Impacts of Low-severity Fire and Fuel Treatments on Ponderosa Pine Resistance to Mountain Pine Beetle.
Location
USU Eccles Conference Center
Event Website
https://www.restoringthewest.org/
Abstract
Fire frequency in low-elevation coniferous forests in western North America has greatly declined since the late 1800s. In many areas, this has increased tree density and the proportion of shade-tolerant species, reduced resource availability, and increased forest susceptibility to forest insect pests and high-severity wildfire. We investigated how low-intensity fire affects tree defenses and whether fuel treatments in ponderosa pine forests impact resistance to a mountain pine beetle outbreak using a combination of sampling in natural stands for which we had multi-century fire histories and an experimental design of four thinning and burning treatments. Fire stimulated tree resin duct defenses and areas with long-term fire exclusion showed lower defenses. Trees surviving mountain pine beetle attack produced larger and more resin ducts than trees that died from beetle attack. In the experimental treatments, ponderosa pine mortality from the insect outbreak was 50% in the denser, untreated control and 39% in the burn-only, compared to almost no mortality in the thin-only and thin-burn treatments. This study suggests that fuel and restoration treatments designed to reduce fire intensity in fire-dependent ponderosa pine forests can also function to increase resistance to mountain pine beetle outbreaks.
Impacts of Low-severity Fire and Fuel Treatments on Ponderosa Pine Resistance to Mountain Pine Beetle.
USU Eccles Conference Center
Fire frequency in low-elevation coniferous forests in western North America has greatly declined since the late 1800s. In many areas, this has increased tree density and the proportion of shade-tolerant species, reduced resource availability, and increased forest susceptibility to forest insect pests and high-severity wildfire. We investigated how low-intensity fire affects tree defenses and whether fuel treatments in ponderosa pine forests impact resistance to a mountain pine beetle outbreak using a combination of sampling in natural stands for which we had multi-century fire histories and an experimental design of four thinning and burning treatments. Fire stimulated tree resin duct defenses and areas with long-term fire exclusion showed lower defenses. Trees surviving mountain pine beetle attack produced larger and more resin ducts than trees that died from beetle attack. In the experimental treatments, ponderosa pine mortality from the insect outbreak was 50% in the denser, untreated control and 39% in the burn-only, compared to almost no mortality in the thin-only and thin-burn treatments. This study suggests that fuel and restoration treatments designed to reduce fire intensity in fire-dependent ponderosa pine forests can also function to increase resistance to mountain pine beetle outbreaks.
https://digitalcommons.usu.edu/rtw/2017/Oct18/12
Comments
Sharon Hood is a Research Ecologist for the US Forest Service, Rocky Mountain Research Station’s Fire, Fuel, and Smoke Science Program in Missoula, MT. She studies how fire impacts trees and forest dynamics. Her research to date has focused on fire-induced tree mortality, fire-bark beetles interactions, and fuel treatments. Sharon received a PhD from the University of Montana in Organismal Biology and Ecology, a MS from Virginia Tech in Forest Biology, and a BS from Mississippi State University in Forest Management.