AWRA Summer Tour
Pine Beetle Effects in Summit and Grand County August 8, 2008 The AWRA Colorado Section took its summer tour to Summit and Grand counties to witness firsthand the effects of the mountain pine beetle (Scolytidae) on Colorado’s Lodgepole Pine on August 8th. The tour started with a chartered bus ride up I-70 to Summit County. Jeff Witcosky, with the U.S. Forest Service, provided an overview of the Pine Beetle and its effects on Colorado’s forests. Jeff explained that the female pine beetle burrow into the inner bark (phloem) of its primary host trees (ponderosa, lodgepole, sugar, and white pines). Once the female manages to burrow into the inner bark, it releases odors called aggregating pheromones that attract other beetles (both male and female). The female beetle lays its eggs in July and August, and eggs enter the larvae stage within 2 weeks. The beetle larvae feed on the inner bark of their host tree, and eventually turn into pupae, then into adults which continue to feed on the inner bark of the trees. The mass attack on the trees winds up killing the trees. Beetle attacks on trees are part of the natural cycle of nature, and occasionally conditions lead to a beetle epidemic. Key factors that can and have led to beetle epidemics include available food supply. Beetles seek out larger trees because of the large amount of phloem for food supply associated with larger trees. Beetle epidemics are less likely to occur in tree stands with natural variation in tree sizes when compared to tree stands dominated by larger trees (e.g., tree stands that have been clear cut at one point in time). Temperature is another factor in keeping beetles in control. Outbreaks can be broken by unseasonably low temperatures in early fall or mid spring (i.e., temperatures below 0 degrees Fahrenheit), or extremely cold temperatures during winter months (i.e., temperatures below -34 degrees Fahrenheit). The pine beetle outbreak in Colorado has hit Grand, Jackson, and Summit counties the hardest as shown in Table 1, with 80, 76, and 58 percent, respectively, of lodgepole pine acreage impacted by the beetle. The first stop on the tour was a visit to a forest at Keystone Gulch in Summit County that has been impacted by the mountain pine beetle. During this stop, a presentation was given by Cary Green of the U.S. Forest Service (Photo 1) explaining how the Forest Service is dealing with the beetle outbreak. Cary explained that there was an increase of about 35 percent of the area within Summit County this year alone that has been impacted by the beetle. He suggested one of the main causes of the recent outbreak in Summit County is that there have not been enough prescribed lodgepole stand cuts, which are typically used to mimic natural fires. The lack of prescribed cuts has lead to mature lodgepole stands dominated by mature trees, an ideal habitat for a beetle outbreak. Cary also explained that it typically takes approximately 15 years to develop new lodgepole stands from the time when the trees are killed by beetles.
| Table 1. Cumulative (1996 through 2007) Lodgepole Pine Forest Statistics
The U.S. Forest Service is implementing several projects within the area from the Eisenhower Tunnel to Glenwood Springs to deal with the pine beetle epidemic, primarily focusing on reducing the hazards of dead lodgepole stands near the population corridors. The Forest Service is currently conducting clear cuts on about 1,360 acres of lodgepole pines killed by the pine beetles within Summit County, with the intent of reducing the hazards associated with fire and fallen trees. The Forest Service targets lodgepole stands with at least 50 percent of the stand that has been killed by beetles. The cost of these clear cutting projects is about $1,000 per acre, resulting in a current mitigation cost of about $1,360,000 within Summit County alone. The Forest Service has contracts for similar projects for the upcoming year on 3,200 acres of land within Summit County and 3,100 acres of land within Eagle County. The last stop of the tour was a visit to the new Confluence Energy wood pellet manufacturing plant in Kremmling. This plant is using trees killed by the mountain pine beetle to manufacture a local energy source that would otherwise be left in the forest to burn or decay. The owner of the plant, Mark Mathis, explained that pellet fuel is a renewable energy source that is cost effective, especially when considering the recent increases in the price of natural gas (Photo 2). The group was given of tour of the manufacturing process, which starts with chipping and drying of dead trees. The wood chips are then hammered into small wood chips that are then pressed using pellet mills, which use intense pressure to form the wood pellets without any bonding agents. Wood pellets made at the Kremmling plant will soon be available for purchase at hardware stores within Colorado. The Confluence Energy website, www.confluenceenergy.com has an interactive energy analysis tool that can be used to compare the cost of various competitive fuels.
As with any good summer field trip, the AWRA Colorado summer tour ended with a social hour at one of the member’s homes. This year’s tour was extremely educational, and provided the background information needed by water resource managers to understand the causes and result of a mountain pine beetle epidemic on our state’s water supply. We haven’t decided what our summer tour will be next year, but we hope you’ll provide your suggestions and maybe even join us!