The Ketchum Ranger District of the U.S. Forest Service, in tandem with Sun Valley Resort, is proceeding with a large-scale tree-thinning project on Bald Mountain that was started in June.
By the end of the summer, up to 25 acres in Frenchman’s area of Baldy should be thinned out. The entire project will take several years, with 182 acres of thinning planned over a three- to five-year period.
Following wildfires in the region over the past decade, the mountain’s Douglas fir population has been hit by an increase in Douglas-fir beetles combined with parasitic dwarf mistletoe. The thinning project will dispose of many dead and living trees on the mountain and aims to preserve healthy existing trees by inducing crown separation by 20 to 25 feet, according to Kurt Nelson, Ketchum district ranger.
The secondary goal is to create a glade-skiing environment for winter recreationists with spaced-out trees on the ski slopes, according to Jack Sibbach, Sun Valley Resort’s director of marketing and public relations.
Douglas fir, aspen and alpine fir are targets for thinning. The resort is renting a track hoe with a special “masticator” blade. It’s fitted with a specially designed headpiece and cage for the operator, for the challenges of Baldy’s steep terrain, according to Peter Stearns, director of mountain operations for the resort. The masticator can fell trees that have a 14-inch diameter or less, and quickly turn them into mulch across the forest floor to decompose on site. Larger trees will have to be cut down with a chainsaw later on.
Operator of the masticator is Kerry O’Brien, grooming trail crew manager on the mountain for over 30 years. He’s picking and choosing which trees to fell and which to preserve, in the spirit of maintaining the healthiest-looking specimens.
“The goal is to keep the mountain as green as possible,” Nelson said.
Unfortunately, the mountain’s greenery is marred by the site of browning trees. Baldy has become an “ideal site” for the beetle to reach epidemic proportions, Nelson said at an on-site press conference on Tuesday. While woodpeckers and other insects reduce the beetle population on a smaller scale, it’s not fast enough to keep up with the beetle’s increasing population. The beetle bores into the Douglas fir’s trunk and feeds on the nutrient-rich phloem, according to Forest Health Protection-Boise representative Joel McMillin, and effectively girds the tree.
Over the past few years, with the native tree population declining, the rangers have undertaken initiatives to contain the growth of the beetle population that rely on the beetle’s pheromones—their way of communicating with each other, according to Jim Rinehoft, forester with the Sawtooth National Recreation Area.
There are two pheromones the beetles produce: aggregative, for attracting more beetles, and anti-aggregative, for dispelling beetles. Forest health groups have worked on two efforts to decrease the beetle population on Baldy, using formulas of the hormone MCH, which reproduces the anti-aggregative hormone. The presence of MCH tells incoming beetles to bypass that tree. One method was applying bubble caps with the hormone to tree trunks and another was dispensing aerial microchips of MCH from helicopters. Both these methods targeted smaller stands—a term to classify clusters of trees—while O’Brien will thin out stands in order to give trees a healthier environment that will protect them against invaders.
Trees with dwarf mistletoe, a parasitic plant that resembles a bush around the branches of host trees, are specifically targeted by the beetles because they’ve already been weakened, Nelson said.
The project’s cost hasn’t been estimated yet, but O’Brien says it’ll be cheaper for him to do it as a one-man team rather than contracting the work out. It has multiple funding partners, including Sun Valley Resort and grants from the forest health protection and fuels management program, two branches of the U.S. Forest Service.
While there have been hand-thinning projects over the years, this is the first time a masticator has been brought up the mountain, O’Brien said.
“We’re grateful for this partnership,” Sibbach said.