Wildfires and clear-cutting in the boreal and arctic regions can release harmful gasses into the atmosphere. Experts in fluxes from taiga and tundra ecosystems share their first-hand fieldwork experiences in this episode about the atmospheric consequences of increasingly frequent and intensifying fires.
Transcript
Jess: Arctic forest and tundra fires are getting more intense and starting earlier. According to the World Wildlife Fund, there is enough methane stored in western Siberian peat to equal 73 years of human emissions, which would significantly warm the planet if released. Can you briefly explain your areas of expertise? What motivated you to study climate and how it relates to taiga or tundra environments? What inspired you to do field work in these remote locations?
Anastasia: My name is Anastasia Makhnykina. I'm a researcher from Sukachev Institute of Forest in Russia, in Siberia. I'm interested in seeing fluxes from the soil after different disturbances, especially fires. It's a big, big factor of controlling CO2 emission, such as clear cutting, which is pushing other factors. So, especially, now we have an intensification of fire activity due to climate change. The frequency [or time between events], it's getting smaller, of the intense fire. It could be related to human beings in some areas, also in taiga.
What we are looking for, we try to estimate the periods of recovery of these destroyed systems to the initial stage, to the initial CO2 emissions. So, we need to take the destroyed ecosystem and compare it to the natural one, the undisturbed ecosystem. And then, we can somehow estimate the period of recovery of this site based on the direct measurements of CO2 emission. Why I decided to start this topic, I was really interested in these factors because we know that disturbance is…It's bad. So we should somehow estimate how we can maybe mitigate, or how we can recover faster. Maybe we can do something, or not. That was the, kind of, reason why I decided to study these disturbance areas, yeah.
Jess: Anastasia, I remember there was a heat wave that affected Russia, and it was pretty serious because people didn't have air conditioning. Was that something that you noticed?
Anastasia: The most extreme, I remember from 2018, in our study site. Almost the whole summer period, I mean, it started in June, and the big rains that we observe in August, and it was the time in between that we got some different fire, different intensity fire, so ground cover - big intense fires. It was hard, I mean, hard to breathe, when I was there. At the time I was in the field, because usually during the summer I'm somewhere in the field station. That was hard. There was a moment during this time when the fire came to our station. It was quite close. We just helped other people, just to save us, to save our station. Fire fighters, they came and helped us. We saved the station, we saved this area, but the area all burned in 2018. It is a huge area. In the recent project, actually, we tried to estimate the emission after this. We still can see it. So, six years, 6-7 years, it's not enough to recover after this big replacement fire, and we still can see this.
Jess: So, a taiga is a snow forest.
Anastasia: Yeah.
Jess: Or basically, the environment is adapted to extreme cold and snow, and it's usually evergreens?
Anastasia: Yeah, we do have that. We have evergreen like pine, spruce, other trees. We also have larch, but it's further north.
Jess: So Jackie, a tundra is an Arctic treeless plain covered in mosses, lichens, herbs, or small shrubs with, typically, underlying permafrost.
Jacqueline: Yep, that's exactly it. And the permafrost distribution can vary depending on where you are along the tundra, anywhere from sporadic to discontinuous permafrost to continuous, meaning, it's everywhere regardless of where you try to probe down.
Jess: [It] should be everywhere.
Jacqueline: Should be, yes, or has been historically.
Jess: What is your area of expertise?
Jacqueline: I would describe myself as a terrestrial ecosystem scientist focusing on Arctic tundra ecosystems. I started working in the Arctic back in 2016, when I had my first field season in the Canadian Arctic. I've always been very outdoorsy and drawn to the natural environment. Being from Canada, the Canadian Arctic encompasses such a large land area of the country, but it's…it's an area that not many people have an opportunity to travel to and don't really understand, beyond pictures of a polar bear on sea ice. When I had the opportunity to go there during my masters, it was something that I jumped right into. It's something that has kept me motivated and inspired in science since.
