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Desert dust changing ecosystems in the San Juans
From Silverton Standard, the place where you can write!
Posted on August 20 2009, 12:53am by Mark Esper in Local News category
Study finds plant behavior changing as dust advances snowmelt.
Photo courtesy Center for Snow and Avalanche Studies
Heidi Stetzler, at the Senator Peck Basin research station, uses a “mantis” sensor array designed by the Center for Snow and Avalanche Studies to monitor plant life on the alpine tundra.
 
By Mark Esper
 
When Colorado State University biology researcher Heidi Stetzler looked at results of her field experiments on wildflowers conducted near Red Mountain Pass last year, it became obvious that the implications were huge.
Human activity in the Southwest desert was causing significant changes in a high-alpine ecosystem hundreds of miles away. And it wasn’t about global warming or power-plant emissions. It was just about kicking up dust.
Stetzler summarized her findings in a talk at Silverton Town Hall Thursday evening, Aug. 23.
The event was part of Mountain Studies Institute's summer education series.
Her study was published earlier this year in the Proceedings of the National Academy of Science.
Much research has already been conducted on the impacts of more dust blowing into the mountains due to human-caused disturbances.
Earlier studies conducted through the Silverton-based Center for Snow and Avalanche Studies found the increased dust levels are causing snowpack to melt weeks earlier than usual, impacting water resources.
Current mountain dust levels are generally five times greater than they were prior to the mid-19th century, due in large part to increased human activity in the deserts. This year, 12 dust storms have painted the mountain snowpack red and advanced the retreat of snow cover, likely by more than a month across Colorado.
“This story starts with the dust coming in,” Stetzler said. “It’s very visible. You can see it in the snowpack.”
She noted this past winter a couple unusual spring dust storms left a particularly heavy red layer on the snows of the San Juans.
“It’s a high enough dust loading to advance the snowmelt by two weeks to a month,” Stetzler said.
Stetzler said it’s still too early to gauge the impact of the  “exceptional” dust storms earlier this year.
But results from six years of monitoring are in.
“In most years we have three or four large dust events,” Stetzler said. “By the end of the year the dust layers aggregate into one layer on the snowpack.”
Stetzler said you can’t just blame the wind for all that dust.
She said the “biological crust” across vast stretches of the Southwest deserts has been disturbed from decades of human activity.
“It’s more tied to disturbance of the landscape.”
Stetzler’s experiment involved trying to find out the impact of the earlier snowmelt on wildflowers.
Plots at Senator Peck Basin research station at Red Mountain Pass were treated to mimic higher dust levels and lower dust levels.
The appearance of plant life on the alpine tundra plots was then monitored, typically 9 to 10 species.
“When plants change the timing of their life-cycle events, it changes the ecosystem,” Stetzler said. And that is what appears to be happening in the San Juans.
She said researchers are just beginning to realize the wide-ranging effects the increased dust is having.
“Changes can occur at locations some distance from where the human activities occur,” Stetzler said. “People are influencing the climate other than through producing greenhouse gases.”
Stetzler said the key result of her study was that the earlier snowmelt was causing synchronized plant growth and wildflower blooming.
Stetzler said that in a high alpine environment this is particularly important.
“The staggered process (of plant growth and blooming) in the alpine is critical to how plants evolved and which plants occurred where,” she said.
She said the change may have adverse effects on plants and water quality. And the consequences of plants now competing with each other at the same time of year are unclear.
“We can’t say which won’t survive,” she said. “I can’t tell you that in a one-year study. We need  a 5- to 10-year study so we can see which are less likely to survive. We can make guesses, but they are just guesses.”
Among the biggest concerns, Stetzler said, is that the “lockstep growth” of various plant species, aside from threatening some species’ very survival, could lead to a “feast-or-famine ecology for plants and animals.”
That would mean less distribution of resources over the course of the season.
“The case is building that the transfer of desert dust has environmental consequences for plants, wildlife and people,” Stetzler said. 
She described the finding as frankly startling — that human use of a desert hundreds of miles away is transforming mountain ecosystems here.
She said the issue is global.
“We’re using more and more of these arid landscapes — not just in the Southwest, but in Asia, etc.,” Stetzler said.
Co-authors of the study were Chris Landry, director of the Center for Snow and Avalanche Studies, Tom Painter from the University of Utah, Justin Anderson, an Mountain Studies Institute intern, and Ed Ayres of Colorado State University.
Landry said Stetzler’s collaboration with the Center for Snow and Avalanche Studies demonstrated “some important new methods for investigating the factors influencing mountain ecosystem behaviors, and her very interesting results add a new twist to discussions of the effects of global change on alpine ecosystems. “
 
 
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