Long-term persistence of pioneer species in tropical rain forest soil seed banks.

In tropical forests, pioneer tree species regenerate from seeds dispersed directly into canopy gaps and from seeds that persisted in soil seed banks before gap formation. Life-history models have suggested that selection for the long-term persistence of tree seeds in the soil should be weak because persistence potentially reduces population growth rate by extending generation time and because adult life spans may exceed the return interval of favorable recruitment sites. Here we use accelerator mass spectrometry to carbon-date seeds of three pioneer tree species extracted from undisturbed seed banks in seasonally moist lowland Neotropical forest. We show that seeds of Croton billbergianus, Trema micrantha, and Zanthoxylum ekmannii germinate successfully from surface soil microsites after 38, 31, and 18 years, respectively. Decades-long persistence may be common in large-seeded tropical pioneers and appears to be unrelated to specific regeneration requirements.