Jess: Based on your research, what factors are contributing the most or worsening the atmospheric impacts of fire? For instance, are you seeing changes in higher stream flows, lower water tables, clear cutting?
Jacqueline: In Southwestern Alaska, a lot of the changes that we're seeing broadly are lengthening of the fire season. So typically, it previously started during the summer months: June, even earlier to mid-may. But now, it's starting to shift into the spring season due to lowering snowpacks and decreased snow cover. All that is tied back to the amount of sea ice present and overall warming in the Arctic regions. So, it's really all compounded together and interacting together to contribute to these worsening fire seasons in the area that I'm working out of.
Anastasia: So, we compare the impact of the clear cuttings and fires, and their both-combined effect. And, after this combined effect, these fluxes, they are smaller than just after fire, for example, for moss-covered fires. So, we just estimated it for pine forest with different ground cover, such as lichen and mosses. For mosses, those combined effects of two disturbing factors, it's the worst thing, but for lichens, it was the ground-intense fire.
Jess: Have you ever been there and seen the fire?
Anastasia: Yeah.
Jess: When there's lichen, is it smokier?
Anastasia: So, you need some special thing to breathe - a mask on your mouth and nose. We had some expeditions there, and it was hard. It was just 10 days, but hard days.
Jess: Do you see differences in the forests that have recovered, like more trees or a variety of different species?
Anastasia: You just need to find the areas with different times after fire. Let's say, first from one year after fire, 10 years after fire, 15 years after fire, 30 and more years after fire, and then you'll get this range. You can exactly find the place where, for our case after the big fire, it was 24 years after fire when the fluxes from the soil were comparable to the natural ecosystem. Also, you can see in the ground cover, it will be more or less recovered. For the trees, it depends on the fire. If it was a big stand-replacement fire there will be coarse woody debris around and it takes more time to decompose these big trees. But if it was groundcover, probably they are still alive, the trees, and maybe you'll get more trees like birch or aspen, and also marks of recovery.
Jess: What's causing the difference in birch versus aspen?
Anastasia: They are faster than pine at recovering after some disturbance events.
Jess: I've heard of what you're talking about, where you select for certain time frames. That's a really cool thing where you can go back in time.
Anastasia: It's called succession.
Jacqueline: A fire chronosequence?
Anastasia: Chronosequence.
Jess: Chronosequence, yeah, that's so cool. How is the fire season changing in the boreal and arctic, and what is driving those changes in fire intensity and duration of the fire season in those ecosystems? What does it mean for methane (CH4), CO2, and water vapor coming from those ecosystems? Conditions are getting drier, warmer, and those are creating opportunities for more out of control fires that were accidentally set or set naturally through lightning and can spread faster.
Anastasia: To have peatland can stop the fire. It will stop because the water. However, some fire, very fast, just runs through the cover of the peatlands and goes to another forest. That's also possible. It depends on the fire.
Jacqueline: Yeah, I would say in the tundra, a lot of the patchiness doesn't really work very well as a fire or fuel break, because at least in the southwestern part where I've been working with wildfire and fluxes, the landscape is so flat, and being a large coastal plain, the wind can really travel and carry that fire. And, the fuels are really readily flammable, so things like cottongrass and other sedges and lichen species that burn and combust really quickly. Back to the question driving changes in fire intensity, as I mentioned, the earlier and longer onset of the fire season and with tundra, some regions drawing out a little more in upland areas concurrently with wetting & wetland formation in the lowland areas.
Also, the northern encroachment of shrubs and other types of fuels for fire. You're having more to spark from, as well as the increased intensity and frequency of high-latitude lightning ignitions. That being said, what was interesting, at least for a paper that I recently put out last year, looking at a paired eddy covariance study of an unburned and a burned tundra fire that burned in 2015, we actually found that the net carbon strengths of both CO2 and CH4 was stronger. So, more uptake of carbon in the burned tundra relative to the unburned tundra, and this was within 7 years after the wildfire. So, relative to some of the boreal systems where you have stand-replacing fires that take many decades to recover from, the tundra systems are quite resilient in that the vegetation that seems to come up immediately post-fire is very good at sequestering carbon.
