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'Recipe for restoration' developed for endangered whitebark pine trees

Climate change is threatening endangered whitepark pine trees.

BANFF – From bears to birds, many animals rely on the nutritious seeds of endangered whitebark pine trees as a critical food source.

The Clark’s nutcracker, which is responsible for most whitebark pine dispersal and regeneration, uses its long, sharp bill to rip apart cones for the seeds to eat and store for winter and spring when other food is scarce.

“The Clark’s nutcracker is the only species that really hammers apart the cones so that the seeds are available,” said Canmore's Cyndi Smith, a retired Parks Canada conservation ecologist and whitebark pine expert, during a Bow Valley Naturalists’ presentation on Feb. 22.

“The nutcracker can put up to 150 seeds in their sublingual pouch under the tongue and then they fly off and bury these seeds in caches.”

A single bird can bury up to 90,000 seeds in a year.

“They’ll make these caches anywhere from a few metres away from the seed tree to 35 kms away,” said Smith, who is also a past director of the Whitebark Pine Ecosystem Foundation.

“Each bird, if there’s enough seed around, can bury 35,000 and 90,000 seeds in a cache.”

While the birds have a phenomenal memory for re-locating their seed caches, they do not find all of them.

“There’s been some very interesting studies to show how they basically triangulate using rocks and stumps on the landscape to relocate these caches,” said Smith.

“Of course, if you’re getting that many, there are times when they don’t retrieve them all, and those are the ones that can germinate to become whitebark pine seedlings.”

Squirrels and bears are also a cool part of the ecological relationship with whitebark pine trees.

Red squirrels go after the seeds, storing them in their underground middens. Even if they do not eat all of the seeds, the seeds are usually buried too deeply to germinate.

In many areas, including in several locations in Banff National Park, grizzly bears have learned to raid these middens to devour the nutritious seeds.

“The bears will come along, particularly grizzly bears, and they’ll dig into these middens and steal the cones,” said Smith. “They will dig down, even through quite a depth of snow to get at the cones, especially in the spring or in the late fall.”

Extensive research in Yellowstone National Park has shown whitebark pine seeds are a major food source for grizzly bears.

“It has shown how reliant a grizzly bear can be on whitebark pine seeds,” said Smith.

“In years where there’s basically a failure of the cone crop, there were a lot more incidents of bears at lower elevations getting into trouble around human food and garbage. They were not getting that resource they normally would from the pine cones.”

Black bears also love whitebark pine seeds. They don’t need to steal seeds from the squirrel middens, but they’ll often climb the trees to get seeds directly from the cones.

“In B.C., they’re finding quite a few places where grizzly bears are climbing into the trees and breaking off the branches,” said Smith.

“The branches fall to the ground and then the cubs can get at the cones and the bears go down and feed on the branches on the ground.”

While whitebark pine provides food for many animals and has an intricate mutual relationship with Clark’s nutcrackers, the endangered pine plays other important ecological roles, too.

The tree species helps retain snowpack at high elevations, which lengthens the snowmelt period. “Whitebark and limber pine do help to let the snowmelt move more gradually off the mountains through the spring and into the summer,” said Smith.

Threats to whitebark pine include white pine blister rust, which is a fungus introduced from Europe around 1910, and attack by native mountain pine beetle.

Wildfire is considered both friend and foe; it kills off faster growing conifer trees like Engelmann spruce and Subalpine fir that can choke out whitebark pine, but whitebark can also be killed by large, hot wildfires.

On top of all that, climate change interacts negatively with the other threats.

Higher summer and winter temperatures and reduced year-round precipitation associated with climate change can stress whitebark pine. As growing conditions become less suitable, the tree may run out of habitat because it is already growing at the upper limit of soil and nutrient conditions at high elevations.

“As we run through climate scenarios, some of these species may be getting pushed or trying to move further northward in latitude as well as upward in elevation,” said Smith.

“But of course, these species are at the treeline already … so it’s going to be hard for them to go much further up in elevation.”

As a result of all these threats, whitebark pine was legally listed as endangered under the federal Species at Risk Act (SARA) in 2012.

