Yukon Wildlife and Wildfire
Wildfire can leave a landscape looking like a lifeless moonscape, but the forest isn’t dead. Beneath the blackened stumps and charred ground, new life emerges. Equipped with field guides, binoculars and a healthy dose of curiosity, Carrie and Karen, intrepid naturalists with the Government of Yukon’s Wildlife Viewing Program, trek through post-fire landscapes to see what’s sprouting, who’s passing through and why it all matters for the boreal forest.
Yukon Wildlife and Wildfire
After the fire: The plants came back
Use Left/Right to seek, Home/End to jump to start or end. Hold shift to jump forward or backward.
The boreal forest and wildfire tell a story of resilience that stretch deep in time. Wandering through a fresh burn, Karen and ecologist Jill Johnstone unearth clues about the forest’s future. They investigate tree corpses and itty-bitty plants and some amazingly fast-growing ones as well. In a few years, shrubs and small aspen will entice Moose, Black Bear and other animals, but these early stages of regrowth are ephemeral. Eventually, coniferous pine and spruce trees will take over, changing everything.
Show notes
Key topics
Succession (3:25)Takhini Bridge Fire (5:22)
Fire mosses and liverworts (7:35)
Organic layer (7:55)
Conifer seedlings (8:27)
Lodgepole Pine (9:25)
Twinflower and Fireweed (10:00)
Sedges (10:45)
Willow (11:58)
Shrub-dominated forest (13:00)
Moose (13:18)
Grey Wolf (14:42)
Black Bear (16:25)
Soapberry (16:50)
Ants (17:52)
Trembling Aspen (18:45)
Climax forest (21:00)
Interviews and audio clips:
- Jill Johnstone, affiliate research faculty with the University of Alaska Fairbanks and research associate appointment with Yukon University; specializes in post-fire dynamics of boreal forests.
- Tyler Ross, ungulate biologist with the Yukon Department of Environment
- Tom Jung, senior wildlife biologist with the Yukon Department of Environment
Episode artwork
Photo of Black Bear by Gordon Court.
Music credits
- Acoustic guitar melody #011 by GuitarStringTheory – freesound.org/s/735192/ – License: Attribution 4.0
- Acoustic guitar melody #005 by GuitarStringTheory – freesound.org/s/734305/ – License: Attribution 4.0
- Acoustic guitar melody #007 by GuitarStringTheory – freesound.org/s/734660/ – License: Attribution 4.0
Yukon Wildlife/Wildfire is produced by the Government of Yukon’s Wildlife Viewing Program and hosted by Karen McColl and Carrie McClelland. Sound design is by Mark Koepke. The podcast logo was designed by Dan Bushnell and Department of Environment.
The theme song, White Bark Pine, was written and produced in the Yukon by Dana Jennejohn and performed in collaboration with the Bennett Sun.
Learn more about Wildlife Viewing in the Yukon, including free events and publications.
Sign up for the Wildlife Viewing newsletter.
Follow Yukon Environment on Facebook.
Music and sounds credits – intro:
- Thunder/raven: Mark Koepke
- Fire ignition: Lighting a Fire by plasterbrain—freesound.org/s/534702/ – License: Creative Commons 0/
- Black-backed woodpecker: Aiden Place, XC488401. Accessible at xeno-canto.org/488401
- Red Squirrel: Backyard squirrel by SoundsLikeYukon—freesound.org/s/820322/ – License: Creative Commons 0/
- Woodpecker: SMA13024_20230620_051500
- Boreal Chickadee: Logan McLeod, XC610278. Accessible at xeno-canto.org/610278
I am quite intrigued or spellbound by the frequent observation of a fire and it looked so black and the life has been removed. And as human beings we think, oh, this is this was a catastrophic event. But from the perspective of the plants, it's not catastrophic at all.
