Effects of repeated fires on native plant community development at Hawaii Volcanoes National Park

Abstract

Catastrophic fires in wet forest have been highlighted as examples of drivers that overcome community resilience by altering feedback processes such that ecosystems are shifted into alternative, often less-desirable stable states. Recent successive lava-ignited wildfires, in slow-growing evergreen Myrtaceae-dominated mesic and wet forests at Hawaii Volcanoes National Park, provided an ideal opportunity to examine how forest species’ responses differ after single and repeated fires. In mesic (Metrosideros polymorpha–Dicranopteris linearis) and wet (Metrosideros–Cibotium glaucum) forests, the first fire was stand-replacing where 99% of the dominant overstorey trees (M. polymorpha) were top-killed; however, nearly half of these individuals survived by basal sprouting. The second fire dramatically increased mortality by killing the basal sprouts. Similarly, native tree fern C. glaucum survival was significantly reduced after repeated fires in the wet forest. The composition of the understorey in both communities after repeated fires differed in unexpected ways from once-burned and unburned forests. Repeated fires resulted in lower tree survival and rapid occupation by aggressive herbaceous species, potentially limiting tree growth and recruitment. The expected consequence is that native forest recovery will be delayed or even prevented by feedback processes established post-fire serving to maintain novel treeless alternate states.