Sierra Nevada Network high elevation white pine monitoring: 2021 annual report
Authors: Ward Kimiora 
Published: February 2024

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 2021 field season, which was the eighth year of monitoring in Sequoia and Kings Canyon National Parks (SEKI) and Yosemite National Park (YOSE). The 2021 goal was to complete the third full re-measure of the second of three rotating panels (Panel 2) 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.

The first full measure of all Panel 2 plots was completed over two years in 2013-2014, then a full remeasure of both parks? whitebark pine Panel 2 was conducted in 2016, with 10 of 12 SEKI-foxtail plots sampled that year. A third remeasure of all Panel 2 plots was not possible in 2021 because a smaller crew size was necessary during the COVID-19 pandemic.

In total, the crew visited 37 sites, and sampled 31, during the 2021 field season. One plot in the YOSE whitebark pine frame was uninstalled before reading and one plot in the SEKI whitebark pine frame was uninstalled after reading, both for safety concerns. Four plots were not visited due to lack of capacity with the reduced crew size: one in each of the YOSE and SEKI whitebark frames, and three in the SEKI foxtail frame. A plot from Panel 3 in each of the parks? whitebark frames was measured, for a total of 11 plots measured in each whitebark pine frame. Nine plots were measured in the SEKI foxtail pine frame. Within the 31 plots completed, a total of 5,728 trees was 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, female cone production and regeneration were recorded. During the 2021 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, 11 whitebark pine plots were re-measured, from Panels 2 and 3. A total of 2,810 trees were sampled, which included 586 live whitebark pine trees and 2,097 other live conifers. An additional 127 trees (including 17 whitebark pine) were recorded as dead. The forest crew noted little sign of white pine blister rust (WPBR) in Yosemite in 2021, and just a single inactive canker was observed on one whitebark pine in Panel 3, Plot 42, near Dana Meadows. This infection was new to plot 42, and it expands the total number of plots where white pine blister rust has been documented in Yosemite to six. The crew also noted little mountain pine beetle activity, documenting beetle galleries on 15 lodgepole pines in three Panel 2 plots. Dwarf mistletoe was not observed. The average number of live whitebark pine trees per plot was 53 (SD = 56). This was a low cone crop year for whitebark pine, with two percent of live whitebark pine trees producing female cones. Cone bearing trees averaged 2 (SD = 1) cones per tree. Whitebark pine seedling density averaged 90 (SD = 157) seedlings per hectare. The largest number of whitebark pine seedlings found in a plot was four, and three of the eleven plots contained whitebark seedlings.

In SEKI, 10 of 12 Panel 2, and one Panel 3, whitebark pine plots were re-measured. Within these plots, 1,246 live whitebark pine, 30 live foxtail pine, and 861 other live conifers were sampled. WPBR was infrequently documented in the SEKI whitebark frame as well, with indicators of infection in Plot 31 near Window Creek and Plot 44 near Upper State Lake. These were the first infections documented in these plots, bringing the number of plots where WPBR has been documented in the SEKI whitebark panel to nine. Although WPBR was documented in Plot 27 near Charlotte Dome in 2016, it was not documented this year because putative cankers showing three signs of infection in 2016 showed only two or fewer signs in 2021. Mountain pine beetle activity was observed in one live lodgepole pine and two recently dead whitebark pine, within three plots in the SEKI whitebark sample frame. An exception to the low levels of mountain pine beetle activity was outside Plot 31 in the Window Creek area, where the forest crew noted many recently dead whitebark pine with signs of beetle activity. Dwarf mistletoe was not encountered. The average number of live whitebark pine trees per plot was 113 (SD = 86). Less than one percent of live whitebark pine trees produced female cones, each producing on average 2 (SD = 1) cones. Whitebark seedling regeneration averaged 303 (SD = 319) seedlings per hectare. The largest number of whitebark seedlings found in a plot was eight, and eight of the 11 plots contained whitebark seedlings.

Nine of the 12 SEKI foxtail Panel 3 plots were remeasured. Within these plots, 413 live foxtail pine, 67 live whitebark pine, and 402 other live conifers were sampled. Ninety-two dead or recently dead trees were also documented, 65 of which were foxtail pine. No signs of blister rust infection, mistletoe, or mountain pine beetle were observed in the foxtail plots sampled. The average number of foxtail pine trees per plot was 46 (SD = 33). Fifty-four percent of the foxtail pine trees produced female cones, averaging 14 (SD =15) cones/tree. Only one foxtail pine seedling was recorded within the 9 foxtail pine plots, resulting in an estimated 14 (SD = 41) seedlings per hectare. Eight whitebark pine seedlings were also found within two plots.