SPEAKER_03I'm standing beside ecologist Jill Johnstone on a bluff above the blue-gray Tikini River, west of Whitehorse. In the distance, mountains rise above the wide valley floor, the glaze with the first traces of snow for the season. Below me, in the valley, there are trees as far as the eye can see.
SPEAKER_02In many cases, the same individuals, the same genetic individuals that were there, simply re-sprout and regrow, and then new individuals can come in from seed when otherwise they would have had no opportunity.
SPEAKER_03This forest, like all boreal forests everywhere, has seen fire before. But looking at it now, there's little evidence that the trees, mostly coniferous, spruce, and pine, are full-sized, about fifteen meters tall in the Yukon. To the lay person, it's a typical Yukon forest. But to Jill, an expert on the boreal forest, there's meaning behind what we're seeing.
SPEAKER_02To me, the boreal forest and fire is a story about resilience. And there's actually threads of continuity that stretch d into deep time that we can't perceive as humans but are very much real to the plant community.
SPEAKER_03That story about how a forest comes back from the dead and how it creates habitat for animals as it goes through this process is what we're exploring today. This is Yukon Wildlife and Wildfire.
SPEAKER_04In this series, we take a walk in the woods and look at how the forest changes and evolves after wildfire. At every step, we're on the lookout for plants and animals, big and small. And sometimes we ask passionate researchers and experts to chime in. I'm Karen McCall, and I'm Carrie McClelland. We're both naturalists with the Yukon Department of Environment's Wildlife Viewing Program. We don't leave home without binoculars and field guides. This podcast is for everyone who has burning questions about wildlife and wildfire.
SPEAKER_03That's good. I see what you did there.
SPEAKER_04I feel like here in the Yukon, we're pretty lucky. For most of us, walking in the forest is something we take for granted. I mean, even in Whitehorse, it's easy to get outside and into the trees.
SPEAKER_03Totally. But I know I'm guilty of kind of just looking at the forest like, oh, it's just another tree, instead of thinking, like, how old is this forest? Or when's the last time it burned?
SPEAKER_04Yeah, I'm I'm more often trying to remember where I put my bear spray or wondering where my dog went. But sometimes I come across a very old log in the forest that's been burned. And I wonder how long ago did a fire pass through here?
SPEAKER_03Yeah, once a forest gets to this mature phase where it has fully grown spruce and pine trees, it's not changing very quickly, at least not to our eyes. But the process of going from a fully burnt to the ground forest to a mature forest is called succession. This is how Jill Johnstone describes it.
SPEAKER_02Succession is an orderly transition of dominance from usually it refers to vegetation. So from one type of vegetation to another. And there's often a very predictable sequence.
SPEAKER_04Oh, I've seen Jill's name on papers and news articles about forest fires and ecology for, I don't know, years, decades. It's so awesome that you got to talk to her about this. I know. She's so knowledgeable.
SPEAKER_02My name's Jill John Stone. I'm a plant ecologist and I specialize in the post-fire dynamics of boreal forests. I have a research associate appointment at the Yukon University in their Yukon Research Center. And then I also am an affiliate research faculty at the University of Alaska in Fairbanks.
SPEAKER_03Jill talks about fire as resetting the successional clock for the area, which is a cool way of thinking about fire.
SPEAKER_04Oh, I've definitely been bushwhacking through forests that are in need of a hard reset. Just so much debris has accumulated on the forest floor. No sunlight is getting down there. It just feels clogged, like it needs a good clean out.
SPEAKER_03Fires do a good job of cleaning out an old forest and letting a new forest start over, which sounds pretty straightforward. But to really understand that process, I'm gonna go into the field with Jill. We're gonna go back to that burn that you and I visited in our last episode.
SPEAKER_04Uh yeah, the Tikini Bridge Fire of 2023.
SPEAKER_03Yeah, Jill and I visited this burn in 2024, so just one year after the fire. Something to keep in mind is that the observations that Jill and I make are quite Yukon specific. Boreal forests are characterized by short, cool summers and long, cold winters, but conditions are even more extreme in the Yukon than in boreal forests further south.
