Status: Not Listed
Quaking aspens, also called trembling aspens, are named for their leaves. Flat leaves attach to branches with lengthy stalks called petioles, which quake or tremble in light breezes. Quaking aspens regularly grow in dense, pure stands, creating a stunning golden vista when their leaves change color in the fall. The white bark is one identifying characteristic of this tree, but the bark is special for more than just its unique appearance. The bark layer of quaking aspens carries out photosynthesis, a task usually reserved for tree leaves. In winter, when other deciduous trees are mostly dormant, quaking aspens are able to keep producing sugar for energy. Deer, moose, and elk seek shade from aspen groves in summer. These same animals consume bark, leaves, buds, and twigs of quaking aspens throughout the year. Ruffed grouse are especially dependent on quaking aspens for food and nesting habitat. People use quaking aspens for fuel and to make paper, particle board, furniture, and hamster bedding. In terms of height, quaking aspens are relatively small. They are usually less than 50 feet (15 meters) tall.
Quaking aspens are the most widely distributed tree species in North America. They grow in Alaska and Canada, all the way south to Mexico. They withstand such a wide range of climatic conditions by growing at lower altitudes in the north and higher altitudes in the south. Quaking aspens are conspicuously absent from the Southeast because there are no high-elevation mountains where it can live.
Quaking aspens can reproduce via pollen and eggs that are contained in hanging flowers called catkins. However, it’s much more common for them to reproduce asexually by sending up new stems from a single root system. The combination of all of the stems and their single root system is a structure called a clone. Aboveground, the many different stems appear to be separate trees, but they are all genetically identical. Dendrologists (scientists that study trees) have a couple of simple tricks for telling one clone from another. For starters, all trees of the same clone will change leaf color at the same time in the fall. The synchrony continues in spring when the trees gain flowers and regrow leaves.
The lifespan of quaking aspens is unique. Individual quaking aspen stems usually live for about 50 to 60 years, sometimes up to 150 years in the West. However, in many cases, each tree is actually part of a much larger organism, since multiple stems can sprout from the same root system. When trees that are a part of these large clones die, they are eventually replaced with new growth. Therefore, while one stem has a relatively short lifespan, the entire clone can live for tens of thousands of years.
Quaking aspen clones are virtually impossible to kill. Individual stems can be destroyed by humans, wildlife, and disease, but the belowground root system is resistant to almost all of these factors. Pocket gophers, which feed on the roots, seem to be one of the few creatures able to curtail the growth of aspen groves. The other major inhibitor of aspen growth is fire suppression. Quaking aspens require intense sunlight to grow, but when other trees spring up in the forest, aspen stems are shaded out. Fire reduces canopy cover and allows for the continued growth of quaking aspens. While the root system will survive with little care, proper management of the stems aboveground is important, since both people and wildlife make use of the trees.
A grove of quaking aspens in Utah is the largest known living thing on Earth. Nearly 50,000 stems protrude from a single root system. The entire organism covers over 100 acres and weighs 6,000 tons.
National Park Service
The Nature Education Knowledge Project
USDA Plant Database
Utah State University
U.S. Forest Service
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