USFS Western Wildlands Environmental Threats Assessment Center
Forest managers in the western US are facing more fires and the most extensive bark beetle outbreaks recorded for the region. • Interactions of wildfire and bark beetle outbreaks and their reciprocal influences on fire behavior, bark beetle dynamics, and ecosystem structure are critical research issues in many western coniferous forests. For the effects of bark beetles on fire: o There is increasing evidence that spruce beetle outbreaks have no effect on the occurrence and severity of stand-replacing fires in spruce-fir forests. o The effect of mountain pine beetle infestations on fire occurrence and severity in lodgepole pine forests are unclear; research results are ambivalent. o Effect of bark beetle outbreaks on fire in other forest types are unknown (ponderosa pine, pinyon-juniper) or need more research (Douglas-fir). o Time-since-beetle outbreak is an important factor to consider in the relationship between bark beetle outbreaks and fire risk because fuels change over time. For the effects of fire on bark beetle outbreaks: o There is increasing evidence that Douglas-fir beetle attack rates are higher on fireinjured Douglas-fir trees. o The evidence regarding effects of fire injury in lodgepole pine on mountain pine beetle attack rates is inconclusive, and whether attacks on fire-injured trees lead to subsequent attacks on healthy trees and/or outbreaks is not known. o Effects of fire injury on attack rates of tree-killing bark beetles in other systems (spruce beetle-Engelmann spruce, mountain pine beetle-ponderosa pine, Jeffrey pine beetle-Jeffrey pine) need more research. o Non-aggressive bark beetles such as Ips and wood borers have higher attack rates on fire-injured trees. o More studies are needed to test whether the above trends in attack rates result in changes in bark beetle reproductive success.
Simard, Martin; Powell, Erinn N.; Griffin, Jacob M.; Raffa, Kenneth F.; and Turner, Monica G., "Annotated Bibliography for Forest Managers on Fire-Bark Beetle Interactions" (2008). The Bark Beetles, Fuels, and Fire Bibliography. Paper 207.