SPEAKER_04Yeah, I think you can apply some general principles elsewhere, but you can't take what you see here necessarily and compare it directly to what happens in the boreal forest in Alberta or northern Ontario.
SPEAKER_03Exactly. Plants and trees grow slowly here, and we have fewer species as well. A lot of things just aren't tough enough to survive this far north. Nice to see you.
SPEAKER_02Good to see you too. So where are we heading? We are going to the 2023 burn that is by the Eney Bridge on the Alaska Highway. About a half hour west. Great. All right. Let's go. Let's do it. The nice thing about doing the podcast is that I don't have to worry about how I look. Oh yeah.
SPEAKER_03Jill leads us up the small access road towards the burn.
SPEAKER_02So the first thing that we see as we're entering a burned area is usually the edge of a fire has a mixture of burned and unburned trees. And as we move along in, we can start to see more and more of the dead trees. And once we get all the way into a core part of the burn, we will just see black trunks of trees.
SPEAKER_03Black trunks, indeed. That's all that remains here on first glance. There's no sign of the shrubs or bushes of the understory of the forest we just walked through. That's all been burned away. It also looks like there's nothing growing on the ground at all. It's just dirt. Until we look closer.
SPEAKER_02We're looking at a little patch of scorched earth here on the ground. In post-fire succession, the first type of set of plants that dominates is actually the fire mosses and liverwart. And they are coming in in the very first season after fire.
SPEAKER_03Okay, so there's some moss here. Quite subtle. In a mature forest or fully grown forest, the ground is covered with several inches of plant material and moss. That's the organic layer. Fires typically burn off that layer, and that exposes the mineral soil below. You can think of the organic layer like an old rug in a house. Pull that up to reveal a hardwood floor below, the mineral layer, also known as dirt. But once exposed, this bare earth offers a fresh palate for plants.
SPEAKER_02There's a few patches of mosses that have come back in the year after the fire. I see a tuft or two of fireweed. And then here are the little lodgepole pine seedlings. There's quite a number of them. Here's one, two, three, four, five, six, and there's a spruce, seven, another spruce, eight. So we've got in just a square meter, we've got something on the order of eight to ten conifer seedlings coming back. Is that the spruce? Yeah, that's the spruce with the shorter needles. The lodge will look uh a little scraggly and weird, like tiny um eccentric pom-poms.
SPEAKER_03But that's their first year of growth. This scorched earth already has a lot going on, but it would be easy to overlook. Crouching down, I see the mosses, plants, and mini trees as Jill points them out. I take a photo of Jill pointing to a lodge pool pine seedling. When I look back at it on my computer later, I can't even see the seedling without zooming in. It's only about an inch high.
SPEAKER_02It'll be a couple of years, maybe three years, four years before they start to produce any branches and start to really look like something you could imagine is going to be a tree.
SPEAKER_03We only have one species of pine tree in the Yukon, lodge pole pine. That's why it's easier to be a naturalist in the north than other places. There's less names to learn. But if you did need to identify a lodgepole pine, its needles grow in bundles of two. What else do you see resprouting here?
SPEAKER_02Well, there's quite a number of species that you would find in the typical understory of the forest that have been able to re-sprout.
SPEAKER_03Jill says many of the first plants to grow back post-fire were present when the site burned and are regrowing from parts of the plant that survived below ground.
SPEAKER_02I'm seeing some twin flower, which is a ground shrub that's really common in the forest. The early growth of fireweed is usually a resprout plant from a plant that's been growing in the understory and not producing flowers, but then once it re-sprouts and grows in the burned forest, it can produce abundant flowers.
SPEAKER_03Fireweed may be present in a mature forest, but without access to the sun, it won't flower. There's got to be a metaphor in there somewhere. This aptly named plant is the Yukon's territorial flower. Charred forest full of its brilliant fuchsia flowers is stunning.
