Is Tansy Ragwort Invasive in Montana

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Is Tansy Ragwort Invasive in Montana?

• M.S. Thesis Results
• Brad Bauer LRES

Committee Bruce Maxwell, advisor George
Markin Lisa Rew Tad Weaver Cathy Zabinski
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Tansy Ragwort Background

• Biennial, Short lived Perennial, Annual (Wardle
  1987), 0.3 2 m tall (Frankton and Mulligan
  1987)
• Germinates spring and fall (Harper and Wood 1957)
• Over-winter as seedling or rosettes (Forbes 1977)
  

www.idahoweedawareness.org
weeds.ippc.orst.edu
kitsap.wsu.edu
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Research Objectives

• To determine the probability of occurrence of
  tansy ragwort across a range of environments.
• Under what environmental conditions does tansy
  ragwort present the greatest threat of invasion.
• To understand the sources of the population
  growth rate variability.
• To investigate the role slashpiles play in the
  establishment of tansy ragwort.
• To quantify the demographics of tansy ragwort in
  response to the addition of biological control
  agents.

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Objective 2

• Demographic monitoring in
• Wildfire burned and salvaged logged
• Burned forest
• Non-burned meadow

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Objective 2 Hypothesis

• Ha Tansy ragwort population growth rate (?) will
  be the highest for the burned and salvaged logged
  environment, followed by burned forest, and
  non-burned meadow

gt
gt
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Objective 2 Methods

• Population Invasibility Analysis (PIA)
• Expressed in terms of population growth rate (?)
• ? Population density Nt / Population density
  Nt-1
• N rosettes flowering plants

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Objective 2 Methods

• Started in 2001 Seven years following wildfire
• Establish Transects
• Along transects placed 10 - 1m2 plots
• 95 total plots 94 plots

Azimuth
Transect
(Plot )
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Objective 2 Methods

• Map populations in spring and fall
• Seedlings
• Rosettes
• Flowering
• Seed Bank
• Seed Produced

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Objective 2 Methods
Seedlings(SDL)
SF
FS
SF
FS
Rosettes(ROS)
FS
SF
FS
SF
Flowering(FLW)
FS
Seed Produced(SP)
SF
Seed Bank(SP)
SF
FS
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Objective 2 Methods

• Calculate transition rates for each population (1
  m2 plot)
• Distributions of transition rates for each
  environmental type are compared with box and
  whisker plots

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Objective 2 Results
Seedling to Rosette for Spring to Fall
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Objective 2 Methods
Seedlings(SDL)
SF

• Project the population dynamics
• Difference Equations Xt Xt-1(Rate)
• Run simulation using randomly selected transition
  rates within a plot
• Simulated until stable stage distribution (20
  generations)
• Calculate ? Nt/Nt-1 (population growth rate)

Difference Equations Xt 10 (0.40)
Difference Equations 4 10 (0.40)
Rosettes(ROS)
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Objective 2 Methods

• Monte Carlo simulation - 1000 reps/environment
• Create distribution of ? for each environment
• Compare ? among environments

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Objective 2 Results
Prob. ? gt 1.0 0.209 0.319
0.015
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Objective 2 Results
Elasticity values (0-100) Difference Equation SF
and FS
Fall to Spring Spring to Fall
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Objective 3 Results
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Objective 2 Management Implications

• Most populations not invasive.
• Occasional highly invasive population.
• Prioritize management
• Burned and Salvage-logged
• Burned
• Meadow
• Target management at seed bank and rosette
  survival.
• Increase cover of native species.