Sierra Nevada Network white pine monitoring: 2022 annual report
Authors: Ward Kimiora 
Published: December 2023

Five-needle white pines (Family Pinaceae, Genus Pinus, Subgenus Strobus), and in particular whitebark pine (Pinus albicaulis), limber pine (P. flexilis), and foxtail pine (P. balfouriana) are foundation species in upper subalpine and treeline forests of several National Park Service Pacific West Region parks, including Sequoia and Kings Canyon National Parks (SEKI) and Yosemite National Park (YOSE). The Sierra Nevada Network Inventory & Monitoring Program, in collaboration with the Klamath Network, Upper Columbia Basin Network, and Mojave Desert Network have implemented a joint long-term monitoring protocol to assess the current status and future trends in high elevation white pine communities. Key demographic parameters within white pine forest communities will be estimated by monitoring individual trees within permanent plots through time.

This report documents the results of the 2022 field season, which was the ninth year of monitoring in SEKI and YOSE. The 2022 goal was to complete the first full measure of the third of three rotating panels (Panel 3) for each species-park population: YOSE-whitebark pine, SEKI-whitebark pine, and SEKI-foxtail pine. Each panel consists of 12 permanent 50 x 50 m (2,500 m2) plots that were randomly selected for each of the three populations. The full sampling array thus includes a total of 36 whitebark pine plots in YOSE, 36 whitebark pine plots in SEKI, and 36 foxtail pine plots in SEKI. Data from plot surveys will be used to characterize white pine forest community dynamics in SEKI and YOSE, including changes in tree species composition, forest structure, forest health, and demographics.

Partial measures of Panel 3 were completed in 2017 (11 plots) in Yosemite whitebark pine, in 2017 (9 plots) in SEKI whitebark pine, and in 2014 (7 plots) and 2017-2018 (8, 1 plots) in foxtail pine. In 2022, the first full measure of all Panel 3 plots (and 2nd or 3rd remeasure of most plots) was successfully completed, and installation was completed on four of these plots in SEKI whitebark pine and two in foxtail pine.

In total, the crew visited 36 sites during the 2022 field season, all from Panel 3. Within the 36 completed Panel 1 plots, a total of 6,398 trees were measured. Species composition, forest structure, and factors affecting tree health and reproduction including incidence and severity of white pine blister rust (Cronartium ribicola) infection, mountain pine beetle (Dendroctonus ponderosae) infestation, dwarf mistletoe (Arceuthobium spp.) infection, canopy kill, and female cone production were recorded. During the 2022 field season crews continued to count the total number of mature cones per tree for whitebark and foxtail pine, use crown condition codes to assess crown health, and tag individual seedlings to be tracked through time. All three of these procedures started in 2017 and are to be evaluated by each of the three participating networks over several years, to determine whether they should become permanent changes to the monitoring protocol.

In YOSE, all 12 Panel 3 whitebark pine plots were measured. A total of 2,720 trees were sampled, which included 977 live whitebark pine trees and 1,605 other live conifers. An additional 135 trees (including 26 whitebark) were recorded as dead. The average number of live whitebark pine trees per plot was 81 (SD = 94). White pine blister rust (WPBR) aecia were observed on five whitebark pine in one plot in YOSE in 2022, and no trees in any plot had inactive cankers showing three or more indicators of WPBR. WPBR had previously been documented in this plot, so the number of plots where rust has ever been observed in Yosemite remains unchanged at six. However, an infection documented in plot 42 in 2021 was not observed again when the plot was resampled in 2022, so it is possible this number should be five. Mountain pine beetle activity was observed on one live whitebark pine and three live and one dead lodgepole pine in YOSE in 2022. Despite documentation of many stands impacted by beetle attack in the field crew notes, the quantified rate of MPB attack was lower than in 2021. Twenty-one percent of live whitebark pine trees produced female cones. Cone-bearing trees averaged 7 (SD = 10) cones/tree. Whitebark pine seedling density averaged 80 (SD = 152) seedlings per hectare. The largest number of whitebark pine seedlings found in a plot was 51 and five of the twelve plots contained whitebark seedlings.

All 12 Panel 3 SEKI whitebark pine plots were measured in 2022, and installation was completed on four of these, so this Panel is now fully installed. Within these plots, 2,179 live whitebark pine, 10 live foxtail pine, and 297 other live conifers were sampled (including 5 live western white pine). The average number of live whitebark pine trees per plot was 181 (SD = 125). Although the crew observed white pine blister rust in seven SEKI whitebark Panel 3 plots, no active cankers (aecia) were observed, and no trees displayed 3 of 5 indicators, so no infections were quantified. Mountain pine beetle activity was observed in 18 live and 23 dead whitebark pine and 1 live and one dead lodgepole pine within three plots in SEKI. Dwarf mistletoe was not encountered. Seven percent of live whitebark pine trees produced female cones. Cone-bearing trees averaged 3.7 (SD = 3.6) cones/tree. Whitebark seedling regeneration averaged 700 (SD = 752) seedlings per hectare. The largest number of whitebark seedlings found in a plot was 19, and two of the 12 plots did not contain any whitebark seedlings.

In the foxtail pine Panel 3, all 12 plots were measured in 2022, and installation was completed on two of these, so installation of the panel is now complete. Within these plots we measured 309 live foxtail pine, 302 live whitebark pine, and 380 other live conifers, including four live western white pine. An additional 112 dead or recently dead trees and 22 unidentified snags were also measured, 19 of which were foxtail pine. The average number of foxtail pine trees per plot was 26 (SD = 26). No signs of blister rust infection or mistletoe were observed on foxtail pine. Mountain pine beetle activity was observed on one dead foxtail pine, one live whitebark pine, and seven live and one dead lodgepole pines within four plots. Sixty-two percent of the foxtail pine trees produced female cones. Cone-bearing trees averaged 33 (SD = 53) cones/tree. Seven foxtail pine seedlings were recorded within five plots, resulting in an estimated 72 (SD = 98) seedlings per hectare. Eight whitebark pine seedlings and three lodgepole pine seedlings were also found within three additional plots.