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Weed spread in New Zealand

Weed spread in New Zealand. Jon Sullivan Lincoln University sullivaj@lincoln.ac.nz. Weed spread. New Zealand is still in the early stages of plant invasion Weed spread occurring across many scales; different processes dominate at each

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Weed spread in New Zealand

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  1. Weed spread in New Zealand • Jon Sullivan • Lincoln University • sullivaj@lincoln.ac.nz

  2. Weed spread • New Zealand is still in the early stages of plant invasion • Weed spread occurring across many scales; different processes dominate at each • We need better ways of predicting the what, where, and when of weeds • We lack long-term monitoring data necessary to understand spread

  3. Source: Hal Mooney

  4. National naturalisation Data: Hazel Gatehouse, unpub.

  5. 1991–2000 • 164 new plant species naturalised • (avg. 143 per decade 1851-1990) • include: • 18 annuals/biennials (41.4) • 43 herbaceous perennials (54.1) • 78 shrubs and trees (36.1) • 150 ornamental • 4 forestry,1 hort. Cartoon: Auckland Regional Council

  6. Lag phase, SE Australia Source: Michael Mulvaney (2001), in Groves et al. (eds.), Weed risk assessment, CSIRO Publishing, Collingwood, Australia.

  7. Propagule pressure, SE Australia Source: Michael Mulvaney (2001), in Groves et al. (eds.), Weed risk assessment, CSIRO Publishing, Collingwood, Australia.

  8. Most species in <3 provinces • All naturalised species. ?

  9. Province scale (NZ)

  10. City scale: Auckland

  11. City scale: Auckland Data: Alan Esler and Ewen Cameron

  12. Settlement scale: Northland N.Z.J. Ecology, 29:1–10 (2005)

  13. DOC weeds on roadsides

  14. Should we be alarmed? • Scenario 1: Most ornamentally-sourced naturalised plants are dependent on the habitats in and around urban areas and will remain there. • Scenario 2: Most ornamentally-sourced naturalised plants are in the early stages of invasion.

  15. Spread modelling examples • Pest spread (John Keane, Jake Overton) • Porter’s Pass Hawthorn (John Keane, Peter Williams, Rowan Buxton) • Wilding pines (Yvonne Buckley, Nick Ledgard, et al.) • Craigieburns Hieracium lepidulum (Alice Miller PhD)

  16. Dispersal mechanisms • National/provincial scales: People • City scales: People + natural dispersal • Local scales: People + natural dispersal

  17. Sandra Anderson’s starlings • Collected seeds under starling roosts from two Auckland islands, Tiritiri Matangi and Motuihe, both dominated by native plants • Tiritiri: 20% seed exotic • Motuihe: 65% seed exotic

  18. The hitchhikers’ guide to dispersal • Nursery industry and informal plant trade • Garden waste dumping • Seed contaminants in/on seed, hay, produce, farm stock • In and on road and railway vehicles • Attached to people and their equipment

  19. people = new naturalisations • close correlation between province population and naturalisation

  20. Population biases in the sites of recently naturalised plants: New plants where people were

  21. Some questions • Where, when, and at what scales is weed spread usefully predictable, and for what weeds? What time-series data needs to be collected? • To what extent can we infer the likely mechanism(s) of spread from spatial distribution data? • What is the relative contribution of human and natural dispersal vectors for the spread of different weeds, at different scales?

  22. Weed spread • New Zealand is still in the early stages of plant invasion • Weed spread occurring across many scales; different processes dominate at each • We need better ways of predicting the what, where, and when of weeds • We lack long-term monitoring data necessary to understand spread

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