|Koch, Frank -|
|Hain, Fred -|
Submitted to: Forest Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 20, 2010
Publication Date: July 25, 2011
Citation: Duehl, A.J., Koch, F.H., Hain, F.P. 2011. Southern pine beetle regional outbreaks modeled on landscape, climate and infestation history. Forest Ecology and Management. 261:473-479. Interpretive Summary: The southern pine beetle (SPB) is the major insect pest of southern pines and can for multi-state epidemics. In order to successfully reproduce the beetle must kill pine trees and since pine species are the main managed tree species in the southeast United States the development of better tools for management is important. Scientists from the USDA in collaboration with university scientists developed statistical models to determine what the important landscape and environmental factors are that lead to SPB infestation at the county scale. The most important factor was the existence of an outbreak in the same county in the previous year. Other important factors included average climatic conditions and how much forest area existed in a county. These models can be used to locate counties that are at higher risk for infestations and then target management dollars to protect forests. Extending these models with smaller scale data should help to further improve their predictions.
Technical Abstract: The southern pine beetle (Dendroctonus fromtalis, SPB) is the major insect pest of pine species in the southeastern United States. It attains outbreak population levels across the landscape at scales ranging from a single forest stand to interstate epidemics. This county level analysis selected and examined the best climatic and landscape variables for predicting infestations at regional scales. The analysis showed that, for a given county, the most important factor in predicting outbreaks was a successful outbreak in the previous year. Other important factors included minimum winter temperature and the greatest difference between the average of daily minimums and a subsequent low temperature point, precipitation history, seasonal synchrony of beetle populations and the relative percentage of total forest area composed of host species. The statistical models showed that climatic variables are stronger indicators of outbreak likelihood than landscape structure and cover variables. Average climatic conditions were more likely to lead to outbreaks than extreme conditions, supporting the notion of coupling between a native insect and its native host. Still, some extreme events (i.e., periods of very low temperature or very high precipitation) did precede beetle infestation. This analysis suggested that there are predisposing factors at the large scale but the driving factors leading to individual infestations operate at smaller scales.