L. Lőkös szerk.: Studia Botanica Hungarica 26. 1995 (Budapest, 1995)

Dobolyi, Konstantin Z.: Phytosociological studies of the habitat of Achillea ochroleuca Ehrh. on Szamár-hegy (Visegrád Mts, Hungary)

METHODS Sampling, classification and calculation of the values of the different variables were carried out according to DOBOLYI (1992). The only difference in the calculation is, that in this case one species can belong only into one category of the variables. The samples were analysed on the basis of the following characteristics of the species: floral element, Raunkiaer's life-form, phytosociological character (SIMON 1992), social behaviour type, degree of naturalness and ecological indicator values (BORHIDI 1993). RESULTS The relevés contained 92 vascular plant species altogether (Tables 1 and 2). Constant and subconstant species are the following: Achillea ochroleuca, Festuca pseudodalmatica, Acinos arvensis, Alyssum alyssoides, Euphorbia cyparissias and Stachys recta. Concerning the floral element composition the Eurasian (incl. South Eurasian) elements are represented the most (Table 3). The exposure of the relevés ranges from South to West, therefore the microclimate of the investigated sites is relatively warm and dry. This fact explains the high proportion of Pontic, Mediterranean and Submediterranean elements. The high quantity of Pannonian and Carpathian elements show that rocky grasslands of the Hungarian Central Mountains are special habitats, and could be réfugia for endemic and subendemic species. The life-form distribution indicates the relatively high proportion of Therophytes and Chamaephytes (Table 4). These life-forms offer an adequate survival strategy for plants under extreme circumstances. According to the phytosociological preference of the species, dry grassland elements and members of rocky grasslands (Festuco-Brometea, Festucetalia valesiaceae, Asplenio-Festucion and Festucion rupicolae) are predominating (Table 5). Based on the phytosociological analyses, the investigated habitat belongs to the Asplenio-Festucion pallentis Zólyomi association group, with some resemblance to the Minuartio-Festucetum pseudodalmaticae Klika and Poetum pannonicae Zólyomi communities. The considerable mass of Chenopodietea and Secalietea elements indicates that degradation processes take place on that area. The same conclusion can be drawn from the high quantity of weeds and ruderal competitors (Table 6). The presence of the natural pioneer species shows that open rocky grasslands - because of the rapid erosion - have a pioneer character. The relatively high proportion of specialists proves the high botanical value