SPECIES COMPOSITION OF ADVENTITIOUS FRACTION OF FLORA ON THE DRAINED LANDS OF VOLYN POLISSIA
Considering the important role of the alien species in actual florogenesis of different regions and insufficient knowledge on the issue in Volyn Polissia in general and for its reclaimed areas in particular, in present the adventitious flora study has a great relevance. The importance of such studies is also growing due to the prevailing of drainage objects at the time that was caused by a number of reasons. The purpose of our study was to determine the species composition of alien flora in the drainage systems of the region, analyze its features, define the phytocoenotic role of alien plants. 11 drainage systems of Polissia area in Volyn and Rivne regions were investigated in order to receive the data on the species composition of the alien flora. According to research of the drainage systems of Volyn Polissia the spread of 68 species of alien flora that belong to 60 genera and 25 families was found. The most numerous were such families as Asteraceae (17 species or 25 % of total species), Brassicaceae (9 species or 13,2 %), Poaceae (7 species or 10,3 %), Lamiaceae (5 species or 7,3 %), Fabaceae (4 species or 5,9 %). Together these families present 42 species or 61,8 % of all described alien species. The remaining 20 families account for less than 26 species, each one represented by 1 - 3 species. The archeophytes represented by 41 species significantly dominate by the time of entry into the registered alien species. The kenophytes include 27 species. According to the results of our study the prevalence of archeophytes is possibly associated with the peculiarities of the natural environment of the region and the specific environmental conditions in the reclaimed areas. At the same time, the distribution of alien species by the future entry indicates that the reclaimed areas are primarily populated with those species which have already entered into the territory of Ukraine. The epekophytes represented by 55 species predominate by the degree of naturalization among the registered alien species. The investigated alien species were quite varied by the origin. The most numerous species is a group of Mediterranean origin represented by 19 species. 11 species are of Mediterranean-Iranian-Turanian origin. The group of North American species is represented by 9 species. Other groups have single representative or small number of species. The annuals represented by 46 species considerably dominate by the spectrum of life forms in the registered alien species. The predominance of the annuals is the hallmark of the alien flora. The kseromezophytes represented by 42 species and the mezophytes represented by 18 species stand out significantly in the hydromorphs of alien species in drainage objects. Only 19 species from the registered alien species of the drainage systems are presented in all the investigated objects. As a rule most of these species grow in certain phytocenosis. Among them there are archeophytes represented by 15 species and kenophytes represented only by 4 species. The spread of other alien species is random. Most of them are found along the roads, on the borders and in the abandoned places. As part of many plant communities in the drainage areas the most constant kenophyte is Conyza canadensis (L.) Cranq. (about 50 %). Atriplex prostrata Boucher, Ballota ruderalis Sw., Phalocroloma annum (L.), Tripleurospermum perforatum (Merat.), Lactuca serriola Torner are quite constant for ruderal lands. Most of alien species are characterized by the low projection surface. The notable phytocenotic role of such species is specified in the most transformed areas. In general, as the analysis of published data shows, the alien flora fraction of Volyn Polissia has a very high potential for practical use. At the same time most of the plants have valuable properties, but the potential is not used fully yet. That is why the research in this direction is quite promising.