What adaptations would a tree need to survive an area with monthly fires?

Question

Imagine a plain made of tall grass that sways in a gentle breeze. Everything is a deep green and there is a riot of life sprouting from the black ground. A few days later, the grasses turn brown and the animals burrow deep underground. Another day later and an inferno sweeps through the area, completely burning all of the grass and leaving only ash in its wake. The grasslands regrow from their roots or the seeds they dropped and have adapted well to the season cycle, but how would the trees survive?

This biome would look like a savannah, so the trees aren't very dense, but they are bordered by grass. The grass grows very dense and burns hot. The fires sweep through about every month, and an area of grass probably burns for around 5 minutes. On earth, natural fires can reach 800 C, which is probably the ballpark of what these fires would be at.

I know redwoods store water in their bark, but there isn't as much water in the savannah as there is in redwood forests, so I don't think that would be a complete solution.

So the question I have is what is the main adaptation that trees(or tree-analogs) would need to survive and thrive in this climate? Thee trees are carbon-based, and the solution also has to work for saplings of the tree otherwise, the species would just die out.

There are a few questions about fire and plants, but none that cover this exactly. This question deals with what a plant would need to not catch on fire: Fireproof Plants

This question deals with a flash fire(conclusion, no effect): Fire Resistant Flora

Answer 1

The roots do not die.

This is one way real fire resistant things persist - like your grasses. A bur oak or cork oak can survive fire because they just do not burn; they have fireproof bark. But they need to grow that bark first and a fire every month is not long enough for a tree growing from seed to grow a fire resistant bark.

The trees in your world are a clone - like Pando the clonal aspen grove. or a grove of bamboo. The root system of the grove extend great distances underground. When a new trunk shoot is sent up (right after a fire) the tree has the resources of the entire clone to tap. The new tree grows preternaturally fast and builds up its bark armor in the few weeks it has before the next fire. These trees are tall and thin because if they can get their leaves high enough those might not burn in your monthly fire; there cannot be that much biomass from a month of grass and so probably they are not that hot.

Dispersal of trees happens during storms. The tall thin trunks can break in the wind and tumble away. They take root where they land.

Answer 2

There are locations on Earth that are regularly swept by fires so this type of environment is entirely possible. However if you are looking for something slightly different then how about this:

The established trees are fairly resistant to fires as they have very thick bark that does not burn well so the main issue is with saplings. In this world the trees propagate by sending up large thick branches straight up into the air terminating in a very large seed pod that gets bigger as the branch extends. Eventually the weight of the pod bends the branch downward until it touches the soil and at that point it takes root.

Once rooted in this way the arch of branch connecting the main tree sprouts branches of its own growing straight up which are already above ground level when they start. Eventually when the “sapling” is well established the arch breaks in the middle and there are now two trees.

Answer 3

If some sort of a flame sweeps through "monthly", you need something that grows bark at a tremendous rate. Which is not impossible. Some bamboos have been observed to grow at up to 91 cm (0.91m, or 35 inches) PER DAY, according to Guinness Book of World Records. So for a hypothetical plant, it is NOT hard to imagine that it can grow a layer of bark that can be burned away and it still survives. The problem is how would such a tree grow in girth, so it can grow taller.

Another adaptation could be to grow fire resistant or fire-proof bark, along with fire-resistant leaves (maybe with extra moisture?) that would burn off the leaves but leave the trunk and branches mostly intact for regrowth.

Third could be just stay smaller, close to the ground like a brush, that grows roughly globular or hemispherical so the central trunk survives even if the outer layers burned.

I guess the problem I have with a "monthly" scenario is the growth rate of these plants must be tremendous, to grow a new set of leaves every month, rather than every YEAR like Terran plants.