Banco de sementes de espécies arbóreas em floresta estacional no Rio Grande do Sul, Brasil

摘要

Soil seed bank composition provides basic informations about the potential regeneration of a community, allowing further inferences about successional processes. In a permanent 0.5 ha plot (50 square 100 m2 sample units) of seasonal forest located on a south facing slope in the State Park of Itapu?, municipality of Viam?o (RS), the composition and distribution of tree species in the soil seed bank were analyzed. Litter and soil from two depths (0-5 and 5-10 cm) were collected in all sample units, in the spring (September 2002) and fall (March 2003). The collected material was left to germinate in a greenhouse under two distinct light conditions, natural and with a lattice-shade cover (50%). Species composition and density was relatively similar (Jaccard index = 0.67) for the two seasons. A comparison with the known tree composition of the same area indicated a very low similarity, for both seasons. The absence of significative difference between periods may reflect a relatively homogeneous humid subtropical condition, in which the seasonality does not show strength. The presence of both shade-tolerant and light-demanding species in the seed bank indicates a high potential of regeneration for the tree component, in the case of gap formation or other disturbances to the present forest structure.