Multi-stem Trees - Measuring Circumference

Native Tree Society Tree Measuring Guidelines and related materials.

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#1)  Multi-stem Trees - Measuring Circumference

Postby dbhguru » Mon Jan 02, 2017 3:48 pm

Hello Ents,

As many of you know, the American Forests National Cadre was created to provide AF with a corps of expert tree measurers to certify national champions and train others to correctly measure trees for championship contests. The Cadre was originally conceived by Don Bertolette and has since been developed by Don and yours truly. The Cadre drew most of its initial membership from NTS. The majority of members are still in NTS. However, the Cadre is a separate organization. Cadre members carry a special membership card from American Forests, and act under its authority. But NTS and the Cadre continue to share a base of common measuring interests. One of those is how to accurately measure trees for championship competitions.

We still have plenty of room in the Cadre for members and any of you who are NTS, but not Cadre, have a leg up in joining us in the Cadre. With this promotional pitch out of the way, I’ll turn to the real purpose of this communication – measuring trunk circumference and the multi-stems.

Arguably, the biggest challenge that American Forests has faced since the beginning of the national champion tree program in 1940 has been defining what a tree is for measuring purposes and specifying the rules to be used in measuring circumference. That challenge has been exacerbated by the fact that most of the national champion tree program coordinators have not been expert tree measurers. Until the current measuring guidelines were published in 2014,

http://www.americanforests.org/wp-conte ... nes_LR.pdf,

the instructions for measuring height, circumference, and average crown spread amounted to a measly three Internet pages.  Basically, the national coordinator left it up to the state coordinators to certify nominees to the National Register. The state coordinators used a combination of state forestry personnel and independent volunteers, i.e. big tree hunters. This has led to what we have now, a combination of the good, the bad, and the ugly, with the ugly becoming more the rule than the exception (Yes, beauty is in the eye of the beholder, but ….).

In May 2017 we’re planning to hold another tree measuring workshop in Virginia with Virginia Tech as the administrative sponsor and the AF National Cadre members doing the instructing. We’re looking at holding the workshop in Charlottesville, VA, but that location is not yet firm.

In contrast to previous workshops we have held where measuring tree height took the lion’s share of the time, in this event, we’ll concentrate on measuring circumference. We’ve got height down to a fine science, but circumference remains hostage to the battle between single and multi-stem forms. We’re going to try to crack this tough nut for American Forests, and hopefully for those state programs trying to get in sync with the national program.

We plan to consider: (1) the definition of a tree for AF measuring purposes, (2) methods of handling tree forms with multiple stems at 4.5 feet above ground level, and (3) rules and techniques for determining whether nominees are single or multiple tree forms.  

It is (3) where most of the trouble lies.  Under the current rules, if you can keep a tape in contact with a bark surface as you encircle the trunk at the chosen measurement height, you may treat the result as though you measured a single trunk regardless of how many pith lines might be included internally. Basically, the rule had been if the tree form is divided into separate stems at 4.5 feet, the measurer finds the smallest circumference between 4.5 feet and the ground and use that, again keeping the tape in continuous contact with bark - even if there are seams along the trunk suggesting that multiple trunks (stems) are pressed together with an outer covering of bark that hides the individuality of the stems.

Now we perform a pith analysis. If the stems extend down to the root collar and if tracing their assumed pith lines result in the lines reaching ground level before coming together in a point, then we treat the result as multiple trees. If a trace has the pith lines coming together before the base is reached, we have one tree. This new method provides for a resolution for clear-cut cases, but there are always tree forms that don't submit easily to pith tracing. That occurs more frequently than we'd like because the pith lines are seldom in the centers of trunks that press together. Still, the new rule is a vast improvement. Here is why.

The old rule for measuring circumference led to a lot of mischief and gave multi-stems a huge advantage over even the best, most perfectly formed single stems. However, in fairness, the old rule also enabled forms for species like willows that prolifically sprout multiple stems from the root collar to be treated as a single organism. There is still a legitimate difference of opinion as to whether or not the multi-stem willow form should be treated as a single tree. But how far do we go in this direction? In the past, the practice basically was that if you couldn’t conclusively prove that a candidate was actually multiple trees via someone's challenge, the candidate was given the benefit of the doubt.

