Banco de sementes ao longo de um gradiente sucessional no semiárido brasileiro

• Ano de defesa: 2018
• Autor(a) principal: Gomes, Fernanda Melo
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Palavras-chave em Português: Cronossequência; Dormência de sementes; Florestas tropicais sazonalmente secas; Persistência de sementes; Similaridade; Sucessão secundária
• Link de acesso: http://www.repositorio.ufc.br/handle/riufc/47437

The understanding of the seed bank on the composition of the vegetation, and its potential to restore richness and maintain species diversity, are some of the reasons that have motivated researchers to analyze the structure and composition of the seed bank, as well as to compare the vegetation composition with seed reserves in the soil. In order to understand the role of seed banks in the ecological succession of dry forests, we propose to test the following hypotheses: (1) there is a high similarity between the seed bank and the vegetation along the succession, and the persistence of seeds is important to determine this resemblance; (2) community parameters (richness and diversity of species) are maintained during the succession by the seed input by dispersion and the presence of persistent seeds. In order to verify these hypotheses, we combine the three chronosequence approach with dormancy-breaking methods to analyze the similarity between the seed bank and the vegetation, the composition and the structure of the seed bank, and its germination strategies during succession of dry tropical forests. We conducted the work in two lines: (1) we compared the similarities between vegetation and seed banks and evaluated the relative contributions of seed dispersal and persistence to the composition of the seed bank; (2) we analyzed the changes in the abundance, structure and composition of the seed bank, as well as the germination time along the chronosequence. We found that, in a total of 154 species identified in the vegetation, only 30.1% are also present in the seed bank of the three sites studied. The composition of the seed bank is dissimilar to the vegetation, and the seed dispersion and persistence have basically the same importance in forming the soil seed bank. During the chronosequence, seed density and community parameters decreased. Seeds of herbaceous species dominated the seed bank at all ages of cronossequences, and although some seeds germinated after treatment with phytohormone, there was no difference between the succession categories and the germination time of the three evaluated sites. Although it is not a sufficient source to give continuity to the succession process, the seed bank of initial stages of succession can be used in reforestation projects.