Hacker News Reader

Comment by seadan83 | Hacker News Reader

To your last paragraph - it's not just dead wood that is the issue - right?

In CA, there is a lot of shrubbery that turns brown and grasses.

Second, (west coast) forests that have not burned in a while look like a big brick of plant matter. Mostly living, dense, from ground to 30 feet high of plant matter that will combust when it is dry, windy, and a fire that is plenty hot to even burn the roots several feet deep.

View on HN

You are correct that there is typically more to wildfires than dead wood, as in they typically start with dry pine needles, leaves, tall dry grasses, and spread quickly via slightly taller vegetation up to the trees. There is a science to when a prescribed burn can happen, and there are seasons that will not be right for any given location, so the burn is a no go. The conditions need to be just right (wind so it does not cross a highway / blow into a farmer’s livestock, humidity, time since last rain fall. This has a lot to do with the rate at which the fuel will burn. Fuel less than 0.25 inches will burn within an hour of the last rain and may burn for an hour after igniting. 0.25 – 1 inch 10-hour, 1 - 3 inch 100-hour, 3 – 8 1,000 hour. So, the smaller stuff burns quickly but may or may not start a larger hour fuel. Once the larger fuel starts is when it becomes a serious problem since now it’s hotter and hotter and eventually starts the living trees on fire. If you were to manually remove the 100 – 1000 hour fuels, some of which are dead trees still standing or held up by living trees (unable to fall / stuck sideways). The risk of an all-out forest fire starting would go down, but still not be zero (like you say in a drought / super dry conditions). In the end you can only reduce the risk, never eliminate it (short of clear cutting).

> big brick of plant matter

as an avid outdoorsman, please explain this. I’ve never seen a “brick of plant matter”.

I have seen overgrown shrubs and grass, but I’ve never seen the forest form a compressed brick of plant matter.

Also if plants are living they have water in them.

Big brick is a metaphor. Not compressed, but solid. Essentially enough plant matter that you can't walk through it, plant matter that is "solid" from ground to the tree branches.

For example, on this site: http://willhiteweb.com/washington_fire_lookouts/miller_hill/...

This image: http://willhiteweb.com/washington_fire_lookouts/miller_hill/...

I've seen unburned forests where that undergrowth is more dense and taller. The more time, the more that underbrush thickens and grows. Eventually there is an old growth forest and that stuff is shaded out. AFAIK that process plays out o er centuries. We're typically in the first century of growth for west coast forests (few old growth forests remain)

Compare for example with these images of a post-burn forest: https://www.nytimes.com/2018/09/25/nyregion/nj-pine-barrens-...

ah yea i think we agree then.

Reply on news.ycombinator.com