Are trunks in a multitrunk tree separate trees?

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edfrank
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Are trunks in a multitrunk tree separate trees?

Post by edfrank » Mon Jul 22, 2013 10:34 pm

Are trunks in a multitrunk tree separate trees? How do different trunks in a multitrunk tree relate to each other?

This may seem a strange question, but it is an important one to answer especially when we are trying to determine how to measure and represent multitrunk trees in our tree listings. Multitrunk trees typically grow from a single root mass after the previously existing tree was damaged or downed. As such they are genetic clones of each other.

If you look at relationships between organisms, both plants and animals, in nature these can be broken down into a number of broad categories: mutualistic, parasitic, commensal, predator/prey, competitive, and a handful of other special cases. Are the separate trunks just different parts of one whole, or are they acting as independent trees growing in close proximity, or something in between?

I have brought up the question previously if trees growing from a pre-existing root mass is simply growing to the size it would have been if the original tree had not been lost. This idea was based upon the ides of the Leonardo Da Vinci “The Da Vinci sequence http://www.ents-bbs.org/viewtopic.php?f=143&t=3271 "Expressed mathematically, Leonardo’s rule says that if a branch with diameter (D) splits into an arbitrary number (n) of secondary branches of diameters (d1, d2, et cetera), the sum of the secondary branches’ diameters squared equals the square of the original branch’s diameter. Or, in formula terms: D2 = ∑di2, where i = 1, 2, … n. For real trees, the exponent in the equation that describes Leonardo’s hypothesis is not always equal to 2 but rather varies between 1.8 and 2.3."

The question was does it work the same for trunks directly growing from the roots? I don’t thinks this is the case. The sum of the branches above ground is limited by the size of the water/sap flowing through the trunk farther down. There would be some initial burst of growth because of the preexisting root stock would not need to be regrown and all of the energy of the growth could be put into growing height and girth. This is the same thing that happens when grafting trees. There is not any evidence that would support the concept, and evidence indicates that the large multitrunk trees are often much larger than any single trunk trees for the species in a similar setting. So I must conclude at this stage that the size of the trunks are not directly related to the size of the initial root mass, nor of the original tree which was lost.

What do we know about multitrunk trees? 1) Often the primary trunks are of similar size, 2) they are both growing from the same root mass, 3) they are genetic clones with identical growth potential.

This is all mixed up with the idea of competition between trees. You can view all of these relationships as one of competition. You can even consider the relationship between branches to be competitive as branches are lost on the lower portions of the tree as light is being sucked up by higher level branches. It can countered that they are cooperating as well because the upper leaves are more transparent than lower leaves and smaller. If it was all out war the upper leaves would be completely opaque and suck up all of the light they could. This is a degree of cooperation for the greater good of the whole tree. Trees send out chemical weapons to prevent the growth of nearby trees or sprouting of other trees in close proximity. But they also send out warning chemical signals to warn other trees of insect infestations so the other trees can build up their leaf poisons.

So how do trees fight among themselves? By limiting resources. Trees are primarily made up of air, which is unlimited. In many or most situations there is sufficient water that one tree is not stealing it all from other trees, soil nutrients are the luck of the draw of position and besides they are not a tool in tree warfare. That leaves light and chemical warfare between trees – allopathy isn't just for insects anymore. Presumably the chemicals being produced by the roots are not affecting the tree producing it, so the genetic clones would be equally unaffected by the chemicals used in the battle.

Light – if you look at trees we all know they have a distinct form associated with open growth where there is no competition for light. There are trees that are growing in the understory that are suppressed by the lack of light. Then look at a typical mature forest. These are generally fairly open and often the group of trees of one species of similar ages are similar in size. There were hundreds of seedling and saplings that died off before growing to much size. These are lost from competition with other trees for light, maybe water when they are tightly packed, and perhaps alleopathy. In addition many are lost through simple attrition from other processes like browsing and insects independent of the competition with other trees.

Over time this more open arrangement is reached where the trees are fairly evenly spaced, but most notably often similar in size. Since they have had different individual histories, different positions in the forest, grew next to different trees, and so forth, why are they similar in size? The basic idea I would suggest is that outside of the extremes of suppression and open growth there is a range of light levels that all produce similar amounts of growth.

How does any of this apply to multitrunk trees? They have a preexisting root system so maybe they avoided some of the early stand thinning processes. So you have two or more trunks grown to a certain size. They continue to grow. They do shade each other to some degree, but they each get enough light to maintain approximately the same growth rate. Each has essentially claimed a part of the original root system for themselves. Their growth parallels each other as they grow bigger. When trunks are lost at this stage, I don’t think it is competition from the other trunk or trunks but generally other factors such as damage from wind, insects, and rot.

