Arrival and Survival in Tropical Treefall Gaps

Abstract

Most tropical tree species require light from a treefall gap at some time during their lives to reach maturity. Responses to light conditions have been dichotomized as shade-intolerant pioneers or shade-tolerant climax species (e.g., Whitemore 1975, 1982, 1989). The former typically have small, widely dispersed seeds from which juveniles establish only in gaps, while the latter typically have larger seeds that can germinate beneath the forest canopy and can persist as suppressed juveniles or grow slowly until a gap forms. According to this framework, a new gap promotes shade-intolerant regeneration through germination and shade-tolerant regeneration through release of suppressed juveniles. Truly shade-tolerant species can grow to maturity beneath the forest canopy, but even these are likely to benefit from any increases in light levels beneath the canopy (Uhl et al. 1988, Canham 1989, Lieberman et al. 1989b, Martinez-Ramos et al. 1989).