Salt Range, Bridger-Teton National Forest, Wyoming. NPS / Shanahan.
The monitoring
This is the second article in a Park Service series on monitoring five-needle pines — whitebark and limber pine — on Bureau of Land Management (BLM) forests in Wyoming, in the Greater Yellowstone Ecosystem. It reports 2023 results for four objectives:
- estimate how many live five-needle pines taller than 4 m have white pine blister rust;
- document how severe infections are, and where new ones appear;
- measure mortality and what may be killing trees;
- assess recruitment — young pines growing into the reproducing population.
The study area has eight geographic strata; each year one panel of two strata is sampled, so each is revisited every four years. In 2023 crews surveyed Panel 4 — the Brent Creek and Sublette Range/Huff Creek frames: one permanent transect in each, plus up to 5 of 10 possible rapid transects per map unit, 57 transects in all. On permanent transects every five-needle pine taller than 1.4 m is tagged; rapid transects record only some measurements, so changes over time come from the permanent ones. Methods are in the series' methods article.
Blister rust spores erupting from a canker caused by the nonnative fungus Cronartium ribicola. The canker kills the bark and the cambium beneath, cutting off nutrients to the branch above. NPS / Shanahan.
1. How many trees are infected
Of 347 live trees examined in 2023, 169 (49%) had blister rust and 178 (51%) did not. Of the infected trees, 112 (66%) had infections on the bole (trunk).
The 169 infected trees by size class and infection location, Panel 4, 2023. NPS.
On the two permanent transects, 15 live tagged trees were surveyed in both 2019 and 2023:
| Infection status | Trees |
|---|---|
| stayed uninfected | 9 (60%) |
| stayed infected | 5 (33%) |
| became infected | 1 (7%) |
| infected to uninfected | 0 |
(A tree can appear to recover through observer error, an earlier call that no longer meets the standard of three indicators in one place, or an infected branch that self-pruned.)
Orange spores under the bark of a five-needle pine, with signs of chewing. Cankers on the trunk block nutrients from everything above them, so they harm a tree more than canopy cankers. NPS / Shanahan.
2. How severe
Among trees infected in both years, one larger tree (over 10 cm in diameter) moved from a canopy-only infection to the more serious bole infection, and four kept bole infections.
Infection changes by diameter class for the 15 tagged trees surveyed in 2019 and 2023; none was over 30 cm. NPS.
3. Mortality
No tagged tree on the permanent transects died since the last survey. Dead trees are no longer recorded on rapid transects.
A mountain pine beetle caught in a "pitch tube" — sap the tree pushed into the boring hole to fight off attack. NPS / Shanahan.
4. Recruitment
Five-needle pine seedlings. NPS / Shanahan.
- Young trees: crews counted 268 understory five-needle pines (1.4 m or shorter) on the 57 transects — about 5 per transect — of which 11 had blister rust. No tree on the permanent transects had grown past 1.4 m since the last survey. The count varied widely: one Sublette Range/Huff Creek map unit had 94, several had none.
- Cones: 21 trees showed cone production — current cones, old cone scars or male pollen cones — across three of the four diameter classes; none shorter than 2.5 m had cones, and 8 (38%) of the cone-bearers had blister rust. Most (15) showed only cone scars; the rest had 1–5 cones. Pollen cones identified another 29 whitebark and seven limber pines, though the two are hard to tell apart once pollen cones wither.
Whitebark pine cones. NPS / Shanahan.
Cone-producing trees by number of cones and diameter, Panel 4, 2023; 20 of the 21 were over 10 cm in diameter. NPS.
- Subplots: crews completed 166 recruitment subplots of 1/300 acre, counting five-needle pines in four height classes and other trees — lodgepole pine, fir, spruce, sometimes aspen — in two, and checking every five-needle pine for rust. 2023 is the last year subplots are done on rapid transects, since their statistics can't track the same trees over time; they continue on the eight permanent transects.
Next
Crews will keep revisiting the permanent transects on the panel schedule, run rapid transects in the assigned map units, and record stand structure to find chances for silvicultural treatments that help five-needle pines on BLM land. If dwarf mistletoe keeps turning up in limber pine, they may study it more closely.
More: the 2023 resource brief, results for 2013 to 2017 (Shanahan and others, 2022), and the Greater Yellowstone Network's whitebark pine page. The series begins with the program overview.
Sources
Based on "White Pine Blister Rust Infection Status, Mortality, and Recruitment of Five-Needle Pines on Wyoming Bureau of Land Management Forests in the Greater Yellowstone Ecosystem," Greater Yellowstone Inventory and Monitoring Network, National Park Service; a work of the United States government in the public domain. The source gives the cone-scar trees as 15 but also as 79% of 21; this page gives the count.
Licence: CC0 1.0 (public domain) · Adapted from www.nps.gov
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