Surprising effects of fire in North America's boreal forests

[Glenn MacGrady]

"Historically, fires in North American boreal forests have led to coniferous trees being supplanted by deciduous trees, which are faster growing, take up more carbon and reflect more light, leading to cooling of the climate and decreased likelihood of fire.

"The study, led by Northern Arizona University and published today in Nature Climate Change, found that surprisingly, while forests do become more deciduous, they don't stay that way; a few decades later, the same forests gradually start to shift back toward coniferous trees."

New study shows surprising effects of fire in North America's boreal forests

A new study, using a first-of-its-kind approach to analyze satellite imagery from boreal forests over the last three decades, has found that fire may be changing the face of the region in a way researchers did not previously anticipate.

phys.org

 

[tketcham]

Interesting study. I could see how increased reproduction of willows, birches, and aspens in those big burn areas might provide additional forage for beavers and moose, increasing their populations. But there's likely to be a decrease in the flora and fauna that are associated with coniferous forest habitat. Winners and losers is the name of the game with most large-scale disturbances.

 

[yellowcanoe]

Jackpine forests require fire for the cones to open and the pioneer species of aspen willow and fireweed provide shade for the germinating seeds. Over time these die back and the jackpines are standing on their own. I am not sure what is new about this study but the variables of scale and climate change might be different.

 

[memaquay]

Not sure why the findings are such a surprise, Yellowcanoe hit the nail on the head, after fires, the hardwoods always come up first, but are eventually supplanted by the conifers. This is the natural cycle up here. The only major change up here has been the active suppression of hardwood trees on new cutovers so that the human planted conifers can more rapidly establish themselves, for the future machine led slaughter 30 years down the road.

 

[jdeerfoot]

Read Fire Weather by John Valliant, published May 2023. The book is about the catastrophic wildfire which destroyed Fort McMurray Alberta in May 2016. Much of book summarizes the science which describes the reasons the wildfire became so severe.

 

[tketcham]

Not sure why the findings are such a surprise

yellowcanoe:

I am not sure what is new about this study but the variables of scale and climate change might be different.

It's not so much a surprise that hardwoods are the pioneering species after a fire but the interesting part is that with the earth's climates warming the response of boreal forest conifer species may be inhibited by a warmer climate, more conducive to maintaining deciduous species for a longer period of time. Here's one article that shows a trend of increasing deciduous occupancy in northern latitudes; i.e., hardwoods are moving northward.

https://esajournals.onlinelibrary.wiley.com/doi/10.1890/ES14-00111.1

 

[BWCA66]

Not always true, in the BWCA the last couple of big fires have created jack pine forests that look like they are a nursery,

 

[tketcham]

Not always true...

That's nature for you. The diversity in plant communities, the mosaic of fire effects and the variability of ecological responses to disturbance is going to result in a range of outcomes. What the articles show are trends. And as pointed out in the climate shift article, there were noticeable differences in the responses of the tree species they studied.

 

[memaquay]

Not sure if it is related to climate change, but we have a new invader up here, a pine beetle that only targets jack pines. Anyone familiar with the spruce bud worm will know what vast tracks of dead, orange needled trees look like. This new pine beetle is doing a similar thing to jack pine stands in our area. MNR is unsure of what approach to use on them, they are doing some test blocks at the moment, studying the effects of spraying as opposed to letting nature run its course.

Other indicators of climate change in our area are new animal and bird species. I saw my first turkey vulture around 2010, and since then they have become quite regular. Pelicans arrived around the same time, and have become quite a concern to the local fisherman. The one that concerns me the most is the recent incursion of deer. North and North east of Thunder Bay has always been deer free, and hence, tick free. But the deer are moving in now, and bringing ticks with them. They also bring brain worms, a parasite that they can live with, but which destroys moose.

And of course, there is the water level thing. A buddy of mine who was in management of forest fire suppression in the area told me that we would need three really wet summers to get the water table up to where it should be. This past summer was one of the worst forest fire summers we have had. Active suppression of fires has had to be re-examined, due to the shortage of labour and the number of fires. A huge fire up on the north side of Ogoki Lake was allowed to burn unchecked all summer.

Interesting times!