SPEAKER_02There's a whole bunch of sedges that are little grass-like plants that we don't really notice in the forest understory, but they are re-sprouting very effectively and they will form a dominant cover. All of these resprouts really help prevent soil erosion and they create vegetation that wildlife can use really quickly.
SPEAKER_03These plants that grow back quickly after fire are known as pioneer species. They will dominate the burn for the first few years post-fire. Are there seeds that blow in or that are like get pooped out by animals, that sort of thing?
SPEAKER_02Yes. So we right where we're standing in the year after fire, we might see maybe 10 different plant species. But that's going that diversity is going to increase over the next several years as things like animals are bringing in seed, uh, birds and mammals, as well as during the winter, a lot of these plants will shed seed and that'll blow in.
SPEAKER_03This early stage forest attracts animals that love grazing on these little nutrient-rich plants, like elk, deer, meadow voles, and all the animals that eat those animals. But change is inevitable in the forest, and the little plant or herbaceous stage is ephemeral, but pretty soon bigger plants overtake them. Jill stops beside a huge willow with multiple large burned stems growing up from the base. It looks dead, but dozens of new stems are sprouting up.
SPEAKER_02How old is this individual? You can easily imagine that it has successfully grown, been killed by a fire, resprouted again and again and again. Like the that whole mythology of the phoenix rising from the ashes is very true for these species that can regenerate from these underground plant parts. And it is conceivable that this individual established in this location thousands of years ago and is just continuing along, which I find really remarkable.
SPEAKER_03That is remarkable, and something I'll try to appreciate the next time I'm bushbashing through head high willow, which one might be doing in this forest several years down the road, when this willow and its kin fill out the understory. In ten years, this burn will look very different.
SPEAKER_02And so we move from an herbaceous phase into a shrub-dominated stage, and a lot of willows, and maybe some alder or evergreen shrubs if you're in a cooler part of the landscape.
SPEAKER_03In the shrub-dominated phase of the forest, berry bushes and willows shine. Unlike the lonely lodgepole pine tree, there are more than 40 species of willow, and they're diverse. Some are less than 10 centimeters tall, while the scowler's willow grows up to 9 meters. When a forest reaches this bushy phase, it will attract animals that like to eat and take shelter in shrubby habitats. Like the Almighty Moose, who can eat 19 kilograms of food a day, about 40 pounds.
SPEAKER_01By far their favorite food is willow. And then beyond that, they will eat other tree species, so birch, aspen, and kind of these earlier ex-sectional um species that we do find in birds.
SPEAKER_03My colleague Tyler Ross knows moose. He's an ungulate biologist with the Yukon Department of Environment. He says in the spring and summer, moose target the fresh buds and leaves.
SPEAKER_01Those are by far the most important in terms of like nutrition. They contain lots of minerals, calcium, potassium, magnesium, all those important things. And they're high in protein as well. Then when the fall and winter come, obviously those those leaves drop off. And so then they're switching to eating the more of the woody stems of those plants.
SPEAKER_03It makes sense then that moose would favor areas with lots of shrubs and young trees, but moose habitat actually varies quite a bit by the season. Tyler says in the spring and summer, they're often found close to water, as they also eat aquatic plants. Fun fact, moose can dive underwater to pull up pond weeds. After mating season in September and October, Tyler says these long-legged animals often move up to the subalpine where shrubs are abundant and predators are fewer. Wolves are the main predator of moose in the Yukon. It's fairly common to see wolf tracks in the mud or snow, but spotting this elusive canine is much harder. By November, when Tyler and colleagues are doing aerial surveys, he says they typically spot the greatest number of moose in wildfire burns.
SPEAKER_01Usually within the 10 to 15 years old, like that's the sweet spot in terms of um where we kind of find the moose. And again, that's because you're seeing lots of these shrub species in those areas where they like to concentrate and feed.
SPEAKER_03But as Tyler says, there's no guarantees in nature.
