Sudden Aspen Decline

Aspen Trees Die Across the West

This should be the golden season across the West, when aspen paint hillsides in shades of fall.

But a mysterious ailment -- or perhaps a combination of factors -- is killing hundreds of thousands of acres of the trees from Nevada, New Mexico and Arizona through Utah, Colorado, Wyoming and into Canada, according to the U.S. government and independent scientists.

The aspen die-off comes on the heels of a pine-beetle invasion that has destroyed millions of acres of evergreens. Foresters expect to lose virtually every mature lodgepole pine in Colorado -- five million acres of them.

Aspen and lodgepole pine intermingle across many Rocky Mountain slopes at elevations of 5,000 to 8,000 feet. Millions of the trees are now down or brown, transforming the landscape into a huge fire risk. To the dismay of hunters, the dying trees are decimating habitat crucial to elk, as well as to such smaller animals as wolverine, lynx and yellow-bellied marmot.

What is killing the aspen is unclear.

In 2002, the U.S. Forest Service began investigating reports that entire stands of aspen were dying in the San Juan Mountains in southwest Colorado, and in an odd way. Usually when mature aspen fail, they send out hundreds of new shoots, called suckers, through their root systems. Those shoots sprout quickly, and the grove regenerates.

But in the San Juans, the shoots were dying, too, or were failing to sprout. That phenomenon was named Sudden Aspen Decline, or SAD, but scientists say they don't fully understand it.

www.msnbc.msn.com...

Another Forest Service researcher, however, said there is no conclusive evidence of any long-term decline. In fact, Claudia Regan said it appears the number of aspen in Colorado has actually increased in the past century.

If there is a decline, it might be a natural correction to human interference, University of Wyoming botany professor Dennis Knight wrote in a paper for the Forest Service back in 2001.

“Widespread disturbances caused by timber harvesting and fires in the late 1800s and early 1900s may have enabled aspen to become unusually abundant in the Rocky Mountains,” he wrote. “If aspen is now declining, the explanation may lie in natural processes. ... There is no basis to suggest that aspen is threatened globally, nor are most aspen groves likely to be lost in the near future.”

lewis-clark.org...

Aspen life strategy

Aspen’s broad distribution is not due to tolerance toward a range of climates. Just the opposite. It has a narrow range of environmental tolerance. But it produces trillions of wind-disseminated, short-lived seeds each year with the probability that one will land in a suitable environment, germinate, and develop into a sapling. This life strategy is referred to as “fugitive” species--many seeds scattered so one will land in a rare but suitable refuge. The requirements for successful germination and seedling establishment are so exacting that the probability of success is near zero. The secret is that when a rare seedling establishment occurs, the sapling develops into a grove that may persist for hundreds or even thousands of years by periodic rejuvenation.

Aspen seed requires a flat seedbed that remains moist throughout the summer, free from shade, and free from browsing by wildlife. The last time such seedbeds occurred on a wide scale was on protected silt beds left by retreating glaciers at the end of the ice age. Most of today's aspen groves are believed to have originated at that time, rejuvenating periodically over the ten millennia since the original seeds germinated. If age is calculated from seed germination, these groves are America’s oldest living trees, even though the aboveground portions are generally younger than 100 years.

Leaves of the aspen produce a hormone called auxin that inhibits the development of lateral root buds. As the grove develops, enough hormone is produced and transferred to the roots that sucker buds become dormant.

Originally posted by WyrdeOne
...I tend to think positively about changes of this sort in the environment. Just because we don't understand the mechanism, or the larger context in which the change takes place, doesn't mean the change is a bad thing.

Originally posted by WyrdeOne
I dunno - rapid change is not unprecedented in nature.

...

Being that we're city builders we tend to value the stability of stasis more than the uncertainty of change, and we're most comfortable thinking in linear patterns, this kind of stuff is scary. That said, there is plenty of stability to be found in the cycles of nature, we just have a hard time appreciating it. It's outside our comfort zone = the range is too big and the scope too large.

...

I'm just playing devil's advocate here, obviously, but I do it to make a point.

I truly believe that if we are to have faith in anything, we ought to have faith in the ability of the earth to get along just fine without us, even despite us.

In my view, understanding environmental change and responding to it appropriately are forms of self preservation.

Maybe that explains my perspective more clearly.