Surface fire is one of the major disturbances in forests in northern Japan. In a surface fire, canopy gaps occur and understory vegetation disappears. Understory vegetation, especially dense dwarf bamboo, inhibits tree seedling regeneration in heavy-snow region in Japan. We hypothesized that 1) gap formation and understory vegetation recovery, especially dwarf bamboo, would regulate survival and growth of tree seedlings interactively and that 2) the effects differ depending on successional traits of tree seedlings. We established 6 types of study sites under closed canopy or gap combined with three forest floor conditions (only dwarf bamboo cleared, all understory vegetation cleared and control) in a deciduous broad-leaved forest after a surface fire. Vegetation, especially dwarf bamboo, decreased the survival rates (SR) and the relative growth rates of some species. However, understory vegetation increased SR of some species under the gap. These indicated that understory vegetation inhibited the regeneration but favored the regeneration of some tree species under gaps. Site conditions affected the seedling dynamics of early- and mid-successional species but not late-successional species, which implies effects of gaps and vegetation recovery differ depending on successional traits of tree species.