QUANTITATIVE DATA REGARDING INVASIVE PLANT SPECIES FROM HABITATS OF EUROPEAN INTEREST IN THE PESCEANA RIVER BASIN, VÂLCEA COUNTY

Invasive allochtone species cause the degradation of the natural habitats they invade through the negative impact they have on native plant communities, which they tend to alter, even replace, through their increased competitiveness and their high potential for reproduction and spread. The main objective of the study was to identify and evaluate the spread potential of allochtone invasive species observed in some habitats of European interest in the Pesceana river basin (Vâlcea county), starting from the quantitative evaluation of their populations within the plant associations specific to different types of habitats. The assessment of invasive species was carried out by determining the number of individuals and assessing the percentage abundance-dominance of these species in relation to the total abundance-dominance of the species in the plant associations specific to the different types of analyzed habitats. Observations were carried out in the following types of habitats affected by different allochtone invasive plants: habitat 91M0 Pannonian-Balkanic turkey oak-sessile oak forests; habitat 9130 Asperulo-Fagetum beech forests; habitat 91Y0 Dacian oak & hornbeam forests; habitat 9170 Galio-Carpinetum oak-hornbeam forests; priority habitat 91E0* Alluvial forests with Alnus glutinosa and Fraxinus excelsior (Alno-Padion, Alnion incanae, Salicion albae); habitat 6430 Hydrophilous tall herb fringe communities of plains and of the montane to alpine levels and habitat 3150 Natural eutrophic lakes with Magnopotamion or Hydrocharition – type vegetation. The primary factor that significantly contributed to the introduction and rapid spread of these plant species in the analyzed habitats was zoo-anthropogenic. Among the invasive plant species that affect the floristic composition of the plant associations in the assessed habitats, the most frequent were: Erigeron canadensis, Ambrosia artemisiifolia, Robinia pseudoacacia, Erigeron annuus subsp. strigosus, Xanthium orientale subsp. italicum, Elodea nuttallii and Ailanthus altissima, all being classified as neophytes. Interpretation of the field date showed that the most affected types of habitats were 91E0* and 6430 and the most affected plant associations, depending on the share of invasive plant species, were Aegopodio podagrariae-Alnetum glutinosae Karpati et Jurko 1964, respectively Scirpetum sylvatici Ralski 1931 em. Schweich. In the case of the association Aegopodio podagrariae-Alnetum glutinosae Karpati et Jurko 1964, the percentage values of the abundance-dominance of the invasive species are very high compared to the value of the total abundance-dominance of the component species, which denotes a high degree of damage and the high potential of dissemination to the associations adjoining plants and to other similar types of habitats.