Seed ecology of native and non-native plants in a Hawaiian lowland wet forest

Seed ecology studies are an important resource for understanding the regeneration dynamics occurring in forest systems. Information gained from this study will assist in developing comprehensive restoration strategies needed to preserve Hawaii’s threatened forests. I examined the impact removing non-native species had on the seed ecology of native and non-native species in an invaded Hawaiian lowland wet forest. Composition and relative abundance of species present in the seed rain and the seed bank was ascertained by employing seed traps and by germinating soil cores taken within 1m of the seed traps. Seeds were also collected and germinated under various light conditions (~ 1%, ~55%, and 95%) to research light requirements for germination. Results showed total non-native seed rain (in number) was nearly equal to the total native seed rain. The endemic tree o’hi’a (Metrosideros polymorpha) dominated the seed rain and was significantly higher in the removal plots. The seed bank was comprised entirely of non-native species except for a few individuals of the native species mamaki (Pipturus albidus). There was also no significant difference between the number of non-native seedlings germinating in 2005 and 2006. Although native seed is available for regeneration it is not being incorporated into the seed bank and therefore requires optimum germination conditions to be met at the time of dispersal. Consequently, restoration efforts will need to encourage native seedling regeneration while also removing invasive species to increase native canopy cover, as the seed bank alone will not be a path for recovery.