Seed ecology of selected Amazon Basin successional species.

Two adjacent forest sites-a mixed forest on well-drained Oxisols and a caatinga forest on waterlogged Spodosols-were similar in the number of viable seeds m^-2 in the seed bank: 180 for the mixed-forest site, 200 for the caatinga site. Most germinated seeds were of successional pioneer tree species. Seeds were entering the mixed-forest seed bank at a rate of approx 50 seeds m^-2 yr^-1. Agricultural and pasture sites tended to have larger seed banks (580-1250 viable seeds m^-2) composed almost entirely of grasses and forbs. By coupling an absolute light requirement for germination with long-lived seeds, successional species of the upper Rio Negro region are able to persist in the soil seed bank until conditions favor their successful establishment.-from Authors