Bark Beetles, Fuels, and Short-Interval Fires in Douglas-Fir and Lodgepole Pine Forests of Greater Yellowstone

Abstract

Recent increases in insect and fire activity throughout the western US have presented forest managers with formidable challenges. The extent and severity of bark beetle (Curculionidae: Scolytinae) epidemics have reached unprecedented levels, and the frequency of large, severe fires continues to increase. These trends are expected to continue because climate change is implicated for both disturbances. Insects and fire have tremendous ecological and economic effects in western forests, yet surprisingly little is known about how fire hazard may change following bark beetle epidemics, and how changing fire regimes may potentially alter forests of Greater Yellowstone. We are employing a combination of field studies, remote sensing and simulation modeling to understand how bark beetle infestation affects fire hazard in Douglas-fir (Pseudotsuga menziesii) forests. The Douglas-fir type is a key component of Rocky Mountain landscapes, and is experiencing extensive and severe bark beetle outbreaks. However, almost no studies have examined Douglas-fir. We hypothesized that differences in fire regime, stand structure, regeneration potential and decomposition of woody fuels lead to important differences in fuel profiles, fire hazard and, in turn, the effectiveness of alternative mitigation strategies in Douglas-fir. Our studies are being conducted in Grand Teton and Yellowstone National Parks, and the Bridger-Teton and Shoshone National Forests within the Greater Yellowstone Ecosystem (GYE), where we build on >20 years of research and our recent studies of bark beetles and fire in lodgepole pine forests. During the summer of 2011, we conducted a significant portion of the field component of the project, collecting ancillary data in our previously measured chronosequence of Douglas-fir forests of differing time since beetle attack (TSB), and measuring burn severity and forest regeneration following a 2008 fire that burned a recently beetle-attacked Douglas-fir forest on the Shoshone National Forest. We also sampled forest regeneration and dead wood biomass following a short (28-year) interval ‘reburn’ in lodgepole pine forests to test whether reduced seed sources associated with younger trees at the time of burning might reduce postfire regeneration potential. Data analyses are ongoing and results will be forthcoming.