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NAU Researcher Works to Save a Species

Later this summer and into early fall, tree-climbing crews will be using ropes to pull themselves up into 40, 60 even 80-foot tall Southwestern White Pine trees in Arizona’s high elevation mixed conifer forests. Researchers have only about a four-week window during the year when the tree’s pinecones are ripe to gather them for genetic research aimed at keeping these trees from dying out.

The Southwestern White Pine is under attack from a parasite called the blister rust fungus. Kristen Waring, Ph.D., a professor in Northern Arizona University’s School of Forestry, says almost all of these specific pines infected by the fungal pathogen die.

“The spores enter through a [pine] needle and the fungus grows down into the twigs and branches and eventually into the main stem of the tree,” said Waring. “The tree will eventually become girdled, so nutrients can’t flow up and down the tree.”

The blister rust creates a canker on the tree. It gets its name from the bright orange spores that come out at the edges of the canker and create blisters.

Waring says the disease was brought to North America when infected trees were shipped from Europe to Canada in the early 1900s. Since then, it has traveled south, causing widespread die off in the Southwestern White Pine populations of Colorado and New Mexico. She says it is now killing the species in eastern Arizona on the Fort Apache Indian Reservation.

“Because it’s a non-native disease, the trees don’t have a natural immunity,” explained Waring. “We’ve so far only identified a few trees in one stand in central New Mexico that has the major gene, the immunity gene essentially, that will keep it from getting the disease.”

She says there may be more Southwestern White Pines, but not many more, that have a partial resistance, which means they’ll become infected but they will survive.

In an effort to protect the species, the seeds that she and her colleagues will be collecting from the pinecones will go to seed banks for long-term storage. “Even if those trees die from blister rust or something else, we will still have their genetics,” she said.

That something else could be climate change. “Ultimately, we would like to know where in the landscape we have genetic resistance to the blister rust and where we have high frequencies of other traits that will be helpful in the future under climate change such as drought resistance or cold hardiness. We also want to know whether those match up with the resistance traits because they may not be the same genes.”

To add climate change scenarios into her research, Waring and her colleagues will be planting Southwestern White Pine seedlings in test gardens throughout Northern Arizona at different elevations to determine where the tree will survive best in a projected warmer, dryer future. Some 8,100 Southwestern White Pine seedlings are being grown in NAU’s Greenhouse; another 1,000 are growing at The Arboretum at Flagstaff.

Waring’s studies are being made possible by a $4.1 million grant from the National Science Foundation, the largest ever received by NAU’s School of Forestry. “I’m not surprised that NAU’s proposal was the only project out of 50 presented to the National Science Foundation that received funding,” said Jim Allen, Ph.D., executive director of the School of Forestry. “It’s important work that brings together climate change, genetics and disease and may well serve as a model for other research. There are a lot of non-native tree diseases that cause a lot of damage, and climate change is happening everywhere.”

Waring says the Southwestern White Pine and its pinecones are critical for food and shelter to a number of forest creatures, including the rare Mexican spotted owl, other birds and squirrels that live in mixed conifer forests.

“I feel strongly that people are responsible for moving these non-native pathogens around,” she said, “so we have a responsibility to manage for them.” QCBN


(Photo) Forester Kristen Waring removes seeds from pinecones of the Southwestern White Pine in her NAU lab. She and others will climb the 40- to 80-foot tall trees to retrieve the cones in August and September.

Photo and story by Bonnie Stevens






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