Editor’s note: This is the second of two parts. The first part ran in Saturday’s Vail Daily.
EAGLE COUNTY — Native tribes used aspen trees medicinally. They made tea to reduce fever using the bark, which contains a chemical similar to aspirin, and used a white powder found in the outer bark as sunscreen. Today, people use the wood of the tree for things such as lettuce crates and wood chips. The wood grain makes beautiful ornamental items. Because it is a soft wood, it is not good for structural purposes. Animals make use of the aspen tree, too. Beavers use aspen bark for food, and the wood and twigs for building dams and lodges. Elk, moose and deer eat the bark, twigs and foliage. The black on the bark of aspen trees is the result of some damage caused by broken limbs, bear scratches, carvers, elk and rabbit chewing, and insects. Various rots and fungi cause the black coloration on the damaged bark.
Aspen are sun-loving trees. They tend to grow in disturbed areas — often places where fires or logging operations have opened the forest floor to full sunlight. As a grove grows, the branches on the lower parts of the inner trees do not receive enough sunlight and therefore do not produce leaves. These branches die off and fall from the tree, leaving a characteristic mark like the silhouette of a flying bird. The tree continues to grow straight up, losing more branches. This produces a tall thin trunk topped by a crown of leaves. Eventually the tree reaches a height where nutrients, picked up from the soil by its roots, can no longer efficiently reach its top. The interior wood then begins to rot, and the tree begins to die. The maximum age of these trees is a little more than 100 years.
Since the aspen trees shade the floor of the forest, no new aspen can grow beneath them until the aspen forest dies off. This may open the ground to sunlight and more aspen begin to grow or they are replaced over time with shade-loving trees — in this region, generally fir or spruce — that can grow in their own shadow. Eventually, the spruce and fir trees become the dominant vegetation. The suckers can live for hundreds of years. That allows the aspen to return if fire or logging destroys the forest and produces open areas where they can grow in full sunlight.
Another unique feature of aspen is that the bark is thin and a close look will reveal a slight green tint. When the bark is cut, a bright green layer of chlorophyll is revealed. This allows aspen bark to carry on photosynthesis. Some believe that more photosynthesis go on in aspen bark than in the leaves in the spring. This also “extends the growing season” because the tree can continue to photosynthesize before the leaves appear and after they drop off in the fall.
Most of the huge expanses of aspen across Colorado are actually the result of logging activity or fires caused by careless miners and sparks from steam engines more than a hundred years ago. Today, environmental consciousness is reducing logging activity and man can now prevent as well as fight forest fires. This is actually leading to a decline in the number and size of aspen groves across the state. There has been a seemingly unrelated die-off in aspen groves across the Rocky Mountain West in recent years, the cause of which is not fully understood.
If you drive through the hills in virtually any direction in mid-September through mid-October, you will find aspen turning to gold, but nowhere in Colorado can one see as many acres of aspen as on the drive over Kebler Pass. Kebler Pass, located west of McClure Pass in the West Elk Mountains of Colorado between Somerset and Crested Butte, is home to the largest grove of aspen in Colorado. Genetic testing has show that it is, for the most part, one continuous colony and therefore (depending on definitions) is one of the largest living organisms in the world.
Rick Spitzer is the author of “Colorado Mountain Passes,” published by Westcliffe Publishers and available at The Bookworm of Edwards, City Market, Amazon and many stores across the state. The book provides photos and text about the history, lore, wildlife and scenery around the passes of Colorado.