Abstract
Many native plant species confined to isolated semi-natural grasslands are threatened by local extinction. We evaluated, therefore, the potential role of soil seed banks in the persistence and recovery of native grassland plant populations. We compared species richness and composition between aboveground vegetation and soil seed banks from both surface and lower layers using a seed germination test in isolated grasslands dominated by Miscanthus sinensis and Pleioblastus chino. Although the aboveground vegetation was dominated by native species, exotic species were much more abundant in the surface seed bank than native species, seeds of which were also few in the lower soil layer. The large difference in community composition between aboveground vegetation and seed banks for both native and exotic species, and the similar species compositions between surface and lower soil seed banks suggest that soil seed banks do not contribute to the persistence and recovery of native grassland plant populations in isolated semi-natural grasslands. Moreover, if seed banks were used as restoration tools, the dominance of exotic species poses an unexpectedly high risk of invasion.
