Provo • In an arid mountain range of southwestern Utah stands a ponderosa, stubby by the standards of this stately red-barked pine species, that botanist Stan Kitchen came across in 2003 while researching the Wah Wah Mountains’ wildfire history.
Showing a conspicuous burn scar that he calls a “cat face,” this tree looked ideal for his study, so he plunged a chainsaw into the trunk to remove a flat horizontal wedge, large enough to reveal all the growth rings but small enough not to harm the living ponderosa.
Back in his Provo lab, Kitchen counted these rings, some so thin he needed a microscope to see them, and determined the tree sprang to life around 1075. That’s right, more than 940 years ago — before the first of the Crusades was launched, before Richard the Lionheart took reign, before Genghis Khan was even born. Kitchen was clutching a piece of the world’s oldest ponderosa known to science.
Utah, in fact, is home to four trees that rank as the longest-lived members of their species. And these senior sentinels are helping scientists unlock secrets of the past that could hold clues to the future.
“If I had known [the ponderosa] was that old, there is no way I would have put a saw to it,” says Kitchen, a researcher with the U.S. Forest Service’s Shrub Sciences Laboratory. The tree wasn’t particularly tall or wide, reflecting its rocky environment on an 8,400-foot-elevation ridge that receives a meager 13 inches of annual precipitation.
These harsh conditions ironically led to this tree’s longevity, long beyond the 300 or 400 years ponderosas typically survive. For Kitchen and other tree-ring scientists, known as dendrochronologists, these trees, whether standing or down, open windows to yesteryear.
“The best tree for recording fire in Utah is ponderosa pine,” Kitchen says. “It has a thick, insulating bark. They have high branches, kind of open architecture, all that helps them survive fire, plus they produce needles that are quite flammable and carry fire on the ground surface. I’ve sampled 10 [species of] trees, but ponderosa is the bread and butter.”
His prized tree succumbed in 2016 to pine beetles infesting the Wah Wahs, a range that tops out at 9,100 feet west of Milford, according to Utah State University entomologist Barbara Bentz, who conducted an autopsy on the tree last year. But Kitchen located a living ponderosa hardly 50 yards away that a pencil-diameter core sample showed is just about as old.
The forest is a library
Both of these ponderosas are in select company. They are among four Beehive State conifers crowned as the longest-lived members of their species, according to a database maintained by Rocky Mountain Tree-Ring Research in Fort Collins, Colo. The others are a limber pine at the head of American Fork Canyon, 1,700 years old; a dead pinyon in Nine Mile Canyon that lived for 1,101 years; and a Utah juniper in Diamond Fork Canyon whose trunk revealed 1,020 growth rings.
Ancient trees abound in Utah, particularly in rugged, remote landscapes that ensure slow growth and some protection from pathogens and loggers. Thanks to data encoded in their rings, old trees are a boon to researchers exploring past climates, fire histories, stream flows and American Indian communities. Ancestral Puebloans and Fremonts used tree limbs to build habitations and granaries that, after hundreds of years, cling to cliff faces and alcoves to this day.
The knowledge derived from these rings sheds lights on civilizations that once flourished in unforgiving landscapes and can help land managers predict future stream flow volumes and understand the complex relationship forests have with insects and wildfires.
“The size of the ring reflects the weather, precipitation and other factors that can accelerate or retard the plant’s growth,” Kitchen explains. “They record in those rings injuries or other kinds of events. Sometimes insect infestations leave a specific signal in the rings.”
Scientists compare growth rings from standing trees with those seen in older wood on the ground to build a deeper record, according to Matt Bekker, a Brigham Young University geography professor whose lab is not far from Kitchen’s on the edge of the Provo campus.
“Think of the forest as a library and the trees as books. They are recording information about the environment that they lived in, or are still living in. That information is primarily climate. That can be precipitation, snowpack, soil moisture,” says Bekker, who discovered the oldest limber pine on Utah’s elite list.
“One tree is not all that useful. It’s nice for bragging rights, but you need more than one to put together a useful climate study. You need a minimum of a good 15 or 20,” adds Bekker, who turns to tree-ring data to reconstruct past stream flows in northern Utah. “Matching the patterns of wide and narrow rings on living trees with those same patterns on dead and down trees, you can extend that record back even further. The more living trees and dead trees you have at a site the better chance you have of going back in time.”
