Study: Warming and drought, harmful to pinion trees | TahoeDailyTribune.com

Study: Warming and drought, harmful to pinion trees

Associated Press

RENO ” A new study by researchers at the University of Arizona suggests a combination of global warming and drought could prove exceptionally deadly to pinion pine, Nevada’s state tree.

Scientists at the university’s Biosphere 2 research station found pinion pines could die five times faster during droughts of common duration if the climate warms by 7 degrees.

Half the pinions studied were kept in normal temperatures, the others in an environment 7 degrees warmer. Some trees in each group were then deprived of water to simulate droughts common in the past.

Trees subjected to higher temperatures died at a far greater pace than the other trees, suggesting that even short droughts could produce widespread tree mortality in a warmer climate, researchers said.

“What this highlights is that together, drought and temperature can kind of provide a double whammy,” David Breshears, a researcher involved in the experiment, told the Reno Gazette-Journal.

The Arizona research focused on double-needle pinion pines common in the Southwest, not the single-needle pinion designated as Nevada’s state tree in 1953. But the results, scientists said, likely would apply to Nevada’s pinion species and many others.

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“If this pinion species is very sensitive to temperature, we would speculate the species out there would probably be sensitive too,” Breshears said.

The study was conducted in Biosphere 2, a glass and steel laboratory that includes recreations of the planet’s savannas, deserts, oceans and forests.

“The results say that if the climate is warmer, then it takes a shorter drought to kill the trees,” said lead researcher Henry Adams. “And there are many more shorter droughts than longer droughts in the historical record.”

The Arizona research, to be published in the Proceedings of the National Academy of Sciences, follows the release of another study that indicated the death rate of many types of trees in old-growth forests across the West is doubling every 17 to 29 years. Scientists also linked that trend to a warming climate.

Breshears said the latest study didn’t include other factors that could accelerate the death rate for pinion trees.

“I don’t want to be alarmist, but that is a very super-conservative projection because the result relates only to temperature, not to increased drought or bark beetles, which we know will exacerbate the problem,” he said.

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Information from: Reno Gazette-Journal, http://www.rgj.com