An insight into the ecology of Woodsia alpina newly recorded for the flora of the Balkan Peninsula

The arctic-alpine species, Woodsia alpina (Woodsiaceae), was recorded on the Balkan Peninsula for the first time as a result of an intensive floristic and phytocoenological investigation of the rocky habitats located on the Stara Planina Mt. The record represents the first finding of this species and the family Woodsiaceae in general for the flora of Serbia. This new finding shifts the southern limit of its distribution in Southeastern Europe significantly. Five small subpopulations, consisting of a few up to dozens of specimens, were found above the forest belt, at an elevation range between 1671 and 1718 m a.s.l. They inhabit fissures in what are almost vertical rocks composed of Permian red sandstone with western exposition. Woodsia alpina shows affinities to semi-shaded places, which are moisturerich, slightly acidic and poor in nutrients. It grows alongside mosses, other ferns (Asplenium septentrionale, A. trichomanes, Asplenium × alternifolium, Cystopteris fragilis) and flowering plants. According to the results of the cluster analysis, the communities of W. alpina recorded in Serbia are clearly distinguished from those of this species in other European countries regarding their floristic composition. Hence, it is necessary to clarify the syntaxonomical rank of this association within the class Asplenietea trichomanis (Br.-Bl. in Meier et Br.-Bl. 1934) Oberd. 1977 and the Androsacetalia vandellii order Br.-Bl. in Meier et Br.-Bl. 1934 in future research. Applying Huisman-Olff-Fresco models on a dataset from the Balkans, it is revealed that W. alpina has narrow ecological valences regarding elevation, exposition and 19 bioclimatic parameters. On the other hand, according to the literature, it grows successfully in a wide range of elevations in Europe, as a result of its affinity to colder climates and the arctic-alpine type of distribution