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Walking through the Arb, it is not uncommon to run across a quaking aspen. And when you run across one, you are likely to run across a whole stand of them. But why is this?
The answer is simple: you are surrounded by clones.
Though aspen can reproduce sexually, the more common mode of growth for this tree is called root suckering. This asexual process allows the underground root system of the aspen to send up new sprouts, creating a stand that commonly spans anywhere between one and twenty acres.
Stands can be made up of a single clone or of multiple, intermingling clones. For the careful observer, clones can be differentiated by the fact that trees from a single clone will all change color at the same time and have branches extended at the same angles.
This early successional species is highly dependent on light for growth. As a result, they are quickly outcompeted by later successional trees, such as pines or oak, which create too much shade for the aspen to survive. However, this fast turnover is misleading; the aspen is not a short-lived tree. The root systems of aspen can survive indefinitely underground, and if an event like a forest fire opens up the canopy, aspen are able to resprout.
Indeed, the quaking aspen is perhaps the longest-lived organism on earth. While clones are commonly 5-10,000 years old, the oldest known root system is growing in Fishlake National Forest in Utah, and is approximately 80,000 years old. This impressive clone, named Pando, is made up of about 47,000 trunks and weighs over 13 million pounds, making it the heaviest known living organism.
The quaking aspen is an impressive tree, so as the weather warms up, go out in the Arb and keep an eye out for the best old clone around.