Comparison of ground cover (a–d) and light environment (e, f) between sampling points with or without saplings (>40 cm tall and <12 cm DBH) of A. altissima. Values originate from recently undisturbed forests (this study), and from a forest analysed four years after a fire (Maringer et al. 2012). The dashed line in (e) shows a threshold value that is optimized for sensitivity and specificity to distinguish sampling points with or without saplings of A. altissima in recently undisturbed forests. Asterisks indicate significant differences between sampling points with and without saplings of A. altissima (** P < 0.01, *** P < 0.001). See text for differences in the sampling procedure between this study and Maringer et al. (2012).