Trees as pipes (Wulkowicz tune in please)

[Babberney]

Several years ago, I came across Wulkowicz' essay on trees as 2-dimensional entities (http://users.rcn.com/bobw.enteract/article1.html). As a young, developing arborist, this was enlightening and has made me think differently about trees ever since.

But, over the years, more and more I begin to think about trees as pipes (tubes, straws, etc.). Engineers do not usually spec 3" solid steel rods for support beams; they use pipe, because most of the strength is in that outer tube, anyway. A hollow tree is not significantly weaker than a solid one, as long as the outer column is intact.

So now I see a codominant tree and I think about how that tight crotch has included, unattached bark that means the attachment is weak. But I also think about those two straws, and how they are getting progressively flatter on one side. I could build a pretty heavy model of a building on soda-straw piers, but if I pinched a straw and flattened it, it would collapse instantly.

So I'm wondering: How accurate is my analogy? How much of a failure in a V-shaped crotch is due to the fact that the stems were no longer round vs. the weak attachment due to included bark?

I assume there isn't any real research on this. I just want to shoot the sh*t a little and hear what other arborists think.

 

[mrtree]

Rather than blaming failure on weak crotches and included bark we need to be looking at cross sectional areas of each of the stems and realize breakage will occur where CA is least and the stem that breaks will be the one with the lower CA.

At a microscopic level perhaps the cells are flatten and have reduced strength. I think that this would make a great M.Sc. or even Ph.D. and could certainly win a prize for a kid in a science fair. The model actually sounds pretty convincing.

 

[wulkowicz]

[ QUOTE ]
Several years ago, I came across Wulkowicz' essay on trees as 2-dimensional entities (http://users.rcn.com/bobw.enteract/article1.html). As a young, developing arborist, this was enlightening and has made me think differently about trees ever since.

[/ QUOTE ]

Keith, thank you for the broad opportunities in starting this thread. For a very long time, I have been trying to re-assemble many different perspectives in biology as well as engineering to provide coordinated, consistent explanations for trees and tree growth. As I've stated before, I enjoy going back to the 1800's to watch the unfolding of discoveries, theories, and mis-informations that have led us to our thinking today.

Many readers and authors are quite satisfied with contemporary explanations and scholarly confirmations. My trouble is, for as long as the sciences have existed, there have been small and large upsets in what was considered eternally true and unarguable.

My expectations have been that our time and beliefs as well are not immune from change; so we ought to relax and soften a few things that have been fossilized in the dogma of textbooks and pontifications.

Thank you again for the quiet confirmation that I could help you think differently about trees. I will divide my posts into the various parts and questions that you have asked.

mrtree has already asked about another perspective, and I will certainly try to include his thoughts in what we can examine. However I have the responsibility to make my posts succinct and digestible--and I'm often not a good enough writer to write shorter.

These are important questions and I look forward to sharing many insights on each side of the keyboards.


Bob Wulkowicz

 

[cerviarborist]

We've historically used all kinds of fruits and nuts as ingredients for a plethora of different kinds of pastries, and I think we'd be hard-pressed to find among us, even one person who didn't enjoy one variety or another, but I think that incorporating an entire tree, in addition to tasting awful, would be nearly………………oh… you said pipes.





nevermind

 

[cerviarborist]

Seriously though, great topics and concepts. I'm looking forward to seeing where this goes!

 

[guymayor]

Pipes and Plumbing and Pruning--Coder

radical approach to structural pruning of large trees. love it:

Generate only nodal, targeted cuts which help a tree defend stem - branch confluence areas.
– Always cut back to shaded branch unions within crowns.

http://www.forestry.uga.edu/outreach/pub...%20pub08-13.pdf

 

[wulkowicz]

[ QUOTE ]
Pipes and Plumbing and Pruning--Coder

[/ QUOTE ]
Gack! 82 pages. A formidable challenge if I want to keep my mutterings brief.

It will take me a while to change my toner cartridge--and perhaps a bit longer, if the neurons falling into the back of my skull had those memories that I intended to find the cartridge.


Wulkie

 

[NickfromWI]

Nah. Your analogy would make sense if trees were perfect cylinders. But they really aren't. Imagine a same shaped tree- flat on one side but WITHOUT a codom partner. That tree can still be very strong.

The codom has increased likelihood for failure because it is actually being pushed against by the other limb and it's being forced to grow deformedly by the presence of the other limb.

