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

 Background Methods Results Conclusion

Landscape Structure and Function Structure Function

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.

R. Coulson R. Billings R. Billlings

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

Background  Methods Results Conclusion

LANDIS (LANdscape DIsturbance and Succession) ● Cellular model ●Scalable ● Cohort-based treatment of vegetation with a decadal timestep

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)

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

BDA Parameters Resource ValueDisturbance Severity Host Age SpeciesMinorSecondaryPrimaryResistantTolerantVulnerable Acer rubrumNA Carya glabraNA Nyssa sylvaticaNA Oxydendrum arboreumNA Pinus pungens Pinus rigida 20 Quercus albaNA Quercus rubraNA Quercus coccineaNA Quercus prinusNA Quercus velutinaNA Robina pseudoacaciaNA

Experimental Design Factors –Proportion of landscape in pine 2 Levels –Fractal dimension of landscape 6 Levels Replications –50 Replicate landscapes

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

h = 0h = 0.1 h = 0.3 h = 0.4 h = 0.5 h = 0.2

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.

Clumpiness

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

LANDIS runs No fire BDA active to simulate SPB outbreaks 150 year runs

Background Methods  Results Conclusion

Sample Simulation

Size and Timing of Outbreaks

Persistence of Pine p = 25 %p = 40 %

Infested Area vs. Aggregation p = 25%p = 40%

Background Methods Results  Conclusion

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.

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.