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Whitebark pine distribution and regeneration in mixed-species stands

Status: 
Complete
Dates: 
January, 2012 to September, 2018

Dead whitebark pine trees in the Frank Church-River of No Return Wilderness Area, Salmon-Challis National Forest, Idaho.
Dead whitebark pine trees in the Frank Church-River of No Return Wilderness Area, Salmon-Challis National Forest, Idaho.
Whitebark pine (Pinus albicaulis) is an ecologically important species in high-altitude areas of the West due to the habitat and food source it provides for Clark’s nutcrackers, red squirrels, grizzly bears, and other animals. Whitebark pine stands 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. This project seeks to quantify the current distribution and regeneration status of whitebark pine throughout its US range.

If resource managers want to maintain whitebark pine and the numerous species that rely on it, they need quantitative information about how to encourage regeneration and recruitment. The Forest Inventory & Analysis (FIA) Program collects information about whitebark pine regeneration, growth, and mortality across all forest types. This project uses FIA data to assess seedling densities, factors related to seedling presence, size-class distributions, growth, and mortality of whitebark pine trees in mixed-species stands throughout the US portion of its range.

Approach

  1. Identify all FIA plots with a whitebark pine component, which is defined as any plot with at least one whitebark pine tree, sapling, or seedling (i.e., live whitebark pines of any size or dead whitebark pines at least 5 inches d.b.h.);

  2. Assess whitebark pine seedling and tree density, by size class, among multiple forest types;

  3. Develop statistical models that identify site factors related to whitebark pine seedling presence;

  4. Quantify growth and mortality rates of whitebark pine trees of all sizes, among multiple forest types;

  5. Synthesize our results as a list of recommendations for managers who seek to facilitate regeneration and recruitment of whitebark pine.

Key Findings

Landscape-level forest monitoring data shows the following patterns in whitebark pine:

  • As of 2016, 51% of all standing whitebark pine trees in the US were dead.

  • Although whitebark pine occurred across 4.1 million ha in the US, the vast majority of this area (85%) fell within forest types other than the whitebark pine type.

  • Growth rates of whitebark pine trees are highest, and mortality lowest, at sites that meet the following criteria: low total stand basal area, relatively high whitebark pine basal area, and relatively high stem density of whitebark pines.

  • The lodgepole pine forest type represents a potential management target for silvicultural treatments (such as daylighting) that seek to facilitate the recruitment of whitebark pine seedlings into larger size classes.

  • The highest seedling densities occurred in stands dominated by lodgepole pine, and 83% of sites with whitebark pine seedlings present occurred in forest types other than the whitebark pine forest type.

  • Factors related to whitebark pine seedling density included cover of the understory shrub grouse whortleberry (Vaccinium scoparium), whitebark pine basal area, elevation, and seasonal temperature.

     

Publications

Deliverables

Goeking, Sara A.; Izlar, Deborah K.; Edwards, T.C. In press. A landscape-level assessment of whitebark pine regeneration in the Rocky Mountains, USA. Forest Science.



Project Contact: 

Principal Investigators:
Collaborators:
Deborah Kay Izlar - USDA Forest Service PNWRS
Thomas C. Edwards - Utah State University