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—Data Summary of Monitoring in 2023

Salt Range, Bridger-Teton National Forest, Wyoming.

NPS/Shanahan

This is the second article in the article series, “Five-Needle Pine Monitoring on Wyoming Bureau of Land Management Forests in the Greater Yellowstone Ecosystem.” It summarizes data collected to meet the following four objectives of monitoring five-needle pine species on Wyoming Bureau of Land Management (BLM) forests in the Greater Yellowstone Ecosystem:

Objectives:

1. Estimate the proportion of live, five-needle pine trees (>4 m tall) infected with white pine blister rust.

2. Document blister rust infection severity by the occurrence and location of persisting and new infections.

3. Determine mortality of five-needle pine trees and describe potential factors contributing to the death of trees.

4. Assess the multiple components of the recruitment of understory five-needle pine into the reproductive population.

Within the study area of eight geographic strata, one panel containing two strata is sampled each year, for a four-year revisit schedule (see Methods article in this series). Each geographic stratum is considered a sample frame and may contain multiple map units. In 2023, we sampled one permanent transect in each of the two strata and up to 5 of 10 possible rapid transects for each map unit within a stratum on Panel 4, which includes the Brent Creek and the Sublette Range/Huff Creek sampling frames (Table 1). This resulted in 57 total transects surveyed in 2023.

Table 1. Two Panel 4 sample frames from the five-needle pine monitoring program on Wyoming Bureau of Land Management lands were surveyed in 2023. Brent Creek sample frame contains 10 map units and Sublette Range/Huff Creek has three. While three to five transects within each map unit are targeted for rapid sampling (out of a total of 10 possible transect locations), plus one permanent transect at each sample frame, not all transects attempted will meet the protocol requirements (number of transects visited but not sampled). Once the desired number of transect surveys are accomplished, the remaining transects are not attempted (number of transects not visited). Asterisk indicates that one permanent transect is included in the count.

Sample Frame/ Geographic Stratum	Map Unit and Number of Transects Sampled within It	Number of Transects Visited but Not Sampled	Number of Transects Not Visited
Brent Creek	Brent1 = 5*	2	4
Brent Creek	Brent2 = 5	5	0
Brent Creek	Brent3 = 2	8	0
Brent Creek	Brent4 = 5	1	4
Brent Creek	Brent5 = 1	9	0
Brent Creek	Brent6 = 6	2	2
Brent Creek	Brent7 = 5	1	4
Brent Creek	Brent8 = 5	1	4
Brent Creek	Brent9 = 5	1	4
Brent Creek	Brent10 = 5	0	5
Sublette Range/Huff Creek	SRHC1 = 5*	3	3
Sublette Range/Huff Creek	SRHC2 = 3	7	0
Sublette Range/Huff Creek	SRHC3 = 5	5	0

Sampling methods for each objective are detailed in the Methods article of this series. Results for past years are available on the Greater Yellowstone Network website, including a summary of results for 2013 to 2017 (Shanahan et al. 2022). We will revisit Wyoming BLM permanently established transects according to the panel schedule in the Methods article to conduct rapid assessment transects in those assigned map units within the targeted geographic strata. In addition, we will collect stand structure and composition information to inform potential silvicultural treatment opportunities for enhancement of five-needle pine on Wyoming BLM lands. Should we continue to note dwarf mistletoe infection in limber pine populations from targeted geographic strata, we may consider more in-depth data collection on this metric.

White pine blister aeciospores erupt from a canker caused by the nonnative fungus, Cronartium ribicola. The canker will kill the underlying bark on this branch, including the cambium layer. This prevents nutrients from reaching areas of the branch above the canker.

NPS/Shanahan

Results for Objective 1—White Pine Blister Rust Infection

Within permanent transects, all five-needle pine trees >1.4 m tall are tagged. Rapid assessment survey transects trees are not tagged and only a subset of individual tree measurements are recorded. Therefore, infection status is documented for all 57 transects, whereas change in infection status can only be documented in the two permanent transects.

