Pith Trace Perspective

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Matt Markworth
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Pith Trace Perspective

Post by Matt Markworth » Wed Apr 08, 2015 5:51 pm

All,

I think this specimen is a good example of how the perspective of the photograph can have a big impact on the pith trace. If the measurer is trying to determine the best perspective to take the photograph, I think the best place is perpendicular to the imaginary line that connects the two suspected piths. If more than two piths are suspected, then separate photos could be taken focusing on two at a time (in addition to the four quadrants).

For this specimen, it's possible that more than two stems could have been apparent in the past, however for the purposes of this pith trace I am only showing two. The pith traces are straight, although I think some curvature may have been warranted, in particular to help with the curving side stem and to help avoid crossing the clear bark separation. Wrapping a tape around the entirety of this Missouri-grown cottonwood results in a circumference of 26'10" at 3.5' above the ground. It stands at 99' tall.
Missouri-grown cottonwood.jpeg
Missour-grown cottonwood, full tree.jpg
pith trace - 1.jpg
pith trace - 2.jpg
pith trace - 3.jpg
pith trace - 4.jpg
pith trace - 5.jpg
pith trace - 6.jpg
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dbhguru
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Re: Pith Trace Perspective

Post by dbhguru » Wed Apr 08, 2015 7:04 pm

Matt,

Any thought to the following tracing? Yellow line follows what may be the separation of touching trunks. That would force the left red trace to curve, wouldn't it? Then there is the beige line. It is the most interesting. Different species?
Screen shot 2015-04-08 at 7.58.30 PM.png
Bob
Robert T. Leverett
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Co-founder and President
Friends of Mohawk Trail State Forest
Co-founder, National Cadre

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Matt Markworth
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Re: Pith Trace Perspective

Post by Matt Markworth » Wed Apr 08, 2015 8:05 pm

Bob,

Yes, I agree. You chose the perspective that I think is the closest to being perpendicular to the two suspected piths and I like your pith trace.

Without the bark separation (like, for example, in a sycamore), I wonder how much of an impact that would have on the final pith trace. Lots of variables and lots of art and science! I've observed stems that put on a much thicker ring on the outer side for support. I wonder how much that "bends" the pith trace inward in certain stems.

Oh... I think that species over to the left is slowly morphing into some kind of human/tree hybrid:)

Matt

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Re: Pith Trace Perspective

Post by edfrank » Wed Apr 08, 2015 8:48 pm

Missouri-grown cottonwood.jpg
Missouri-grown cottonwood.jpg (173.02 KiB) Viewed 2064 times
I really liked some of the traces that Matt did initially. I think it is a low branch rather than a separate trunk. The image Bob chose is not exactly perpendicular to the junction. The tree is going slightly away from the viewer as it approaches the tree. The brown rather than being a merger line might be growth along a fracture or more likely from epicormic sprouts, ie burl like growths formed as the main trunk enveloped the base of the branch. If it were a separate trunk why would it abruptly bend outward at the point where it splits from the other trunk while remaining straight in the area below? There is nothing forcing it to bend outward at this point, so I think that is its natural angle from being a branch. Some of the shape elements to me implies that the base of the branch has just become more deeply embedded as the main trunk grew around it. This is my best guess.

Ed 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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Matt Markworth
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Re: Pith Trace Perspective

Post by Matt Markworth » Wed Apr 08, 2015 9:34 pm

edfrank wrote: If it were a separate trunk why would it abruptly bend outward at the point where it splits from the other trunk while remaining straight in the area below? There is nothing forcing it to bend outward at this point, so I think that is its natural angle from being a branch.
Ed,

This statement made me think of another possible scenario in the history of this tree, which is better illustrated by these different angles. Maybe this hollowed area is partially the result of a fallen stem/branch, and it's presence could have caused the still present stem/branch to bend outward while both of them were still present and growing.
037.jpg
036.jpg
032.jpg
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Don
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Re: Pith Trace Perspective