To sum up I am proposing that the multitrunk trees bypass the early thinning stages because they are growing from a preexisting root set. Each trunk claims a portions of that root system for itself and continues to grow. They are immune from the chemical alleopathy from the other trunks in the group. They by this time are large enough they can hold their own in terms of canopy and light gathering for a fairly long term and will continue to grow. The loss of trunks at this stage I suggest is typically a result of other factors than direct competition from the other trunks. Each trunk is essentially a separate tree growing in close proximity or even pushing or impinging against each other. It becomes more complex if the trees fuse together in a way that allows sap to be transferred between trunks, but overall they are still separate trees growing in close proximity. The proposal is that they are genetic clones, but separate individuals even when they are juxtaposed into a massive clump.

Now everyone can pick this idea apart, but I wanted to suggest it and see if it leads anywhere.

Edward Forrest Frank

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"I love science and it pains me to think that so many are terrified of the subject or feel that choosing science means you cannot also choose compassion, or the arts, or be awe by nature. Science is not meant to cure us of mystery, but to reinvent and revigorate it." by Robert M. Sapolsky

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Larry Tucei
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Re: Are trunks in a multitrunk tree separate trees?

Post by Larry Tucei » Tue Jul 23, 2013 3:33 pm

Ed- In some cases the trunks are separate trees and in other cases they are not. It depends on many factors as you have pointed out. Live Oak for example splits at ground level in some cases and forms one, two, three or more trunks butt have the same root mass. In other cases they form trunks from 1' to as much as 10' above ground with the same root mass. They also can grow from clumps of trees and form trunks that have different root mass. They can fuse together over time and look like one trunk. It sometimes can be difficult to decide just exactly what type of example they are. Several tree species seem to fall into this category and these types of examples should be counted as such. We are all at NTS in agreement on this subject and glad you brought it up again. Larry

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edfrank
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Re: Are trunks in a multitrunk tree separate trees?

Post by edfrank » Tue Jul 23, 2013 3:49 pm

Larry,

I think that while these trees growing from preexisting root masses are nominatively sharing a root mass, that in actual practice the preexisting root is partitioned into sections that serve only one of the trunks. So effectively they are separate trees. They should be treated as separate trees for measurement purposes. When they are fused into a giant mass they need to be treated as a multitrunk tree.

Ed
"I love science and it pains me to think that so many are terrified of the subject or feel that choosing science means you cannot also choose compassion, or the arts, or be awe by nature. Science is not meant to cure us of mystery, but to reinvent and revigorate it." by Robert M. Sapolsky

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DougBidlack
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Re: Are trunks in a multitrunk tree separate trees?

Post by DougBidlack » Wed Jul 24, 2013 7:17 am

Ed,

what evidence is there that root masses are partitioned into sections to serve individual trunks? And how good is this evidence? I feel that an organism resulting from one seed that happens to have several trunks and one, physically intact, root mass is a tree...a single tree with multiple trunks. I'm not even sure I would change my opinion if it is actually true that the root mass is partitioned. I guess I would always have the sneaking suspicion that the root mass may be partitioned in some ways but not others and that some species almost certainly have stronger partitioning than others. Identical twins in humans and other animals are, almost always, physically separate individuals. Naturally, this brings up 'Siamese Twins' and that wonderfully complicates things.

Doug

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Will Blozan
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Re: Are trunks in a multitrunk tree separate trees?

Post by Will Blozan » Wed Jul 24, 2013 7:40 am

Ed,

Separate- as regardless of biological or mechanical origin, the end result is a collective effort, not the result of a single individual.

Will

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DougBidlack
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Re: Are trunks in a multitrunk tree separate trees?

Post by DougBidlack » Wed Jul 24, 2013 7:59 am

Will,

every multicellular organism is the result of a collective effort.

Doug

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dbhguru
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Re: Are trunks in a multitrunk tree separate trees?

Post by dbhguru » Wed Jul 24, 2013 11:15 am

Will, Ed, Don, Doug, et. Al.,

Understanding the nature of trees above and below ground across species will continue to challenge us. Measuring the diversity if forms by an artificially simple process was always bound to present problems. When we try to dumb everything down to one size fits all, we should expect exactly what we have now. Dumbing down is what we do through the AF measuring procedure.

I give full recognition to the nobility of purpose for the register. It isn't the purpose or concept, but the execution. I don't think I could have done better job if crafting a single formula, had I been around then, but we do now have the benefit of 20-20 hindsight. To stubbornly hang on the the original design so that we keep everything artificially simple will, I fear, be our downfall. If AF will not entertain some form of official distinction between single and multi-stem trees and adopt a method (pith rule) to purge doubles, triples, etc.. I fear we will be left with a charter to produce some cosmetic changes, but nothing substantive. I am not saying that this is what will happen, but it very well could. This is why Don and I need every ounce of wisdom the rest of you can send our way.

