A new University of Colorado Boulder study indicates the infestation of trees by mountain pine beetles in the high country across the West could potentially trigger earlier snowmelt and increase water yields from snowpack that accumulates beneath affected trees.
Led by CU-Boulder geological sciences department doctoral student Evan Pugh, the study was undertaken near Grand Lake, Colo., adjacent to Rocky Mountain National Park, an area that has been devastated by mountain pine beetle attacks in recent years. Mountain pine beetles have killed more than 4 million acres of lodgepole pine trees in Colorado and southern Wyoming since 1996, the most severe outbreak on record.
Pugh and his team monitored eight pairs of tree stands, each pair consisting of one live stand and one dead stand roughly an acre each in size and located adjacent to each other, sharing the same topography, elevation and slope. The team monitored the two distinct phases of pine beetle tree death during the three-year study -- the "red phase" in which dead trees still retained red needles, and the "gray phase" in which all of the tree needles and some small branches had been shed, said Pugh.
The study showed that there was roughly 15 percent more snow accumulation under the gray phase stands than under living stands or red phase stands, likely due in large part to a lack of "snow interception" by needled tree branches that can cause snowflakes to "sublimate" into gas and return to the atmosphere, he said. Gray phase trees also allow more solar radiation through their canopies than live trees and red phase trees, increasing the potential for earlier melt, said Pugh, lead study author.
Snowmelt rates were highest under red phase trees, with snow disappearing up to a week earlier than snow in adjacent, healthy stands even though both received the same amount of snowfall at their bases. Pugh showed the earlier snowmelt in red phase tree stands is due in large
|Contact: Evan Pugh|
University of Colorado at Boulder