Acta Botanica 41. (1998)
1998 / 1-4. szám - KEVEY BALÁZS - BORHIDI ATTILA: Top-forest (Aconito anthorae-Fraxinetum orni) a special ecotonal case in the phytosociological system (Mecsek Mts., South Hungary)
climate for the herb layer species of the mesophilous forests conserving their domination. ” By reading the dissertation of B. Kevey in 1977, Borhidi encouraged him to study more thoroughly this community supposed to be an undescribed plant association. Kevey made 50 phytosociological relevés of this community named later as “top-forest” and the same amounts of plots also from the contacting communities for comparative studies. The short characterization and the nomenclatural type of the top-forest community were published by Borhidi and Kevey ( 1996). In this article a comparative study of the top-forest with other 5 forest associations is given based on 120 phytosociological relevés (20 of each) as a complementary contribution to the former studies of A. O. Horvát (1946, 1956, 1958, 1959, 1961). MATERIAL AND METHODS The phytosociological study of the communities is based on field work. Sampling plots were studied with the square-method of the Zürich-Montpellier school according to Braun-Blanquet (1928). All the sampling plots were studied twice for the spring and the summer-autumn aspects as it may be seen in the basic data tables of the relevés. Table ordination of the species and relevés calculations of the score of coverages were carried out with the PC-program developed by Kevey and Hirmann (Kevey 1993a, 1997). The phytosociological separation of the studied communities was carried out based on the differential species of higher constancy (111—V) in case when in comparison of two communities they were represented with at least two degrees of difference in constancy. Besides, the relative frequency of the characteristic species was also seriously considered. Within the phytosociological tables, species are grouped according to their place in the syntaxonomic system following the catalogue of Sod elaborated for the Hungarian Flora (Synopsis III. 1968 and VI. 1980) amplified and critically revised by Borhidi (1993, 1995, Horváth et al. 1995). For the plant names Simon 1992, for the syntaxonomic nomenclature Borhidi and Kevey 1996, Borhidi 1997 were considered. RESULTS SHORT CHARACTERIZATION OF THE FOREST COMMUNITIES CONTACTED WITH THE TOP-FOREST Before a detailed treatment of the top-forest association, it is convenient to give a short systematical review of characteristics of the forest communities being in contact with it. Among these communities can be found the Italian oak forest of the steep southern slopes (Tamo-Quercetum virgilianae Borhidi et Morschhauser in Borhidi and Kevey 1996), the turkey oak-sessile oak forest on the deeper soils of the highplains (Potentillo micranthae-Quercetum dalechampii A. O. Horvát 1981), the rock-forest community on the steep northern slopes (Tilio tomentosae- Acta Bol. Hung. 41, 1998