 

[JeffL]

Which would be easier to bend to failure, a 2x8 piece of lumber, or a 4x4? Both have the same cross sectional area, but we all know the answer to that. Love this idea.

 

[guymayor]

[ QUOTE ]
Which would be easier to bend to failure, a 2x8 piece of lumber, or a 4x4?

[/ QUOTE ]

Wellll it depends on what angle ya bend it from, doesn't it?

 

[JeffL]

Ok fine, a 90* pull to the side! You know what I meant! I wonder what the ratio of breaking strength would be in relation to the ratio of length and width?

Would a 4x4 be twice as strong as a 2x8, or would it be 4 times as strong as the ratio would be 1:1 and 1:4. Would a 2x8 be 4 times stronger than a 1x16, where the ratio gets to be 1:16? Would the bending/breaking strength of a 3x5.3 be 1.766 times less than a 4x4, where cross sectional area is the same, but the ratio of 1:1 vs 1:1.766 is there?

 

[wulkowicz]

[ QUOTE ]
Ok fine, a 90* pull to the side! You know what I meant! I wonder what the ratio of breaking strength would be in relation to the ratio of length and width?

Would a 4x4 be twice as strong as a 2x8, or would it be 4 times as strong as the ratio would be 1:1 and 1:4. Would a 2x8 be 4 times stronger than a 1x16, where the ratio gets to be 1:16? Would the bending/breaking strength of a 3x5.3 be 1.766 times less than a 4x4, where cross sectional area is the same, but the ratio of 1:1 vs 1:1.766 is there?

[/ QUOTE ]
-----------------------

If I may make a single post response to a number of different comments:

I believe that there are many relatively perfect circles in most all tree structures. Certainly there are flares and reaction woods, and other circular distortions based on internal and external conditions. The majority of circles may be young and seemingly uninfluenced, but they are also surprisingly accurate in their aspirations. I'd like to offer the perspective to Keith that the solid wooden cylinders are remarkably well disciplined in creating and maintaining themselves as circles. With that, we can then look at the hollows and cavities that give us the sense of pipes in his first questions.

------------------------

I also must respectfully point out that the latest comments are all about lumber and not about trees. That is a significant blind spot for us as a group. Trees do not grow as dimensioned lumber; we cut lumber out of trees first grown as solid cylinders--and we can't unring the bell. I can't glue lumber together into some CSA and then plant it and reference it as a tree's structural strength.

In my vascular cambium trees, the solid woody cylinders are easily considered as generic. The cylinders are reiterations of their neighbors. The oldest vertical one is often called the trunk, and its surrounding attachments at whatever the angles, are duplicates of the same biological components and processes.

Please tell me, if in your experiences, you can take a 4 inch tall isolated section of a 4" solid woody cylinder and tell me what angle, position and placement it was on a subject tree. Was it a young 4 inch DBH trunk, or a 10 year old branch on a 60 inch DBH established tree?

Dendrocronologists may have all sorts of clues and discovered histories that I'd love to know about, but no one has yet shared with me a positioning chart based on quadrants for example that employ different structures or processes as a requisite of being in that category.

As I said, I'm going to continue for a bit on the two-dimensional, or sheet property of a tree. I hope to infect you and your curiosities about looking into some shadows. If I do my job right, you will never think about trees same way again.



Bob Wulkowicz

 

[Babberney]

Sorry to dredge this back up, but I wandered off and forgot I'd started it.

Nick, I hear what you're saying, but I'm not sure I agree. A tree that grows a flat side naturally is an anomaly. A tree (or branch) that starts out circular and then gets compressed into a flattened circle may be a different story. What you say is what I've heard and repeated many times, but I can't remember ever seeing solid research to back it up. Really, how much force are the two codoms exerting? Does anyone really know?

In a way, this goes back to roots and foundations. Sometimes a root gets under a slab and fills the spaces, then the slab moves as the soil shrinks or expands, and the root fills a new space; over time, the root seems to be lifting the foundation. But, really, I question whether the root is exerting any significant upward force. It just opportunistically turned itself into a fulcrum by accident. In other words, it is a secondary factor in a problem that started with elastic soil.

When those two codoms begin to distort each other, are they really exerting outward force? Or are they just filling the empty space around their partner as a reaction to the fact that the partner is in the way? I still have suspicions that the straw is getting pinched flat and losing strength as a result.

