Bouncing back from bark beetles

The forest is resilient. That was the message from the United State Forest Service and The University of Wyoming Thursday night at the Platte Valley Community Center on the Medicine Bow-Routt National Forests.

The dead trees are hard to miss when traveling through the forest by vehicle. Brent Ewers, an associate professor with the University of Wyoming Department of Botany, said there is a mosaic of living and dead trees in the forest, which has always been the case.

Ewers is part of a research team which studies how the trees die and the process, and what some of the ecosystems processes are that change.

One of the studies includes an instrument in the Snowy Range which measures 3D sonic wind at 10 times a second and the concentration of Carbon Dioxide (CO2) and Water (H2O) all the time.

Ewers explained that the instrument tells those studying the forest how the forest in breathing in and breathing out all the time.

With the bark beetle epidemic, the mosaic of dead trees has grown not only in the region, but in the continental area. A map in his presentation shows the epidemic has spread into the northwestern part of the United States and western Canada.

The beetle epidemic started in British Columbia and moved south. Ewers explained the beetle did not physically move, but the conditions which allowed the bark beetle epidemic have been moving southward over the past five to eight years.

Ewers said there are four different types of beetles affecting the trees in the forest, the pine beetle spruce beetles, mountain pine beetles and pinyon beetles.

The spruce beetles are affecting the high elevation forests where the snowpack is located.

“Every place we have conifers in western North America, we also have beetles attacking those forest, right now,” Ewers said. “This is a region-wide almost continental-scale epidemic of bark beetles and they are in almost all of our major conifer species.”

Ewers showed photographs of trees that had been attacked by bark beetles. The trees had what appeared to be a leaking sap, which Ewers called “pitch tubes”. These were created within minutes of the bark beetle attacking the tree. This is where the resin ducts of the tree are trying to push the beetles out.

A tree has so many resources to produce resin, Ewers said, so when 2,000 beetles attack a tree, there are more beetles than defenses in the tree.

Within a year of being hit by the beetles, the trees turn red as they die. Ewers said they don’t know when the tree actually dies.

Ewers said the beetles get all of the attention, but it is not the beetle that kills the tree in this forest, but the blue stain fungus. The fungus moves into the arteries of the tree, called xylem, and plugs them up. The tree then goes into a massive drought stress and can no longer access soil moisture.

The tree dies from lack of water, Ewers said.

British Columbia studied the bark beetle epidemic and the release of CO2 in 2005, Ewers said. The amount of CO2 released from the dying trees was the same as from all the forest fires that year combined. This is a huge impact on the climates and the region, Ewers said.

This causes several other ecological changes including the amount of nitrogen available to smaller trees, Ewers explained. As the older trees die, there is more nitrogen available and the succession is occurring faster than expected, Ewers said. “The next forest is coming.”

Other ecological changes affect the snowpack and since there is no longer the canopy cover the snowpack melts faster, Ewers said. Studies show the rate of melting has increased by about a week. Evaporation levels have also increased. As the forest recovers, Ewers said, we can expect to go back to the type of conditions we had before.

Resilience and recovery

Dan Tinker, an associate professor of botany at the University of Wyoming spoke to the audience about the forest’s resiliency. He used the Yellowstone National Park fire in 1988 as an example of forest’s ability to come back after a major catastrophe like a forest fire.

Tinker said lodgepole pine was the dominant tree in the forests from central Colorado to Canada. “It is an important species,” Tinker said. Many of these forests have had large stand replacing fires every 100 to 500 years.

Tinker said the forest conditions in Yellowstone National Park were almost the same in 1987 as they were in 1988. The difference was the weather conditions in 1988. It was the driest season in recorded history.

The 1988 fire in Yellowstone affected about 40 percent of the park and burned thousands of acres outside of the park’s boundaries. High winds and drought conditions fueled the fire.

It burned all ages of the forest, Tinker said, which at the time was a big surprise.

In the past, fires that came upon young regenerated parts of a forest, the fire would “lay down”, Tinker said, and in 1988 that did not happen.

The fire burned through a young stand just like it did an old stand. “These fire didn’t behave like we thought they should behave,” Tinker said.

The fires did not stop until it snowed in Sept., 1988.

Tinker shared a photo of Yellowstone National Park taken from the air in Oct., 1988. He said that everybody thought the photo should have shown nothing but black ash from the fires, but in fact there was still a lot of green. This is the first example of a forest’s resilience, Tinker said.

The lodgepole trees have cones, some are serotinous cones, which may remain unopened for several years and only burst open during a forest fire. Other cones open at maturity of the tree. Tinker said not every stand has serotiny stands.

In Yellowstone, the serotinious seeds that were opened varied from 30 to 500,000 per hectare. A hectare is two acres.

Initial densities can persist for decades, Tinker said.

The forests evolve with the disturbances, Tinker said and the future forest is likely going to be an uneven-aged forest with mixed species.

Medicine Bow-Routt

National Forest

The Medicine Bow National Forest has 650,000 acres of dead trees and Routt National Forest has 615,000 acres of dead trees, Larry Sandoval, the USFS public relations officer, said.

In 2009, it was estimated that 90 percent of the trees would be affected by the bark beetle epidemic, Sandoval said. The Medicine Bow and Routt National Forests have shown their resilience and are no where near that figure, Sandoval said.

An average of 60 percent of the trees have been affected, Sandoval said, with the lowest rate at 37 percent and the highest rate at 70 percent.

The dead trees are being removed from the forest and so far 660 miles of the main road system has had trees removed, Sandoval said.

The forest service removed trees from 160 campsites, administrative sites and trail heads and have about 41 sites left to work on.

As the dead trees are removed, Sandoval said, the USFS will now start looking at the recovery side.