High-Elevation Forest Monitoring

Whitebark pine trees on a snowy ridge in Yosemite National Park. Photo: copyright Michael Durham
Whitebark pine on Gaylor Ridge in Yosemite National Park.

Photo: copyright Michael Durham.


High-elevation subalpine forests define the upper limit of tree growth in the Sierra Nevada. While these trees intermingle with other tree species at their lower edges, at their upper limits, known as treeline, they usually grow in single-species stands. They must withstand harsh growing conditions, including cold temperatures, severe winds, and a short growing season. The two high-elevation species we monitor are foxtail pine and whitebark pine.

These trees are known as white pines or "five-needle" pines, as their needles grow in bundles of five. These pines play important roles where they grow, regulating processes such as snowmelt and stream flow and providing habitat and food for birds and mammals.

All western species of five-needle white pines are threatened by an invasive pathogen that causes the disease white pine blister rust. The threats of blister rust and mountain pine beetle coupled with warming temperatures and projected changes in type and timing of precipitation heighten the importance of monitoring white pine forests. Information about the health of these forests and how they are changing helps park managers work with partners within the region to plan for and address anticipated declines in these iconic forests.

A stand of whitebark pine growing in a rocky, rugged landscape, Kings Canyon National Park. Photo by Peggy Moore.
Whitebark pine in Goddard Canyon, Kings Canyon National Park.

Photo: Peggy Moore

Species Monitored

Whitebark Pine

Whitebark pine has a wide geographic range in the west, including in the Rocky Mountains, the Cascades, and the Sierra Nevada, where it reaches its southern limit near Mt. Whitney in Sequoia National Park. Whitebark pine occurs on both the west and the more arid east side of the Sierra crest in scattered treeline stands. The seeds of whitebark pine provide an important food source for many seed-eating birds and mammals. Whitebark pine is entirely dependent upon Clark’s Nutcracker (a medium-sized relative of the crow) for dispersal of its large wingless seeds. While severe declines in whitebark pine are occurring in most of its range, Sierra Nevada populations are still relatively healthy. However, in 2021, local scientists and park staff began observing whitebark pine dieback and mortality in Kings Canyon National Park. Since then, our forest monitoring crew started documenting additional areas of dieback and mortality of whitebark pine and foxtail pine in our network parks, often associated with bark beetles or occasionally with signs of white pine blister rust infection.

A person wearing field clothes and a pack stands on a slope observing scattered dead and live whitebark pine trees below her.
Forest monitoring crew member observing a mix of live and dead whitebark pine trees in Kings Canyon National Park.

NPS / Sean Auclair

Whitebark Pine Listed as Threatened

On December 15, 2022, the U.S. Fish and Wildlife Service (FWS) listed whitebark pine as threatened with potential extinction under the Endangered Species Act. FWS determined that the primary stressor driving the status of whitebark pine is white pine blister rust, a fungal disease caused by the nonnative pathogen Cronartium ribicola. Whitebark pine is also negatively affected by the mountain pine beetle, altered fire regimes, and the effects of climate change.

In 2022, Sierra Nevada Network and US Geological Survey partners received US Forest Service Forest Health funds to investigate the causes and document the extent of subalpine pine mortality in the network parks. Formal surveys of recent elevated subalpine pine mortality started in the summer of 2023.

Foxtail pine in the fog, on a rocky, steep slope in Sequoia National Park.
Unlike most other subalpine tree species that are reduced to sprawling, shrubby growth forms by the fierce conditions at treeline, foxtail pine always grow upright, producing a single stout trunk.

NPS photo

Foxtail Pine

In contrast to whitebark pine, foxtail pine has a limited distribution. It is endemic to California and is confined to two discrete regions: the Klamath Mountains of northwestern California and the southern Sierra Nevada. Foxtail pine nearly always grows as an upright tree (very rarely as a shrubby krummholz form), even on the highest, most windswept and exposed sites. These trees are limited to high-elevation slopes, ridges and peaks, typically growing in open stands that are almost purely foxtail pine with little other vegetation. Like the whitebark pine, foxtail pine provide important habitat and food for birds and mammals. The oldest known foxtail is over 2,000 years old. Both live and dead wood of this species can be dated to produce multi-millennial tree-ring records used to reconstruct long-term variations in climate.

Increasing Dieback and Mortality Observed

In 2022, our forest monitoring crew began documenting branch dieback and mortality of foxtail pine in areas they traveled to our white pines monitoring plots. They photographed and documented signs of mountain pine beetles on some of these affected trees, as well as signs of white pine blister rust infection, noted particularly in the Chicken Spring Lake area just outside of Sequoia National Park.

Map of Five-needle pines in western North America
Map of five-needle pines in western North America and NPS Inventory & Monitoring networks and parks where this monitoring occurs. Networks are: Klamath, Sierra Nevada, and Upper Columbia Basin. Parks include: Crater Lake, Lassen Volcanic, Yosemite, Sequoia & Kings Canyon, and Craters of the Moon.

Approach and Objectives

This monitoring project was developed collaboratively with the Upper Columbia Basin and Klamath Networks (see map to right). This collaboration will provide comparable data on blister rust infection rates and damage, pine beetle outbreaks, and tree mortality across a large region. Since the protocol was implemented, another network has implemented it: Mojave Desert Network began monitoring limber pine and Great Basin bristlecone pine in Great Basin National Park.

Randomly located permanent plots in white pine stands are monitored on a three-year rotation to obtain tree-and plot-level data. For white pine forest communities in Klamath, Sierra Nevada, and Upper Columbia Basin Network parks, we quantify status and trends in:

  • Tree species composition and structure
  • Tree species birth, death, and growth rates
  • Incidence of white pine blister rust and level of crown kill
  • Incidence of pine beetle and severity of tree damage
  • Incidence of dwarf mistletoe and severity of tree damage

Quick Reads

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    Publications and Other Information


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    The following reports are associated with this monitoring project or with closely associated research projects.

    Source: Data Store Saved Search 1004. To search for additional information, visit the Data Store.


    These protocol documents provide detailed information about how this monitoring project is conducted.

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    6 minutes, 53 seconds

    Follow along as we study the subalpine forests of the Sierra Nevada, including whitebark pine and the rare and long-lived foxtail pine.

    Last updated: September 1, 2023