But I also still appreciate the elegance of bob's two-dimensional model. Light is a wave and a particle simultaneously. Maybe trees are responding to two phenomena at once.

 

[wulkowicz]

[ QUOTE ]
Sorry to dredge this back up, but I wandered off and forgot I'd started it.

[/ QUOTE ]

<font color="blue"> hi Keith,

I'm glad that you reintroduced a number of important issues. I've been thinking a lot about how to present in words and images in an even more basic understanding of trees before they become cylinders.

Lying on my table, is a little show and tell that I made four or five years ago, as a physical representation of the gossamer engine. I was very pleased with its simplicity and physical accuracy--so much so, that I put it away and recently rediscovered it in a drawer.

I took a sheet of tracing paper, architectural grade tracing paper, and glued blue and green soda straws, one color vertically on each side, with double-sided scotch tape. This is the gossamer engine.

The tracing paper is the cambium; one sheet thick just like our single sheet of cells. It is generally agreed that the cambium is only one cell thick and please tell me in any literature or discovery beyond the earlier debates where a vascular cambium tree produces a thickness of cambium as a product.

The cambium reproduces itself as a template for another cambium division with the immediate and disciplined creation all the daughter cells that become xylem and phloem respectively on their predetermined sides.

Xylem and phloem cells do not re-create cambium. They stay that way for the rest of their lives. If new cambium is needed, those dedicated cells do not reform as meristematic substitutes.

The tracing paper and soda straws are not only conceptually correct, but they are also interestingly close to scale and physical truths. I'll try to take some photographs, but my machines aren't my friends at the moment--so we'll see how we do.

Bob W

 

[guymayor]

Sounds like an interesting model, but we must keep in mind that parenchymal cells capable of dividing are not found only in the cambium, but in rays and elsewhere in the symplast. Keeping this in mind may avoid some undue rigidification of our understanding of the physical truths involved.

As usual, the trees know more than we do, and have options for adaptation that we can only guess at.

 

[treesandsurf]

I'm a little confused by the original question? Are you asking if the failure is due to the weak attachment point or the change in the shape of the tree because of the co-dominant stems?

Frank Rinn was here in Honolulu a few weeks ago doing pull tests and resistograph readings on several large tropical trees. He stressed numerous times as he always does in his talks about the importance of understanding strength loss in relationship to stem diameter, basically as trees grow in diameter (despite being hollow) the tree gains dramatic increases in stem strength.

Another really fascinating point he made was in relationship to Ken James research regarding wind dampening and how our understanding of crown reduction work to lessen the bending movement on stems needs to be re-visited. Through James' work it's been discovered trees dampen significant (80%+??) percentages of the load through stem deflection (my terms may be off here) and crown reductions may actually inhibit the trees natural ability to dampen the load. I couldn't help but be reminded of the industries long history of using cement and wound sealer to 'fix' a problem with the tree.... anyway food for thought.

jp

 

[TC]

[ QUOTE ]

So now I see a codominant tree and I think about how that tight crotch has included, unattached bark that means the attachment is weak. But I also think about those two straws, and how they are getting progressively flatter on one side. I could build a pretty heavy model of a building on soda-straw piers, but if I pinched a straw and flattened it, it would collapse instantly.

So I'm wondering: How accurate is my analogy?

[/ QUOTE ]

it's good, but when a tree collapses, buckles, breaks, what is actually happening is a shearing action between the wood fibres?

are all failures in trees shear failures? probably unless someone has another idea? maybe it's not that simple?

Look at this tree, yes the two stems were weakly attached to each other, but in order for the tree to fail there had to be a shear fracture at the base, did the poor structure of the two stems (like pinched straws) lead to the shear failure? - probably

this pic below is a great example of shear failure in a tree -

 

[wulkowicz]

[ QUOTE ]
Sounds like an interesting model, but we must keep in mind that parenchymal cells capable of dividing are not found only in the cambium, but in rays and elsewhere in the symplast.

[/ QUOTE ]

<font color=" blue"> yes indeed, let's keep that in mind, if we bother to keep our minds open, that parenchymal cells are ubiquitous. To name a few, they are space fillers, a function in transport, and a very critical part of the totipotent reserve capacity for dealing with damage and defense.

