Banco de sementes do solo de um fragmento de floresta estacional subtropical na região central do estado do Rio Grande do Sul

Abstract

Studies on the structure and dynamics of forest fragments in the state of Rio Grande do Sul are scarce and do not include all forest formations found. The few studies in the literature are punctual and do not evaluate the variations over time. Moreover, there are few studies that characterize the soil seed bank of these local, which have great interest in understanding and restoration of forest ecosystems. The present study aimed to evaluate the floristic composition and phytosociological parameters of tree and shrub species in the soil seed bank of a Seasonal Subtropical Forest fragment and determine the differences between edge and interior areas. Thirty soil samples were collected in a Seasonal Subtropical Forest fragment, in the county of Sao Sepé, RS, whit ten samples collected in each location: west edge, east edge and interior of the fragment. The collected material was stored in plastic bags and then transferred to perforated plastic trays, whit 50 % of these were maintained under 50% shadow and remaining in full sun. Twelve tree and shrub species were identified in the soil seed bank. The families most characteristic were Euphorbiaceae and Moraceae. The species Trichilia Claussenii, Ficus sp. and Trema micrantha were the most abundant and, together with Banara parviflora, presented higher importance value index. 36 % of the species were classified as pioneers, 6 % as early secondary and 58 % as old secondary. The Jaccard index showed high similarity between the east edge and the forest interior (0,81) for the floristic composition. However, the similarity between the west edge and interior forest and between the edges was lower. By comparison Tukey test at 5% of probability, it was found that the west edge and the forest interior differ from other sites, considering the seedlings density. The study of soil seed bank showed potential for use in degraded areas restoration, because its composition ensures the succession dynamics advance.