Bark Beetles, Fuels and Fire A synthesis of our present understanding and implications for management

*Michael J. Jenkins1, Christopher J. Fettig2, and Elizabeth G. Hebertson3

1Professor, Department of Wildland Resources, Utah State University, Logan, UT 84322, USA. 2Research Entomologist, Pacific Southwest Research Station, USDA Forest Service, Davis, CA 95618, USA. 3Forest Health Specialist, Forest Health Protection, Ogden Field Office, USDA Forest Service, Ogden, UT 84403, USA.

FOR MORE INFORMATION *CONTACT Michael J. Jenkins Professor Department of Wildland Resources Utah State University Logan, Utah, 84322, USA Phone: 435-797-2531 Fax: 435 797-3796 Email: mike.jenkins@usu.edu

It is important to develop fuels and bark beetle management alternatives that are ecologically appropriate, economically feasible, and satisfy resource values. Landscapes where management activities can best enhance long-term forest sustainability and resiliency should receive treatment priority, especially in light of climate change scenarios. The attainment of these goals however, can only be achieved through the development of strategies aimed at bridging the disconnect between the forest health and fire communities. Increased coordination and communication is, therefore, essential.

Prevention treatments may increase activity fuels and potential fire behavior in the absence of proper slash management Long-term suppression of wildfires may increase hazardous fuels, particularly in seasonally dry forests that historically experienced frequent, low to moderate intensity surface fires

Interactions between fire and bark beetles (Coleoptera: Curculionidae, Scolytinae) operating over various spatial and temporal scales primarily determines the composition and structure of coniferous forests in western North America (Fig. 1).

2. HOW TREATMENTS MAY INCREASE BARK BEETLE AND

FIRE RISK AND HAZARD

1. INTRODUCTION

Hazardous fuels reduction treatments (e.g., chipping or mastication) may exacerbate bark beetle attacks on residual trees Residual tree damage, green slash, and host volatiles may increase bark beetle risk Fire suppression results in stand structures and compositions more conducive to the initiation and spread of bark beetle outbreaks

3. WAYS TO MITIGATE BARK BEETLE RISK AND HAZARD

Several measures can be taken to mitigate bark beetle activity when implementing silvicultural treatments with a primary objective of reducing hazardous fuel loads. For example, Forest Health Monitoring survey maps may be used to determine future bark beetle risk. The susceptibility of stands surrounding treatment areas should be assessed to determine their potential for infestation. In areas of high risk, silvicultural treatments that result in the production of large quantities of host materials may be timed to coincide with periods of low bark beetle flight activity. Furthermore, guidelines are available that aid in the treatment of slash to reduce the likelihood of Ips colonization success. In many cases, and with minimal additional effort, fuel reduction treatments may be implemented in such a manner that they also reduce bark beetle risk and hazard in treated and adjacent areas.

4. BRIDGING COMMUNICATION GAPS

REFERENCES Bebi, P., D. Kulakowski, T.T. Veblen. 2003. Interactions between fire and spruce beetles in a subalpine Rocky Mountain forest landscape. Ecol. 84(2): 362-37. Cunningham, C.A., M.J. Jenkins, D.W. Roberts, 2005. Attack and brood production by the Douglas-fir beetle (Coleoptera: Scolytidae) in Douglas-fir, Pseudotsuga menziesii var. glauca (Pinaceae), following a wildfire. West. N. Amer. Nat. 65, 70-79. DeGomez, T., C.J. Fettig, J.D. McMillin, J.A. Anhold, and C.J. Hayes. 2008. Managing slash to minimize colonization of residual leave trees by Ips and other bark beetle species following thinning in southwestern ponderosa pine. AZ1448. Tucson, AZ: University of Arizona, College of Agriculture and Life Sciences Bulletin. 21 p. Fettig, C.J., R.R. Borys, C. Dabney, In press. Effects of Fire and Fire Surrogate Treatments on Bark Beetle-Caused Tree Mortality in the Southern Cascades, California. For. Sci. 55 (3). Fettig, C.J., R.R. Borys, S.R. McKelvey, 2008. Blacks Mountain Experimental Forest: bark beetle responses to differences in forest structure and the application of prescribed fire in interior ponderosa pine. Can. J. For. Res. 38: 924-935. Fettig, C.J., J.D. McMillin, J.A. Anhold, M.H. Shakeeb, R.R. Borys, C.P. Dabney, S.J. Seybold, 2006. The effects of mechanical fuel reduction treatments on the activity of bark beetles (Coleoptera: Scolytidae) infesting ponderosa pine. For. Ecol. Manage. 230, 55-68. Hood, S., B.J. Bentz. 2007. Predicting post-fire Douglas-fir beetle attacks and tree mortality in the northern Rocky Mountains. Can. J. For. Res. 37, 1058-1069. Jenkins, M.J., C.A. Dicus, E.G. Hebertson. 1998. Postfire succession and disturbance interactions on an Intermountain subalpine spruce-fir forest. In Teresa L. Pruden and Leonard A. Brennan (eds.). Fire in ecosystem management: shifting the paradigm from suppression to prescription. Tall Timbers Fire Ecology Conference Proceedings, No. 20. Tall Timbers Research Station, Tallahassee, FL. 219-229. Jenkins, M.J., E.G. Hebertson, W.G. Page, C.A. Jorgensen. 2008. Bark beetles, fuels, fires and implications for forest management in the Intermountain West. For. Ecol. Manage. 254, 16-34. Page, W.G., M.J. Jenkins. 2007a. Mountain pine beetle induced changes to selected lodgepole pine fuel complexes within the Intermountain region. For. Sci. 53 (4), 507-518. Page, W.G., M.J. Jenkins. 2007b. Predicted fire behavior in selected mountain pine beetle infested lodgepole pine stands within the Intermountain region. 53 (6), 662-674.