Maoya: Is there cooperation between restoration or conservation and fire management in these areas?
Jacqueline: In the tundra regions, because they are relatively still few and far between tundra fires and because there are many wetlands within tundra regions, it is still not something that has been fully explored yet. But, I'm sure in boreal regions in interior Alaska, for example, as a wildland fire management strategy, part of that is looking at protecting wetlands and using those to help mitigate and act as fire breaks.
Anastasia: It's too big [of an] area of forest, still. With the clear cutting, we have some problems, because after the clear cutting we have disturbed groundcover, not-good-for-timber industry trees - they just took some of the best ones. Also this area, it's getting more and more, let's say, sensitive to other disturbing factors. For the destroyed ecosystem, the other factors can be worse than for the natural ones. And the period of recovery for these sites, it's more than for a natural one.
Jess: What kind of tree species are ideal?
Anastasia: They're usually looking for the pine, good-quality pine.
Jess: How will fire and its climate impacts alter the environment by, for example, shifting species composition of shrub regeneration?
Anastasia: There is some opinion that it's also positive effects after the fire, such as the recovery, such as fast growing of grasses, for example, berries as well. As an ecologist, I'm interested in this emission part. For more, these “positives”, they are much smaller than the negative.
Jacqueline: Yeah, in southwestern Alaska, where I've been studying wildfire effects, berry picking is an important subsistence activity for the Indigenous communities there, the Yup'ik people. A lot of the low shrub species like the cloudberries, bearberries, blueberries lie in these regions, and these are areas that are being affected by wildfire. What was interesting when I went in 2022 and went to a fire scar 3 months after the fire, the first species that were popping up in this tussock tundra area were the cloudberries. So, it actually seems like the wildfire can expose some of the nutrients that were previously either locked up in permafrost or deeper in the soil horizon and allow for some of the more resilient shrub species to come back first, like cloudberries.
That being said, it does kind of shift the species composition of the shrubs that come back. So, where there might have been a mix of blueberries and cloudberries, there might be a dominance and cloudberries or vice versa. These would also shift the regions of where these berries are. A lot of that knowledge of where these locations are and where they're best, and the timing of it, is passed on through generational knowledge. The wildfires can then have subsequent negative effects on subsistence lifestyles in southwestern Alaska.
Jess: Have you seen, at any of your sites, collapsed permafrost, like a collapsed hole in the ground?
Jacqueline: Yeah, I've definitely seen some of those. And, I've definitely also seen people accidentally stepping into those if you don't pay attention to where you're walking, because there can be what we call thermokarst or permafrost thaw “features” in the ground. When you're walking on tundra, to the naked eye, it appears flat and seems like it's pretty easy to walk on. But, it's actually very much undulating because of the permafrost freeze-thaw and also, thawing small features. That all impacts the hydrology and the movement of water through ecosystems.
It's kind of a little bit like a chicken and the egg situation. Fire can exacerbate permafrost thaw and accelerate it. But then in regions where you do have slow permafrost thaw and changing aboveground species composition, then you're changing possibly the fuels and the types of vegetation that can then burn, or makes it more flammable, makes the landscape more flammable. But, it's definitely something that's hard to tease apart. We're still trying to work through that when we're looking at our flux data and our soils data, looking at whether it's a gradual permafrost thaw event that's causing increased nutrient inputs or whatnot, or whether it's linked to the fire and fire regenerating what's in the soils and increasing nutrient pools. The main thing is the acceleration of permafrost thaw with wildfire.
Jess: Fire helps the permafrost more, and then once it's thawed it's more prone to fire.
