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Global warming: Yet another threat to Southwest's iconic pinyon pine?

Add to the long-studied global-warming perils of drought, insects, and wildfires, a new potential threat to the pinyon pine: dramatically lower production of seed-bearing cones.

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This May 30, 2012 image shows hotshots during burnout operations at the Gila National Forest blaze which raced across the area's steep, ponderosa pine-covered hills in New Mexico. Global warming is a threat to southwestern pine trees, say researchers.

AP Photo/U.S. Forest Service Gila National Forest, Steven Meister

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Over the past decade, researchers have documented the increased vulnerability of large stands of a Southwestern forest icon – the pinyon pine – to the dangers associated with a warming climate: drought, insects, and wildfires.

Now, it appears that rising temperatures could also put a damper on pinyon reproduction, potentially limiting the ability of trees that survive the other scourges to recolonize disturbed areas, a recent study says.

Across nine stands of pinyon – two at the western tip of Oklahoma's panhandle and seven throughout New Mexico – the production of seed-bearing cones dropped 40 percent from a 10-year period centered on 1974 to another centered on 2008.

Looking only at years of exceptional seed-cone production, known as masting years, cone production fell 43 percent from the earlier decade to the recent one.

Meanwhile, the average temperature during the growing season in the two periods increased by 1.3 degrees Celsius (2.3 degrees Fahrenheit).

The study represents a first look at the potential impact of a warming climate on the production of pinyon seeds, which, in addition to being vital to repopulating pinyon forests, are also an important source of food for wildlife, notes Miranda Redmond, a University of Colorado PhD student who led the study.

The work doesn't attempt to address potential mechanisms that would tie seed production to temperature changes. Nor does it examine the potential impact on pinyon-forest regeneration, she adds.

But it does show a broad pattern over a wide expanse of the pinyon's range that is suggestive enough to warrant closer looks at these issues, she suggests.

The results come at a time of rising concern over the future of the West's forest in general and the Southwest's in particular.

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