Trees Infected with White Pine Blister Rust

We examined 347 live tagged trees in the two permanent transects and 55 rapid assessment survey transects from Panel 4 for blister rust infection in 2023. A total of 169 (49%) trees were documented with blister rust infection and 178 (51%) had no infection present. Of these 169 infected trees, 112 (66%) had bole infections (Figure 1).

Figure 1. Blister rust infection was detected on 169 live five-needle pine trees during 2023 surveys of permanent and rapid assessment transects in Panel 4 on Wyoming Bureau of Land Management land. Trees are grouped by size class and blister rust location (canopy only or bole infection).

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Change of Infection Status Over Time: Tagged Trees Live in 2019 and 2023

Because live tagged trees on the permanently established transects are visited every four years, infection transition can be documented through time. Infection transition is not reported for rapid transect data. Of the 15 live trees on the two permanent transects that were surveyed on Panel 4 transects in 2019 and again in 2023, approximately 9 (60%) had no evidence of blister rust infection, 5 (33%) were infected in both years, 1 (7%) transitioned from no evidence of infection to infected, and none went from infected to uninfected (Table 2). A transition from infected to uninfected could result from observer error, an earlier-documented infection based on indicators that upon resurvey no longer meet the established standards of three indicators in the same location, or infected branches that self-pruned.

Table 2. Blister rust infection and transition status among live, tagged five-needle pine trees on Wyoming Bureau of Land Management Panel 4 transects surveyed in 2019 and again in 2023.

Infection Status	Number of Live Trees (n = 15)
Remained Uninfected	9 (60%)
Remained Infected	5 (33%)
Uninfected to Infected	1 (7%)
Infected to Uninfected	0

Orange aeciospores are visible just under the bark of this five-needle pine tree, along with visible chewing. Cankers on the bole of a tree prevent vital nutrients from reaching areas above the canker and therefore are more detrimental to the overall health of the tree than canopy cankers.

NPS/Shanahan

Results for Objective 2—White Pine Blister Rust Infection Transition

On the two permanent transects, infection location changed for trees that were documented with blister rust in 2019 and again in 2023 (Figure 2). One tree with a canopy only infection in 2019 that remained infected in 2023 transitioned to a more severe state of infection in the bole by 2023. This transition occurred in the larger size class, >10 cm DBH. Four trees remained infected in the bole between 2019 and 2023.

Figure 2. Infection transition status by DBH (diameter at breast height) category for live, tagged five-needle pine trees on Panel 4 transects surveyed in 2019 and again in 2023. The total count of live, tagged trees surveyed in both years was 15. Note that none of the trees were >30 cm DBH.

NPS

Mountain pine beetle (black oblong insect) deterred from entering a boring hole that the tree has filled with pitch to fight off attacking beetles. This is a pitch tube.

NPS/Shanahan

Results for Objective 3—Mortality

In 2023, we observed no new dead tagged trees on the two permanent transects. Dead trees are no longer recorded on rapid assessment survey transects.

Five-needle pine seedlings.

NPS/Shanahan

Results for Objective 4—Recruitment

On both permanent and rapid transects, recruitment data are collected at two scales: the 10 × 50 m belt transects, and 1/300 acre subplots associated with the belt transects.

10 × 50 m Belt Transects

Regeneration and Growth

In 2023, we counted 268 understory five-needle pines (≤1.4 m tall) on 57 transects (Table 3). This equates to an average density of approximately 5 small trees per transect. Eleven of these small trees were infected with blister rust.

No new trees had surpassed 1.4 m tall since the last survey in the permanent transects.

Table 3. Number of small five-needle pine trees <140 cm tall documented on the Brent Creek and Sublette Range/Huff Creek sample frame transects on Wyoming Bureau of Land Management land in 2023. Permanent transects Brent1-41 and SRHC1-262 are included in this table.

