Comovement and cyclical patterns of southern pine beetle outbreaks
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2009 Nova Science Publishers, Inc. Insect infestations have been a major driving force of landscape change, leading to severe ecological and economic consequences. The southern pine beetle (SPB), Dendroctonus frontalis Zimmermann, is the most destructive insect to pine forests in the U.S. South. This study probes the spatial and temporal patterns, particularly comovement and cyclical patterns, of SPB infestations at broad scales in the Southern United States. Cluster analysis in terms of comovement shows that SPB infestations in the region can be classified into three subregions: Alabama-Florida-Louisiana-Mississippi-Virginia, Georgia-Carolinas-Tennessee, and Arkansas-Texas. SPB infestation risk has increased over time in Florida, South Carolina, and Tennessee, but decreased in Alabama. The magnitude of bi-state comovements of SPB infestations is in general quite large whereas that of regionwide comovements is small, and comovments of small outbreaks are more pronounced than those of big ones. SPB infestations in North Carolina best resemble (synchronize with) the regions median, and thus it can be used as the regions reference for monitoring and forecasting. Though regionwide cyclical outbreak patterns are not detected, statistic evidence of cyclical outbreaks for some states and especially for the identified clusters/subregions is apparent; and the sinusoidal component is commonly concentrated over a range of low frequencies. These results will be of value for monitoring and mitigating SPB outbreaks in the region.
