Soil reaction is one of the main factors that are positively correlated with total species diversity and richness in forest communities (Schuster and Diekmann, 2005; Chytrý et al., 2007). In our study, only the richness of herbs was found to be correlated with soil reaction in the case of plots at higher altitudes, a result indicating this predictor has a minor role (see Fig. 3). The afore- mentioned authors report that the strongest effect of soil reaction on species richness in forests occurs below pH 5.5, as recorded in the present study. This is presumably the result of more favourable growing conditions and greater resource availability with a slight increase in pH in predominantly acidic soils (Peet et al., 2003).