Successful restoration of Metrosideros polymorpha (ʻōhiʻa) is possible in forest sites with active Rapid ‘Ōhiʻa Death infections

Abstract

Rapid ʻŌhiʻa Death (ROD), caused by the fungal pathogen Ceratocystis, is killing large numbers of ʻōhiʻa trees (Metrosideros polymorpha) in Hawaiʻi. ʻŌhiʻa are a dominant tree in Hawaiian forests, have a range that goes from arid to wet forest climates, and are important for endangered species habitat and ecosystem function. To test whether actively planting ʻōhiʻa seedlings is a viable restoration strategy in areas with high ROD mortality, we planted ʻōhiʻa in a ROD-affected forest and crossed this with weeding and fencing treatments to compare ROD mortality to other stressors. We also tested for viable Ceratocystis spores in soils around planting areas. We found that seedlings were more likely to die in unweeded and unfenced treatments than controls. Although viable Ceratocystis spores were found in soil, none of the 41 dead seedlings tested positive for Ceratocystis. This indicates that competition from exotic plants and exotic feral ungulate damage are more likely to kill seedlings than ROD within the first year after planting.