Jacqueline: And we're seeing that, too, in our empirical data- deeper thaw depths, increased nutrient pools in burnt tundra relative to unburnt tundra.
Jess: Monitoring wildfires can be very complex in the Arctic and boreal regions, because high temperatures from fire can destroy sensors in your study site. What are the challenges of monitoring the impacts of fire, for instance, collecting data in the remote wilderness of Alaska and Russia?
Anastasia: The main thing here, it's far. It's far from villages, from any sort of civilization. So, you need transport and you need some roads there to find a place. We can use satellites to estimate the fire areas. When you need to estimate something direct like we do, estimation of emission rates, you need to go there. You just need to go. In our region, it could take all the time just to visit this destroyed site.
Some other problems, but it's not really a problem, they live there, you know. We are there like aliens. If you don't really want to meet them, the bears, you need to be loud. They are smart, and they will not go to the people because it's dangerous. So, I recommend just to be loud in the forest. If you like, you can sing. Some bears, they destroyed our cables, from sensors. They just came, and they tried to find something, I don't know, and one of them, not destroyed, but damaged our equipment, this LI-COR chamber. We had some long-term measurements in one area for a long period of time. The bear came and then, just damaged [it]. Maybe just because also he found something unusual. We just recovered some stuff. Anyway, we had one situation.
Jacqueline: The region where we've been studying fires is kind of smack-dab in the middle of the Yukon Delta National Wildlife Refuge, so we're not very close to any communities. It's not really an area that a lot of people transit through either because the communities are so spread out. Even devoid of fire, there are many challenges of just doing field work in Arctic tundra. A lot of it is the remoteness, but bringing everything in that we need to do the science and to live at our field site for 2-3 weeks. Also, bringing all that out. Travel to our field site requires commercial flights out to the community and then about a 45-minute float plane ride to our base campsite, which usually requires at least three or four flights because we have to bring all our gear, water, fuel for cooking and things like that, in addition to all the science equipment. When we are doing longer or bigger overhauls of our tower equipment, for example, we'll also enlist the help of a helicopter so that we can sling some of our equipment from our base camp area to the towers.
The one thing about the YK (Yukon-Kuskokwim) Delta region is you can never really hike out to your field site as the crow flies because it's so dotted with fens or wetlands or other small water bodies. Your trip usually takes at least 3x or 4x as long because you're having to meander and cross around all these water features, which adds to all the fun, because you're also trying to avoid falling into these water features. Once in a while, you'll come across a beaver dam that was built over a stream, and you can use those to cross over. That's half the battle with working in remote areas.
A couple years back, our team at Woodwell was helping out in reinstalling this, but a flux tower of our collaborators actually burned down during a forest fire in the Northwest Territories. Batteries were charred, the whole structure had been compromised by the fire. Instruments were basically shot. Data loggers were all gone. The initial goal of that flux tower wasn't to monitor forest fires necessarily. It was an opportunistic sampling moment for that tower, and it was actually able to capture fluxes almost right up to the moment it burned down. A neat study. The SD card or the data card, it managed to stay intact somehow, some way. A Campbell system, I think it was.
We have all the small rodents that like to chew on wires: foxes, sometimes beavers, lemmings, and all those things. You'll find, like, a soil sensor chewed up, and then you have to trace it back to where it came from, and then try to figure out which one it corresponds to, and at what depth. That's half the fun.
Jess: What research question are you currently most interested in? What research questions still need to be answered to fully understand the impacts of fire on climate?
Anastasia: Now, we are interested in different disturbance factors. Fires and clear-cutting, in our region they are most popular. We need to compare this impact using direct measurements. Also, we will try to measure exchange fluxes, not just emission from the ground cover, but also some differences between the emission rates and respiration and GPP (gross primary productivity) of the ground cover there to estimate this balance in this layer, because the destroyed area is open space.
