Photo Credit: C. Lafon Interaction of landscape structure and
function in Southern Pine Beetle outbreaks David M. Cairns 1, John
D. Waldron 2, Charles W. Lafon 1, Maria D. Tchakerian 3, Robert N.
Coulson 3, and Kier D. Klepzig 4
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Background Methods Results Conclusion
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Landscape Structure and Function Structure Function
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Why the Southern Pine Beetle? The economic, social, and
ecological impact of the SPB is catastrophic across the Southern
US. Recent damage caused by this insect exceeds all historical
records. Ca. 89 million acres of forest land in the South are at
risk to the SPB. Timber losses alone attributable to the SPB
outbreaks exceed 2.5 billion $$. Outbreaks cycle within the
Southern region and we cannot anticipate when or where they will
occur or predict their severity. Consequently, when outbreaks do
occur the effects on forest health are devastating. The geographic
range of the insect continues to expand and new host tree species
are being infested. The existing knowledge base for the insect is
inadequate to explain the causes for the epidemic or provide
insight into how it can be managed.
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R. Coulson R. Billings R. Billlings
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Objectives Determine the impacts of SPB on landscape structure
Determine the relative impact of the amount and arrangement of
landscape elements to SPB outbreak characteristics and the
persistence of pine on a landscape
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Background Methods Results Conclusion
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LANDIS (LANdscape DIsturbance and Succession) Cellular model
Scalable Cohort-based treatment of vegetation with a decadal
timestep
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What does BDA calculate and what does it do? Cell-based
probability of infestation. Site conditions (species and age
structure) Neighborhood conditions Regional outbreak status
Severity of individual outbreaks Site conditions (species and age
structure)
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Outbreak Severity Calculations Species Age Cohort Resource
Value Site Resource Dominance Site Vulnerability Outbreak? Outbreak
Severity Class 1, 2 or 3 End Mortality Class 1: VulnerableClass 3:
Resistent, Tolerant & VulnerableClass 2: Tolerant &
Vulnerable
Experimental Design Factors Proportion of landscape in pine 2
Levels Fractal dimension of landscape 6 Levels Replications 50
Replicate landscapes
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Landscape Creation RULE (Gardner 1999) 512 x 512 cells Binary
(host / non-host) landscapes Variability in two parameters
Proportion of landscape as host Fractal dimension
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h = 0h = 0.1 h = 0.3 h = 0.4 h = 0.5 h = 0.2
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Representation of Landscape Structure h can only be used for
landscape creation, not landscape description. We used the
Clumpiness Index in Fragstats to represent patch aggregation.
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Clumpiness
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Populating the Landscapes All trees placed on the landscape in
year 0 are 10 years old Host Trees Table Mountain Pine: (Pinus
pungens) Non-host species 11 species Randomly placed in non-host
cells
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LANDIS runs No fire BDA active to simulate SPB outbreaks 150
year runs
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Background Methods Results Conclusion
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Sample Simulation
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Size and Timing of Outbreaks
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Persistence of Pine p = 25 %p = 40 %
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Infested Area vs. Aggregation p = 25%p = 40%
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Background Methods Results Conclusion
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Conclusions Pine cover on the landscapes declines regardless of
landscape characteristics. The proportion of the landscape in pine
is less important than the aggregation of the elements for the
persistence of pine. Pine landscapes become more fragmented over
time.
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Conclusions Highly aggregated landscapes are more likely to
have larger and more severe infestations than are less aggregated
landscapes. The proportion of old pines on the landscape influences
the form of the response of infestation area to aggregation.