Whitebark pine (Pinus albicaulis) is an ecologically important species in high-altitude areas of the Western United States. It provides habitat and is a critical food source for Clark’s nutcrackers, red squirrels, grizzly bears, and other animals. Whitebark pine stands throughout its U.S. range have recently experienced high mortality due to wildfire, white pine blister rust, and a mountain pine beetle outbreak, leading to questions about the species’ long-term viability.
A recent series of studies assessed the health of whitebark pine populations throughout the western U.S. using data collected from more than 1400 plots managed by the USDA Forest Service’s Forest Inventory & Analysis program. Landscape-level forest monitoring data showed definitive patterns in whitebark pine mortality and regeneration.
-The studies found that as of 2016, 51 percent of all standing whitebark pine trees in the U.S. were dead.
-Whitebark pine trees are dying faster than young trees can regenerate.
-Whitebark pines occur across 10 million acres in the United States. Surprisingly, most of the forests that host whitebark pine trees (85 percent) are actually dominated by other tree species.
-Most sites with seedlings present (83 percent) occurred primarily in lodgepole pine (35 percent) and Engelmann spruce/subalpine fir (23 percent) forest types.
-Statistical models of whitebark pine seedling presence showed that seedlings are most likely to occur at sites where at whitebark pine occurs in the overstory, where grouse whortleberry (Vaccinium scoparium) is present, and are at relatively high elevations.
-The lodgepole pine forest type represents a potential management target for silvicultural treatments (such as “daylighting,” or removal of nearby trees to reduce competition) that seek to facilitate the recruitment of whitebark pine seedlings into larger size classes.
-These results highlight opportunities for managers to encourage growth of whitebark pine seedlings in mixed-species stands, especially within the lodgepole pine forest type.