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Biological mediation of invasive plant impacts in ecosystems

Biological mediation of invasive plant impacts in ecosystems. Duane A. Peltzer Landcare Research Lincoln, New Zealand. What is covered in this talk?. NZ weeds and ecosystem processes What are weed impacts? Field removal experiments. NZ Background.

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Biological mediation of invasive plant impacts in ecosystems

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  1. Biological mediation of invasive plant impacts in ecosystems Duane A. Peltzer Landcare Research Lincoln, New Zealand

  2. What is covered in this talk? • NZ weeds and ecosystem processes • What are weed impacts? • Field removal experiments

  3. NZ Background • > half of NZ’s flora is naturalised non-native plants; many are weeds • Weeds are widely thought to reduce biodiversity and alter ecosystem processes • >340 weed species are currently managed

  4. Predicting weed impact IMPACT = DISTRIBUTION x ABUNDANCE x EFFECT

  5. Weed effects Least well understood, include: • Gene-flow • Biogeochemical changes (C, N, P) • Disturbance regime • Ecosystem engineers • Interaction modification

  6. Invasion Ecology Understanding what controls the ecosystem-level impacts of exotic species as a basis for management

  7. Modest effects Reversible threshold effects Non-reversible threshold (different stable states) After Cote et al. 2005 ARES

  8. Kowhai River, Kaikoura, NZ

  9. Dominant native Dominant exotic Coriaria arborea Buddleja davidii ~97% of total plant biomass

  10. Other exotics Other natives ~25 species ~3% of biomass ~15 species <0.1% of biomass

  11. Peltzer et al. 2009 Oikos 118: 1001

  12. Dickie et al. 2010 New Phytologist

  13. Nematode community shifts Dehlin et al. 2008

  14. Preferred Not selected Avoided Forsyth et al. 2002, Richardson et al. unpublished

  15. Kurokawa, Peltzer, Wardle 2010 Functional Ecology

  16. Kurokawa, Peltzer, Wardle 2010 Functional Ecology

  17. Control Rats Possums Birds Inverts? Vegetation /fruit

  18. Key points • Small species matter! • Weeds have biological legacies + change ecosystem processes (effects) • Containment or early control is best

  19. Peltzer et al. 2010 GCB 16:732.

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