In his AF Measuring Guidelines Working Group capacity, Don Bertolette, has shown what the prevailing practice has led to in his recent analysis of the forms that have been accepted into the National Register - forms that have many of us rolling our eyes and shaking our heads. Even with pith analysis attempting to distinguish forms that represent what started as different trees that subsequently began pressing together with bark growing around and over the areas of compression. We still have unresolved issues.

We are soliciting ideas from the NTS membership on how to deal with the multi-stems. BTW, NTS President Will Blozan, who is also AF National Cadre and MGWG favors the normal form that a species assumes as a qualifying criterion. A tree may be injured multiple times in its life giving rise to additional stems developing from the root collar, all of which may eventually press together at some point giving the appearance of a single trunk to untrained eyes. Will rejects these forms as eligible for championship status. At least, he rejects including all the stems in calculating circumference points. I agree with Will for species that are not prolific at stump-sprouting. However, I leave room for species that take on shrub-like forms more frequently than development as single stems. Some of the western junipers appear to fall into this class. Many members of this class are the small trees, but if I understand our friend Larry Tucei, live oaks can develop as a multi-stem form when grown from a single acorn. When they get to be enormous, we admire them and are less concerned about their origin, but I’d hate to see one rejected because there was some doubt about how it began life. Either way, there is lots of room for discussion.

Also, tree appearance plays a big role in these debates, at least informally. The peach-leaf willow champ from California (I’ll leave it to Don to supply an image) does not look remotely like a champion to me. I would not nominate such a shape regardless of what might eventually be proven about it genetically. I could give other examples, but I prefer my champions to have forms that we can all admire, forms that do justice for the species. For me, choosing our champion trees should not devolve to a contest among the bizarre and deformed. Let me offer an example based on one of my favorite species.

For a historic and charismatic species like the white pine, shouldn’t we seek its Olympian ideal? White pines are subject to being deformed by attacks from the white pine weevil. The result is an asymmetrical, contorted form that lumbermen reject as worthless. It is certainly not the normal shape of the species, but because it becomes multi-trunked at the point of weevil damage, it can develop a large crown. This leads to more photosynthesis and a larger lower trunk. This in turn leads to a higher point total on the champion tree formula. So, we can end up with an almost grotesque national champion that is rejected by the forestry community and violates the notion of the Olympian ideal. Is this really what we intended?

One way we plan to better analyze what appears to be multiple stems is to collect photographs of cut stumps. Ideally, we'll take before and after shots where the opportunity prevents itself. Actually, Will did that with a red maple several years ago, if I remember. It was a good start.

Well, I’ve rambled enough. Although, this is primarily Cadre business, the MGWG is happy to keep the discussion going here in our NTS BBS if enough of you are interested. Any thoughts? Who votes for what? Where do we draw the lines?

Bob
Robert T. Leverett
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Native Native Tree Society
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#2)  Re: Multi-stem Trees - Measuring Circumference

Postby Larry Tucei » Tue Jan 03, 2017 10:41 am

Bob-  Well said you have made many valid points. I agree with you Will and others if the pith goes all the way to the ground it is a multi trunk. Coppice trees should not even bee considered and yes Live Oak can at times be all forms making it tough for the untrained eye. In my early measuring years I would struggle making determinations but through experience I'm very confident in calling it like it is. Thanks also to all of the discussions we've had over the years as well.  On the Live Oak listing I have noted if a tree is a single or multi-trunk and have been doing so for many years. I hope I can come up to that workshop this spring.      Larry
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#3)  Re: Multi-stem Trees - Measuring Circumference

Postby mdvaden » Wed Jan 04, 2017 2:26 am

Larry Tucei wrote:Bob-  Well said you have made many valid points. I agree with you Will and others if the pith goes all the way to the ground it is a multi trunk. Coppice trees should not even bee considered and yes Live Oak can at times be all forms making it tough for the untrained eye. In my early measuring years I would struggle making determinations but through experience I'm very confident in calling it like it is. Thanks also to all of the discussions we've had over the years as well.  On the Live Oak listing I have noted if a tree is a single or multi-trunk and have been doing so for many years. I hope I can come up to that workshop this spring.      Larry


