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The setting is Earth, millions of years in our future. In this setting a species of tree has made an evolutionary leap, allowing it to bypass the water transport constraints currently thought to be the primary limiting factor for tree height in extant species. This leap occurred roughly in our 'present day', so this new species of tree has had millions of years to refine and perfect this newfound ability, as well as allowing it to spread to new niches where it hadn't previously been able to compete. Spreading to new places will allow it to eventually colonize areas where near-ideal conditions exist (weather, water availability, nutrient availability, etc.), allowing it take full advantage of its new height reaching abilities.

The exact nature of this evolutionary change are a subject for a separate question.

For trees (in many, though not necessarily all, environments), genetically taller individuals are often evolutionarily selected for, since height means more access to light. Given that the previous water transport height limit is no longer a factor, genetically taller individuals in this new species, which already had better reproductive chances than their shorter neighbors, will be able to outcompete their neighbors much more significantly. This will provide evolutionary pressure to drive the new species toward taller and taller individuals. However, the new species is otherwise composed of the same stuff as it's evolutionary ancestor (other than the newfangled water transport imrpovement). For the purposes of this question, the change does not improve, nor detract from, the structural integrity of the rest of the tree's composition, except as new height/weight/leverage and similar considerations are involved, the wood itself is otherwise unchanged in this regard.

With this new freedom to reach new heights, and the time to do it, how tall can a tree get?

Obviously, I don't believe that removing that one limiting factor will suddenly allow trees to grow arbitrarily tall. Surely they will encounter some new limitation.

I conceived of this question from a 'square cube law' and 'structural integrity of living wood' perspective. My guess is that the next limiting factor they encounter will be related to structural integrity of the living material of which they are made. This could include things such as compression strength to hold it's own weight, or flexibility vs rigidity issues to flex in the wind without breaking now that much longer leverages are involved, or related issues.

However, I accept the possibility that 'structural integrity' may not be the next limiting factor, and welcome answers that identify and use some other limiting factor I hadn't considered. In that light, please assume that any changes to climate, atmosphere, sunlight intensity, gravity, and other environmental factors that are certain to change over the course of millions of years, have a negligible effect on this species, at least regarding its ability to reach record heights. Let's not get bogged down in "what else might change in that time?", and stick with "this one thing changed, so what's the new result?"

This part of the EDIT is to address concerns regarding lack of focus on the question:

My original wording of the question included this:

"While not strictly required, I suspect best answers will be based on a species that is currently one of the tallest species (redwoods, yellow meranti, mountain ash, coast Douglas-fir, etc). How tall will this new species of tree be before it encounters that limiting factor, whatever it happens to be? (bonus points for identifying the next limiting factor)"

This led to concerns about failing to identify a specific species of tree in my question. However, the question is about what the new height limit would be for trees in general, which is why I intentionally didn't specify an origin species. The original water transport limitation applies to all current species, and whatever factor produces the new height limit should, in theory, also apply to all species (though, like the current water transport limit, relatively few species would challenge that limit). The list of already very tall species was based on my assumption that these species were already challenging the current limit, and so are among the most likely to push past it, given the opportunity, and challenge the new limit.

Whatever that new limiting factor might be, some species will have a head start, so to speak, in achieving new record heights, since they will already have better form factors or strength characteristics that will be particularly suited to going beyond their current heights. Unfortunately, I don't know which species that might be (included in my list or not). Limiting the question to a single origin species will not necessarily yield the answer to the question "How tall could 'trees' get? in this scenario, unless I accidentally (miraculously?) stumbled on to the species that is already best suited to it on my own.

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    $\begingroup$ please explain how your needs are not met by the many existing questions about tree size. $\endgroup$
    – John
    Mar 9 at 0:45
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    $\begingroup$ The question listed as a duplicate is very obviously not a duplicate. That question asks about unmodified trees. This question explicitly asks to disregard the limitations related to water transport; basically this question asks how high can we build a building out of wood. $\endgroup$
    – AlexP
    Mar 9 at 2:05
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    $\begingroup$ @AlexP agree it is not a duplicate of that question, rather it is a duplicate of the world tree question also linked in Gault Drakkor's comment. $\endgroup$ Mar 9 at 2:46
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    $\begingroup$ This Q is in the VTR queue, but I can't VTR. It doesn't matter if it's not a duplicate. This is a badly formed question. What is it you really want to know? What the possibilities are that can limit tree height? (like the compression limit of the wood?) That varies substantially by the type of tree - which you don't identify. Ask just one question (needs more focus), identify the specific tree, where it's growing, and the details about the environment (needs details). Remember the help center says Qs "must be specific." $\endgroup$
    – JBH
    Mar 9 at 4:59
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    $\begingroup$ You made the Q worse by adding more text that said the same thing as before, and then rationalized why you shouldn't make the question better. Trees are just tall bushes, so almost every woody plant on Earth qualifies for your question, making it impossible to answer (aka, a percentage increase on average across all species of tree?), and by not defining the nature of the limiting factor, you're still asking two questions (what's the limiting factor and how high would the tree get because of it?). Identify the target tree, identify the limiting factor, reduce the question to two paragraphs. $\endgroup$
    – JBH
    Mar 14 at 4:52

