Quaking Aspen

[photo] Fall colors on the San Francisco PeaksAspen….those white-barked beauties are known for their golden fall foliage and leaves that tremble in the breeze. Butaspen have more than just their good looks working for them. They are a critical component of our northern Arizona forests. Lots of wildlife species call aspen “home”, such as mule deer and the red-naped sapsucker, to name a couple of residents.

The red-naped sapsucker drills shallow holes in aspen to drink the sap. They also excavate larger holes for nesting. This particular woodpecker is called a "double keystone" species, because both types of holes that they drill are vital to their fine feathered friends. The lush [photo] Red-naped sap sucker working on his sap-hole in an aspen tree.understories of an aspen clone are where a deer comes to rest its weary head and put the kids to bed. Their understories also make aspen clones hard to burn. They act as a natural fire break, protecting the cabin over the hill from wildfire. They provide cool, summer shade to a weary hiker. Their golden, fall foliage draws a family from “down the hill”, who then stays the night in a local motel and goes out to dinner at a local restaurant. Their wood may even be keeping you warm this winter. Aspen are truly amazing. They are one of the most biologically diverse and ecologically unique sites in our Arizona forests. And their health (or “illness”) is the “report card” of the forest.

Check your aspen knowledge. Did you know…

Aspen is a clonal organism? All of the aspen trees within a clone sprout off of a common, massive root system and are considered to be “clones” or genetically identical. While the aspen trees themselves usually only live 80-120 years, their root systems are one of the longest lived organisms in the world and can live for thousands of years.

Aspen is adapted to fire but cannot withstand fire. What????

Historically what would happen is this… About every 50-100 years, a wildfire would burn through an aspen clone, killing the overstory trees. The overstory trees die easily from fire because their bark is very thin and offers little protection. But their root systems would not be harmed. When the overstory trees die, they stop producing a certain hormone, which signals the root system to send up thousands of sprouts. In this way, aspen regenerates itself.

Why are all of the aspen dying?

[photo] Dying aspenAspen communities have been in a gradual state of decline over the past 50 years due to a number of factors, including fire suppression, conifer encroachment,  and extreme browsing pressure from elk, deer, and livestock. More recently, years of drought and defoliation by a severe frost event in June of 1999 have made aspen more susceptible to insects and disease and have accelerated the decline rate.  Many aspen clones are nearing 100% mortality.  This phenomenon has been dubbed “Sudden Aspen Decline” or SAD.  If aspen had a report card, it would be making an “F”.

Why do you hardly ever see young aspen seedlings in the forest? Why can’t I get a wilding permit for aspen seedlings?

This is what happens when elk remove bark from treesBrowsing by elk, deer, and livestock is compounding the decline of aspen clones across the forest by preventing successful regeneration of aspen clones and causing a shift in age-class distributions. Mortality of mature aspen, combined with fire exclusion and continued browsing damage, can potentially result in the complete disappearance of aspen from our northern Arizona forests within the next 80-200 years. Loss of aspen clones at a landscape scale signifies a tremendous loss of biodiversity, with aspen decline cascading into losses of vertebrate species, vascular plants, and likely species from a myriad of other organismal groups (perhaps our red-naped friend?).

What’s the problem with browsing?

Regenerating AspenBrowsing by elk, deer, and livestock damages tender, young aspen sprouts (photo left). When done repeatedly on an annual basis, the sprouts cannot survive. Eventually, the root systems runout of reserves and stop sending up new sprouts. Surveys on the Coconino National Forest have shown that 100% of aspen sprouts were browsed over a 7 year period, so that not a single young stem is greater than 3 feet in height. Unbrowsed, they would be over 10 feet high.

Elk cause damage to young aspen in a couple of other ways. They like to rub their itchy antlers on young aspen trees, which wound the bark. Elk also do what is called “barking” (see photo at right), where they peel the bark off with their teeth. Once the bark is wounded, fungi can get in and infect the tree. And the trees eventually die. This also occurs when people carve into aspen trunks.

What is the purpose of those fences around some aspen clones?

[photo] Aspen exclosure fences

Currently, the Peaks and Mormon Lake Ranger Districts have 40 aspen exclosure fences to protect aspen seedlings from browsing. These fences are monitored and maintained on a biannual basis by a variety of volunteer groups, including the Friends of Northern Arizona Forests, the Coconino Sportsmen, the Flagstaff Nordic Center, the NAU Forestry Club, W.L. Gore, the Ecological Restoration Institute, and various individuals. The Coconino National Forest asks that you please leave these fences intact so that aspen seedlings remain protected. To report fence damage, please contact the Peaks Ranger Station at 928-526-0866 or through “contact us”.


What have you done for me lately?

A mule deer making a home in the aspensDuring the 1980s and 1990s, fuelwood harvests were conducted to provide firewood to the public and to encourage aspen regeneration. When aspen regeneration failed in these areas, the first fences were erected to protect aspen regeneration from browsing damage. These fences proved difficult to maintain and, for many years, were in various states of disrepair. In 2004, the “Adopt an Aspen Fence” program was created to aid in fence maintenance. To date, the program has been successful in rebuilding and maintaining the aspen fences. However, these fences continue to be cut annually by hunters, wood cutters, and various culprits, allowing deer, elk, and livestock to get in and munch on the tender, young aspen.

The Coconino National Forest is also currently working on a project called the Hart Prairie Fuels Reduction and Forest Health Project. Nearly half of the aspen on the forest is located in and around the Hart Prairie area. One of the main purposes of the project is to restore over 3000 acres of aspen in and around Hart Prairie. For more information, please see [News Release]

As a part of the Hart Prairie Project, the Coconino National Forest is working with the Arizona Game and Fish Department to reduce elk numbers in this specific area to reduce the impacts of elk browsing on aspen regeneration. Rocky Mountain elk are actually a non-native species that was introduced to the area in the early 1900s. Although some theorize that northern Arizona contained a very small population of native elk, early explorers and trained naturalists who visited the area around the San Francisco Peaks and described the area in detail did not detect their presence. If a population of native elk existed, it is theorized that it was a very small population. Between 1913 and 1928, elk from Wyoming were released in this area. Since 1950, elk numbers and distribution have increased tremendously in Arizona and have had damaging effects on the ecosystem. One of the reasons for the drastic population increase is due to an increased availability of water. Prior to settlement, this area contained few live streams and wet meadows. During the twentieth century, this situation was greatly altered when thousands of stock tanks were constructed in northern Arizona to facilitate livestock grazing. These additional water sources also provided the non-native, translocated elk with new country to exploit.

Where can I get more information about our SAD aspen?

See the following websites for more information:


You can also contact the Flagstaff Ranger District at 928-526-0866 or through “contact us” in the navigation bar on your left.

How can I get involved in the aspen effort?

To adopt your own aspen fence or for other volunteer opportunities, please contact the Flagstaff Ranger District at 928-526-0866. 

To get in touch with other like-minded aspen huggers or to get involved with aspen projects on the forest, please visit the Friends of Northern Arizona Forests website.


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