Fig. 4

Number of vascular plant species (all plant species, beech forest species, oak forest species, and species of disturbed forests) in the plots of dolines covered with different forest age classes (class 1: 5–10-year-old forest stands with mature forest patches, class 2: 40–45-year-old forests, class 3: 60–65-year-old forests, and class 4: more than 90-year-old forests) (mean ± SE). Significant differences (p < 0.05, based on the GLMMs with Bonferroni post hoc tests), are indicated by different lower case (a–d) letters