First lodgepole pine, now spruce trees: succession in our mountain forests
by Allen Best
GUNNISON, Colo. – With not much left to feed on, the mountain bark beetles of northern Colorado have been faltering the last few years. But spruce trees in south-central Colorado have been getting hit hard.
Foresters estimate 30 percent morality of spruce trees on the Grand Mesa, Uncompahgre, and Gunnison National Forests.
“What we’re really facing is a natural process exacerbated by all the droughts we’ve had,” said Scott Armentrout, the forest supervisor.
In one area of the San Juan Mountains, near Lake City, all spruce trees larger than 3 inches in diameter have been attacked.
In response, the Forest Service plans to “treat” up to 120,000 acres during roughly the next decade. In most cases, the agency “treats” forests by cutting trees, sometimes in clear cuts but also in techniques such as shelter cuts. But agency spokeswoman Lee Ann Loupe points out that at high-use locations, such as near campgrounds and around ski areas, the agency has used pheromones, or sexual attractants, to draw bark beetles and then applied pesticides to kill them.
Beetle epidemics are nothing new. Scientists don’t have the techniques to document beetle infestations before American settlement of the West. That leaves just a brief recorded history. Even so, there have been scourges before.
In the late 1930s, for example, a windstorm blew spruce trees down on the Flat Tops between Glenwood Springs and Steamboat Springs. Bark beetles took their time but by the late 1940s were proliferating. Adopting militaristic jargon, the Forest Service declared war. Newspapers, too, urged eradication of the enemy.
The agency recruited Navajos, what used to be called “bums” from Denver, and also recent college graduates to dump pesticides on trees. As more pitched battles were being laid in 1951, reports began trickling in: The beetles had disappeared. In February the previous winter, it had gotten cold—real cold: 56 degrees below zero Fahrenheit in Eagle, located west of the future Vail. If not that cold, it stayed plenty cold for a couple of weeks.
Those spruce trees preserved well, even when dead, and the snags were harvested off the Flat Tops well into the 1990s for use as logs in houses.
In the case of spruce in southern Colorado, the spread began from the Weminuche area of the San Juan Mountains in the early 2000s, says Bob Cain, regional entomologist for the U.S. Forest Service in Colorado. He attributes the cause to a combination of drought and blown-down trees.
The epidemic is much in evidence on Wolf Creek Pass, where most trees, once forest green, now gray, have died. The beetles have been migrating north and east, but not so much west to places like Durango and Telluride, says Cain.
Can the spruce beetle be stamped out? Yes—and no. Cain and other foresters point out that areas that have been cut in the past now look green, as the younger trees are better able to withstand the beetles.
But what the Forest Service understands now, which it didn’t 65 years ago, is that beetle infestations are just too broad and natural to try to suppress them.
What comes after the spruce?
George Sibley, an author and resident of the Crested Butte-Gunnison area since 1967, sees several upsides to the spruce epidemic, including reduced water needs.
“A lot of the beetle-kill places are projected to come back as aspen stands, and I consider that a plus. According to my Forest Service friends, aspens use less water over the course of a year, even though when they are in leaf they use more; most of the year they are leafless and are not ‘drinking’ much and evapo-transpiring not at all. And—possibly a big bonus — they are not catching snow on leafy branches like the spruce and fir do, most of which sublimates directly to vapor during the cold season,” he says.
“Just because they’ve been here for a hundred-plus years doesn’t mean the spruce are the best thing that could be inhabiting the land. My Eden complex has gradually disappeared as I’ve learned more about the natural history of stuff in the West. This place has never been very well organized.”
This article originally appeared in the Sept. 23, 2015, issue of Mountain Town News, Please consider subscribing. Cost is $45 per year. See red buttons at the upper-right of this page.