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ŠUMARSKI LIST 3-4/2018 str. 21     <-- 21 -->        PDF

units (Matuszkiewicz and Matuszkiewicz 1981). The sociological species affiliation was determined according to Vukelić (2012). The analysis of the floral composition of the association Equiseto hyemali-Alnetum incanae (=Alnetum incanae Lüdi 1921) from north-western Croatia demonstrates a high degree of floral similarity with colline stands of the same association presented in the forest vegetation of Austria (Willner and Grabherr 2007). As grey alder stands in Podravina grow on lower altitudes, they lack or have considerably less of the following species: Fraxinus excelsior, Lonicera xylosteum, Cardus perssonata, Picea abies, Anemone ranunculoides, Salvia glutinosa and others. On the other hand, some species in them have certain differential significance, namely: Ulmus laevis, U. minor, Quercus robur, Fraxinus angustifolia, Populus alba, Valeriana dioica and others. Table 1 shows 11 new relevés of grey alder-scouring rush stands. Due to major anthropogenic interventions, grey alder-scouring rush forests have seen considerable regressive changes in the distribution and floral composition, hence just like the species Equisetum hyemale, they should be considered an endangered type of habitat. A large part of the original forests and shrubbery has been cleared over the last 50 years due to the construction of two accumulation lakes and other melioration and infrastructural needs. Meliorations have greatly impacted the hydrological regime of the entire area, which resulted in alterations in the habitat, and eventually in the disappearance of areas that used to be covered by grey alder forests. In order to determine the changes in the floral composition of grey alder-scouring rush stands, we compared our phytocoenological relevés with those from 1964 (Trinajstić 1964). Table 2 specifies 35 species that indicate changes in the habitat and composition of the association. The table clearly demonstrates that the number of hygrophytes has been reduced, and the share of mesophilic species and species from less wet habitats considerably increased (column 2, table 2), especially from the order Fagetalia and class Querco-Fagetea Br.-Bl. et Vlieger 1937.
The association Equiseto hyemali-Alnetum incanae has been compared with the stands from Gorski kotar, i.e. with the association Lamio orvalae-Alnetum incanae, where it was found that they differ significantly both from the ecological and from the floral point of view (Figure 2). Floral differences of the said forest communities result primarily from the climate and orographic factors of biogeographic regions, and the share of species from zonal forests in whose belts they grow. Table 3 specifies 76 differentiating species: seven for the association Equiseto hyemali-Alnetum incanae and 69 for the association Lamio orvalae-Alnetum incanae. The criterion employed to single them out was that they grow in only one association with at least 20% of relevés, or that the difference between the level of representation in associations is in excess of 35%. The largest number of differentiating species are mesophytes from the alliances Aremonio-Fagion /Ht. 1938/ Borhidi in Törek et al. 1989, Tilio-Acerion Klika 1955, Erythronio-Carpinion (Ht. 1938) Marinček in Wallnöfer et al. 1993 and the order Fagetalia (33 species in total). The large number and frequency of those differentiating species is the reason for clear independence and identity of the association Lamio orvalae-Alnetum incanae compared to other European grey alder forests (Vukelić et al. 2017). The most important differentiating species of the association Equiseto hyemali-Alnetum incanae is Prunus padus. With regard to syntaxonomy, the analyzed associations Equiseto hyemali-Alnetum incanae and Lamio orvalae-Alnetum incanae belong to the suballiance Alnenion glutinoso-incanae Oberd. 1953, alliance Alnion incanae Pawl. in Pawl. et al. 1928, of the order Fagetalia sylvaticae Pawl. in Pawl. et al. 1928 and class Querco-Fagetea Br.-Bl. et Vlieger 1937.
Key words: Alnus incana, Lamio orvalae-Alnetum incanae, Equiseto hyemali-Alnetum incanae, floral composition, Croatia