Gap dynamics can be quite different in areas where advance regeneration (seedlings and saplings established prior to gap formation) comprise most of the gap colonizing species. Uhl et al. (1988) observed only minor new colonization and high subsequen mortality in recently formed Amazonian treefall gaps; advance regeneration fared much better. In the mixed Norhofagus forests of New Zealand, Stewart et al. (199 1) found no relationship between pattern of regeneration and gap size. They also conclude that most gap occupants were present prior to gap formation and that little subsequent establishment occurred. In both studies, gap size influenced growth rates of established individuals. For Nothofagus
(Stewart et al., 1991), gap size influenced the competitive relations between the two dominant species, with the more light-demanding species gaining an advantage in gaps > 400 m’.