood plain cenofloras, as well as preserving their unique ecosystem functions.