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Kootenay National Park

Whitebark Pine: restoring a keystone species

Importance to Wildlife
Threats to Whitebark Pine
What is Parks Canada doing?

Whitebark pine is declining over much of its range, especially in southern British Columbia and Alberta, and the northern states. Its survival is threatened by the combined effects of blister rust, fire suppression and pine beetle epidemics.

Whitebark pine is found high in the mountains of western North America. Its range extends along the Rocky Mountains from the Peace River in northern British Columbia, south to Wyoming. It also grows in BC's Coast Ranges, the Cascades, the Sierra Nevada, and some interior ranges.

Whitebark pine occurs in high elevation forests in seven of Canada's national parks: Mount Revelstoke, Glacier, Jasper, Banff, Kootenay, Yoho and Waterton Lakes. It grows in mixed forests and on rocky, wind-swept areas where no other trees grow. Slow growing, a whitebark pine may not produce cones until it is 50 – 80 years old. This tree species plays a vital role in sub-alpine ecosystems as it helps stabilize steep slopes, influences the rate of snow melt, and provides food, cover and shelter for many species of wildlife. It is a keystone species: its loss would radically change the Rocky Mountain sub-alpine ecosystem as we know it today.

Importance to Wildlife

Whitebark pine seeds are about the size of a pea and high in protein. Not surprisingly they're an important food source for several wildlife species, notably the Clark's nutcracker, but also the red squirrel, grizzly and black bear.

Whitebark pine and Clark's nutcracker have co-evolved a mutualistic relationship: each species depends on the other for survival in the harsh, high elevation environment. Both have evolved complementary adaptations.

Whitebark pine cones do not open on their own for seed dispersal. Instead Clark's nutcrackers, using their long pointed beaks, break apart the large, purplish cone to pull out the seeds. To create a reliable food source to get them through winter, the birds cache the seeds. A specialized pouch under their tongue can hold up to 100 seeds, allowing them to carry seeds to caching sites. While squirrels cache whole cones in middens at the base of the tree, nutcrackers choose areas likely to remain snow free or windswept most of the year. Coincidentally these open, sunny areas favour whitebark pine growth.

Caching up to 15 seeds at a time just below the soil's surface, Clark's nutcrackers use adjacent rocks and woody debris to create memory maps that help them relocate the seeds when needed. Unlike squirrel middens, bears and other seed eaters are less likely to find small, widely distributed seed caches. Though one bird caches thousand of seeds each year, roughly half are overlooked on their return. Many of these seeds grow into pine seedlings.

Threats to Whitebark Pine

Fire Suppression

Whitebark pine establishes at an early stage in forest succession; the species is gradually replaced or succeeded by other tree species if disturbance is minimal. But natural disturbance events, like fire and avalanches, are the norm in mountain forests, constantly resetting the successional clock. When fire creates openings in the forest canopy, nutcrackers key into these areas for seed caching. Stimulated by higher light levels, overlooked seeds germinate, giving the seedlings a competitive edge over other conifers (cone-bearing trees) like sub-alpine fir and Engelmann spruce that require shade and greater soil moisture.

Historically, sub-alpine forest stands burned every 90 to 300 years in the Canadian Rockies. This natural fire cycle prevented forest fuels (living and dead wood) from accumulating and fueling intense, hot burns. Though large, high-intensity burns did occasionally happen, small, patchy low-intensity fires were most typical. Past forest management practices geared toward total fire suppression has reduced the number of open areas preferred by nutcrackers for seed caching. This has in turn reduced whitebark pine regeneration.

Insect Infestations

Fire suppression has also created older, even-aged lodgepole pine stands prone to epidemics of mountain pine beetle. While insect infestations are a natural disturbance and play an important role in maintaining biodiversity, epidemics fueled by fire suppression and increasingly, climate change can spread into higher elevation whitebark pine stands. Here another natural check, the immunity of healthy trees has been compromised; whitebark pine stands are already battling another stress.

