Matskási István (szerk.): A Magyar Természettudományi Múzeum évkönyve 90. (Budapest 1998)

Dobolyi, K.: Phytosociological studies on the andesite rocky grasslands in Visegrád Mountains (Hungary)

The ten investigated sites were the following: Vár-hegy (Visegrád), Szamár-hegy (Esztergom), Eastern Part of the Búbánat-völgy, Sas-hegy, Berseg-hegy, Vadállókövek, Rám-hegy, Kis-Pap-hegy (Lepence), Vörös-kő, Kartalia (Pomáz). In these sites there are large, homogenous grassland areas of natural condition but changes of their vegetation are expectable or possible. (Vörös-kő is considerably degraded because of tourism). METHODS Sampling was carried out so that the visibly different plots of rocky grasslands were represented. The relevés have been taken from 2 x 2 m quadrates according to BRAUN-BLANQUET (1964). Cover is expressed in values transformed by VAN DER MAAREL (1979) on a scale 1 to 9. The scientific names of the species were taken from HORVÁTH et al. (1995). The relevés were classified by several agglomerativc methods and analysed by principal component analysis (PCA) on the basis of floral composition and the cover values of the species (PODANI 1993). The distance optimizing methods were: single linkage, complete linkage and average linkage (UPGMA). During classifications the following distance functions were used: Jaccardcoefficient. correlation and similarity ratio (PODANI 1997). Six groups of relevés were separated according to the results of clustering and the PCA. First of all similarity ratio was taken into account at constituting the groups. One group consists of minimum five relevés. The groups of relevés of the ten investigated sites were analysed statistically on the basis of the following characteristics of their species: life form, phytogeographical area (floral element), phytosociological character, social behaviour type, degree of naturalness and ecological indicator values (BORHIDI 1993). The values of features characterizing the sample groups were calculated according to percentage pro rata of plant mass (DOBOLYI 1992). RESULTS AND DISCUSSION The relevés contain 154 vascular plant species altogether. Cover values of the relevés are given in Table 1 to 5. Table 1. Cover values of the species in the relevés of group I Relevés Group 1 Species 1 2 3 4 7 9 11 12 13 14 16 17 19 20 23 25 76 77 Achillea nobilis 4 3 2 3 - 3 2 4 2 1 Achillea ochroleuca 5 6 7 2 5 3 1 6 3 4 2 5 1 5 1 2 5 4 Acinos arvensis 1 2 2 1 2 1 1 1 2 2 2 1 Agropyron repens 2 2 1 - - 2 2 - ! Allium flav urn 1 1 A lyssum alyssoides 2 1 3 1 3 1 1 2 1 1 -