Figure 3. Predicted changes in fire behavior in Engelmann spruce, lodgepole pine and Douglas-fir stands during the course of a bark beetle “rotation”

Many federal, state and local policies presently fail to adequately address issues associated with bark beetle and fire relationships. As a consequence, treatments implemented for the management of one agent often lack sufficient measures to mitigate for potential changes in the risk and hazard of the other. Additionally, the interaction of other factors, such as warming temperatures and invasive species, may exacerbate this issue (Fig. 5).

Figure 8. Pheromone-baited traps used to capture Ips bark beetles emerging from infested slash

Photo: Brytten Steed

Fig. 6. A thinning treatment implemented to reduce the susceptibility of spruce-fir stands to spruce beetle

Photo: Steve Munson Photo: Mike Jenkins

Fig. 7. A mechanical fuel treatment implemented to reduce hazardous fuels

PREDISPOSE TREES TO BARK BEETLE

Bark beetle-caused tree mortality affects both the quantity and quality of forest fuels and has long been assumed to increase hazardous fuels and potential fire behavior (Fig. 2). Consequently, land managers often cite the accumulation of hazardous fuels and/or the potential for extreme fire behavior resulting from tree mortality attributed to bark beetle attack as a rationale for implementing bark beetle management treatments. In reality, little research has been conducted to support this assertion. Recent efforts suggest that while bark beetle-caused tree mortality alters fuels complexes and consequent fire behavior, these changes vary considerably depending on such factors as forest type, stand conditions, and site characteristics (Fig. 3). Conversely, fire damages trees that may predispose them to bark beetle attack, although it remains unknown whether this increases bark beetle risk (Fig. 4). MANAGEMENT

DISCONNECT

Fig. 5. Conceptual model illustrating bark beetle and fire relationships and where lack of understanding has lead to policy and management disconnects

HUMAN LANDSCAPE

AGENCY ORGANIZATION POLICIES

CHANGING SOCIAL VALUES

BARK BEETLES FIRE

INVASIVE SPECIES

Photo: Mike Jenkins

BARK BEETLES FIRE

Fig. 1. Natural disturbance regimes in coniferous forests of western North America (Jenkins et al., 2008)

ALTER FUELS

Photo: Mike Jenkins

Figure 9. FARSITE projections showing differences in the probability of fire sizes in endemic lodgepole pine stands (a) and stands infested by mountain pine beetle (b)

(a) (b)

Pacific Southwest Research Station

CLIMATE CHANGE

Fig. 2. Fuels in an Engelmann spruce and subalpine fir stand 10 years after spruce beetle, Dendroctonus rufipennis Kirby (Coleoptera: Curculionidae) outbreak

Fig. 4. Fire predisposes injured trees to bark beetle attack

Photo: Liz Hebertson Photo: Chris Fettig

ACKNOWLEDGEMENTS: Funding for this project provided by: USDA Forest Service Technology Development Program Forest Health Monitoring Evaluation Monitoring Program