During my Ph.D., we tried to modify some exponential model of CO2 emission. We will try to use this model for disturbed areas, because it was made for natural ecosystems. We will try to modify the model. Other stuff, for our emission measurements, to combine them with eddy towers.
Jacqueline: Since starting our work with the wildfire scar that we're working in, we've gotten involved with the group that's been looking at the age of the carbon lost from these wildfires. So, using 14-C or radiocarbon to date the soils. We're still in the thick of examining some of the data and analyzing the data and putting it together with other sites, looking at how old the carbon that was lost from our site was, can tell us whether it's permafrost carbon, and how long it's been there, and what that means for the ecosystem. That carbon won't come back and it's also taken a long, long time to accumulate. [We want to know] what that means for the carbon balance and the tundra system, but also what that entails for the emissions and the uptake balance.
Yeah, interested in seeing what comes of that in terms of radiocarbon and then possibly down the line, maybe taking some greenhouse gas radiocarbon measurements to see the age of the carbon that's coming out in the gaseous form between the land and the atmosphere.
Jess Is it solid when you're doing the coring? Or is it really tough with the wetland soils?
Jacqueline: It really can vary depending on the time of year and antecedent conditions, whether you're coming right after a rainfall, but typically it does tend to stay quite nicely intact. And we've developed a pretty good technique of doing it with a soil corer and putting them into tubes. It can get pretty messy, but that's part of the gig. You can definitely tell you're in a peatland because it's very smelly.
Jess: So, is the best time of year winter, to do it?
Jacqueline: It's definitely cleaner, but then you run into questions of whether there's some seasonal variability in different things that you're looking at within the soils. So, we sample at different times a year. You definitely get nice clean cores in the winter, but it's also a bigger operation requiring a bigger rig in the summer. It's actually quite nice to sample in these peatlands because it's so organic-rich and peaty, so it's very soft. It's quite easy to go down all the way to the top of permafrost.
Jess: When you say rig, how long are these [soil cores] that you're talking about?
Jacqueline: For what we're doing, we're only sampling down to, say, 60 centimeters or so because we're interested in the active layer down to the top of permafrost. In the winter time, we're taking a big auger head with a SIPRE core, so that's usually at least a meter long. You can put on attachments after to allow it to go deeper, so it happens in chunks.
Maoya: Would you each share a little bit of what is really so special about getting this ground truth, and what people might not really appreciate that you would want to kind of highlight? What might be, sort of, underappreciated from people about the significance of going out in the field and getting this type of ground-truth data at specific locations? Especially since people are more and more obsessed with remote sensing and models, this is a special episode, to have both of you talk about your work in the field, and I want you to share why this is unique and important.
Anastasia: So, from the maps and the satellite data, you'll see some information about this area, of course. You can just use this information, but one thing which is really important from my point of view, you need to check because this satellite can show a not-really-exact situation. So, I have some experience with that. That's why we've decided to start to choose the site from satellite data. Then, we'll go to the forest, to the field, and [say] “okay, that's correct, and this one, that was not really true”. Borders, especially on the different forests on the different sites could be different, definitely.
Also, some people just use just the remote sensing data. They cannot really understand how it works, especially special features of this forest. [There are] some biological things which you just need to go and see and touch that will be better for your understanding.
Jacqueline: There's a lot of value in actually seeing your study site and touching your study site and living in your study site to really appreciate it. And I do work with some modelers, providing input data into models. Sometimes it's underappreciated that a nutrient point or a gas concentration is not just one number. It's the collection of flying into your field site, hiking another three hours, schlepping a lot of gear in really inclement weather to get that one point of data. Then, bring it back all the way and analyze it and run it through an instrument, whether it's like a gas chromatograph, or whatever. So, a lot goes into one data point, and even more goes into continuous data that needs to be maintained, especially in remote areas. When you're considering things like flux towers that run semi-autonomously, a lot goes into the data beyond just a fun trip out to the field.