Trees are spectacularly successful, and have been for millions of years. They now cover ~30% of Earth’s land. So trees should be pretty well designed to do what they do. Yet the basic design of trees seems odd in many ways. Might this tell us something interesting about design?
The constructal principle can explain the configuration of systems pretty well in terms of the physics of flows and the realization that systems that survive in time will tend to evolve towards a configuration that minimizes the resistance to the flow (the constructal principle).This paper would explain the overall configuration of trees which addresses points 1 and 3. http://www.constructal.org/.... As for self blocking consider first the movement of the sun during the day and throughout the year. Then the shape that maximizes surface area would be a sphere subject to mechanical constraints of the material. But if you also consider that leaves that block each other don't block each other out completely because of light diffracting and movement from the wind, then having what seems to be a self blocking structure may actually increase the effective surface area of leaves. This falls in line with a casual observation (from memory not many leaves on trees now), most leaves that block each other are far enough away that they can receive diffracted light while most leaves that are close to each other aren't self blocking and are roughly on the same plane.
1. Trees aren't irregularly shaped, they follow very regular growth and branching rules, but they are not symmetrical. Symmetry is hard. It takes effort coordinating growth at a distance over time. Symmetry is not in itself good design, it is only good design if it benefits the organism. It is useful for coordinating movement. Organisms that don't move, don't bother with it.2.Self blocking may cost the tree some sunlight, but it produces shade, which makes it hard for any competing plant to sprout up from below it and usurp the tree's spot in the sun.3. Multiple supports are mostly useful for stiffness, not strength. Trees don't gain anything by trying to hold their top levels steady. Buildings that sway too much have a difficult time getting tenants on upper stories, trees don't have that problem.
Insightful and interesting post. I was writing a longer reply when I realized you just said what I was going to say in your seventh paragraph. Especially regarding cities and trend towards local maximum.
3. I haven't done strength mechanics but skyscrapers rarely have more than single branch. Skyscrapers don't lean to each other for support though either.
Also related article regarding bird flight and mechanical flight. Interesting.
The design and arrangement of tree leaves is quite well understood. The leaves at the top of the tree are generally orientated at a greater angle - they absorb some light whilst avoiding direct exposure to the harshest midday light. The light that passes through is absorbed by the 'shaded' leaves below. The structure of the canopy changes from top to bottom in line with this phenomena - thinner,flatter, larger leaves with less chlorophyll per unit area right at the base. Interestingly these shade adapted leaves at the base are often right at the margin in terms of energy production/cost.The total light absorption through the complete crown is often very high (spp dependent of course), and can be described with the Beer-Lambert law.
Now this is weird - some studies suggest that trees can 'see' their neighbours by responding to shifts in the incoming spectra when a neighbouring tree begins to grow and intercept light. Some trees seem to respond to this by focusing more growth in such a manner as to out-compete these interlopers.
Though Dr. Hanson answered "I only want them to be as well designed as animals", I still think "Evolution is dumb" is the best answer to these questions. Evolution ties itself into knots, committing a species to certain technologies, and has difficulties untying those knots.
The confusion comes from assuming either a firm or a tree are indivisible units rather than collections of independent actors with some mutually beneficial goals.
Hmm - Robin already wrote on that in the post. Aerial roots do exist (banyan, mangrove. I'm not 100% sure why they aren't more common - but probably predation is involved. Plenty of plants do physically hold each other up - e.g. bamboo supports its nearby relatives.
I think I can explain why trees are somewhat asymmetrical. Tree growth is adaptive - it takes place where light is good. There's selection on growing branch tips. The result is an adaptive fit to the tree's environment - which rarely results in a particularly symmetrical form.
It also has a lot to do with the random distribution of sun at any particular moment and during the day. If you have a regular pattern (or a formative distribution) you'll run into issues when it's cloudy. The pattern has to be disjointed to allow the possibility to capture a random distribution of sunlight.
Look at mem arrays of solar cells. They also have any spot pattern that is disjointed and might look random, but the point is each microstructure is optimized for sunlight at that moment. Trees don't have this luxury, so instead typically go for the random distribution. This gives them a good chance of collecting sunlight no matter what position the sun is in and what the cloud structure might be at any one moment (barring full obscurity).
If you limit the overall distribution of sunlight to a small window and regular pattern all plants will grow towards that particular spot and develop a canopy to capture the available light.
Neighboring tree connections might try to grab more support than they offer, or pull one down when they die. But it isn’t clear why tree connections couldn’t be weak and breakable to deal with such issues, The tree is working at the margin, without a long term plan tightly optimized for the specific situation. It has no way to evaluate the structural stability of adjacent objects, and no immediate incentive to develop such an evaluation mechanism. In the absence of such an evaluation, cross-bracing directly conflicts with the structural resilience requirements, because every connection to an unknown structure means taking on unknown structural liabilities.
Most of all, a "weak and breakable" support would not be structurally useful, because it would fail at the very moment when it was needed most! How could that not be clear?
www.adormi.com
this will be the consequence if there is no right managment!