Post by Don » Thu Apr 09, 2015 7:13 am

Matt/Ed/Bob-
I'm jazzed, a challenging cottonwood, three guys delineating pith lines, why it doesn't get much better!
I noticed that some of you are constraining yourselves in delineating pith lines with only straight lines.
I'm snipping a piece from the Measuring Guidelines (MG) that is for Powerpoint, but is close to Word's version, below:
"PowerPoint Directions:
1. Once you have the image placed, click on “Insert”.
2. Click on the “Shapes” icon, sliding cursor over to the
downward triangle, and dragging it down to the top
row choice “Lines and Connectors”.
3. Select the third icon on the third line of “Lines” (when you hover the cursor over the
icon it reads “Freeform”). Clicking on that icon changes your cursor symbol to a cross,
which becomes the beginning of a line when you click on it.
4. Click on a point some ten feet in the image or so above the base, just to get used to
the delineation part of the exercise, and try running the cursor down the middle of the
trunk, clicking as you need to, to turn left or right to stay with the assumed pith line.
5. When you get to the bottom of the trunk, double click at the base, which ends the line,
and leaves it in a box. If you are happy with the result, you can go on to the next one."

As to why you might want to curve the lines, and for what reasons, I'll also grab a piece from the MG that can support your decisions:
"Unless external forces can be determined to have an altering influence on the tree’s natural
tendency towards a circular cross-section, generally running pith lines down the center of
the tree’s presented ‘front’ is going to be relatively close. Having four images from each
quadrant of the tree helps to more accurately inform the delineation. Should there be
noticeable external forces in play, adjust the delineated pith line appropriately (recalling an
angiosperm’s tension wood reaction, or a gymnosperm’s compression wood response).
"

External forces, reaction wood, what's that about? Grabbing again from the MG, here's some more support:
"TRUNK DEVELOPMENT
In the absence of external forces, the trunk of a tree will annually add a layer of new wood. Looking at a cross-section of a trunk, this strategy is revealed as concentric annual rings that approach the geometric shape of a circle. In a perfect tree world, a trunk’s cross-section would be nearly circular.

In the actual world, a tree must contend with external forces…gravity, ground slope, adjacent objects (trees, rocks, etc.), solar incidence, forest openings, and prevailing weather patterns. Some forces remain constant through the life of a tree (topographic features, solar incidence patterns), some change slowly over that time (tree gaps or forest openings resulting from natural and human-caused disturbances), and some can bring about sudden change (earthquake, floods, soil creep, a fallen tree).

Trees respond to these external forces. The response to gravity and solar incidence is to re-orient in order to attain a vertical position. How much and how fast the tree responds determines the degree to which the cross-section will display deviation from circular by creating what we call reaction wood patterns.

The following drawing displays the differing reaction wood patterns in angiosperm and gymnosperm responses to growing on a steep slope. In general, conifers “push” up from below, and hardwoods “pull” up from above.

ReactionWoodGraphics.docx
(229.14 KiB) Downloaded 87 times
Gymnosperms express eccentricity in reaction wood…here, in a deodar cedar, by growing compression wood on the underside to buttress or ‘push the branch up’, as captured by Mario Vaden in a 2011 photograph below of a deodar cedar.
DeodarVaden.docx
(1.1 MiB) Downloaded 85 times
Angiosperms express eccentricity in reaction wood…as noted by Hoadley (1980, p. 32) by forming ”…predominantly toward the upper side of the leaning stem…where gravity causes the upper side to be in tension…” and “…is termed tension wood”



Another example of tree(s) responding to external forces is seen below in an expanded, annotated version of the multiple stems below, though externally appearing to be an almost oblong single tree.
TripleAnnoAnalysis.docx
(2.91 MiB) Downloaded 85 times
Adjacent stems go from rounded oblong, to elliptical, to circular (as they go from bark extrusion phase to base inclusion phase).

Here the force of opposing objects (adjacent stems of same species in this case) causes the trees to push (extrude) growing concentric annual rings out of round, and to the sides (note eccentricity occurring after a dozen or so years, as each tree’s stems begin pushing against the others). When of the same species, such tree’s stems will begin to ‘grow around’ the extrusion (not unlike a tree ‘growing over’ a fire scar), and eventually surround, or include the tree’s base. Over time, the exterior appearance approaches circularity, as each successive annual ring ‘averages’ the oblong to an elliptical cross-section. After several hundred years of bark inclusion, it can be difficult to discern the dynamics of annual ring growth response, and the tree(s) origin."[/i][/b]

If there are problems downloading the graphics, the current version of MG has some of them on pages 75, 77 at:
http://www.americanforests.org/wp-conte ... nes_LR.pdf
Hope this helps!
-Don
Don Bertolette - President/Moderator, WNTS BBS
Restoration Forester (Retired)
Science Center
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dbhguru
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Re: Pith Trace Perspective

Post by dbhguru » Thu Apr 09, 2015 3:18 pm

Matt, Ed, Don, et. al.,

The pith tracing I presented was meant as another possibility, not necessarily my choice. The curvature of trunk/limb suggests a limb, but limbs growing naturally from a parent trunk usually don't have growth of the main trunk engulfing them, as would be the case for a foreign object. So, for me, the jury is still out on Matt's cottonwood.

