Climate changes and tree migration in the floristic subregion South Black Sea Coast (Bulgaria)

Abstract

A natural process of occurrence of some exotic woody plant species has started in different habitats of the floristic sub-region Southern Black Sea Coast (Bulgaria) during the last years. Most of these plants were known before only as decorative and grown in parks and botanical gardens, in private gardens and yards, and as a part of forest plantations. Natural reproduction and distribution of these species were not observed before in the studied floristic sub-region of Bulgaria. Besides the widespread naturally established exotic and invasive species like Robinia pseudoacacia, Gleditsia triacanthos, Amorpha fruticosa, Acer negundo, Ailanthus altissima, Morus alba, Spartium junceum and Ficus carica, also distribution of other species was recorded. These species were not considered to be able to reproduce in climate conditions of the southern Black Sea Coast. This group of species includes Quercus rubra, Fraxinus americana, F. pennsylvanica, Pinus pinaster, P. brutia, Platanus orientalis,
Laburnum anagyroides, Partenocissus quinquefolia, Catalpa bignonioides, C. ovata and even some rarer species like Olea europaea, Eucommia ulmoides and Ptelea trifoliata. Some of these species could become invasive in the course of time and under specific conditions. For each newly found species in the floristic sub-region, we present data of the locality: name of the location, geographical coordinates and altitude, slope and exposure of the terrain, floristic composition of the habitat, where the locality is found, date of collection of the herbarium material and the number of the herbarium sheets at the herbarium, where materials are deposited. The appearance and migration of this group of foreign woody plants are related to the climate changes, observed during the last years, such as increased temperatures and softening of the climate during the winter season, which leads to the reproduction of the above-mentioned species. . It is suggested to monitor the established localities of alien species because it is possible that some of them may become invasive to the flora of Bulgaria.