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Timber strength limit is about 100 MPa. Timber density when wet is about 1000 kg/m3. At 1m hight stress will be 0.01 MPa. Thus height limit is 10 000 m. This is assuming either no wind, or cube tree. Elongation 10, that is dia to height ratio, would limit max height to just about 1000 m. Giving half the mass to leaves to live will bring it down to 500 m. leaving some safety factor so that errors are allowed, branching is possible, wind resonance is tolerated, small earthquakes are ok... leaves 250 m or so.

Trees are actually pretty close to a limit of what they can be, as you start to account what they need to endure, and what competition leads to.

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    $\begingroup$ This assumes no taper. Real world trees have taper. $\endgroup$ Mar 28 at 3:48
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To become structurally stronger than they would be by themselves, trees would likely 'lean' on each other for support, and would gain strength as they get larger and more intertwined. Of course, the lower levels would become compressed, and the ground the trees would be growing on would be themselves. The height of the tree now also depends on the philosophical question of whats tree and whats not, that is: is the tree under the ground part of the height of the tree above the ground, if the tree is the ground?.

However, the planet has limited resources, and could only produce so much wood.

The largest limiting factor for the trees now is carbon dioxide, which they would quickly run out of unless some other force were to release some large portions of it from the reservoirs of coal and oil in the ground(makes me think of algae blooms and dead fish...).

So they can only grow until they run out of source material.

But also more oxygen produced by the trees could create a more volatile atmosphere, which would result in more forest fires before they run out of carbon dioxide.

But whether these forest fires damage them depends on how thick the forest growth is, as the fire needs more fuel to spread, but larger trees would also(theoretically) be less likely to be damaged, because of their large size. Al the same time, their large size would mean certain death if the trees around them were to die, and would also mean any damage done to their roots would be that much more deadly.

But if there are larger forest fires in one part of the globe, then that means more CO2 in another, perhaps rain-forests, and therefore taller trees there. Which means the limit of CO2 can not be applied to the entirety of the trees, as some trees would get more CO2 than others, the others being dead, releasing the CO2 for these other trees, in other areas potentially not affected by CO2.

To know exactly how tall the tree can be depends and these factors and more. If you have the time you will be able to make a computer model and get an approximation. That's how a lot of information is gotten for such things anyways.

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  • $\begingroup$ Good idea with trees supporting each other. That can greately improve their hight limit. Still limit is the same as with a cube tree, but much taller than existing trees that are less altruistic $\endgroup$ Mar 27 at 21:02
  • $\begingroup$ I don't mean for them to be altruistic, as in sentient trees. They would continue to compete for resources, and as such be hurt by the trees next them, and still need to grow taller, but the limit on height is also reduced, because the presence of nearby trees also reduces the structural stress on the individual tree. $\endgroup$
    – LWS SWL
    Mar 27 at 21:20
  • $\begingroup$ If trees are competitive, then things like grape vine will dominate trees that dont actively try to kill surroundings - it will grow without spending resources on strength. Currently trees actively try to overshadow stuff around them to make sure it wont grow, and try to take all the resources from the soil nearby. All of this need to change to alow trees to grow closer, to lean on each other $\endgroup$ Mar 27 at 21:23
  • $\begingroup$ There are evolutionary pressures to be beneficial to ones offspring, but trees have no way if knowing if another tree is their offspring $\endgroup$
    – LWS SWL
    Mar 27 at 21:27
  • $\begingroup$ You do have a point,even if the trees were a single organism, then there would be less reason for them to grow taller. $\endgroup$
    – LWS SWL
    Mar 27 at 21:28
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https://en.wikipedia.org/wiki/Sequoioideae According to Wikipedia, is a subfamily of coniferous,..

The largest current trees on Terra, [] so regarding ideas from comments, to build a very large wood structure/building , you first have to have the further conditions:

  1. Genetic modified tree seeds, ex( recent developments of energy trees grow in 4 years at 16 + meters.) -> https://en.wikipedia.org/wiki/Energy_crop

  2. human attended growth and tree spacing calculations for the trees growth perspectives/expectations

  3. due to recent wood technologies you could build very big wood segments from multiple smaller glued wood segments.

  4. so I think that its not feasible to wait 200 years for a tree to grow to a dizzying height ..

  5. soo its more feasible to grow a forest with your required technical specifications tree, that in 10 years will grow desired specimens , from which .. :)) go to point 3..

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