Several years ago, he recorded what is likely Utah’s oldest tree, the twisted, mostly dead 1,700-year-old limber pine rising from the Central Wasatch Divide. Lots of millennial-vintage limber spires still stand at the heads of Little and Big Cottonwood and American Fork canyons. Miners denuded this area for timber to shore up tunnels and shafts during the mining era of the late 19th century. But the limber pines along the ridges were too inaccessible to bother cutting, Bekker says, so they were left to tell their stories.
Teaming up with colleagues from the Forest Service and USU, Bekker has analyzed rings from ancient trees to reconstruct flow characteristics for the Bear and Weber rivers and the Great Salt Lake.
A forthcoming study on the Provo relies on 1,000-year-old junipers he and his students documented in Diamond Fork, a tributary to the Spanish Fork and, ultimately, the Provo River.
Experts have longed dismissed Utah junipers because this species’ irregular rings defy interpretation. Their trunks can develop a second growth ring in response to late summer monsoons, so scientists don’t know if they are looking at one or two years of growth.
Bekker developed a technique, however, for distinguishing between a juniper’s true and false growth rings, making that species suddenly useful to science, at least in certain growing conditions.
“We were trained to avoid Utah juniper because it doesn’t have reliable annual rings,” Bekker says. “We found for this area [in Diamond Fork] it does, and it is extremely sensitive to moisture-related variables. It is a fantastic species.”
Nine Mile’s tree trove
Utah’s Nine Mile Canyon harbors wood stretching back to before the Christian era. It’s from pinyon pines and Douglas firs that died hundreds of years ago, offering an even deeper window into the past.
The oldest pinyons were discovered in the canyon’s Wells Draw by Chris Baisan, a scientist with the Laboratory of Tree-Ring Research in Tucson, Ariz., and then-University of Arizona graduate student Troy Knight. The longest-lived specimen died about 400 years ago and its desiccated trunk, sporting 1,101 growth rings, lies slowly rotting on the ground.
“There are more live trees down there that are quite old, 800 or 900 years, and there’s lots of old dead wood. It’s very dry. It’s a cold desert,” Baisan says. “There are thousands of acres of this stuff. You would need several lifetimes to give it a thorough going over with a crew of people. So what’s the oldest tree? Who knows? There are old trees and old dead wood all over that area, like really old.”
His colleagues applied radiocarbon analysis to one piece of pinyon and dated it back 4,000 years.
“That single piece at this point is a curiosity. It’s interesting. It demonstrates that there is wood that old on the landscape,” Baisan says, “but there is no way to identify which pieces would bridge back to that because stuff that has been on the ground for several hundred years looks the same as the stuff that’s been there for 1,500 years.”
Counting to 10
The counters in Kitchen’s lab are cluttered with cores and wedges from trees and discs of sagebrush, as well as pieces of sandpaper, microscopes and other tools of his craft. The samples are all marked with identification numbers and dots at regular intervals in their rings.
“I make a dot every 10 years,” he says. “To do this job, I only need to be able to count to 10.”
For his fire-history study, he took samples from dozens of trees while roaming the Wah Wah Mountains.
The wedge Kitchen cut from the aged ponderosa revealed much about the Wah Wahs’ history with flames. It shows two major scars, both occurring in the 1500s, that indicate the tree survived blazes that scorched part of the trunk, disrupting its concentric growth and leaving obvious marks that can be read 500 years later.
“By looking at where the injury occurs in that ring sequence, we can know the very year that fire occurred. Sometimes we can look at the seasonality of the fire,” Kitchen says, rubbing his finger across the wedge surface, finely sanded to accentuate its growth rings. “This here, an inch from the bark, is 1900. From 1900 to 2003, it grew an inch worth of wood, very slow growth; 1700 is about the same; 1600 is here, was a little better.”
But in the period between the two fires, the rings are much wider.
“There’s nothing like that in the rest of the record. For a decade or so, really good,” Kitchen says. “We are not sure why that is. It wasn’t a particularly wet period. It must have been, with this fire, the tree was standing alone on the hillside and not much competition going on.”
Because of their bounty of old trees, the Wah Wahs are among the most rewarding ranges in the Great Basin for dendrochronological studies, according to Kitchen. Joining the ponderosas are bristlecone pines, the globe’s longest-lived organisms. Kitchen cored one that proved to be 1,450 years old.
Yet that tree was a youngster compared with the eldest bristlecone, a 5,068-year-old Methuselah still growing in California’s White Mountains.
Bristlecones are thought to be immune to mountain pine beetles, but Kitchen’s bristlecone, like his ponderosa, perished in a recent attack. Perhaps the veteran botanist brings bad luck to the trees he studies.
Nah. A more likely culprit is the warming climate, a modern threat to ancient trees and the answers they hold.