The constructal principle can explain the configuration of systems pretty well in terms of the physics of flows and the realization that systems that survive in time will tend to evolve towards a configuration that minimizes the resistance to the flow (the constructal principle).This paper would explain the overall configuration of trees which addresses points 1 and 3. http://www.constructal.org/.... As for self blocking consider first the movement of the sun during the day and throughout the year. Then the shape that maximizes surface area would be a sphere subject to mechanical constraints of the material. But if you also consider that leaves that block each other don't block each other out completely because of light diffracting and movement from the wind, then having what seems to be a self blocking structure may actually increase the effective surface area of leaves. This falls in line with a casual observation (from memory not many leaves on trees now), most leaves that block each other are far enough away that they can receive diffracted light while most leaves that are close to each other aren't self blocking and are roughly on the same plane.
1. Trees aren't irregularly shaped, they follow very regular growth and branching rules, but they are not symmetrical. Symmetry is hard. It takes effort coordinating growth at a distance over time. Symmetry is not in itself good design, it is only good design if it benefits the organism. It is useful for coordinating movement. Organisms that don't move, don't bother with it.2.Self blocking may cost the tree some sunlight, but it produces shade, which makes it hard for any competing plant to sprout up from below it and usurp the tree's spot in the sun.3. Multiple supports are mostly useful for stiffness, not strength. Trees don't gain anything by trying to hold their top levels steady. Buildings that sway too much have a difficult time getting tenants on upper stories, trees don't have that problem.
Insightful and interesting post. I was writing a longer reply when I realized you just said what I was going to say in your seventh paragraph. Especially regarding cities and trend towards local maximum.
3. I haven't done strength mechanics but skyscrapers rarely have more than single branch. Skyscrapers don't lean to each other for support though either.
Also related article regarding bird flight and mechanical flight. Interesting.
CO2 is the most limited resource for trees,so they maximize their ability to get this by touching a lot of air,hence the tree shapes.
If energy was a limiting resource, trees would be black, or purple, since most of the energy in light is in the green colours.
The design and arrangement of tree leaves is quite well understood. The leaves at the top of the tree are generally orientated at a greater angle - they absorb some light whilst avoiding direct exposure to the harshest midday light. The light that passes through is absorbed by the 'shaded' leaves below. The structure of the canopy changes from top to bottom in line with this phenomena - thinner,flatter, larger leaves with less chlorophyll per unit area right at the base. Interestingly these shade adapted leaves at the base are often right at the margin in terms of energy production/cost.The total light absorption through the complete crown is often very high (spp dependent of course), and can be described with the Beer-Lambert law.
Now this is weird - some studies suggest that trees can 'see' their neighbours by responding to shifts in the incoming spectra when a neighbouring tree begins to grow and intercept light. Some trees seem to respond to this by focusing more growth in such a manner as to out-compete these interlopers.
Though Dr. Hanson answered "I only want them to be as well designed as animals", I still think "Evolution is dumb" is the best answer to these questions. Evolution ties itself into knots, committing a species to certain technologies, and has difficulties untying those knots.
The confusion comes from assuming either a firm or a tree are indivisible units rather than collections of independent actors with some mutually beneficial goals.
Hmm - Robin already wrote on that in the post. Aerial roots do exist (banyan, mangrove. I'm not 100% sure why they aren't more common - but probably predation is involved. Plenty of plants do physically hold each other up - e.g. bamboo supports its nearby relatives.
I think I can explain why trees are somewhat asymmetrical. Tree growth is adaptive - it takes place where light is good. There's selection on growing branch tips. The result is an adaptive fit to the tree's environment - which rarely results in a particularly symmetrical form.
Thanks, this cleared up a lot of the issue with leaves that seem to be blocking other leaves.
Why aren’t tree leaves on a common surface?
Palm trees tend to have larger leaves, fewer of them, and all at the top of the tree.
It also has a lot to do with the random distribution of sun at any particular moment and during the day. If you have a regular pattern (or a formative distribution) you'll run into issues when it's cloudy. The pattern has to be disjointed to allow the possibility to capture a random distribution of sunlight.
Look at mem arrays of solar cells. They also have any spot pattern that is disjointed and might look random, but the point is each microstructure is optimized for sunlight at that moment. Trees don't have this luxury, so instead typically go for the random distribution. This gives them a good chance of collecting sunlight no matter what position the sun is in and what the cloud structure might be at any one moment (barring full obscurity).
If you limit the overall distribution of sunlight to a small window and regular pattern all plants will grow towards that particular spot and develop a canopy to capture the available light.
Mario.
"Perhaps an analogy with trees"
Will not work. How is that?
Trees are rational paradigms and firms are just paradigms. The difference is a condition known to me as intrinsic. Firms lack that condition.
Neighboring tree connections might try to grab more support than they offer, or pull one down when they die. But it isn’t clear why tree connections couldn’t be weak and breakable to deal with such issues, The tree is working at the margin, without a long term plan tightly optimized for the specific situation. It has no way to evaluate the structural stability of adjacent objects, and no immediate incentive to develop such an evaluation mechanism. In the absence of such an evaluation, cross-bracing directly conflicts with the structural resilience requirements, because every connection to an unknown structure means taking on unknown structural liabilities.
Most of all, a "weak and breakable" support would not be structurally useful, because it would fail at the very moment when it was needed most! How could that not be clear?