Light availability is clearly important, but other factors also play a role in regeneration success. Putz (1983) observed that shade-intolerant tree species were more common on mineral soil and concluded that since large treefall gaps are often caused by uprooted trees, the abundance of shade-intolerant tree species in large gaps could be partially explained
by the higher incidence of exposed mineral soil. Several other studies have shown different tree species to be concentrated on specific substrate types within gaps (Lawton and Putz, 1988; Peterson and Pickett, 1990; Stewart et al., 1991; Lertzman, 1992; Hofgaard, 1993).