• Rocky Mountain Research Station
• 240 West Prospect
• Fort Collins, CO 80526
• (970) 498-1100

What’s Happening to the Western Aspen?

The sight of a spectacular stand of aspen trees displaying their bright fall colors is one of many perks that make living in or visiting the Rocky Mountain region a spectacular experience. But complete die-offs of aspen trees in recent years have compelled forest researchers and managers to launch new research studies to better understand how to restore aspen or reverse the recent trend in rapid die-offs.

Although gradual changes in the development of aspen forests are expected, the recent widespread and rapid loss of trees is concerning to foresters and communities of the western U.S. Aside from the damage to the scenery, aspen loss is associated with declines in water quality and quantity (because the conifers that are replacing aspen require more water), species biodiversity, livestock forage, wildlife habitat, and recreational opportunities.

The development of aspen forests is closely linked to fire or disturbance. After a stand-replacing disturbance by fire, the root systems of aspen usually survive and send up new stems to regenerate the forest. One of the restoration strategies forest researchers and managers have pursued is modifying the fire cycles, such as determining the frequency of fire required to sustain aspen in areas where fire has been suppressed in the past.

Aside from regeneration following fire events, aspen stands sometimes regenerate following a massive die-off of mature trees. But in some cases the root system is completely dead, which results in a complete die-off of the aspen stands, a phenomenon called Sudden Aspen Decline (SAD) that is currently pronounced in western Colorado, southern Utah, and southwest Wyoming. Researchers are looking at the impact that insects and diseases have on regeneration associated with SAD as well as the effect of drought.

Researchers and managers are focused on finding ways to restore aspen throughout the West, participating in numerous workshops and field tours including a 2008 summit that drew 100 managers and researchers from western states.

For more information, see Effect of Conifer Encroachment Into Aspen Stands on Understory Biomass.