Seed size, seed germination, and seedling survival of Brazilian tropicaltree species differing in successional status

摘要

Seed germination and seedling establishment patterns have been used to classify species as shade tolerant or intolerant. The main objective of this research was to investigate, under controlled conditions, seed germination of species from different successional positions as well as to follow seed germination and seedling survival under natural shade in the field. The species studied were Solanum granuloso-leprosum, Trema micrantha, Cecropia pachystachya, Croton piptocalyx, Bauhinia forficata subsp. pruinosa, Senna macranthera, Schizolobium parahyba, Piptadenia gonoacantha, Chorisia speciosa, Pseudobombax grandiflorum, Ficus guaranitica, Esenbeckia leiocarpa, Pachystroma longifolium, Myroxylon peruiferum, and Hymenaea courbaril. Field trials were carried out at Santa Genebra Municipal Reserve, Campinas, SP, Brazil, at the forest edge and in the understory. No significant correlations were detected between successional status and seed size or seed water content. Light-regulated germination was resent only in small-seeded species. In field experiments, most species, including the light-sensitive ones, were able to germinate under the canopy, where a low red/far-red ratio predominates. Most species, mainly those of early- and intermediate successional positions, presented low seedling survival rates under shade. Myroxylon peruiferum was the most shade tolerant species, while S. granuloso-leprosum, C speciosa, P gonoacantha, E guaranitica, T micrantha, and S. parahyba were the most shade intolerant. These latter species showed little or no survival under the shade conditions.