Aspen

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Aspens are also aided by the rhizomatic nature of their root systems. Most aspens grow in large clonal colonies, derived from a single seedling, and spread by means of root suckers; 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 long-lived. In some cases, this is for thousands of years, sending up new trunks as the older trunks die off above ground. For this reason, it is considered to be an indicator of ancient woodlands. One such colony in Utah, given the nickname of "Pando", is estimated to be 80,000 years old, making it possibly the oldest living colony of aspens. Some aspen colonies become very large with time, spreading about 1 m (3. 3 ft) per year, eventually covering many hectares. They are able to survive forest fires, because the roots are below the heat of the fire, and new sprouts appear after the fire burns out. The high stem turnover rate combined with the clonal growth leads to proliferation in aspen colonies. The high stem turnover regime supports a diverse herbaceous understory.