WOODY SPECIES CULTIVATED FOR ORNAMENTAL PURPOSES WITH INVASIVITY CAPACITIES IN OLTENIA, ROMANIA

Changes in climatic conditions influence the expansion on ever larger surfaces as well as the exacerbated development of populations of invasive species introduced in southern Romania initially for ornamental purposes. In the last decades, an increasing number of species that were cultivated for different purposes but also that accidentally entered Oltenia became successful invaders in different habitats. Many factors may contribute to the increased invasiveness of these species, including seed production, germination, and their relatively high growth rate. The impact of invasive species on native vegetation in a region can have different intensities, but they can increase with the accentuation of the drought and the aridification of the lands in the south of Oltenia, this may lead to the loss or irreversible degradation of habitats or species populations. In recent years in Oltenia, especially in the southern part, in the large hydrographic basins of the Danube, Jiu and Olt, the number of invasive species has increased considerably, their ability to spread and invasiveness being very high. Some of these species exert a high degree of aggression on wet, practical and forest habitats, influencing the structure and functionality of edifying phytocoenoses. Among the invasive species introduced for ornamental purposes in Oltenia, particularly important populations have developed: Acer negundo, Rhus typhina, Amorpha fruticosa, Ailanthus altissima, Eleagnus angustifolia, Fraxinus pensylvanica, F. americana, Parthenocissus inserta, P. quinquefolia, Robinia hispida. It should be noted that in recent years the species Albizia julibrissin was introduced for ornamental purposes in Romania, but also in Oltenia. This species is cultivated excessively, in gardens, green spaces, private yards and especially in the open spaces in front of private yards in most locations in Oltenia. Following the studies carried out regarding the invasive potential of this species, we can mention the fact that this species has a very high spreading power, quickly conquering new territories, each individual produces a very large number of seeds that have a very high germination power, is a species extremely resistant to drought, to various anthropogenic factors, including atmospheric pollution, to harmful mechanical factors, very high temperatures of over 400 during the summers in the south Oltenia, growing on the sides of roads, alleys, on several types of soil, including sandy. Around each individual, but also at distances between 2-80 m from it, vigorous saplings were identified, with increased vitality and accelerated growth, being able to reach up to 30-40 cm in height in one year of vegetation. Thus, we can specify that this species can be considered a new invasive species for Romania.