Posted by: greeningwashington | April 15, 2009

Perils of the Pinyon Pine

(c) Radeka Photography. "Pinyon Pine and Sandstone, 2004. El Malpais National Monument, New Mexico"

(c) Radeka Photography. "Pinyon Pine and Sandstone, 2004. El Malpais National Monument, New Mexico"

Yesterday, I listened to a story on NPR about research that links rising temperatures and massive tree die-offs.  

More specifically, the researchers at the University of Arizona posed this question: Do warmer temperatures make trees more susceptible to drought?

My response is an intuitive, yes! I was correct. However, the science behind the answer is what really matters.

When asked about the basic nature of the hypothesis, biologist David Breshears, one of the Arizona scientists, admitted that there is still much scientists do not know about trees.

“Like, what does it take to kill a tree, and do warmer temperatures matter in terms of killing trees?” Breshears says.

Breshears and his colleagues’ questions also grew out of the differences between drought related tree die-offs during the 1950s and 2002, which affected New Mexico pinyon pines. Why did more trees die in 2002 even though the drought was less severe than the droughts of the 1950s? One significant factor that had changed was the temperature of the region.

In order to study the effect of warmer temperatures on the drought tolerance of trees, the University of Arizona scientists uprooted 20 mature pinyon pine trees from their native location in Ojitos Frios, N.M., and transported them approximately 600 miles to Biosphere 2 in the Arizona desert outside Tucson, AZ.

Biosphere 2 is essentially a giant greenhouse with simulations of different climate zones inside.

The researchers then put the trees into two areas: one where conditions resembled those in the trees’ native habitat, and the other with a temperature of about 8 degrees Fahrenheit warmer.

Finally, they stopped watering half of the trees in both of those spaces.

“What we saw was that trees in the warmer area died 30 percent faster on average than trees in the ambient area,” says Adams.

“If what we see for this pinyon pine species also applies to other widespread tree species,” says Breshears, “then there’s potential that we could have a lot of die-off in a lot of places.”

“It was important to do this sort of work to demonstrate that this does occur in biological systems,” he says.

In a controlled environment, it is easy to test singular independent variables. Did the scientists factor intervening variables into their equation? Without actually reading the full report, I am assuming that they did. If they did not, then the possibility of experimental error remains.

The researchers’ findings have been published in the Proceedings of the National Academy of Sciences.

Once again, the results seem obvious, but that is what good scientists do — they test their hypotheses and support them with cold, hard facts instead of relying on their feelings.

Until next time.

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