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Drought and bark beetles threaten bristlecone pine trees

Forest pathologist Martin MacKenzie strode a narrow path through California’s mythical pine forest in the White Mountains near the Nevada border, methodically tracking skeletal limbs for intruders are threatening the lives of some of the world’s oldest trees.

These intruders are bark beetles, a threat smaller than a pencil eraser, but they carve thousands of trees into the bark and feed on the moist inner core, where the tree transports nutrients from its roots. to the top. They then carve out egg galleries, where the hungry larvae will hatch.

A fungus with a green stain carried by an insect causes a coup – a clogged circulatory system.

For thousands of years, bark beetles have been controlled or eliminated by the harsh conditions of rocky peaks and storms, where grotesque, twisted trees have developed an arsenal of survival strategies. exist.

US Forest Service workers work around the ancient Feather Pine Forest

At Bristlecone Ancient Pine Forest, US Forest Service pathologist Martin MacKenzie examined the trees with ecologist Michele Slaton, right, and spokeswoman Mary Matlick.

(Carolyn Cole / Los Angeles Times)

Now, these vivid symbols of longevity, strength and perseverance may be at an evolutionary crossroads, scientists say. According to a recent study published in the scientific journal Forest Ecology and Management, droughts and bark beetles for the first time in recorded history killed the beetles.

Since 2013, thousands of trees between 144 and 1,612 years old have died on Telescope Peak – the site of Death Valley National Park’s only planned tree population – the study said. Many more were killed in the tall bristle forests that dot southern Utah.

On a recent morning, MacKenzie, 74, wanted to confirm that the culturally significant Old Pine Forest is home to Methuselah, a 4,853-year-old specimen that some say is the oldest living tree on Earth. soil, still no insects.

“We were lucky – there was no sign of beetles in these trees,” MacKenzie told a companion with a smile.

But a few minutes later, as he was walking along the path, he noticed a color that tells the story of tree stress: red. It was just beginning to emerge on bright green tinsel that crept over a steep slope in the distance.

His face darkened. “I have to go check it out.”

A stiff pine tree.

A large bristle pine tree has fallen, exposing its roots in the Old Furry Pine Forest.

(Carolyn Cole / Los Angeles Times)

Great Basin bristlecone pines are a marvel to woodworkers like MacKenzie.

In difficult times, they die almost completely, leaving behind a few strips of shell that can continue to grow for thousands of years – leaning along the ground or slanting into the sky. They keep needles for up to 40 years and drown hungry insects in plastic.

They are survivors of bristle pine forests that were pushed up more than 11,000 years ago, by rising temperatures that have caused major changes in flora and fauna and created California’s deserts.

“Unlike people, pine trees don’t die of old age,” he likes to say.

But they can be killed. Research led by US Forest Service biologists Barbara Bentz and Candace Millar has found that bark beetle mortality is most likely to occur in areas with hairy pines mixed with other tree species known to house beetles.

A pathologist takes a sample from a tree.

US Forest Service pathologist Martin MacKenzie takes a sample from a dying hardy pine.

(Carolyn Cole / Los Angeles Times)

The study found that solitary bristles deal with beetles by immersing them in the sap. But in hot, arid mixed forests, bark beetles first land on nearby green pines and tubers, creating new swarms that can attack the stiff, overpowered systems. their defense.

In an interview, Millar recalled what she described as “the shock I felt when I first saw hundreds of hairy trees being killed by bark beetles on the highest slopes of Telescope Peak in Death Valley. .”

The study found that hornet mortality rates at Telescope Peak and in the Wah Wah Forest in southern Utah were likely due to a combination of warming temperatures, reduced rainfall, and defenses. of trees decreases and bark beetle attacks originate in nearby pines and pinyons over a period of time. Severe drought started in 2013.

“Do I think this is the death knell for bristlecone pine elsewhere? Well, maybe not,” Millar said. “But it’s time to consider taking action to protect these trees.”

Proposals to control errors have included both sublime and controversial. The study calls for annual surveys to provide advance notice of beetle attacks, as well as public education programs and posting interpretive signs.

Another idea involves creating a chemical attractant to lure insects into a bait trap, although such an attempt also runs the risk of summoning an uncontrolled swarm of bugs into groves that are currently dormant. affected.

Close-up of a pine cone.

Stiff-necked pine cone.

(Carolyn Cole / Los Angeles Times)

The hairy pine, identifiable by its bottle palm-like branches with short needles, is found in the semiarid parts of the Great Basin, extending from the Sierra Nevada range of California eastward to the Rocky Mountains.

But the ones found in the White Mountains are the oldest. The slow-growing trees are only about 25 feet tall and expand 1 inch in diameter every 100 years.

Of particular interest to the researchers is the oldest species of the group, Methuselah. Its exact location is carefully guarded to prevent vandalism, although the forest around it is a tourist attraction that attracts 30,000 people each year.

In certain emergency situations, such as to protect Methuselah from potentially fatal intrusions, the study found that “a very aggressive defensive strategy would be to manually remove the pine trees. nearby are known to host mountain bark beetles.”

The intricately gnarled wood of a bristly pine

In difficult times, the bristle pine almost completely dies off, leaving behind a few strips of bark that can continue to grow for thousands of years.

(Carolyn Cole / Los Angeles Times)

However, whether Methuselah secures the title of “oldest living organism” remains controversial. Researchers in Chile announced a month ago that an ancient cypress tree there called Gran Abuelo may be 5,400 years old. If confirmed, it would defeat Methuselah by about six centuries.

Meanwhile, the daunting task of tracking bark beetle attacks on public lands belongs to forest pathologists like MacKenzie.

After a long hike, MacKenzie stepped into the shade of a hard-haired pine with an unpleasant red color and peered into its bark and needles, his eyes alive with expectation.

There are lots of red needles indicating stress, but no evidence of scarabs.

“Drought kills the trees – not the beetles,” he said. “But I noticed some other trees in the area that I had to check out.”

https://www.latimes.com/environment/story/2022-06-27/drought-and-bark-beetles-now-threaten-earths-oldest-trees Drought and bark beetles threaten bristlecone pine trees

Edmund DeMarche

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