Note to Editors: A press embargo is in place by the Proceedings of the National Academy of Sciences for this study and will lift at 3 p.m. MDT on Monday, June 29. For interviews with Heidi Steltzer, contact Kimberly Sorensen at (970) 491-0757 or Kimberly.Sorensen@colostate.edu.
A new study by a Colorado State University researcher indicates that accelerated snowmelt by desert dust that blows into the mountains changes how plants respond to seasonal climate cues that regulate their life cycles. As a result, climate warming may have a greater influence on their annual growth cycle.
"The observed changes in plant life cycles due to desert dust synchronize plant growth and flowering across the alpine, which vary greatly in the absence of dust" said Heidi Steltzer, a Colorado State University researcher in the Natural Resource Ecology Laboratory, who led this study. "Synchronized growth was unexpected and may have adverse effects on plants, water quality and wildlife."
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. Under climate change, warming and drying of the desert southwest is likely to result in greater dust accumulation in the mountains.
"It is striking how different the landscape looks as result of this desert/mountain interaction," said Chris Landry, director of the Center for Snow and Avalanche Studies, Silverton, Colo., who along with Tom Painter, assistant professor of geography and the 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, even though snow cover was extensive and deep in April, and the snow that remains will be barely distinguishable from the surrounding soils."
"Earlier snowmelt by desert dust depletes the natural water reservoirs of mountain snowpacks and in turn affects the delivery of water to urban and agricultural areas," said Painter.
New research published this week by the Proceedings of the National Academy of Sciences now shows that this early snowmelt also affects the life cycles of alpine plants and that the dust effect on these plants differs from the effect of climate warming.
In an alpine basin in the San Juan Mountains, the researchers simulated dust effects on snowmelt in experimental plots to measure dust’s acceleration of snowmelt on the life cycles of alpine plants. The timing of snowmelt signals to mountain plants that it is 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 greater effect on the timing of growth and flowering," said Steltzer.
Greening and flowering times were more similar across the alpine tundra when snowmelt occurred earliest in the researchers’ study plots. Steltzer predicts that increasing dust inputs could synchronize plant life cycles in the alpine tundra but the full consequences of this synchronization are not yet understood. 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.
The case is building that the transfer of desert dust to the mountains has environmental consequences for alpine plants, wildlife and people. 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 climate warming.
"Desert dust alters the ecology of alpine landscapes from staggered to more synchronized plant growth. With increasing dust deposition from drying and warming in the deserts under global warming, the composition of alpine meadows could change as some species increase in abundance, while others are lost, possibly forever," Steltzer said.
Ed Ayres, researcher at CSU’s Natural Resource Ecology Laboratory, is also a co-author of this study.