Autumn in the mountains of Colorado, Utah, Wyoming, and Arizona is traditionally heralded by aspen stands aflame with heart-shaped golden leaves that shake in the cool breeze. Unfortunately, due to a rapid die-off of aspens across the American West, appropriately named SAD for Sudden Aspen Decline, aspen groves are disappearing.
Foresters noticed the decline in aspen in Colorado in 2004, and according to the U.S. Forest Service, by 2006 nearly 150,000 acres of Colorado aspen were dead or damaged.
An aerial survey completed last year in Colorado revealed that more than 500,000 acres of aspen in that state were affected by SAD. And in northern Arizona, Forest Service officials report a 60-to-95 percent mortality rate for low-elevation aspen groves.
What's killing the aspen trees? Research points to several factors, primarily severe droughts and higher temperatures making the aspens more vulnerable to pests and diseases. These include fungi and bark beetles, which are also responsible for the death of many pine and spruce trees as well.
The fact that the worst cases of SAD are in the lower, southern-facing slopes point to both drought and rising temperatures. There has been a drought in Colorado for more than ten years, and the year 2000 was the worst drought year ever in Arizona. According to the federal Rocky Mountain Research Station, the month of June 2006 was six degrees hotter than average. A study by scientists there forecast the near complete disappearance of aspen in the Rocky Mountains by 2090. Climate experts are predicting warmer and drier weather to continue throughout the Southwest.
Declines in aspen affect wildlife, industry, and mankind. Aspens offer a habitat for deer, elk, birds, and other animals, and ailing aspen forests have a negative impact on sawmills, already suffering from the recession and fewer home being built. Aspen groves also act as natural firebreaks as they do not burn easily.
Aspens grow differently from other trees by sending out shoots, or “suckers” from their root systems rather than spreading seeds. Only a few aspen suckers survive more than one or two decades, and new stems aren't growing back as quickly as usual due to drought and heat putting stress on the trees.
Plus, deer and elk like to browse among the suckers, depleting an already short supply of potential new trees. The Forest Service is planning a five-year prescribed burn of close to 4,000 acres of Aspen on the Battlement Mesa in the Grand Mesa National Forest in hopes of slowing or reversing SAD. And foresters in several Colorado national forests are cutting aspen stands affected by SAD to whether the stands can regenerate. Regeneration, according to Forest Service experts, is key in the war against sudden aspen decline, as it appears to foster the growth of more young trees.
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