How a non-pioneer tree attains the canopy of a tropical semideciduous forest

A non-pioneer canopy tree having Aubr,ville architectural model overcomes seasonal water-light shortage alternation in tropical seasonal semideciduous forest with the same allometric shifts along the ontogeny as a rainforest tree. In tropical rainforests (TRF), the gap-understory gradient is occupied by a shade-tolerant/intolerant tree species continuum, and is among the main mechanisms explaining tree species distribution and coexistence. In tropical seasonal forests (TSF), the effects of gap formation are poorly known and are much subtler due to canopy deciduousness. In both forest types, light intensity increases from the ground to the canopy. We investigated whether the life-history pathway along the ontogeny of TRF shade-tolerant canopy trees holds true for a functionally similar TSF tree species. We identified seven ontogenetic stages in a population of Esenbeckia leiocarpa Engl. (Rutaceae): seedling, infant, juvenile, immature, vegetative adult, reproductive adult, and senile. Esenbeckia leiocarpa conforms to the Aubr,ville architectural model, which is well adapted to understory dimness. Little overlap in size was found among the different ontogenetic stages, indicating that changes in height and diameter play an important role along ontogeny. Seedlings responded to spatial variability in light, and other early stages exhibited plagiotropic branches and greater investment in height per unit of diameter as a strategy for resisting dimness. In the adults, the investment in diameter was greater, thus allowing the tree to support crown reiteration and reproductive structures and to resist wind forces and liana load. These findings show that the studied species has the same shade-tolerant strategy as tropical rainforest canopy species, and support the idea that light gradient in the forest profile is an important driver of canopy tree ontogeny31193103CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPsem informaçãosem informaçãosem informaçã