Sample Frame / Geographic Stratum	Map Unit and Number of Transects Sampled	Number of Small Trees (<140 cm)	Number of Small Trees Infected	Number of Small Trees Uninfected	Number of Small Trees Infection Unknown
Brent Creek	Permanent Brent1-41 = 1	3	0	3	0
Brent Creek	Brent1= 4	18	2	16	0
Brent Creek	Brent2 = 5	3	0	3	0
Brent Creek	Brent3 = 2	7	1	6	0
Brent Creek	Brent4 = 5	13	0	13	0
Brent Creek	Brent5 = 1	0	0	0	0
Brent Creek	Brent6 = 6	29	1	28	0
Brent Creek	Brent7 = 5	46	4	42	0
Brent Creek	Brent8 = 5	11	2	9	0
Brent Creek	Brent9 = 5	14	0	14	0
Brent Creek	Brent10 = 5	14	1	13	0
Sublette Range / Huff Creek	Permanent SRHC1-262 = 1	0	0	0	0
Sublette Range / Huff Creek	SRHC1 = 4	5	0	5	0
Sublette Range / Huff Creek	SRHC2 = 3	11	0	11	0
Sublette Range / Huff Creek	SRHC3 = 5	94	0	94	0

Whitebark pine cones.

NPS/Shanahan

Cone Production

Cone production evidence (current year cones, previous year cone scars, or male pollen cones) was recorded for 21 trees in 2023 (Figure 3). Reproducing trees ranged across three of the four DBH size classes. No cones were recorded on trees <2.5 m tall. Of the trees with cone evidence, 8 (38%) had signs of blister rust infection.

For reproducing trees, cones are counted and categorized into five bins: 0 = no cones, 1 = 1–5 cones visible, 2 = 6–10 cones visible, 3 = >10 cones visible, and S = cone scars but no current year cones visible. Of the Panel 4 trees documented with cones, the largest number, at 15 (79%), fall into the cone scar category, while the remaining trees were observed with 1–5 cones. An additional 29 whitebark and seven limber pine were identified to species due to the presence of male pollen cones. While this is a reliable metric to determine species, once pollen cones begin to senesce, it can be difficult to positively tell the difference between the two trees. By tracking cone production over time, we will gain valuable insight on the trajectory of future five-needle pine recruitment.

Figure 3. Number of cone-producing five-needle pine trees (21 total) grouped by number of cones visible (cone bin) and DBH category on Wyoming Bureau of Land Management Panel 4 transects in 2023. The majority of trees, 20 (95%), were >10 cm DBH.

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1/300 acre Recruitment Subplots

In 2023, we completed 166 recruitment subplots (typically three per transect). In these 1/300 acre recruitment subplots, we recorded the number of five-needle pines in four height categories (>0–15 cm, 15.1–61 cm, 61.1–140 cm, >140 cm; note that trees in the >140 cm category typically have tags already if they are within the 10 × 50 m transect boundary). All other tree species (lodgepole pine (Pinus contorta), fir (Abies lasiocarpa, Pseudotsuga menziesii), spruce (Picea engelmannii), and sometimes aspen (Populus tremuloides)) are recorded in two height categories (15–140 cm, >140 cm). We examined each five-needle pine tree for signs of blister rust. In addition, we recorded ground cover, vegetation cover, and dominant and codominant vegetation species.

Recruitment subplot data will not be collected on rapid assessment survey transects after 2023. This is based on thoughtful review of the type of data needed to assess recruitment of understory whitebark pine into the reproducing population—Objective 4. The goal of this objective is to track change through time, but the statistical method for inference based on rapid transects does not translate to Objective 4 as intended. The methodology was designed to track recruitment on permanently established transects (i.e., long-term monitored transects), where repeat surveys are conducted at the same location on the same individual trees through time. As a result, 2023 will be the final year that we collect data in recruitment subplots for rapid assessment survey efforts. However, we will continue documenting recruitment subplot data for the eight (two per panel cycle) permanently established Wyoming BLM transects.

Learn More

This web article will be updated periodically with new results. Results for 2023 are summarized in a resource brief for 2023. For more results from past years please visit the Greater Yellowstone Network website.