Assessing the future susceptibility of mountain pine beetle (Dendroctonus ponderosae) in the Great Lakes Region using forest composition and structural attributes

The potential expansion of mountain pine beetle (Dendroctonus ponderosae Hopkins) from western North America into the Great Lakes Region (Michigan, Minnesota, Wisconsin, and Ontario) could negatively impact eastern pine forests. Currently, no metrics exist to assess susceptibility in the region. I have developed a hazard rating system for the Great Lakes Region that utilizes common attributes of forest structure and composition and have assessed the current susceptibility using the Forest Inventory and Analysis database. The vast majority of plots (∼90%) that contained at least one living pine species were classified as moderately or highly susceptible. Plots on federal (USDA Forest Service) lands had higher susceptibility ratings than those on private or state-owned lands. Ordination results highlighted differences among the susceptibility scores (high, moderate, and low) across plots. Plots with high susceptibility were associated with greater total plot density and pine density, and plots with low susceptibility were associated with lower total plot density and greater overstory species richness. There are still many unknowns regarding mountain pine beetle in the Great Lakes Region; however, as natural resource managers plan for the future, they may want to consider the potential arrival of mountain pine beetle in eastern pine forests when developing silvicultural prescriptions.