You can’t really consider Aspen tree by itself because aspens typically grow in large clonal colonies, which can be defined as an ‘a group of genetically identical individuals that have grown in a given location, all from a single ancestor. The Colonies usually grow through a process known as vegetative reproduction. A plant sends out horizontal stems or roots, either above ground or below depending on the species, that travel some distance before taking root themselves and growing into new, connected plants.
Other plants that use this system include strawberry plants, grass, and many houseplants (consider the cutting of your favorite ivy or spider plant and those pieces in new pots).
With Aspens, this vegetative growth happens underground among the roots. It means mean new stems in the colony may appear at up to 30–40 m (98–131 ft) from the parent tree.
Each individual tree can live for 40–150 years above ground, but the root system of the colony is much, much, older. By distributing its water and nutrients over its entire expanse, a quaking aspen clone can survive in a patchy environment where other trees might die off.
In some cases, this goes on for thousands of years, sending up new trunks as the older trunks die off above ground.
For this reason, Aspens are considered to be an indicator of ancient woodlands. They are able to survive forest fires, because the roots are below the heat of the fire, with new sprouts growing after the fire burns out.
Consider the “The Pando Aspen clone” in Utah – thought to be 80,000 years old. It is the oldest living organism known on the earth, and at 6,615 tons, it is also the heaviest known living organism on earth (the large fungi organisms you’ve heard of cover more acreage, but the Pando clone is heavier in terms of mass).
Nicknamed the “trembling giant” – the Pando’s current age determination is based the evidence indicating that there are few if any naturally occurring new aspens in most of the western United States since the last glaciation took place 10,000 years ago and eliminated favorable soil conditions for the seedling. (dailygalaxy.com; discovermagazine.com/1993/oct)