SALT LAKE CITY -- Researchers say they've discovered the probable cause behind a mass die-off of aspen trees in the West during the past decade.
Scientists from Stanford University and the University of Utah say a severe drought combined with hot springs and summers to cause "sudden aspen decline."
The Deseret News reports (http://bit.ly/rOgGhJ ) biologists compared the branches and roots of healthy aspens with those from dying aspens. They found the trees affected by droughts developed the equivalent of blood clots and had trouble transporting water.
The trees are an iconic part of the West's landscape and play a key role in housing wildlife and purifying air.
More than a fifth of the trees died off in certain areas during the past decade.