The first question is what to include or not include in circumference measurements. We start from the simple-sounding rule that we measure the trunk of one tree, interpreted to mean one trunk at the point of measurement, which is ideally at 4.5 feet, but actually intended to be at the narrowest point between 4.5 feet and the ground. This rule means we exclude extra trunks. But we also exclude the influence of limbs, roots, burls, and other abnormalities. This is the procedure we've adopted for American Forests. There appears to be an exception, though. We may measure multiple stems at 4.5 feet if at some point between 4.5 feet and the ground the form is that of a single trunk. In this case, we choose 4.5 feet presumably because measuring below that at the point of one pith would include unwanted elements such as root flare. To avoid this, we compute the functional circumference at 4.5 feet using the stems emanating from the single trunk. The method of computation has been explained in past posts.

For complex forms, questions needing to be answered include:

1. When do we have a limb and when do we have a trunk? What is the difference biologically?
2. Can a limb sprout from the root collar, or only trunks?
3. What shapes can subordinate trunks, sprouting from the root collar, take on based both on external forces and on the genetics of the species?
4. Do these secondary trunks always look like smaller versions of the main trunk, or can they bend away from the main trunk and then
right themselves, curving upward, mimicking the shape of a limb ?
5. How do these questions relate to different species? Cottonwoods, Silver Maples, and some other species routinely sprout from the
root collar, but are perfectly capable of being singe-trunked.

To get a handle on these questions, maybe we need to study young tree forms and observe how they change as trunks and limbs thicken and press together. We normally measure older trees that have developed complex growth forms, but if we can back track, maybe we can tease apart the elements. Consider the three images of a young yellow birch, or is it two birches. Double click on each image to expand it into a more visible form.
YB-2a.jpg
YB-2b.jpg
YB-2c.jpg
I would treat this as two trunks right down to the ground. How do the rest of you vote?

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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Matt Markworth
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Re: Pith Trace Perspective

Post by Matt Markworth » Thu Apr 09, 2015 5:09 pm

Bob,

Here's my estimation of the pith traces for the birches. The horizontal line is my estimation of where the piths intersect ground level.
YB-2c - matt pith trace.jpg
YB-2c - matt pith trace.jpg (46.46 KiB) Viewed 1987 times
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Re: Pith Trace Perspective

Post by dbhguru » Thu Apr 09, 2015 6:14 pm

Matt,

Thanks. i expect most of us will draw comparable lines. But let's see.

Here is a different birch. Do we think that the smaller stem is a trunk developed from an adventitious root bud?
YB-1b.jpg
YB-1c.jpg
YB-1a.jpg

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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Don
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Re: Pith Trace Perspective

Post by Don » Fri Apr 10, 2015 3:39 pm

Matt-
I like your estimation...clearly the stem on the left is a straight down proposition; whereas the stem on the right started off close, after just a few years started to get pushed to the right by the bigger stem growing bigger, then takes off on its own to find light and space for itself.
I might have drawn the right stem's pith line a little closer to the left one's, but hey it's a judgement call! What would be really nice is if some of the working arborists in our midst could lop off cookies from trees like these, that pop up in their normal workday?!? Don't wanna cut a tree(s) down unnecessarily, but if it had to go anyway...
-Don
Matt Markworth wrote:Bob,

Here's my estimation of the pith traces for the birches. The horizontal line is my estimation of where the piths intersect ground level.
YB-2c - matt pith trace.jpg
Matt
Don Bertolette - President/Moderator, WNTS BBS
Restoration Forester (Retired)
Science Center
Grand Canyon National Park

BJCP Apprentice Beer Judge

View my Alaska Big Tree List Webpage at:
http://www.akbigtreelist.org

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