Bark beetles, fire and salvage logging in the Greater Yellowstone Ecosystem
disturbance interactions, Douglas-fir beetle, Yellowstone National Park, mountain pine beetle (Dendroctonus ponderosae), insect outbreaks, fire ecology, fuel management, fire risk, disturbance interactions, subalpine forests, lodgepole pine, Douglas-fir, soil nitrogen
Understanding the ecological consequences of the recent outbreaks of bark beetles (Genus: Dendroctonus) that have affected millions of hectares of forest in western North America is of tremendous importance for forest ecology and management. One important question is whether bark beetle outbreaks increase or decrease the severity of subsequent wildfire. With funding from the Joint Fire Science Program (JFSP), we began investigating reciprocal interactions between bark beetle outbreaks and fire in 2006. Previous studies had characterized the independent effects of wildfire and bark beetle epidemics, but very little was known about how these two phenomena interact. Collaborators on this research include Drs. Bill Romme (Colorado State University), Dan Tinker (University of Wyoming), and Phil Townsend and Ken Raffa (both University of Wisconsin).
We began our studies of bark beetles and fire by focusing initially on lodgepole pine forests in Greater Yellowstone. For his PhD dissertation, Martin Simard investigated the landscape patterns of bark beetle infestation in Greater Yellowstone and the consequences of bark beetle infestation on fuels and potential fire behavior across a 30-yr time-since-outbreak chronosequence. Another PhD student, Jake Griffin, addressed the consequences of beetle outbreaks for nitrogen cycling for his dissertation. For her MS thesis, Erinn Powell (a student in Ken Raffa’s lab) asked whether fire-injured trees catalyzed a subsequent outbreak of mountain pine beetle. Our findings are summarized in our final report and in the publications listed below. Research from our team has also been highlighted in a NASA video, a press release from the Ecological Society of America, and in science summaries geared for forest managers, including one brief focused specifically on our project (click here) and a science digest that provides a more comprehensive discussion of current understanding of beetle-fire interactions (click here).
Following a bark beetle outbreak, forest managers may conduct a salvage harvest to extract economically valuable timber and/or to reduce perceived risk of subsequent disturbance. However, the ecological consequences of post-beetle salvage harvest are largely unknown, and empirical studies are relatively scarce. In a Joint Venture Agreement with the USFS Western Wildlands Environmental Threats Assessment Center, we initiated a study on the Bridger-Teton National Forest (BTNF) in 2007 to determine how nutrient cycling, fuels and forest regeneration in lodgepole pine (Pinus contorta) were affected by bark beetles and post-beetle salvage harvest. We used a before-after-control-impact (BACI) study design to compare changes in harvested stands with paired stands that were unmanaged.
Our current research extends this line of inquiry into the interior Douglas-fir forests of Greater Yellowstone and is also funded by JFSP (click here to view PDF of our proposal). This study addresses three main questions: (1) How do effects of bark beetle outbreaks on fuel profiles and subsequent fire hazard differ between lodgepole pine and Douglas-fir forests? Dan Donato is leading this effort in which we are testing hypotheses about how post-beetle fuel profiles and future fire hazard differ between these two widespread forest types. (2) How was the severity of recent fire in lodgepole pine and Douglas-fir forests affected by prior bark beetle infestation, and does the combination of beetle infestation and fire compromise forest recovery? In recent fires (2006-2008) in the GYE, field studies and remote sensing are being used to determine how actual spatial variation of fire severity across the landscape was related to pre-fire beetle infestation. This research is part of Brian Harvey's PhD dissertation. (3) What post-beetle fuel treatments are likely to change the hazard of subsequent severe fire in lodgepole pine and Douglas-fir forests? We are parameterizing the Fire and Fuels Extension to the Forest Vegetation Simulator model (Reinhardt and Crookston 2003) for lodgepole pine and Douglas-fir with our field data. Simulations will explore the effects of a wide range of common forest management practices (e.g., thinning, removal of beetle killed trees or remaining small trees, slash management, etc.) on future fire hazard. This component of the study is led by Dan Donato. Stay tuned for updates, or check our “Recent Abstracts” page for recent results.
Bockino, N. K. and D. B. Tinker. 2012. Interactions of white pine blister rust and mountain pine beetle in whitebark pine ecosystems in the Southern Greater Yellowstone Area. Natural Areas Journal 32:31-40.
Griffin, J. M., M. G. Turner and M. Simard. 2011. Nitrogen cycling following mountain pine beetle disturbance in lodgepole pine forests of Greater Yellowstone. Forest Ecology and Management 261:1077-1089.
Griffin, J. M. and M. G. Turner. 2012. Bark beetle outbreak induces similar changes to the nitrogen cycle in contrasting conifer forests. Oecologia (In press)
Powell, E. N., P. A. Townsend and K. F. Raffa. 2012. Wildfire provides refuge from local extinction but is an unlikely driver of outbreaks by mountain pine beetle. Ecological Monographs 82:69-84.
Raffa, K. F., B. H. Aukema, B. J. Bentz, A. L. Carroll, J. A. Hicke, M. G. Turner and W. H. Romme. 2008. Cross-scale drivers of natural disturbances prone to anthropogenic amplification: dynamics of biome-wide bark beetle eruptions. BioScience 58:501-517.
Simard, M., E. N. Powell, J. M. Griffin, K. F. Raffa and M. G. Turner. 2008. Annotated Bibliography for Forest Managers on Fire-Bark Beetle Interactions. Prepared for USFS Western Wildlands Environmental Threats Assessment Center and available online: (http://www.fs.fed.us/wwetac/publications.html).
Simard, M., W. H. Romme, J. M. Griffin and M. G. Turner. 2011. Do mountain pine beetle outbreaks change the probability of active crown fire in lodgepole pine forests? Ecological Monographs 81:3-24.
Simard, M., W. H. Romme, J. M. Griffin and M. G. Turner. 2012. Do mountain pine beetle oubreaks change the probability of active crown fire in lodgepole pine forests? Reply. Ecology (In press).
Simard, M., E. N. Powell, K. F. Raffa and M. G. Turner. 2012. What explains landscape patterns of bark beetle outbreaks in Greater Yellowstone? Global Ecology and Biogeography 21:556-567.