The soil seed bank and understorey regeneration in Eucalyptus regnans forest, Victoria

The soil seed bank and its relation to the extant vegetation in a Eucalyptus regnans F. Muell. forest in the Central Highlands of Victoria were examined. The average seed density was 430 germinable seeds m(-2) to a depth of 2 cm. There was a polynomial regression relationship between the density and species richness of seeds in soil and forest age (0.6-54 years). Species richness was not significantly different among soil depths (0-2, 2-5, 5-10 and 10-20 cm) in the forest stand of 54 years old. More seeds germinated from the 5-10 cm depth than from the other depths. Forbs accounted for 73% of the total germinable seeds and there was no germination of E. regnans. The number of species, particularly woody plant species, germinating from the soil seed bank were significantly lower than in the extant vegetation. However, almost all species present in the soil seed bank were present in the vegetation. The soil seed bank provides an important source for the rapid regeneration of understorey vegetation following clear-cutting and slash-burning in the E. regnans forest. The rapid understorey establishment may play an important role in protecting soil from erosion, in nutrient conservation, replacement and redistribution. The soil seed bank may also be a necessary source of maintaining genetic diversity in the forest over the long term.