White Pine Blister Rust

Besides the effects of fire suppression, whitebark pine faces another, perhaps more insidious threat. In 1906 a shipment of white pine seedlings arrived in New York from Europe; the seedlings carried Asian blister rust across an ocean to pine trees that had no natural immunity. Around 1910, another shipment of infected seedlings arrived near Vancouver, BC. From these two points, blister rust has rapidly spread.

Conifer forests are inextricably bound to thousands of species of fungi -- many essential to the decomposition process, many essential for conveying nutrients to conifer roots. Other fungal species are pathogenic and plague trees like colds plague people, occasionally having more significant impacts. In North America, blister rust has escaped the natural controls with which it evolved.

Of the five needled pines, whitebark is most vulnerable to the rust. Blister rust is now epidemic on this pine throughout its distribution in southern Canada and the northern states.

The life cycle of the rust is complex, skipping back and forth between its hosts: currant or gooseberry bushes, and five-needles pines. Infecting pines through the needles, the rust sends fine filaments into a tree's vascular system just beneath the bark. Two to four years later, cankers break out on the branches and trunk, typically girdling and killing the top branches where the cones grow. Suffering an impaired flow of nutrients, the weakened tree is more likely to succumb to pine beetle attacks, other diseases, or gnawing rodents attracted to resins associated with the cankers.

What is Parks Canada doing?

Parks Canada is evaluating the use of prescribed burns to revitalize this sub-alpine keystone species. Reintroducing fire to an area where whitebark pine is being overtaken and replaced by other conifers will help restore the health and distribution of this species. Planned or prescribed burns:

create more forest openings, thus increasing the number of areas favourable for seed caching by nutcrackers;
increase pine regeneration which in turn increases the chance of individual pines developing blister rust resistance; and
create a mosaic of forest communities, decreasing the proportion of continuous, older lodgepole pine stands, which are prone to pine beetle epidemics.

However, the positive effects of today's burns lie in the future. As a slow reproducer, whitebark pine is not likely to develop rust resistance across the population in time to counter loss of the species and the unique sub-alpine ecosystem it anchors. Identification, collection, breeding and planting of rust resistant seedlings are also long-term goals.

Parks Canada Research: regenerating a species

In conjunction with active management using prescribed fire, Parks Canada is undertaking long-term research to monitor and evaluate its success in restoring a healthy whitebark pine population and sub-alpine community. The information collected will help inform and refine ecosystem management practices not only in national parks, but across the greater landscape.

Banff National Park: Dolomite Pass Prescribed Burn

The Dolomite Pass prescribed burn, located near Helen Lake occurred in 1998. The total burn covered about 12 hectares (ha) [100 ha = 1 km ² ]. The objective of this planned burn was to create enough canopy openings to promote whitebark pine seed caching behaviour by Clark's nutcracker.

Research plots were established prior to the burn, half within the burn and half outside it. The plots outside provide a means to evaluate if the sites within the burn support increased seed caching behaviour and whitebark pine regeneration. Plots were laid out in mixed forest stands close to stands dominated by whitebark pine to ensure a nearby source of seeds for nutcrackers after the burn. The open patches created by fire must not only be favourable for seed caching but also for seed germination and seedling growth. On-going monitoring and evaluation of whitebark pine restoration will help inform and improve future restoration efforts.

Yoho National Park: Sodalite Creek Prescribed Burn

The Sodalite creek area, located in the Ice River Valley has been identified as a whitebark pine restoration site. Permanent monitoring plots have been established and a prescribed burn is planned for the area.

Kootenay National Park

During the summer of 2000, researchers collected data on whitebark pine sites that are similar in character (aspect, slope, elevation, etc.) but different in tree age. This information will be used to plan restoration efforts by helping to evaluate and identify site characteristics best suited for regenerating whitebark pine with prescribed fire.