Working Paper 30: Impact of Forest Restoration Treatments on Southwestern Ponderosa Pine Tree Resistance to Bark Beetles

Working Paper 30 Cover

Insects can have a wide-range of both positive and negative effects on forest ecosystems. Positive impacts include serving as pollinators, creating snags for cavity nesting birds and bats, helping to increase forest heterogeneity, and aiding in decomposition and nutrient cycling. Negative impacts can range from relatively minor impacts at the individual tree level, such as reductions in growth or form defects, to landscape-level tree mortality (Coulson and Witter 1984, Raa et al. 2008). In the ponderosa pine forests of the southwestern United States, the bark beetle has been the insect most often associated with widespread tree mortality.

Restoration efforts in ponderosa pine ecosystems have the overarching goal of making these forests more healthy and resilient by reducing fuel loads and restoring ecosystem functions. Stand restoration in these ecosystems usually involves varying intensities of thinning or prescribed burning treatments or, more often, some combination of both. These same treatments may also alter tree susceptibility to disturbance events, such as insect attacks and wildfire. This working paper will highlight current research about the effects of restoration treatments on ponderosa pine tree resistance/susceptibility to bark beetles.