Our parenchymal cells do not evolve into xylem and phloem. Xylem and phloem only result from an orderly disciplined cambium as shown In my quaint model. Only the cambium creates what we speak of as a solid product historically understood in dendrochronology as woods. The cambium does not create voids or hollows or spaces.</font>


Keeping this in mind may avoid some undue rigidification of our understanding of the physical truths involved.

<font color=" blue">Sorry, dogma is not physical truth. But I do recognize you as the grand fossilizer happy to step in as the spin doctor for our world of pedantry.</font>


As usual, the trees know more than we do, and have options for adaptation that we can only guess at.

<font color=" blue">That's no big announcement. Most everything knows more than we do anyway. And the humility sop gets a little tiring in its repetition doesn't it?

Bob Wokeawhat's

 

[wulkowicz]

[ QUOTE ]
I'm a little confused by the original question? Are you asking if the failure is due to the weak attachment point or the change in the shape of the tree because of the co-dominant stems?

[/ QUOTE ]

<font color=" blue"> as I read Keith's original post, he was asking an evolving series of questions that began with: </font>But, over the years, more and mor begin to think about trees as pipes (tubes, straws, etc.). Engineers do not usually spec 3" solid steel rods for support beams; they use pipe, because most of the strength is in that outer tube, anyway. A hollow tree is not significantly weaker than a solid one, as long as the outer column is intact.<font color=" blue\

Viewing trees as tubes or as straws is by definition not a solid cylinder. And the hollowness is not a part of its original creation. [n">The cambium manufactures solid wood. [/b]As I pointed out to Guy, the cambium does not create voids, spaces, or hollows;Once solid wood is established, decomposers can indeed be introduced to chew on some component of the original solid.

For their own reasons, engineers remove material from a solid cylinder to save weight and expense. By some rules of physics, in paying attention to the thickness of the remaining wall, a hollow or void is accommodated. Please don't mix a decomposition hollow with an engineered removal of material.

Yes indeed, a straw or a tube, or a steel pipe can buckle or collapse--as a natural failure or as an engineering failure. And Keith's question is a fair one in asking about trees--as natural hollows,


Here's were we shift to a different consideration: Keith:</font> So now I see a codominant tree and I think about how that tight crotch has included, unattached bark that means the attachment is weak. But I also think about those two straws, and how they are getting progressively flatter on one side. I could build a pretty heavy model of a building on soda-straw piers, but if I pinched a straw and flattened it, it would collapse instantly. <font color=" blue">

Keith is still describing cylinders as hollow, but they actually were solid in their first construction until somehow showing up with a void or space (decay likely ) His questions are blended because the dogma and explanations are muddled and confusing with the pious insistence that they are consistent or somehow coordinated.</font>

That's why he keeps coming back to ask the questions. So I'm wondering: How accurate is my analogy?

I assume there isn't any real research on this. I just want to shoot the sh*t a little and hear what other arborists think.



Bob WalpoleWoods

 

[Babberney]

Well, I assume a tree that is not hollow is stronger than one that is, but I have been taught that having the heart rot out is a minor issue compared to an interruption in the outer cylinder.

But, in both cases, I am wondering if having a cylinder that becomes progressively flatter on one side over time also becomes progressively weaker.

If we return to my model on piers, imagine one with straws versus one with rods. Press a finger against the side of each and the straw will collapse pretty quickly, but you would have to snap the rod in two before it failed, no? I mean, assuming the rod is of a fairly rigid material.

So if I have a codominant tree and it has two tubes (possibly full of a semi-rigid material, possibly not) that are essentially pressing each other flat on one side. At some point, does one of them essentially develop a crimp and collapse?

Complicating the issue, of course, is that trees develop tension wood and compression wood. As the back side of the straw is getting flat, presumably the outside is creating a thicker wall that may compensate for the flat side. Then we're back to conventional wisdom, which attributes the weakness of tight crotches to included bark and mechanical loading.

And now treesandturf brings in another question about dampening. My understanding has been that we should stop talking about weight reduction and start talking about sail reduction. Removing an interior branch takes away some dampening ability, but shortening a long branch should not, in my mind. The new long/high point still catches wind, still moves, and still bounces back. Interior growth still absorbs the energy of that movement and dampens it. But, because the sail is smaller, the wind exerts less force, so breakage is not as likely. I'm not sure if that contradicts what treesandturf said or not, but it makes sense to me. http://www.notesfromatreedweller.blogspot.com/2011/08/suckers.html