We’re missing many of our currently employed crew, both FS and not, due to the holidays. So I’m saving up some topics until they return. For now I thought I’d post about some recent forest health pieces in the Southern Rockies.
This piece in Cowboy State Daily is headlined:
Up To 35% Of Wyoming’s High Country Is Dead ‘Ghost Forest’ — And It’s Spreading
It’s estimated 25% to 35% of Wyoming’s forests are now dominated by “ghost forests” — standing dead timber from beetle epidemics and disease. Researchers say it’s time to start paying attention to limber pine before it follows the whitebark into crisis.
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The study calls for a change in strategy: “Confirmed emergence of vcr4 highlights the need to focus on quantitative disease resistance more intensely for limber pine” — basically, stacking multiple genetic defenses rather than relying on just one.
Tomback explained why the single-gene approach is risky.
“Limber and southwestern white pine have what’s called major gene resistance. A single gene confers resistance to the white pine blister rust pathogen,” she said. “The problem is, the gene is present at a fairly low frequency in populations.
You can’t depend on it to save populations. We worry that the blister rust pathogen can mutate and overcome a single gene.”
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Side note about sugar pine:
In the 90’s this was an area of disagreement with sugar pine rust resistance breeding… the researchers at the Institute of Forest Genetics were all for using a major gene, and the national forest scientists at Dorena were for developing multiple gene resistance. Of course, in the limber case, it appears that the single gene is native to the populations. Not many people plant limber pine, so it might follow its cousins sugar pine and western white pine with some planted resistant and the populations otherwise dying off or developing their own genetic resistance. In fact, as I recall, in the 90’s(?) there was an effort to say sugar pine was endangered due to WPBR and Region 5. I couldn’t find this on the internet (maybe too old) but I did find a recent study (2024)
Fire has strong negative effects on survival, resulting in a strongly negative population trajectory on burned sites. Conversely, lower than average forest density (plot-level basal area) results in a positive population growth rate via beneficial effects on individual growth. These results highlight the value of fire hazard mitigation, particularly where it also reduces forest density, in the conservation of this important species.
Yes, being burned can be bad for SP (and many other species) and it likes growing in the open- from Silvics (1965):
Sugar pine tolerates shade better than ponderosa pine but is slightly less tolerant than incense-cedar and Douglas-fir and much less so than white fir (14). A seral species, it becomes less tolerant with age, and overtopped trees decline unless released (11). Thus, dominant sugar pines in old-growth stands were probably dominant from the start, or released by natural causes early in life.
I am not criticizing the 2024 scientists, they were asking important questions. Still there are tendencies of our current scientific institutions to not incorporate directly/rediscover mechanisms by looking at large datasets. More on that in the next few weeks. I mean it’s great that we can quote a peer- reviewed article, better than person experiences of many silviculturists.
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Anyway, back to limber pine.
University of Wyoming botanist Daniel Laughlin is testing whether humans can help trees outrun climate change.
His Medicine Bow Mountain Experimental Garden Array project, planted in a burn scar from the 2020 Mullen Fire, tracks how tree species perform when moved outside their normal comfort zones.
Good news for limber pine: it’s one of the survivors.
Douglas fir, lodgepole pine, ponderosa, bristlecone and limber pines, and desert juniper all showed over 50% survival when transplanted outside their typical zones in fall 2025 monitoring.
What we learned in the past was that these kinds of trends can change over time. It seems kind of ironic that we think the climate is changing, and we also think we can do better at guessing the future of trees than when we thought it wasn’t changing.
A key finding emerging from long-term trials is that poorly adapted seed sources typically were not maladapted because they could not tolerate the average conditions of a site, but rather because they did not tolerate the rare climatic events that occurred every 10 or more years. Although this may sound long, it is only a fraction of the life of many forest trees. For example, in a Douglas-fir provenance plantation (Munger and Morris 1937) established in the Oregon Coast Range (Hebo Ranger District, Siuslaw National Forest), all seed sources performed relatively well from 1915 until 1955. In mid-November 1955, the area had an unusual and prolonged cold spell (Duffield 1956). The frost damaged off-site seed sources, killing some trees and causing serious damage to others. In contrast, the local stand suffered damage but continued to grow well (Silen 1995).
And back to the story:
We’re not at the point where there’s a mandate,” Tomback said. “I think national forests are aware that limber pine is important and that it’s being impacted, but we have a ways to go to actually devise restoration strategies like with whitebark.”
She added: “BLM is an important advocate for limber pine.”
Rocky Mountain National Park in Colorado planted 1,769 limber pine seedlings in October 2024 in areas burned by the East Troublesome Fire.
About 20% of the park’s limber pines show rust resistance, according to the National Park Service.
For those of you not familiar, this is what a restoration plan looks like for whitebark.
The Park Service used BIL and IRA funding to support whitebark restoration (climate resilience).
Here’s a 2012 Forest Service range-wide restoration strategy for whitebark.
Anyway, if you are out hiking these vacation days, enjoy all your sugar pines, western white pines, limbers and whitebarks and eastern white pines. WPBR was introduced to North America in approximately 1900 and here we are in 2026 with these species prevalent throughout the country.
For the last four thousand years as the Anthropocene intensified in the Rocky Mountain region limber pine (Pinus flexilis) receded north and left a few isolated pockets high in the Black Hills, the easternmost population of the five needle white pine species. The oldest known specimen in the US is two thousand years.
Cronartium ribicola or white pine blister rust is native to China but was accidentally introduced to North America around 1900 and can be deadly for limber pine.
Professor Ball has a history of taking on the Republican establishment in the Black Hills.
Native Douglas fir and lodgepole pine are virtually extirpated from the Black Hills National Forest but the agency is trying to restore limber pine in the Norbeck Wildlife Preserve.