Quaking Aspen

Quaking aspen, Populus tremuloides, usually only get attention in the autumn when they turn the hillsides brilliant gold and draw leaf-peeping tourists. I like aspen trees in the winter, too, when their leaflessness reveals the cool twistiness of their trunks.

Aspen trees are especially beautiful in ice fog, when the sparkly crystals attach to each branch with some of the most spectacular beauty of winter.

Aspens are fairly easy to distinguish by both their white bark and their rounded leaves on long, flat stalks (petioles) that really do quake and tremble and almost shimmer in the breeze.  I've noticed that local aspen trunks often have common orange lichen on them.

Steve Nix on forestry.about.com states:  "An aspen tree is the most widely distributed tree species in North America, ranging from Alaska to Newfoundland and down the Rocky Mountains to Mexico. Interestingly, Utah and Colorado is home to the largest portion of the natural acreage of aspen in the World."  Aspen are related to willows, so they produce fuzzy catkins in late spring before the light green leaves emerge.

According to the U.S. Forest Service, elk, deer, moose, rabbits, hare, porcupine, beaver and small rodents all rely on aspens for food.   In some areas, like Rocky Mountain National Park, aspens are sometimes over-browsed by elk.  Since the elk have few natural predators left in Colorado, their numbers become too large for the vegetation.

Global warming may also be leading to a decline of aspen groves, with drought and warmer temperatures leaving trees stressed and vulnerable to attack by beetles, fungus and other cankers.

Besides the usefulness of aspen to wildlife, their absence, were they to decline, would deprive the Rockies of a great deal of their autumn brilliance.