PARENT SESSION
Symposium #17: Science in national parks: Basic research and application.
Sponsored by ESA Sustainable Biosphere Initiative
Organized by: S.T.A. Pickett and W. Robertson.
Wednesday, August 8, 2001. 1:00 PM to 4:25 PM. Madison Ballroom A
Invasive grasses, fire, and nitrogen cycling: applications of basic research in Hawaii Volcanoes National Park.
MACK, MICHELLE1, D'ANTONIO, CARLA2, 1 2
ABSTRACT- Over the past 40 years, the invasion of exotic grasses into the submontane woodlands of Hawaii Volcanoes National Park has altered vegetation structure and composition. The most dramatic consequence of this invasion is the introduction of fire; currently, over 50% of the woodland sites capable of carrying fire have burned in grass-fueled fires. Native woody species are killed by fire and are unable to recruit into the grass-dominated systems that follow fire. Interactions among native species, grasses and fire have fueled both basic and applied research within the Park. In the past decade, our research has focused on understanding the mechanisms through which exotic species impact nitrogen (N) dynamics in an ecosystem where N limits primary productivity. For example, annual N mineralization was three times higher in fire-derived grassland than in unburned woodland, yet plant N uptake in the grassland was only 1/6 of that in the woodland. This decoupling between N availability and plant demand results in increased nitrification and loss of N from the ecosystem, which may, over time, lead to exacerbation of N-limitation and decreased potential productivity. The current management strategy for the submontane zone is focused on the introduction of fire-tolerant, native woody species. While not part of the historical assemblage, these species are native to the islands; there is the hope that their establishment will recapture some of the plant functional diversity and ecosystem N dynamics of the unburned woodland.
KEY WORDS: fire, nitrogen, biological invasions, national park