Phytocoenology and distribution of the species Gymnospermium odessanum in Romania

Gymnospermium odessanum is a threatened plant species in Romania's flora, and its presence ranges from the south to the southeast. In this context, the study aims to update the species distribution and ecological conditions and identify the plant associations in which the species occurs. All the populations mentioned in the literature and other potential localities were investigated for the distribution of the species. For the analysis of the coenotic conditions, phytocoenological relevés were carried out. All relevés were analyzed using the Agglomerative Hierarchical Clustering method to identify the leading plant associations in GINKGO. Direct and indirect ordering methods were used in CANOCO to determine the main gradients that affect the floristic composition of individual vegetation types. For the analysis of the potential distribution, the coordinates of the G. odessanum species and variables such as elevation, slope, aspect, soil type, and geology were used in the QGIS program.Our results show that G. odessanum occurs only in Tulcea County, with two populations in Cerna, two populations in Trestenic, one population in Greci, one population in Niculițel, one population in Izvoarele, and one population in Satu Nou. The numerical analysis revealed five well-defined communities, mainly corresponding to the plant associations described in the taxonomic literature, depending on the diagnostic species: Artemisio austriacae-Poëtum bulbosae , Gymnospermio odessani - Celtetum glabratae , Fraxino orni-Quercetum dalechampii , Sedo hillebrandtii-Festucetum callieri , and Agropyro pontici-Thymetum zygioidis . The variation of the floristic composition of the species G. odessanum is influenced by the slope. The population is approximately 1040 individuals, and the number of individuals / 100 m ² is from 10 to 200. From the observations made in 2007, we mention that the number of individuals is decreasing. Causes of species decline include overgrazing and collection of individuals. The current trend of the area occupied by the population is decreasing. The population's conservation status and changes in the range pattern of the habitat type are unfavourable-inadequate. The analysis of the potential distribution shows a spread of the species in the Dobrogea region.