( The high heat that accompanied the rece...)Underlying cause of massive pinyon pine die-off revealed

The resulting landscape change will affect the ecosystem for decades. Hotter temperatures coupled with drought are the type of event predicted by global climate change models. The new finding suggests big, fast changes in ecosystems may result from global climate change.

"We documented a massive forest die-off - and it's a concern because it's the type of thing we can expect more of with global warming," said research team leader David D. Breshears, a professor of natural resources in The University of Arizona's School of Natural Resources in Tucson and a member of UA's Institute for the Study of Planet Earth.

At study sites in Arizona, Colorado, New Mexico and Utah, the team found that from 40 to 80 percent of the pinyon trees (Pinus edulis) died between 2002 and 2003. The researchers confirmed the massive regional dieback of vegetation through both aerial surveys and analysis of satellite images of those states' pinyon-juniper woodlands.

"Scientists are concerned about how fast vegetation will respond to climate change, but we don't have many examples to test our ideas," Breshears said. "Here we've clearly documented a case that shows how big and fast the die-off can be."

The drought coupled with particularly high temperatures set the trees up to be susceptible to insect infestations. Bark beetles delivered the knock-out punch.

"It was the drought - beetles don't get trees unless the trees are really water-stressed," Breshears said.

Breshears, Neil S. Cobb, director of the Merriam-Powell Center for Environmental Research at Northern Arizona University in Flagstaff, Paul M. Rich, research scientist at Los Alamos National Laboratory in New Mexico, and their colleagues will report their findings the week of Oct. 10 in the online Early Edition
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Source:University of Arizona