Exotic Weed Establishment and Movement Through Landscape Corridors. What are we doing about it?

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Exotic Weed Establishment and Movement Through
Landscape Corridors. What are we doing about it?
John Rademacher
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Hierarchy Weed Classification

• Weed
• Native
  Exotic
• Non Invasive
  Invasive
• 
  Non Noxious Noxious
• 
  Federal
  State

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Corridor Types
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Exotic Weed Establishment within Road and Trail
Corridors
Average viable seeds found on the undercarriage
of United Kingdom vehicles (Hodkinson et al 1997)
Average viable seeds per car
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Exotic Weed Establishment within Road and Trail
Corridors

• Seeds are able to survive livestock digestion.
• On average it takes 2-3 days to completely digest
  forage.
• Cattle can walk up to 14km per day.
• Viability of seeds prior to digestion depends on
  species.
• In forested landscapes livestock use road systems
  as primary travel paths and foraging areas.

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Exotic Weed Establishment within Road and Trail
Corridors

• Historically invasive grass species were used to
  stabilize road sides especially on highly
  stressed or disturbed landscapes.
• Invasive grass species have been used to increase
  wildlife forage, hay and residential landscaping.
  

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Seed viability

• Beal (started in 1879, 1st published in 1911),
  Michigan State University buried seed of 21
  common plant species.  
• 1920, 8 species germinated
• 1940, 3 species germinated
• 1980, 2 species germinated
• Info Source David Priestley's book on Seed Aging
  (Comstock Publishers, Cornell Univ. Press),
  published in 1986.
• Viable common lambsquarters found in
  archeological sites, 1700 years old.

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How patch vegetation effects weed movement
Exotic species richness across an area of road
influence ARI for three road corridors (Tyser
et al 1992)
Exotic species richness
Distance from road (m)
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How patch vegetation effects weed movement
Exotic species richness across an area of road
influence ARI for two closed canopy patch types
(Watkins et al 2003)
Exotic species richness
Distance from road (m)
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How patch vegetation effects weed movement

• Closed canopy forest controls perpendicular
  spread.
• Open canopy forest allows perpendicular and
  parallel spread.
• Potential weed habitat extends 15m into every
  closed canopy forested patch touching the clear
  cut

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Landscape Weed Management

• Eradicate Remove all individuals (newly
  established weed species, small population or
  high economic damage)
• Contain Stop the spread (medium sized
  population and large populations close to
  sensitive habitat)
• Control Slow the spread (large populations)

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Phases of noxious weed invasion. Ease of
treatment declines from left to right (Hobbs et
al 1995)
Contain
Control
Eradication
Invader abundance
Time
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Landscape Weed Management Nez perce National
Forest, Clearwater Ranger District
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Noxious weed control and prevention

• Weed free hay and straw (quarantine livestock for
  3 days)
• Herbicide application
• Biological control
• Mechanical control
• Try to leave at least a 15 meter closed canopy
  buffer around forested roads
• Reduce road densities in susceptible areas

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• Questions?