Bark beetle outbreaksSlide Number 2Mountain Pine Beetle (Dendroctonus ponderosae Hopkins) Attack CharacteristicsFactors Influencing Establishment & OutbreaksSlide Number 6Slide Number 7Slide Number 8 “Perfect storm” of effects of fire exclusion promoting MPB…creating “unprecedented” fire hazard -- Rocky Mountain News "I look at Colorado as the Katrina of the West" in terms of inadequate federal disaster preparation for wildfire in beetle-killed forests. --Sen. Ken Salazar, July 2006. “Beetlemania in Colorado” -- Newsweek, July 2008 Slide Number 10Slide Number 11Slide Number 12Slide Number 13Slide Number 14Slide Number 15Is the current MPB outbreak unprecedented in northern Colorado? Slide Number 17Slide Number 18Temperature regulates rate of development and survival of MPB in lab and field studies* Broad-scale Role of Climate Future trends predicted from modelsSlide Number 22Slide Number 23Slide Number 24Slide Number 25Slide Number 26Slide Number 27In the 1850s-1880s widespread burning in Colorado synchronized stand ages in the subalpine zoneSlide Number 29Slide Number 30Slide Number 31Slide Number 32Slide Number 33Slide Number 34Slide Number 35Slide Number 36Slide Number 37Slide Number 38Slide Number 39Slide Number 40 Conclusions and Practical Implications for Colorado Subalpine ForestsBark beetle outbreaks• General introduction to bark beetles– Focus on mountain pine beetle in lodgepole pine and on spruce beetle in spruce-fir forests• Is the current MPB outbreak in lodgepole pine significantly affecting fire hazard?2007Major Bark Beetles and Hosts in ColoradoMountain pine beetle Lodgepole pine, bristlecone pine,limber pineSpruce beetleEngelmann spruceIps beetlesPonderosa pine, pinyon pine, limberpine, lodgepole pineDouglas-fir bark beetleDouglas firWestern Balsam Bark BeetleSubalpine fir150 million acresaffected since 1997Mountain Pine Beetle(Dendroctonus ponderosae Hopkins)• Bark Beetle• Native to N. America• 1 year life cycle• Outbreaks can lead to significant tree mortality & loss of economic timber• Ecologically important• Primary disturbance agent in forest ecosystemsAdult mountain pine beetleAttack Characteristics• On most pines, attack lower 15 ft. of tree first• Pitch tubes• Characteristic galleries• Exit holes• Frass around base of tree• Blue wood under bark• Tree mortality• In ponderosas, preferentially infest trees > 8”dbhFactors Influencing Establishment & OutbreaksInsect Populations:• Food Supply• Tree Resistance• Predators, parasites & competitionEnvironmental:• May attack fire damaged trees preferentially• Stand Structure (age, density, dbh)• Climate and DroughtMountain Pine Beetle, Grand Lake 2003Spruce Beetle,Routt Divide, 2003 Mountain Pine Beetle, Grand Lake 2003Since 1996 > 1.5 million acres of lodgepole killed by MPB in ColoradoMPB in the Gore Range 2005 Photo: J. Hicke“Perfect storm” of effects of fire exclusion promoting MPB…creating “unprecedented” fire hazard-- Rocky Mountain News "I look at Colorado as the Katrina of the West" in terms of inadequate federal disaster preparation for wildfire in beetle-killed forests. --Sen. Ken Salazar, July 2006. “Beetlemania in Colorado” -- Newsweek, July 2008For northern Colorado subalpine forests1. How unusual are the current MPB and spruce beetle (SB) outbreaks in comparison to outbreaks of the past several centuries?2. What is the role of climate variability in the current bark beetle outbreaks?3. What has been the role of climatic variation in past episodes of widespread severe fires?4. How has 20thcentury fire suppression affected the hazard and risk of fire and beetle outbreak?5. Following previous bark beetle outbreaks, did wildfire increase in frequency, extent or severity?1. How unusual are the current MPB and spruce beetle (SB) outbreaks in comparison to outbreaks of the past several centuries?1940s spruce beetle outbreak, White River NF in 19871940s SB outbreak affected most spruce-fir in White River, southern Routt, and Grand Mesa NFs.In White River NF in the 1940s > 90% of spruce timber volume killed 1940s Spruce Beetle OutbreakUse the 1940’s spruce beetle outbreak to calibrate tree-ring detection of pre-historic outbreaksSynchronous persistent growth releases can detect past canopy disturbance1800sSB outbreaksTree-ring records:Veblen et al. 1991, EcologyEisenhart & Veblen 2001, CJFRKulakowski & Veblen 2006, CJFRHistorical observations:Sudworth 1900Hopkins 1909Tree-ring reconstructions show spruce beetle outbreaks affected even larger areas during the second half of the 19thcenturyIs the current MPB outbreak unprecedented in northern Colorado?• No published tree-ring records of MPB in Colorado…but 19thcentury drought and 16thcentury mega-drought?• A.D. Hopkins (1909) described “enormous” beetle kills for southern Rockies in general (including Colorado)• FS and RMNP reports of widespread MPB but much less than current outbreak*:– 1930s (Ponderosa pine, RMNP)– 1950s (Ponderosa pine, Front Range)– 1970s (Ponderosa pine, Boulder County)– 1980s (Lodgepole pine, Grand County) • Lodgepole forests do not show extensive post-beetle cohorts during 20thcentury implying that the current (post-1996) outbreak is more severe.* Veblen and Donnegan. 2006. HRV.2. What is the role of climate variability in the current bark beetle outbreaks?The Broader Context: Bark Beetle Outbreaks and Warming1997 2006From: Bentz et al. 2008. Bark beetle outbreaks in western North America: Causes and consequences. In press.Temperature regulates rate of development and survival of MPB in lab and field studies*• Maturity and emergence at threshold temperatures• Peak rates of emergence at higher temperatures• Shift from two-year to one-year life cycle• Cold tolerance varies with life-cycle stage• Death from winter temperatures below -29 to 40oCTemperature thresholds vary with location!Prediction of climate effects on MPB requires more on-site studies*Logan et al. 1995; Safraynik 2006; Hicke et al. 2006; Malm and Negron in progressBroad-scale Role of Climate Warming• Accelerates beetle life cycle and population growth• Reduces cold-induced mortality• Beetle range expansions• Drought decreases tree resistanceResearch and Consensus • Logan et al. 1995. Assessing the