Scientists Chris Landry adds simulated dust to snow in the San Juan Mountains of Colorado to study how dust affects snowmelt. Click on image for full size (271 Kb) Courtesy of the Center for Snow and Avalanche Studies

Accelerated snowmelt--precipitated by desert dust blowing into the mountains--changes how alpine plants respond to seasonal climate cues that regulate their life cycles, according to results of a new study reported this week in the journal Proceedings of the National Academy of Sciences (PNAS). These results indicate that global warming may have a greater influence on plants' annual growth cycles than previously thought.

Current mountain dust levels are five times greater than they were before the mid-19th century, due in large part to increased human activity in deserts.

"Human use of desert landscapes is linked to the life cycles of mountain plants, and changes the environmental cues that determine when alpine meadows will be in bloom, possibly increasing plants' sensitivity to global warming," said Jay Fein, program director in the National Science Foundation (NSF)'s Division of Atmospheric Sciences, which funded the research in part.

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.

"Desert dust is synchronizing plant growth and flowering across the alpine zone," said Heidi Steltzer, a Colorado State University scientist who led the study. "Synchronized growth was unexpected, and may have adverse effects on plants, water quality and wildlife."
"It's striking how different the landscape looks as result of this desert-and-mountain interaction," said Chris Landry, director of the Center for Snow and Avalanche Studies (CSAS) in Silverton, Colo., who, along with Tom Painter, director of the Snow Optics Laboratory at the University of Utah, contributed to the study.

"Visitors to the mountains arriving in late June will see little remaining snow," said Landry, "even though snow cover was extensive and deep in April. The snow that remains will be barely distinguishable from the surrounding soils.

Earlier snowmelt by desert dust, said Painter, "depletes the natural water reservoirs of mountain snowpacks and in turn affects the delivery of water to urban and agricultural areas."

With climate change, warming and drying of the desert southwest are likely to result in even greater dust accumulation in the mountains.

In an alpine basin in the San Juan Mountains, the researchers simulated dust effects on snowmelt in experimental plots. They measured dust's acceleration of snowmelt on the life cycles of alpine plants.

The timing of snowmelt signals to mountain plants that it's time to start growing and flowering. When dust causes early snowmelt, plant growth does not necessarily begin soon after the snow is gone.

Instead, plants delay their life cycle until air temperatures have warmed consistently above freezing.

"Climate warming could therefore have a great effect on the timing of growth and flowering," said Steltzer.

Competition for water and nutrient resources among plants should increase, leading to the loss of less competitive species. Delayed plant growth could increase nutrient losses, decreasing water quality.

Similarity in flowering times and plant growth will result in abundant resources for wildlife for a short time rather than staggered resources over the whole summer, Steltzer believes.

"With increasing dust deposition from drying and warming in the deserts," she said, "the composition of alpine meadows could change as some species increase in abundance, while others are lost, possibly forever."

Text above is courtesy of the National Science Foundation

Scientists Chris Landry adds simulated dust to snow in the San Juan Mountains of Colorado to study how dust affects snowmelt. Click on image for full size (271 Kb) Courtesy of the Center for Snow and Avalanche Studies

Dust blown into the San Juan Mountains of Colorado is causing snow to melt faster in the springtime. Scientists have found that this is changing how alpine plants that live on the high mountain tundra react to changing seasons, indicating that global warming could have a big impact on plant growth.

The dust is from the desert areas in the southwest United States. Today, five times more dust blows into the mountains than 150 years ago. More human activity in the desert is creating more dust. Also, climate change is causing the desert to get warmer and drier, which will likely cause even more dust to blanket mountain snow in the future.

"It's striking how different the landscape looks as result of this desert-and-mountain interaction," said scientist Chris Landry, who contributed to the study. The snow that remains in the spring is so covered with desert dust that it looks like soil. Dark colored dust reflects less sunlight than white snow. This retains more heat, causing snow to melt faster.

When snow on mountaintops melts slowly through the warmer months of the year, there is a steady supply of water for the ecosystem and for cities, towns, and farms. However, when dust causes snow to melt quickly in the spring, there is less water for the ecosystem and for humans during summer and fall.

To study the impact of dust on snow and tundra plants, the scientists simulated dust effects on snowmelt in areas of the San Juan Mountains. They measured how much dust sped up snowmelt, and how the life cycles of alpine plants were changed.

The timing of snowmelt signals to mountain plants that it's time to start growing and flowering. Early snowmelt caused by dust could change this, which could affect the whole ecosystem. For example, many species of plants could flower at the same time, increasing competition for water and nutrients.

"With increasing dust deposition from drying and warming in the deserts," said scientist Heidi Steltzer, who led the study, "the composition of alpine meadows could change as some species increase in abundance, while others are lost, possibly forever."

Scientists Chris Landry adds simulated dust to snow in the San Juan Mountains of Colorado to study how dust affects snowmelt. Click on image for full size (271 Kb) Courtesy of the Center for Snow and Avalanche Studies

Dust blown into the mountains of Colorado is causing snow to melt faster in the springtime. This has an impact on plants that live on high mountaintops.

The dust is from the desert in the southwest United States. More dust blows into the mountains today because there are more people living in the desert who change the way land is used, which creates more dust. Also, climate change is causing the desert to get warmer and drier, which will likely cause even more dust in the future.

All that dust makes the snowy mountaintops look different. The snow that remains in the spring gets so covered with desert dust that it looks like soil. Dark colored dust reflects less sunlight than white snow. This means there is more heat, which causes snow to melt faster.

To study how dust affects snowmelt and plants, the scientists spread dust on areas of snow. They measured how much the dust sped melting and how mountain plants were affected.

The timing of snowmelt signals to mountain plants that it's time to start growing and flowering. Early snowmelt caused by dust could change this. For example, many species of plants could flower at the same time, increasing competition for water and nutrients. This could cause the plants that fill mountain meadows to change.