Phytocoenological analysis of grey alder (Alnus incana L.) forests in the Dinarides of Croatia and their relationship with affiliated communities

Abstract

This paper provides a comprehensive survey of the results of phytocoenological research into Alnus incana forests from the alliance Alnion incanae in the Dinarides. Stands from the south-eastern Dinar-ides (Alnetum incanae = Oxali-Alnetum incanae) were analyzed and compared with those from the north-western Dinarides (Lamio orvalae-Alnetum incanae). The comparison reveals significant differ-ences in the floristic composition and in the degree of differentiation – and particularly in the presence of the species of the Illyrian floristic geoelement. Focus was placed on the area of western Croatia where a geographic variant of Helleborus dumetorum had previously been de-fined within the association Lamio orvalae-Alnetum incanae. Two of its subtypes, Salix alba and Alnus glutinosa, were determined in our research. The former subtype thrives on occasionally flooded, moist sites, where the floristic composition is dominated by hygrophytes. The latter subtype grows on elevat-ed and drier terraces and is richer in mesophilous species from the surrounding zonal forests. A floris-tic-sociological comparison of the Lamio orvalae-Alnetum incanae with the related syntaxa indicates the presence of about fourty diagnostic species which accentuate its independence and the need to assess it at the level of an independent, regional association within the alliance Alnion incanae.