FLORA OF TARNOVSKI HEIGHTS ( NORTHERN BULGARIA )

Dimcho Zahariev 1 and Lidiya Taneva 2 . 1. Faculty of Natural Sciences, Department of Plant Protection, Botany and Zoology, University of Shumen, Bulgaria. 2. Master Student in Faculty of Natural Sciences, University of Shumen, Bulgaria. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History

There are 54 floristic elements in the phytogeographical structure of the flora. The largest number of species belongs to following floristic elements: European-Asiatic (15.3%), Sub-Mediterranean (13.8%), and European-Mediterranean (13.8%) floristic elements. The distribution of the floristic elements correlate with the geographic location of the study area.
The endemic taxa are represented by 3 Bulgarian endemic species and 9 Balkan endemic species. The total number of endemic taxa of Tarnovski Heights is 12 species (1.2% of all species). It is significantly lower than the country average, which is 4.9% [34]. The reason for this is the low altitude of the studied area, which is characterized by a smaller number of endemic plant species.
The relic species are 59 species (6.1% of all species). Tertiary relics are 50 species (5.2% of all species). Quaternary relics are 9 species (0.9% of all species). Of these 4 species are quaternary glacial relics and 5 species are quaternary interglacial relics. The small number of quaternary relics is due to the same reason given for the presentation of the endemic species, namely the low altitude: the highest point of Tarnovo heights is located only at 439.8 m above sea level.
The species with conservation status are 64 species (6.6% of all species  The biological spectrum includes all biological types, as well as all possible transitions between them (Table 3).
Most species belong to the perennial herbaceous plants, 528 species (54.8%) and belong to the annual herbaceous plants, 213 species (22.1%). The dominant presence of the perennial herbaceous plants can be explained by the wide variety of communities and habitats that occur on the territory of Tarnovski Heights. The relatively large number of annual herbaceous plants is due to the following reasons: the large area of the arable lands, the significant number of settlements and the road network between them. As a result of human intervention in these territories, the soil is not covered by dense vegetation, which is favorable for the development of annual herbaceous plants. This group of plants is represented with a large number of species also in natural habitats with shallow and eroded soil cover.  In the DASIE List of Worst invasive alien species threatening biodiversity in Europe [35] are included 4 species: Ambrosia artemisiifolia L., Ailanthus altissima (Mill.) Swingle, Impatiens glandulifera Royle, and Robinia pseudoacacia L.
The reasons for the wide diversity of invasive species of Tarnovski Heights are related to the geographic location of the studied territory. The Tarnovski Heights are located in the central part of Northern Bulgaria, where the main roads connecting the eastern and western parts of Northern Bulgaria, as well as Northern and Southern Bulgaria are intersected. In the study area pass many roads and rail lines, which are used very intensively. Road infrastructure is one of the main ways of spreading invasive species. Second is the passage of one of the big rivers that are internal to Bulgaria (Yantra River) through the studied territory. Part of invasive species are spread along its banks.
We recommend monitoring the distribution and number of the invasive species and taking measures to control their numbers in the protected areas and the protected zones.

Conclusion:-
The results of the inventory of vascular plants on the territory of Tarnovski Heights show a considerable variety of vascular plants. The obtained results can be used for comparison with the data on the flora of different geographic sites in Northern Bulgaria as well as in the whole country.