SPEAKER_01Not every burn is the same. And so while generally burns are great habitat for moose and these other ungulates, um, there are often cases where a forest will burn, then all of the trees get blown down, and you have just this cacophony of kind of blowdown, and it makes for really difficult travel. And so actually, those burns, which could be the same age as say like a one that provides great habitat, you'll find virtually nothing in there just because the travel is so difficult and there hasn't been a great opportunity for vegetation to grow in those areas as well.
SPEAKER_03I've tried to hike through forests like that. I don't recommend. Another animal, though, that might make its way into a recent burn is a black bear. These opportunistic foragers are mostly vegetarian and have a hugely varied diet, but also have some staple foods. In the spring, they predominantly eat green plants and grasses, like one might see in a fresh burn. In the fall, their main source is berries, like one might see in a shrubier forest. Bears can throw back thousands of berries in a single feeding. In the Yukon, a bear favorite is soap berry, which I've heard called buffalo berry in other places, or shepurdia canadensis, if you want to get technical. This medium-sized shrub offers good value for bears because it's often densely packed with red berries. Here's another colleague, Tom Jung, senior wildlife biologist with the Yukon Department of Environment.
SPEAKER_00Absolutely. You'll start seeing bears move into uh burns, you know, sometimes right away, uh because they'll be following species like elk and things in in areas where where they overlap, but also they very much will eat lots of things, as we know of bears. So they're attracted to the gramnoids, the grasses. But as it gets shrubbier and we start getting uh uh shrubs that produce berries, uh like soap berries, they absolutely uh will gorge on those a little more in the fall. Uh but uh definitely bears will move in as uh as the forest gets a little bit older. And also as the forest uh gets a little bit older after the fire, it's not just the berries, but some of the trees start to fall down, start to decay, and bears will come in and they'll eat things like ants and other uh insects and larvae that they find in dead wood. So there's a variety of food sources for bears uh in that intermediate stage of a forest regenerating.
SPEAKER_03It's understandable why bears are such flexible eaters. They have just six months to eat enough calories to get them through their long winter slumber. Their habitat is also varied. They live in both coniferous and deciduous forests, but do a lot of their feeding in open areas like meadows and burns. Oh yeah. In about 20 years, the 2023 Tikini Bridge burn will transition again as it takes on the characteristics of an aspen forest. Back in the burn with Jill Johnstone, there are already clues to that.
SPEAKER_02Okay. So we're approaching the aspen stand, and we're still about five meters away from these aspen trees, but you can just see all the stems that have come up. These are all young aspen that have re-sprouted from underground roots.
SPEAKER_03These underground roots allow aspen to grow back much quicker than pine and spruce trees that have to grow up from seed. This is aspen's superpower for regenerating after fire. Can you smell that? I can smell it. But I was recently sick and I feel like I haven't regained my full sense of it.
SPEAKER_02There's sort of a sweet sense with a little bit of putrefaction in there. And it's the it's the aspen leaves, they are so packed full of sugars that as they decompose, they almost ferment. If you walk through these stands just after the leaves have falled, you can smell it. It's it almost smells a bit like a sewer or something because the decomposition is happening so rapidly.
SPEAKER_03Oh, de sewer. Jill picks up a leaf bigger than her palm. Oh, these are the aspen leaves of the suckers. Yeah. They're massive.
SPEAKER_02If you look at one of these leaves, it's probably about five times bigger than the typical leaf that you'd see on a mature tree.
SPEAKER_03Jill says these little suckers are drawing on all the stored sugar of a larger tree, acting as photosynthesis machines. And the leaves aren't the only supersized parts of these trees. These one-year-olds are already chest high on me.
SPEAKER_02These suckers can grow very rapidly. We're standing next to one that's already kind of a meter and a half tall, and there's a lot of them. That's just a single year of growth. So normally, if an aspen started from seed, it would probably take three to five years to reach a similar height. So it's a tremendous advantage to be able to grow back from these roots.
