Death is making the neighborhood begin to look a little shabby.
Pinyon pine trees in south central Idaho, particularly in and around City of Rocks National Reserve are dying in noticeable numbers. There’s a natural war going on between the trees and a few pathogens, one with the ominous name, black stain.
“I can drive through the reserve and probably count 30 to 50 trees that are going to be dead by spring based on the needle changing from green to orange,” said Wallace Keck, City of Rocks National Reserve superintendent. “You know that clearly their root systems are not functioning and the tree is going to die. We might say we’re losing a couple of acres, 3 to 5 acres, across the reserve where pinyon grow each year.”
Of the reserve’s 14,400 acres, Keck estimates about 2,000 acres are pinyon pine forest. It’s the only foothold the trees have in the state. Like an embedded war journalist, Keck records what’s happening on the pinyon pine battlefield.
“So if you’re losing 5 acres per year and you only have let’s say 2,000 acres of pinyon, it’s not long before it starts to get people like me worried about what’s going on here. Maybe we better pay attention.”
Almost all of Idaho’s pinyons, called single-leaf pinyons, are found in Cassia County along the Utah border. These tall desert pine trees produce a tasty little nut loved by critters and people alike. Members of the Shoshone-Bannock tribes make an annual pilgrimage each fall to gather cones. The trees range across the arid Western lands of California, Nevada, Utah, Arizona and that tiny piece of Idaho. (Related species are found throughout the Southwest.) Some pinyon woodlands at the City of Rocks are thriving with 350 to 400-year-old specimens and nearby seedlings popping up. Other areas are dying out, a mere 60 to 90 years old with no offspring nearby.
Keck launched an inquiry into the pinyon deaths in 2019 with the help of researchers from the University of Idaho and universities in Oregon. Since that time he has learned a few things, and is still learning some things.
“We’re trying to inventory what is killing them. What are the pathogens killing the pinyons? There’s quite a list,” Keck said.
Studies like this take time, usually several years. The researchers are looking for facts, taking inventory of the health of the trees, what’s attacking them, their ages, density, etc., by setting up plots. The team worked this summer on the project and plan to visit again this fall.
One of the things researchers are learning is that pinyons have a lot of enemies. It is in competition with other trees, attacked by pitch moths, Ips beetles, pine blister rust, pouch fungus and black stain. It turns out that climate change could also be aiding the enemy’s cause.
Keck said the Ips beetle “is more than capable of orchestrating a kill-zone” but is not the main threat. “Black stain root disease caused by the fungal pathogen Leptographium wageneri is the silent killer,” he said. The fungus gums up the xylem (the tree’s system of sending nutrients up from the roots to the branches and leaves), until the tree is weakened and can die. Beetles also help spread death by tracking the fungus in on their dirty feet.
Keck said the changing climate is fostering an early wet spring for the production of fungus.
“The local change here is that we are having, as one theory puts it, a ‘head fake’, where in the spring, snows and rains cut off early say in February,” he said. “Instead of snowing, it goes to rain, suggesting spring. Then all of a sudden in late March and early April, winter comes back. It does a head fake. What it does is favor fungus to reproduce. Fungus needs wet, dark, damp climate. We have that sort of micro climate changing to favor that. Black stain, which is native, has the ability to fight stronger against the pinyon pine’s defenses.”
“Because of the greater global climate changing and affecting and creating microclimates that are radically different than they were say 30 to 40 years ago or 100 years ago, now we’re starting to see those changes, and you know they’re right in our face,” Keck said.
But pinyon pines do have a few tough defenses to battle these natural enemies. One of its best defenses is to extrude sap to push out invaders.
Paleoecologist Julio Betancourt, who studied ancient pack rat middens at City of Rocks, said one way species such as pinyons can thrive without “predators” is to skip ahead of them. Pinyons in Idaho did just that about 3,000 years ago from areas farther south in Utah, his studies show. Birds such as pinyon jays or Clark’s jays will fly to another area, perhaps over the next mountain range and cache a load of pine nuts, which, when conditions are favorable, grow into a new stronghold without enemies.
“Pinyon jays are known to fly long distances from Elba to the City of Rocks – 25 to 30 miles. They make that trip sometimes every day in the fall,” Keck said. “We’ve put little antennas on them to track them. ... On a rare occasion they might take a 50-mile jump or 100-mile jump and skip an entire mountain range.”
On the topic pine nuts, Keck said this year’s drought is to blame for poor cone production.
“The crop was so bad that the Shoshone-Bannock tribes that came out Saturday weren’t that successful,” Keck said. “They knew coming in they weren’t going to be that successful, but for tradition’s sake they gathered. This is the worst year. Four years ago, it was actually a really good crop.”
Pinyon pine is listed in Idaho as critically imperiled.
“In a few generations or a few centuries, pinyon pine might disappear from the Idaho landscape due to disease, climate change, or other woody competitors,” Keck said. “Or it is possible that pinyons will adapt and advance into adjacent mountains such as the Deep Creek and Bannock Range.”