Ábrahám Levente (szerk.): Válogatott tanulmányok VI. - Natura Somogyiensis 19. (Kaposvár, 2010)

ERDŐS L., BÁTORI Z., MORSCHHAUSER T., DÉNES A. & KÖRMÖCZI L.: Transitional plant communities of the Villány Mts

ERDŐS ET AL.: TRANSITIONAL PLANT COMMUNITIES OF THE VILLÁNY MTS 39 even drier. At the other end of the gradient the shrubforests and the open rock swards can be found, with the highest rate of xerofrequent species (for example W1 species). The proportion of the species with higher nutrient-requirement (for example N7 species) is the highest in the communities of the northern side, while the communities of the southern side grow on nutrient-poorer soils. On the ordination scattergram, two relatively dense groups can be differentiated, with a trajectory between them. This trajectory, referring to a transitional zone, consists partly of top-forest plots, but mostly of closed rock sward plots and north-exposed shrubforest plots (Fig. 2). Discussion The aim of this study was to characterize the transitional communities of the Villány Mts in the context of north-south facing vegetation gradients. The communities under scrutiny have been analysed only separately so far (

DÉNES 1995, 1998, ERDŐS and MORSCHHAUSER 2010, ERDŐS et al. 2010). We found that all of the communities located on the northern side of the ridges or plateaus can be characterized by a combination of xerofrequent plants and plants of beech and oak-hornbeam forests. The analysis of the ecological indicator values also pointed to their dual caharcter (Tables 1-3). Generally, the top-forest Aconito anthorae-Fraxinetum orni is considered a transitional community between the northern and southern slopes of the Mecsek Mts (KEVEY and BORHIDI 1998, 2010). However, situation is somewhat different in the Villány Mts. Here, the top-forest is further from the ridges (Fig. 1). Therefore, the real transitional communities are the north-facing shrubforest, the Spiraea rock-heath community and rock-swards. These communities are in the immediate proximity of the ridges and plateaus. The ordination scattergram also supports this view since the trajectory between the plots of the northern slope and plots of the southern slope is formed mainly by rock sward and shrubforest plots (and not by top-forest plots) (Fig. 2). However, it must be noted that in our analysis, only the field layer was sampled. It is known that the fieldlayer of the top-forest consists mostly of mesophilous plants, whereas the canopy and shrub layers are formed by xerofrequent species (KEVEY and BORHIDI 1998, 2010). Thus it is probable that the top-forest would have shown a more transitional character if not only the herb layer were sampled. Canonical correspondence analysis showed that microclimate of the communities of northern exposures is humid and cool, and soils of the northern sides have a greater nutrient-content, whereas southern slopes are dryer and wanner, with nutrient-poor soils (Fig. 2). These results are in good agreement with the measurements of HORVÁT and PAPP (1964), carried out on Mt Szársomlyó. Acknowledgement The authors are indepted to the Inspectorate for Environment, Nature and Water for allowing us to carry out these studies in the strictly protected nature reserve of Mt. Szársomlyó.