WNTS Trip Report – Colorado – Pike National Forest

Our travels took us to Colorado this September, for Rhonda it was a rural health conference and for me an opportunity to acquaint myself with Colorado. I had visited Colorado a time or two in passing, quite some time ago, both times in winter, which I recall in grades from snow white to gray. Arriving in fall at the peak of leaf color change, the dominant colors this time were the bright, day-glo yellow of quaking aspen (Populus tremuloides) leaves at the peak of their seasonal change, the dark forest green of the spruce (Picea pungens), and intermixed, the red- browns of dying bark beetle ridden lodgepole pines (Pinus contorta).

Hints of aspen were noted coming into to Denver from the airport, but not near enough to prepare us for the drive up into the Rockies on Interstate 70, as we approached our lodging destination near Copper Mountain, sharing boundaries with the Pike and White River National Forests. Just a few hundred feet above 9000’ the sun’s rays were perceptibly brighter in the clear mountain air. The aspens seemed to transfer almost all the brilliance through a yellow filter. Where contiguous with Englemann (Picea englemanii) and blue spruce, the contrast of their blue- and dark green foliage seemed to heighten the color display.

Colors were the prevalent theme on our first day, but it wasn’t yellow that captured as much of our attention as the hues between red and brown. Primarily the cause of predation of the mountain pine beetle (Dendroctenus ponderosae Hopkins), a member of a group of beetles known as bark beetles, the lodgepole pines were dying by the acre. The normal lifecycle of a bark beetle would normally occur within the bark of a single tree. Given the right (wrong?) conditions, the lifecycle continues in new trees, in an epidemic. The extent depends on a number of factors, such as climatic variables (drought, average temperature change, stand age and vigor) or management practices. The primary host of the mountain pine beetle varies regionally, but in central Colorado in 2009, is the lodgepole pine. Less widespread but as seriously, the ‘beetle’ can cause periodic losses of high-value, mature sugar (Pinus lambertiana) and western white pines (Pinus monticola), limber pine (Pinus flexilis), Coulter pine (Pinus coulterii), foxtail pine (Pinus balfouriana), whitebark pine (Pinus albicaulis), and pinyon pine (Pinus edulis) are also susceptible. (Forest Insect & Disease Leaflet 2, U.S. Department of Agriculture, Forest Service Dec. 1989.)

As is apparent from following images, this epidemic, so visible to visitors like myself and residents alike, will alter the current forest ecosystems. Within Summit County Colorado (to the south of Dillon Colorado) the epidemic has spread nearly to the limits of lodgepole pine forest extent, and beyond, especially to the north (see attached map of Mountain Pine Beetle - Northern Colorado Infestation in Lodgepole Pine in 2002 – 2007). What are potential outcomes? They may convert to less desirable timber species, through reproductive advantage or adjacent fire-adapted species (in the event of wildfire, which is not an uncommon event in forest ecosystems already beset by drought and increased annual temperature changes). Dependent on burn severity in those ecosystems conversion to grasslands or woodlands may result. Quaking aspen are a frequent pioneer species in large fire-disturbed areas, especially if present at time of disturbance (via clonal reproduction, where high burn severity didn’t prevent it), or the only seeding species nearby.

What follows are images of the forests around Dillon Colorado, with specifically focused comments, and an old growth Rocky Mountain Bristlecone Pine (Pinus aristata), with associated images.

Major infestations are underway in the forests in Summit County, here just outside of Copper Mountain Ski Resort. Ski Resorts such as Aspen and Vail are within an hour’s drive west, and subject to similar infestations. Real estate values drop precipitously with the arrival of mountain pine beetle.

The series above are of a Rocky Mountain Bristlecone Pine, with the background including the headwaters of the Beaver Creek drainage, an hour’s drive south of Dillon. Willows typical of the wetlands themselves, the vegetation more distant consists of bunchgrass and occasional forbs (unknown specimens in the lower two images).

Orange lichen was well-established on the relatively undisturbed cobble around the tree’s base.

In the images below, taken on drive back down the Beaver Creek drainage, the beaver ponds and dams lend credence to those naming the drainage.

The Rocky Mountain bristlecone pine images above were taken at an elevation of 10,900 feet in elevation, at the head of a long, linear north-south drainage. Other bristlecone pines were seen in the area, ranging from seedlings to saplings to the mature one depicted above and some mortality. I discovered after this visit, that there is another location with a more mature bristlecone forest, in a state protected area not too far from this site, to be investigated at a later date.