Interactive influences of fire and invasive species on native plant community succession in Hawaii Volcanoes National Park.
Ainsworth, Alison*,1, Kauffman, J. Boone2, Loh, Rhonda3, Hughes, R. Flint2, Tunison, J. Timothy 3, 1 Oregon State University, Corvallis, Oregon2 USDA Forest Service, PSW Research Station, Hilo, Hawaii3 National Park Service, Hawaii Volcanoes National Park, HVNP, Hawaii
ABSTRACT- Wildland fires in combination with exotic species invasions are posing increasing threats to native ecosystems in Hawaii and throughout the tropics. The synergism of fire and invasive species may dramatically alter the successional trajectory of lowland Hawaiian mesic forests and rain forests. Yet, predicting the magnitude of effects on post-fire succession must also take into account species-specific responses to other environmental factors, such as rainfall, and invasibility differences among communities. Hawaii Volcanoes National Park is an ideal place to examine how species response to fire varies with environmental factors because of its steep climatic gradient, abundance of biological invaders, and recent occurrence of lava-ignited fire. We examined how fire across an elevational/climatic gradient influenced vegetation at the species, community and landscape scales. Total species richness increased with elevation, but the proportion of native to exotic species was greater at higher elevations. Survivorship and establishment of woody species following fire may be influenced by the herbaceous response to fire particularly in the invaded communities. The average herbaceous vegetation cover was significantly higher in the invaded mesic forest community (62%) than the native-dominated mesic forest community (3%) one year following fire. Rapid revegetation is largely owing to exotic Nephrolepus multiflora that accounts for 85% of the herbaceous vegetation cover in the invaded mesic forest community. In both these environments, greater than half of the dominant tree Meterosideros polymorpha species survived fire by sprouting. However, numbers of native species sprouting and recruiting from seed were lower in invaded than non-invaded communities. The rapid regeneration of the exotic may have long term implications for native recovery after fire.
Key words: fire effects, invasive species, tropical ecology, hawaii
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