Will,

I am not optimistic about AF throwing out the current point system in favor of TDI. However, the issue can be broached as a concept. My approach would be to ask others for their take on TDI and see what kind of responses we get. Then, take it from there.

Bob
Robert T. Leverett
Co-founder, Native Native Tree Society
Co-founder and President
Friends of Mohawk Trail State Forest
Co-founder, National Cadre

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edfrank
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Re: Are trunks in a multitrunk tree separate trees?

Post by edfrank » Thu Jul 25, 2013 2:47 pm

DougBidlack wrote:Ed,

what evidence is there that root masses are partitioned into sections to serve individual trunks? And how good is this evidence? I feel that an organism resulting from one seed that happens to have several trunks and one, physically intact, root mass is a tree...a single tree with multiple trunks. I'm not even sure I would change my opinion if it is actually true that the root mass is partitioned. I guess I would always have the sneaking suspicion that the root mass may be partitioned in some ways but not others and that some species almost certainly have stronger partitioning than others. Identical twins in humans and other animals are, almost always, physically separate individuals. Naturally, this brings up 'Siamese Twins' and that wonderfully complicates things.

Doug
Doug,

Excellent questions. I have no specific evidence of the partitioning of the root masses except some anecdotal accounts and some personal observations. That is why I tried to express this as speculative in nature, but I apparently did not make that point well enough in the post. it was not meant as a statement of incontrovertible fact. I was hoping somebody would post some specific citations of root function in multitrunk trees or more personal observations.

Yes there is both some degree of competition and some degree of cooperation in these trees. What I am trying to see is if it is possible to characterize the individual trunk in a multitrunk tree as growing more like it is a separate individual tree or more like it is a fork in a single organism. To what degree are resources being shared between the trunks? To what degree are the resources being hoarded by each individual trunk?

The section on the thinning process and loss of nearby trees through competition between trees was really trying to consider why multitrunk trees retain multiple trunks instead of them being lost early in the process. Essentially I was arguing that even if they could be considered to be separate trees growing close together, many of the mechanisms for forest thinning might not be applicable to these trunks within the multitrunk specimen. Even if they were acting as separate trees, the presence of an already developed root mass during the early growth stage and their not being subject to their own alleopathic chemical battles might allow them to persist to large size. The same likely would be true if they were acting more cooperatively as forks in a single tree.

I am trying to open up this discussion to more wild speculations on the nature of mutlitrunk trees and see if it leads anywhere. So everyone consider this an invitation to brainstorm with whatever ideas, strange or not, you might have.

Edward Forrest Frank

.
"I love science and it pains me to think that so many are terrified of the subject or feel that choosing science means you cannot also choose compassion, or the arts, or be awe by nature. Science is not meant to cure us of mystery, but to reinvent and revigorate it." by Robert M. Sapolsky

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edfrank
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Re: Are trunks in a multitrunk tree separate trees?

Post by edfrank » Fri Jul 26, 2013 10:03 pm

http://www.youtube.com/watch?v=qt7gPCioqTg
The Key to Science

http://www.youtube.com/watch?v=qt7gPCioqTg

This is a brilliant 60-second segment from one of Feynman's lectures where he talks about the key to science.
"I love science and it pains me to think that so many are terrified of the subject or feel that choosing science means you cannot also choose compassion, or the arts, or be awe by nature. Science is not meant to cure us of mystery, but to reinvent and revigorate it." by Robert M. Sapolsky

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Will Blozan
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Re: Are trunks in a multitrunk tree separate trees?

Post by Will Blozan » Sat Jul 27, 2013 9:12 am

The section on the thinning process and loss of nearby trees through competition between trees was really trying to consider why multitrunk trees retain multiple trunks instead of them being lost early in the process. Essentially I was arguing that even if they could be considered to be separate trees growing close together, many of the mechanisms for forest thinning might not be applicable to these trunks within the multitrunk specimen. Even if they were acting as separate trees, the presence of an already developed root mass during the early growth stage and their not being subject to their own alleopathic chemical battles might allow them to persist to large size. The same likely would be true if they were acting more cooperatively as forks in a single tree.

I am trying to open up this discussion to more wild speculations on the nature of mutlitrunk trees and see if it leads anywhere. So everyone consider this an invitation to brainstorm with whatever ideas, strange or not, you might have.

Edward Forrest Frank
Ed,

I think you are right on in that the multi-trunked clumps are not subject to the same competitive pressures as closely spaced trees. Natural thinning of these clumps does occur but at a much slower rate (my take as an arborist observing trees for nearly 3 decades). All the more reason to never compare to single trunked trees.

Will

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