How will we know if the pith goes to the ground? Evidently, cutting it down is the only way to prove whether or not it does. Since nobody will want to cut down the tree to find out, that pretty much seems to cut-down whether or not the pith matters. That actually makes it simple for visible stems, in just going on where it's wood and bark reach to. Pretty much the "calling it" as it is like you said.
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#4)  Re: Multi-stem Trees - Measuring Circumference

Postby Don » Wed Jan 04, 2017 4:24 pm

Mario-
We've had decades of nominators "calling it" based on American Forest minimalist rules proper girth measurement. We in the AF Measuring Guidelines Working Group are working very hard at creating a more fair way to measure girth of single-stem contenders and multiple-stemmed contenders. We can see no other solution with American Forests strict adherence to a single category (read single column in register).

To achieve parity, we've derived a formula that 'normalizes' the cross-sectional cbh area of multiple-stemmed contenders and converts the combined cross-sectional area to a normalized cbh.
 
For simple folks like myself, Bob Leverett has set up an Excel spreadsheet to do the calculation...all we have to do is enter the respective cbh's of the single-stem tree, and multiple-stemmed tree...and push the calculate button.  If you're interested, contact Bob (dbhguru@comcast.com). This solution will be an essential part of the upcoming revision of the online AF Measuring Guidelines.

Also appearing in the upcoming revision will be a greater emphasis on delineating the central axis of the nominated tree, to determine if it's single or multiple stemmed...this is a conservative approach that allows the nominator to relatively simply estimate where the pith would be, in the absence of external forces.

In the presence of external forces (like an adjacent tree being inosculated, steep slopes inducing lean angle, etc.), standard considerations from Wood Science/Technology will be used. Specifically regarding Reaction Wood as explaining how angiosperms and gymnosperms "react" differently to the same external forces. Please review Appendix in current online Measuring Guidelines (pp.74-81) for a more complete handling of this topic for literature citations; and the glossary of terms that follows.

Hope this will encourage dialogue, do continue this discussion, your inputs are always welcome!
-Don
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#5)  Re: Multi-stem Trees - Measuring Circumference

Postby Darian Copiz » Thu Jan 05, 2017 7:09 pm

Most definitions of "tree" include mention of a single or main stem or trunk. One stem of a multi-stem woody plant could be nominated, but it should be just that stem - including height and canopy spread. I think the pith trace is a good rule, but think that allowing the point of divergence to be anywhere above the root collar is too generous. Pith divergence shouldn't be any lower than 4.5 feet, and for large species of trees even that is very generous. Although in some cases determining pith divergence may be a little tricky, for the majority of trees it's pretty clear. I have a hard time recalling any trees I measured where I couldn't tell.

It's fine to include shrub species as champion trees, as long as they have a tree form. However, including tree species with a shrub form is a different matter. To be a champion tree, for starters it's got to at least be a tree. If there's some magnificent "trees" that branch below 4.5 feet, that's great. People can visit them, admire them, and praise them, but that doesn't mean they have to be champion trees. We've been underwhelmed by champions for years. Modifying the rules can change that. Including multi-trunks doesn't.

Darian

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#6)  Re: Multi-stem Trees - Measuring Circumference

Postby mdvaden » Thu Jan 05, 2017 9:45 pm

Darian Copiz wrote:Most definitions of "tree" include mention of a single or main stem or trunk. One stem of a multi-stem woody plant could be nominated, but it should be just that stem - including height and canopy spread. I think the pith trace is a good rule, but think that allowing the point of divergence to be anywhere above the root collar is too generous. Pith divergence shouldn't be any lower than 4.5 feet, and for large species of trees even that is very generous. Although in some cases determining pith divergence may be a little tricky, for the majority of trees it's pretty clear. I have a hard time recalling any trees I measured where I couldn't tell.