SPEAKER_03So comparing that to the large mole pine, which is like an inch tall, not even, and then these aspen shoots, it's yeah, it's amazing. When these aspen eventually get to be full size, they will remain the big kid on campus for a couple of decades, until about 40 years post-fire. Then, just like the plants and the grasses and the shrubs and the willows before them, aspen too will be outgrown, either by pine trees or spruce trees, or both. These coniferous trees are much slower growing but will catch up eventually. And they cut the aspen off from the sun, which signals the curtain call for leafy trees. Spruce are considered a climax species in the boreal forest. Once established, a spruce forms Will endure indefinitely until the forest burns again or another major disturbance takes them out, like a flood or widespread disease. That should be at least a few decades away, though, for this forest.
SPEAKER_02I'm trying to walk on what's left of the vegetation.
SPEAKER_03On our way out, Jill and I carefully pick our path around a few greasy sections of soft mud that has thawed in the fall sun. She bends to pick up a leaf below a mature aspen tree. It's a fraction of the size of the ones produced by the saplings.
SPEAKER_02Yeah, like you remember that aspen leaf we picked up? Yeah. Compared to this? Yeah. Yeah. Just phenomenal.
SPEAKER_03Back at the office, I regale Carrie with stories of all the things Jill showed me. I loved seeing the difference between the aspen trees and the spruce trees. The spruce and the pine trees were like itty bitty, like an inch tall, and then the aspen trees were a meter and a half tall. So the difference was like the aspen were on steroids. And the leaves, too, of a new aspen are like huge compared to the leaves of like a mature aspen tree. So just seeing those differences was really incredible.
SPEAKER_04That's really neat. And I I'm so jealous you got to go out there with Jill Johnstone.
SPEAKER_03Yeah, it's really cool seeing succession in action. Like we learn about succession in school and how the forest changes, but to actually go and have boots on the ground and see what's growing back is much different. Did uh did Jill have any tips or takeaways from your time together? Uh she said you can approach burns like a detective. So look at what was growing before there was a forest fire to predict what plants are gonna grow back.
SPEAKER_04Okay, wait. So she's saying look at the corpses of the trees and presume that that is what will grow back.
SPEAKER_03More or less. Of course, there are a lot of factors like the nature of the fire. So how hot did the fire burn? If it was a really hot fire, then it might have killed a lot of the roots in the ground, which means that things couldn't grow back from roots. They'd have to rely on being transported in by seed, which would change what's able to grow and when. All right. I understand. The cool thing though about the Tikini Bridge fire burn is that it's so close to Whitehorse that uh it's a place that we can go back to every year and just see how it's changing.
SPEAKER_04Oh yeah, we definitely definitely go back to a fire in the first few years because that growth is so dramatic. Uh we should we should do like a wildlife viewing public walk there. Absolutely, we should.
SPEAKER_03Okay, so where to next? Next episode, we're going to go to the Fox Lake burn of 1998.
SPEAKER_04I love the Fox Lake burn. When I first arrived in the Yukon, it was just a sea of purple and pink fireweed. And I love driving that section of the highway because you can see such dramatic changes in the forest.
SPEAKER_03Yeah, I'm stoked too. Get it?
SPEAKER_04Oh, it's a oh, I'm still like a fire. Oh, okay. Thank you. Thank you for that. That's that's great.
SPEAKER_03Mixing and sound design was by Mark Kepke. Our theme music, White Bark Pine, was written and produced in the Yukon by Dana Jenijon and performed in collaboration with The Bennett Sun. There are no White Bark Pines in the Yukon, but you already knew that. This song was inspired by the White Bark Pine that survived the 2013 Rim Fire in Yosemite National Park, California. To learn more about wildlife in the Yukon, go to yukon.ca slash wildlife viewing. You can download guides, posters, and resources and find out about free walks and talks. If you enjoyed this episode, please subscribe and share it with everyone you know who appreciates wildlife. Thanks for listening. See you on the trails.
SPEAKER_05For my home.