Complex Trunk Forms

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dbhguru
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Complex Trunk Forms

Post by dbhguru » Wed Jul 29, 2015 7:19 pm

NTS,

Several of us have been discussing approximating the cross-sectional areas of single and multiple trunk forms by combining simple geometric forms. Using circles and ellipses and other shapes like trapezoids, we can approximate trunk fusions. The attached spreadsheet (TrunkFormAnalysis.xlsx) presents an example of combining halves of two ellipses and a trapezoid to approximate the fusion of two trunks. This is a simple example, but it points the direction we are headed. We will test half circles combined with half ellipses and other shapes.

In the attachment entitled ToddMTNOG-101a.jpg, you see a downed northern red oak with me at the roots. You can see the shape of the trunk. It certainly isn't circular. An approximation of the cross-sectional shape of a section running for over 40 feet might be the following.
Screen shot 2015-07-29 at 8.15.04 PM.png
Screen shot 2015-07-29 at 8.15.04 PM.png (11.46 KiB) Viewed 1096 times
This form can be approximated by part of a circle and a triangle - maybe. The idea is to be able to take a few simple measurements and then calculate the cross-sectional area using a simple calculation.

Bob
Attachments
ToddMTNOG-101a.jpg
TrunkFormAnalysis.xlsx
(34.8 KiB) Downloaded 60 times
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: Complex Trunk Forms

Post by Don » Fri Jul 31, 2015 12:29 pm

Bob-
Given these were two actual tree forms in front of me, I'd favor the "equivalent circle" one as the 'bigger' tree. The fact that the pair of stems, whether they were from separate stems at ground level, from a later coppice due to injury, or other adventitious budding/re-iteration later, irrespective of age or position on tree,seems irrelevant from any perspective other than volume...if we were awarding championships based on bio-mass or cubic meters/yards, I'd select the twins as co-champion and run them through the mill.
But that isn't what we're about, not in NTS, and not in AF...it may be off in the future that AF may measure the biggest "gobsmackers" (say over 500 AF points) by volume, but that is pure speculation and is in no way intended to support a broad volume measuring philosophy across all sizes/species, as far as I know.

I hope my above pronouncements seem controversial and result in a broad discussion of what "bigness" is...
-Don
Don Bertolette - President/Moderator, WNTS BBS
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Re: Complex Trunk Forms

Post by dbhguru » Sat Aug 01, 2015 3:01 pm

Don,

The challenge of defining what we mean by tree size is complicated by the mix of physical and psychological factors that don't necessarily mesh. Size can be equated to the amount of visible surface area presented to the viewer just as readily as volume or mass. It can also be how that surface area is distributed horizontally,vertically, up close, and at a distance. It also can involve symmetry versus asymmetry. Beyond the incomparable forms of the sequoias and redwoods, I would guess that just a very wide trunk that goes up in a columnar form for at least 30 or 40 feet combined with a very wide crown spread has the greatest visual impact for most folks. Volume measurements would likely best capture the essence of this approach to size.However, the two-dimensional profile of trees can't be dismissed on the psychological side. Which of the two trees will appear larger to our little 7-foot tall spies below? Click on the mage to expand it for better viewing.
Screen shot 2015-08-01 at 3.56.19 PM.png
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: Complex Trunk Forms

Post by Don » Sat Aug 01, 2015 8:56 pm

Odd as it may seem, I'd say they're very nearly the same, whether assessed by the AF formula, or by volume comparison.
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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dbhguru
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Re: Complex Trunk Forms

Post by dbhguru » Sun Aug 02, 2015 7:55 am

Don,

Here is another look at the diagram with AF points and trunk volume added. Obviously, I had to make some assumptions to compute points, e.g. equal crown axes, but the results are interesting. I'm not trying to prove anything, just presenting the information. This is an exercise for two contestants that present nearly the same silhouette areas. On points, the right tree wins convincingly. On trunk volume, the right tree overwhelms the left one. Hopefully, I didn't make any calculation errors.

Comparative.png

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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