DIGITALNA ARHIVA ŠUMARSKOG LISTA
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displacement. The carbonate rocks that separate Vinodol valley from the sea, form an asymmetric Upper Cretaceous limestone and dolomite anticline with a more steeply inclined north-eastern limb of foraminiferal limestones of Lower and partly Middle Palaeogene age. In the north-western part of the Vinodol valley, in the area between the settlements Križišće and Tribalj, the slopes in fact comprise the more or less inclined southwestern limb of the Cretaceous-Palaeogene anticline. In the area to the southeast of settlement Tribalj, the north-eastern slope is stepped into vertical cliffs. These cliffs were formed by destruction of the crest of the Cretaceous-Palaeogene anticline that was overturned in a south-westerly direction. The aforementioned anticline has a reverse fault contact (Šušnjar et al. 1970). In north-western flanks of the valley, within Upper Cretaceous limestones and dolomites, two tectonic dolines app. 370 m apart, Pihlja and Vitra, surrounded by cliffs, ranging from several meters up to 40 m in height, are located. In both of these dolines, coarse-grained sandstones and marls were found that pertain to the younger part of the Palaeogene clastics app. 150 m higher than the highest point of the flysch and are compressed by a fault within the carbonate complex (Blašković 1999). Some basic geographic and meteorological parameters of tectonic dolines are given in Table 1. According to (Horvat 1962), the Vinodol valley, specially its floodplains, represents one of the last remnants of azonal stands developed on flysch deposits with Fraxinus angustifolius and Ulmus laevis (ass. Fraxino angustifoliae-Ulmetum laevis), and Carpinus orientalis (Querco-Carpinetum orientalis carpinetosum betulis) (Randić 2003), once common features of the Vinodol lanscape. Nowadays, a mosaic of meadows with Molinia caerulea (Peucedano-Molinietum litoralis Horvatić 1934) (ibid.), Chrysopogon gryllus and Danthonia alpina (Danthonio-Scorzoneretum villosae Horvat & Horvatić (1956) 1958) prevail. Zonal vegetation on calcareous flanks surrounding the valley between 100–500 m represent degraded and fragmented stands of the association Querco pubescentis-Carpinetum orientalis (Horvat 1962) in various succession stages.
In summer 2013 we took 11 relevés of forest stands in tectonic dolines of Pihlja and Vitra applying the sigmatistic method (Braun-Blanquet 1928; Westhoff and van der Maarel 1973; Dierschke 1994). The plot size used for sampling averaged 400 m2 and further details on the phytosociological parameters of sites are given in Table 3. The nomenclature and taxonomic source for the names of vascular plants was Flora Europaea (Tutin et al. 2001). Prior to numerical analysis, the original cover-abundance values for individual taxa were transformed into an ordinal scale as proposed by van der Maarel (1979). Groups of vegetation types and similarity (Jaccard similarity – J, Euclid distances – ED) between the stands and syntaxa were ascertained using cluster and ordination analysis with the help of the programme package PAST (Hammer et al. 2001). Analysis of similarity (ANOSIM) was used as non-parametric test of significant difference between two groups of relevés – between tectonic dolines, where large positive R (up to 1) signifies dissimilarity between groups. The significance was computed by permutation of group membership, with 10,000 replicates. The results were deemed significant if the probability of the null hypothesis was less than 0.05. Studied forest stands were compared with floristically and