From there, monitoring and restoration activities have ramped up to save this iconic tree species, which can live for more than 500 years, with some individual trees reaching more than 1,000 years old.

Monitoring plots in whitebark pine stands in both B.C. and Alberta have been set up over the past 20 years to help with long-term research.

Brenda Shepherd, a Parks Canada conservation biologist based in Jasper National Park, said 50 per cent of whitebark pine are infected by blister rust, but this is highly variable across the range in Canada.

“About 20 to 30 per cent of trees are dead, though the cause of death can often not be determined, especially from long dead trees,” she said during the BVN presentation.

Shepherd said the infection rates are the highest near Waterton Lakes National Park and in south-eastern B.C., where most whitebark trees are infected.
“In some cases, almost all of the trees are already dead,” she said.

In contrast, the lowest rates of infection are in Banff National Park stretching towards the Columbia Icefield.

“In some stands I’ve been in, it’s difficult to find infected trees and most of the damage that you see on trees are from mechanical damage, from rocks or avalanches,” said Shepherd.

“Infection rates increase again, though, as you move north into the Athabasca Valley in Jasper where rates are about 40 to sometimes 80 per cent, and then decline again up in the Willmore.”

As part of what Shepherd calls a 'recipe for restoration', finding whitebark pine trees that are genetically resistant to blister rust is the critical first step.

“You’re looking in the most highly infected places to find those rare trees that have some level of natural resistance to infection,” she said, adding she’s heard estimates of only one in 1,000 trees have some level of natural resistance.

“This is quite laborious, walking around with binoculars looking and assessing each tree.”

After finding rust-resistant trees, the next step is keeping them alive, which is made even more difficult by the aggressive mountain pine beetle.

Chemical packets that either give off signals that a tree is already occupied by beetles or send out false signals that the tree is deciduous, not coniferous, are attached to rust-resistant trees.

Shepherd said these were applied during the recent five-year mountain pine beetle outbreak in Jasper.

“We reduced the probability of attack by 46 to 60 per cent,” she said. “During that time we lost 44 of our trees that we believe are resistant to blister rust, but we were able to save many more that otherwise would have been killed.”

The next phase in the restoration plan is collecting seeds from rust-resistant trees.

Staff equipped with climbing harnesses cover the cones are at the top of the trees with wire cages in June to protect them from Clark’s nutcrackers and squirrels, then collect the cones in late September or October.

“We climb the trees in spring because we need to protect the young ones with these mesh wire cages, otherwise the birds and squirrels will eat all of the cones before they are mature so we can’t just leave them,” said Shepherd.

The cone seeds are needed to grow seedlings in private nurseries.  

Some two-year-old seedlings go to a lab to undergo testing for genetic resistance to blister rust, which can take five to seven years.

“The seedlings are exposed to blister rust spores,” said Shepherd. “Through this seven-year process, they determine whether or not your tree indeed has a good level of resistance.”

In the intervening years, other seeds from the nurseries are planted back into the national parks.

“We can plant about 200 seedlings a day, whereas a production planter can plant 1,000 seedlings a day,” said Shepherd, noting they are planted in areas where there is a better chance of survival, such as recently burned areas.

“We plant them carefully. It’s taken so much effort to get out there and collect these seeds, they’re so valuable that we really want these seedlings to survive.”

To speed up efforts to save the endangered species, two seed orchards have been established in B.C. to essentially clone whitebark pine.

At these orchards, living branch tips from resistant trees may be grafted onto the stems of established trees to produce resistant seeds more quickly for restoration.

“Biologists would go and collect the very top leaders off of a resistant tree and those leaders would be grafted onto a similar species and planted into an orchard,” said Shepherd.

“That little tree thinks it’s 100 years old and begins to produce cones, as early as sort of a year after being planted.”

Approximately 68,000 seedlings have been planted in the mountain national parks.

“We’ve identified 440 plus trees – these are the trees we think are resistant based on our assessment in the field,” said Shepherd.

“Many of these have been sent into testing trials already and we’re waiting for the results. It takes many years, but we have 14 confirmed resistant trees.”

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