Is Fire Good for the Redwoods?

A friend asked me in a comment on one of my CZU fire posts whether fires were actually good for the forest. It’s a great question so I’m going to try to answer here where more people will see it.

Now, what I’ve got to say about this is my somewhat educated opinion, and I’m no expert so I welcome corrections. Also, I’m talking specifically about our coast redwood forest and not speaking about forests in general.

So, is fire good for our forest. Well, it depends. I think it boils down to whether the fire is a “normal” redwood forest fire or the kind of high intensity fire like the one we’re experiencing now.

In normal times, the redwood forest is very damp. During the rainy season, it’s obviously quite wet and the rest of the year heavy coastal fog blankets the forest. The redwoods catch the fog absorbing a bunch of it and also condensing and raining a lot down to the forest floor. The height of fire season around here is also usually a time of lots of coastal fog so if a fire does start, it doesn’t spread out and up quickly and it doesn’t burn with a lot of heat. This means that most of the redwoods easily survive the fire and can even benefit.

How do coast redwoods benefit from fire? One way is reproduction. Redwoods reproduce both sexually and asexually. Most of the time, the forest floor is so covered in duff and debris (and parasitic fungi) that seeds from sexual reproduction can’t really get down into the dirt to sprout. So, the redwoods reproduce asexually with clones sprouting from the existing root crowns, stumps, or fallen trees or branches. Eventually a (hopefully) low intensity fire comes through and burns some of the forest floor clearing all the duff and parasitic fungi and the redwoods can do more sexual reproduction. For diversity, we want both new trees and clonal trees so it is actually useful for for the forest to experience the occasional low intensity fire.

But the CZU Lightning Complex fire is not a typical low intensity redwood forest fire. Two factors seem to be the cause for an abnormally hot fire that spread out and up very quickly. The first is a longer term issue and that’s that it’s been a good while since the area experienced fire and so the forest floor is thick with fuel, the duff and debris that accumulate as the trees drop leaves and branches over the years and decades. The second factor is a shorter term issue and that’s that we went weeks without any significant coastal fog leading up to this fire and so the forest was all dried out. Combining those two factors and the duff and debris, and some trees, were primed to burn and burn hot.
So, are fires good for our forest? The simplest answer is yes, if they’re the right kind of fires.

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