Summit County Citizens Voice

Desert dust is causing the snow to melt up to two weeks sooner in places like the alpine tundra around Loveland Pass. PHOTO BY BOB BERWYN.

San Juan research shows potential for landscape-level genetic impacts

By Bob Berwyn

SUMMIT COUNTY — Desert dust blown on to high country peaks is not only affecting the timing of snowmelt and runoff, but is also changing the growth and reproductive patterns of plants in Colorado’s alpine zone, according to recent studies conducted in the San Juan Mountains.

Snow is melting off the high alpine tundra earlier — by as much as two weeks. As a result, growth and flowering patterns are becoming more synchronized across the landscape. Instead of growing and blooming in phases, different plants are all flowering at the same time.

This can lead to increased competition for nutrients and for pollinating birds and insects. The changes in timing could have fundamental genetic impacts, with a chance for altered species interactions, including landscape-scale gene flow via pollination, and nutrient cycling. The shifts in vegetation patterns could even affect larger herbivores that browse on alpine plants, including bighorn sheep, as changes in the availability of food impact reproduction.

Human activities such as agriculture, grazing, and resource exploration in semi-arid landscapes of the Southwest have led to a 500 percent increase in dust deposition in adjacent mountains. The dust-on-snow phenomenon of recent years has been widely reported, as hydrologists and water managers look carefully to see how it affects the timing of snowmelt and runoff. Even Denver Water is studying the issue to determine how it affects reservoir operations.

The latest research suggests the more rapid snowmelt is also affecting the timing of the onset of the greening and flowering of alpine plants. Snowmelt occurs earlier, but is decoupled from seasonal warming, the scientists said in a paper that was published by the National Academy of Sciences last year.

Simply said, without dust, the timing of snowmelt is dependent on air temperature. With the dust, the snow melts faster, regardless of air temperature. Some plants showed responses like hastened, constant, or delayed flowering.

In a series of test plots in the San Juans, the researchers manipulated the timing of the snowmelt by using radiation-absorbing fabric and dust additions of finely ground local rock to delay snowmelt by removing background deposits of desert dust from the snow surface. They compared the results against several test plots. The timing of the snowmelt varied by as much as 11 to 13 days. After that, the kept close track of how the plants developed, including how long it took for the first leaf to form completely, and the first blossom to open.

The bottom line, according to the paper, is that human activities in desert ecosystems can be linked directly to changes in alpine landscapes, with as-yet unknown long-term impacts to mountain plants and animals.

Filed under: biodiversity, Environment, seasons, Summit County Colorado Tagged: | alpine wildflowers, botany, Colorado, conservation, desert dust in Colorado mountains, ecology, Environment, phenology, Summit County Colorado, Summit County News