Letter | Published:

Self-reinforcing impacts of plant invasions change over time

Nature volume 503, pages 517520 (28 November 2013) | Download Citation

Abstract

Returning native species to habitats degraded by biological invasions is a critical conservation goal1. A leading hypothesis poses that exotic plant dominance is self-reinforced by impacts on ecosystem processes, leading to persistent stable states2,3,4,5,6. Invaders have been documented to modify fire regimes, alter soil nutrients or shift microbial communities in ways that feed back to benefit themselves over competitors2,5,6,7. However, few studies have followed invasions through time to ask whether ecosystem impacts and feedbacks persist8,9. Here we return to woodland sites in Hawai′i Volcanoes National Park that were invaded by exotic C4 grasses in the 1960s, the ecosystem impacts of which were studied intensively in the 1990s10,11,12. We show that positive feedbacks between exotic grasses and soil nitrogen cycling have broken down, but rather than facilitating native vegetation, the weakening feedbacks facilitate new exotic species. Data from the 1990s showed that exotic grasses increased nitrogen-mineralization rates by two- to fourfold, but were nitrogen-limited10,12,13. Thus, the impacts of the invader created a positive feedback early in the invasion. We now show that annual net soil nitrogen mineralization has since dropped to pre-invasion levels. In addition, a seedling outplanting experiment that varied soil nitrogen and grass competition demonstrates that the changing impacts of grasses do not favour native species re-establishment. Instead, decreased nitrogen availability most benefits another aggressive invader, the nitrogen-fixing tree Morella faya. Long-term studies of invasions may reveal that ecosystem impacts and feedbacks shift over time, but that this may not benefit native species recovery.

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Acknowledgements

We thank M. Mack for previous data. We thank S. McDaniel and S. Doyle for native seed and the National Park Service for field site access and laboratory and greenhouse facilities. N. DiManno, V. Vincent, T. Kalei, T. D’Antonio-Dudley, K. Roehr, W. Buckley, M. Wasser and C. French helped with field work and N. DiManno, V. Vincent and S. Ma helped with laboratory work. We are appreciative of early manuscript comments from E. Mordecai and statistical advice from K. Brinck. This research was funded by National Science Foundation grant DEB 1029168.

Author information

Author notes

    • Stephanie G. Yelenik

    Present address: US Geological Survey, Pacific Island Ecosystems Research Center, Hawai′i Volcanoes National Park, Hawai′i 96718, USA.

Affiliations

  1. Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, California 93106, USA

    • Stephanie G. Yelenik
    •  & Carla M. D’Antonio

Authors

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Contributions

S.G.Y. and C.M.D. conceived and designed the study, managed the project, performed laboratory and field work and edited the manuscript. S.G.Y. analysed the data, developed the figures and drafted the initial manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Stephanie G. Yelenik.

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https://doi.org/10.1038/nature12798

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