It's fine to include shrub species as champion trees, as long as they have a tree form. However, including tree species with a shrub form is a different matter. To be a champion tree, for starters it's got to at least be a tree. If there's some magnificent "trees" that branch below 4.5 feet, that's great. People can visit them, admire them, and praise them, but that doesn't mean they have to be champion trees. We've been underwhelmed by champions for years. Modifying the rules can change that. Including multi-trunks doesn't.

Darian


If tracing the pith is a good idea, how have you seen it done without cutting a tree apart?

I've heard the concept talked about, but never seen anybody actually document doing it without destroying a tree.

Is there any video where someone can show how to do it non-subjectively.
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#7)  Re: Multi-stem Trees - Measuring Circumference

Postby Don » Mon Jan 09, 2017 10:56 pm

Darian[/quote]

If tracing the pith is a good idea, how have you seen it done without cutting a tree apart?

I've heard the concept talked about, but never seen anybody actually document doing it without destroying a tree.

Is there any video where someone can show how to do it non-subjectively.[/quote]

Mario

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Mario-
I see you directed your comment on pith tracing to Darian's post. As another contributor to this thread, I thought I might have something to add.
I'm attaching an image of the species Acer saccharinum.  Knowing that you are a professional arborist, and have felled many trees in your line of work, I like to ask your professional opinion...is this a single stemmed (one pith line at ground level (original)) or a multi-stemmed tree (all pith lines converge somewhere between breast height and base, or?
-Don

               
                       
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#8)  Re: Multi-stem Trees - Measuring Circumference

Postby Darian Copiz » Tue Jan 24, 2017 8:57 pm

Although the examples I've seen appear to be pretty clear to me and I'm not sure why there is so much debate about this, I think there are some potential complications if one is using the root collar for determination, as that area can be somewhat muddled. At 4.5 feet above the ground there is less room for interpretation and things are even clearer. Breast height is where circumference is measured, so that should be where the number of trunks should be determined. Otherwise we might as well measure circumference at the root collar.

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#9)  Re: Multi-stem Trees - Measuring Circumference

Postby mdvaden » Tue Jan 24, 2017 11:58 pm

Darian Copiz wrote:Although the examples I've seen appear to be pretty clear to me and I'm not sure why there is so much debate about this, I think there are some potential complications if one is using the root collar for determination, as that area can be somewhat muddled. At 4.5 feet above the ground there is less room for interpretation and things are even clearer. Breast height is where circumference is measured, so that should be where the number of trunks should be determined. Otherwise we might as well measure circumference at the root collar.


For a big tree registry, it would be a lot simpler to require that the trunk needs to be entire up to at least dbh or it doesn't count. Same rule in all states and nationally.

Easy.

Then anybody can still do volume measuring if they want. But it would make things a lot easier.
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#10)  Re: Multi-stem Trees - Measuring Circumference

Postby mdvaden » Wed Jan 25, 2017 12:04 am

Don wrote:
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Mario-
I see you directed your comment on pith tracing to Darian's post. As another contributor to this thread, I thought I might have something to add.
I'm attaching an image of the species Acer saccharinum.  Knowing that you are a professional arborist, and have felled many trees in your line of work, I like to ask your professional opinion...is this a single stemmed (one pith line at ground level (original)) or a multi-stemmed tree (all pith lines converge somewhere between breast height and base, or?
-Don


I could only guess. Because I've seen people transplant small trees where two or three seeds germinated in a clump. And also seen maples where they started to branch into multiple stems a couple inches above the ground. So having seen the variables, I think it's literally impossible to know or guess for a tree like that unless it was seen in it's first couple years.

From what I'm looking at in the image, I'm certain three, four or more piths are spread across the clump, each pith reaching to close to the earth, that I doubt even cutting off it's stump at ground level would ascertain whether it was one tree or two. DNA test won't even matter because people occasionally root cuttings from the same tree.

One other variation that comes to mind, is where a tree grew to whatever size, someone cuts it flush to the earth, then sprouts around the circumference of the stump, becoming something similar to what's in that photo. In that case they are all attached to the same root system. In a technical sense that could be considered one tree or organism. In which case my personal thought is that it shouldn't be nominated for a big tree registry no matter how cool looking it may be. It could still become a historical or heritage tree.
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