[gibspaulding]

> Native Americans conducted controlled burns for thousands of years until they started getting shot by forestry rangers a hundred years ago.

I've been thinking about this lately. My wife and I were reading about a study of an old growth oak - hickory forest in the eastern US which without human intervention is slowly transitioning to maple - beach forests. Presumably this is because it is no longer experiencing the burns it would have historically.

This transition is generally considered problematic since oak hickory forests supposedly support more biodiversity (and conveniently more profitable timber harvests).

But this all raises the question for me - how did this all work before any human intervention?

What's the natural rate of forest fires? We have species (such as giant sequoia) that seem to require fires, so they must have happened, but they must have been quite rare. Would there have been a truely horrible fire caused by lightning every 1000 years? Or perhaps would the megafauna that went extinct around the time native Americans arrived have played a similar role in clearing out underbrush while foraging?

Does anyone know of studies on this?

[sparker72678]

In the arid American West, at least, lightning caused fires are extremely common. Historically these forests were significantly less dense than they are after 100 years of human fire suppression, which meant less available fuel, and slower burning, “cooler” fires typically.

Here’s an article that talks about a few papers and some research as this relates to Arizona forests: https://azdailysun.com/news/local/setting-the-record-of-ariz...

[pixl97]

I'm on my cell so im not going to be a good help with info on this, but lighting induced fires are actually very common. So you're not talking every 1000 years, but closer to 10 or so. This leads to a much more patchwork design in the forests that leads to natural fire breaks.

[2devnull]

How could that explain places where lightening never or rarely occurs (coastal California)? I can’t think of any lightning sparked fires until a year or two ago. (Inland areas and the sierras obviously do get more lightening.)

[cmrdporcupine]

In the northeast / midwest / great lakes basin, mastodons definitely helped clear underbrush, from what I've read. Not sure how common they were through the eastern woodlands, but they were definitely here (and likely hunted to extinction). You can see plants that have historical adaptation to their form of browsing; black locust (Robinia pseudoacacia) has spikes along its younger, more tender branches that don't effectively deter deer but would be nasty on a trunk, for example.

First nations here also did controlled burns to open cultivation for maize agriculture and to encourage open grazing areas for deer.

Regardless, the forests that are burning in this case causing smoke in the northeast are quite far north, in Northern Quebec mostly, in what is boreal forest; pine & spruce mainly, on thin granite soils (Canadian shield).

[wefarrell]

I know that human expansion has decreased the number of large predators, which has increased the number of dear, who eat more young trees. If they have a preference for one type of tree over another that will certainly change the composition of the forest.

[seadan83]

Certain areas burn with differing frequencies (naturally).

Eg, coast range burns every few centuries while cascades and sierras it is more like every other year.

Sorry for no references, so please have a large grain of salt with those stated frequencies. IIRC those are the tight order of magnitude. Though, we are also talking much smaller fires compared to the mega blades we see today that kills everything rather than rejuvenates. These fires today burn everything and down to 4 feet under the soil. It's a different beast.

[lost_tourist]

Isn't like 99% of old growth forest in the eastern USA pretty much chopped down? I wouldn't think the trees now are much more than 30-50 years old.

[Kaibeezy]

  beech
  truly
  deer
  lightning

Sorry, was bugging me. Better now.