Thursday, February 2, 2012
The quaking aspen is the most widely distributed native North American tree species and is very important to many communities in the West. Locals treasure their presence and view aspens as an indicator of forest health. The medium-sized deciduous trees are visually appealing, and many tourists travel hundreds of miles each fall to view the dazzling red, gold, orange and yellow colors of aspen groves.
In addition to the crowds they draw, aspen stands provide habitat for a variety of wildlife, contribute to good livestock forage, provide biomass and are a source for a variety of wood products. The trees have a fast growth rate and the ability to regenerate from sprouts. Each tree can live for 40 to 150 years above ground, but the root system of the colony is long-lived and widespread.
In some areas of Colorado, that root system was hit hard by drought in the early part of the last decade, and a recent gardening column by Deb Babcock in the Steamboat Today addressed Sudden Aspen Decline (SAD) and cited a recent study that links the die-off to those drought years.
Another study in Colorado by Marchetti, Worrall and Eager shows that contributing factors such as disease and insects kill trees that have been weakened by predisposing and inciting factors. Thus, outbreaks of these secondary agents are what likely increased the rate of mortality in aspen stands that already were affected by the drought.
Aspen are prone to disease and insects and depend on their ability to quickly regenerate in order to survive as a species. They need to be periodically disturbed or destroyed by events such as fire, which then rejuvenates the groves.
Each year during the summer and early fall, aerial surveys are conducted to map forest insect and disease activity in forested areas of the Rocky Mountain Region. Although only a rough estimate, 2011 aerial detection surveys show that aspen decline is letting up on the Routt National Forest. Acres impacted have decreased steadily since 2008, dropping from 55,000 that year to 27,000 in 2009 and 21,000 in 2010. Exact 2011 numbers still are to be announced.
The recovery of the species can be attributed to its aggressive pioneer nature, which is taking advantage of the beetle epidemic in old-growth pine. Foresters have noted regeneration in areas where aspens previously existed and where beetle-killed pine trees have been harvested. Aspen regeneration also is taking place in areas where the canopy has been thinned by the death of old-growth pine.
The Hahn’s Peak-Bears Ears Ranger District is exploring other ways to encourage the growth of aspen groves, as this past year they used a coppice-cutting method to stimulate regeneration within patches of old-growth aspen. Forty acres were cut using this method in northern Routt County, and if successful, it could give the Forest Service a valuable tool to use in the future.
While the overall status of local aspen groves still may be uncertain, it does appear that despite its recent troubles, quaking aspens could be posed to rebound quite nicely on the Routt National Forest.
Much of the information in this column was obtained from the U.S. Forest Service’s Celebrating Wildflowers website at www.fs.fed.us/wildflowers/index.shtml.
Voos is the public affairs specialist for the Routt National Forest.