Trees as pipes (Wulkowicz tune in please)

Pipe or solid bar...the shape still makes a difference in the overall ability to handle certain loads. A pry bar would not be effective with a flattened section halfway down the shank. All the molecules of the shaft are present, just altered in arangement.

I was thinking about the reference of the 2x4, and which direction of force would cause it to break most easily, but torsional loading would also come into play. Most included bark unions I have seen result in poor architecture of the crown above. Geotropism alone would likely not be enough to tear one side down, but when the wind blows, the crown would twist. This twisting would be transferred down to the fat cheeks of the codom. Snow, ice, a Robin (the straw that broke the camel's back), etc, could all be compounding factors.

About reaction wood:

Wouldn't the cells in a codom differentiate in such a way as to maintain as much strength as possible?

How could the wood BELOW the codominant (included bark) attachment know about and react to the situation above it?

Is an included bark failure due to the lack of tension wood or the lack of proper load distribution?

A related thought: I've seen many wide angled codominant unions fail. My thought is that since both stems enlarge during the same part of the growing season, there is little overlapping tissue that would be present in a normal parent/lateral branch union.

Why wouldn't a poor union effect the hormone levels to favor one side vs. another to create a dominant branch?

Can a tree recognize a boulder vs. it's own stem?
 
Babberney said:
Just coming back to this board after a long lapse. I don't know if this thread really broke new ground or made new discoveries, but I'm bumping it because I miss Bob. Still curious to hear ideas on the subject if anyone is so inclined.
Click to expand...
Watching with interest. It was good one to dig up.
 
oceans said:
Pipe or solid bar...the shape still makes a difference in the overall ability to handle certain loads. A pry bar would not be effective with a flattened section halfway down the shank. All the molecules of the shaft are present, just altered in arangement.

I was thinking about the reference of the 2x4, and which direction of force would cause it to break most easily, but torsional loading would also come into play. Most included bark unions I have seen result in poor architecture of the crown above. Geotropism alone would likely not be enough to tear one side down, but when the wind blows, the crown would twist. This twisting would be transferred down to the fat cheeks of the codom. Snow, ice, a Robin (the straw that broke the camel's back), etc, could all be compounding factors.

About reaction wood:

Wouldn't the cells in a codom differentiate in such a way as to maintain as much strength as possible?

How could the wood BELOW the codominant (included bark) attachment know about and react to the situation above it?

Is an included bark failure due to the lack of tension wood or the lack of proper load distribution?

A related thought: I've seen many wide angled codominant unions fail. My thought is that since both stems enlarge during the same part of the growing season, there is little overlapping tissue that would be present in a normal parent/lateral branch union.

Why wouldn't a poor union effect the hormone levels to favor one side vs. another to create a dominant branch?

Can a tree recognize a boulder vs. it's own stem?
Click to expand...

I just realized this is a new post, and after a few more years in trees I'm seeing it differently than I might have when I started the thread.

Twisting definitely comes into a lot of tree failures. That's one reason a triangular configuration of cables is stronger than a straight line or box. Trees work best as a solid unit rather than isolated branches. But, relating to the original point, the torsion would just be factor X that led to failure, and the question is still, did that failure occur where the straw got pinched? For what it's worth, I know where there's a hackberry in a chain link fence that's around 16" diam above and below the top rail and 12" thick X 24" wide with the rail partially absorbed. I'll let you know if it finally breaks and where.

Reaction wood is expected, of course, and maybe that's why some stand as long as they do against all odds. This is not my wheelhouse, but I understand it to be largely a function of physical movement that leads to thicker, stouter cellulose walls. It knows whether that movement relates to Codom or not. Perhaps you have a point that somehow the cramped interior stems don't develop tension wood as well.

Codoms with wide crotches still baffle me a little. I wish Dr. Gilman's could weigh in here, because he has spent years studying tree failures (and successes) from hurricanes and has a lot of data showing them weaker than branches with 80%aspect ratio or less. I think likely it ties into, as you say next, the way the two knit together (or don't). When you split a log with a knot in it, you can see how thoroughly one branch envelops and secures the other.

Can a tree recognize a boulder vs. its own stem? I think my original scenario assumes the strength loss is the same either way. I would expect it to react the same either way. But, I have been surprised so many times by trees, I don't rule out a mechanism that reduces incidence of failures in codoms.
 
Twisting strain is one more reason to reduce overextended limbs, and their whipping movements. On codoms in particular.

Reaction wood on the inside of hollow trees is rarely seen, and the strength gain is rarely factored into defect-based assessments. Closer inspection is needed.
http://www.historictreecare.com/wp-content/uploads/2017/03/DD-Eloquent-Elephant-1610.pdf

“Part 8 of the U.S. ANSI A300 standard expects us to inspect “Conditions in the crown that may reflect root conditions” and “Stem tissue connecting the crown and the roots.” This giant oak’s vertical trunk sections (also called segments, columns, or vascular pathways) that connect to the most vital portions of the crown are expanding the fastest, so they have the deepest grooves cut by the iron strap. Columns on both sides of the cavity are eloquently expanding, telling a tale of hope for this old giant.”

Coditlooked confused. “Howcan something eloquently expand?

“Good question!” Vaughn Verdier said, his hands probing the edges of the north entrance . “If our oldest, most valuable trees are removed for reasons of general liability, their features cannot be familiar to arborists. This type of regenerating growth is actually quite common, if you know where to look. Stored resources, and food made during future photosynthesis, nourishes callus tissue that rolls over hard surfaces—like the new wood inside this cavity!
“The sheer mass and strength of this elephantine expansion is speaking out, “eloquently,” for the tree’s vigor. Beauty’s more than skin deep: high vitality creates these beautiful vascular pathways, from leaves to roots. The orange of the rhytidome shines through when bark cannot be created fast enough. We will mark and measure sections over time, to document regeneration. This phenomenon demonstrates that older trees can grow inward, as well as downward.”
 
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