Biological mediation of invasive plant impacts in ecosystems

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Biological mediation of invasive plant impacts in
ecosystems

• Duane A. Peltzer
• Landcare Research
• Lincoln, New Zealand

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What is covered in this talk?

• NZ weeds and ecosystem processes
• What are weed impacts?
• Field removal experiments

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NZ Background

• gt half of NZs flora is naturalised non-native
  plants many are weeds
• Weeds are widely thought to reduce biodiversity
  and alter ecosystem processes
• gt340 weed species are currently managed

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Predicting weed impact
IMPACT DISTRIBUTION x ABUNDANCE x EFFECT
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Weed effects

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

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Invasion Ecology
Understanding what controls the ecosystem-level
impacts of exotic species as a basis for
management
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Modest effects
Reversible threshold effects
Non-reversible threshold (different stable states)
After Cote et al. 2005 ARES
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Kowhai River, Kaikoura, NZ
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Dominant native
Dominant exotic
Buddleja davidii
Coriaria arborea
97 of total plant biomass
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Other exotics
Other natives
15 species lt0.1 of biomass
25 species 3 of biomass
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Peltzer et al. 2009 Oikos 118 1001
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Dickie et al. 2010 New Phytologist
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Nematode community shifts
Dehlin et al. 2008
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Preferred Not selected Avoided
Forsyth et al. 2002, Richardson et al. unpublished
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Kurokawa, Peltzer, Wardle 2010 Functional Ecology
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Kurokawa, Peltzer, Wardle 2010 Functional Ecology
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Control
Possums
Rats
Birds
Inverts?
Vegetation /fruit
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Key points

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

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Peltzer et al. 2010 GCB 16732.
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