Redbud puzzle

Native Tree Society Tree Measuring Guidelines and related materials.

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#1)  Redbud puzzle

Postby Will Blozan » Mon Nov 17, 2014 10:04 am

NTS,

I came across a huge redbud (Cercis canadensis)r recently that is a bit of a puzzle to measure. I think I know my answer but wanted to present this tree as an exercise to ponder. Where would you measure girth of this tree? Is it a single pith at the ground?

Angle 1
               
                       
Red bud 1.jpg
                                               
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Angle 2
               
                       
Red bud 2.jpg
                                               
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Have fun!

Will
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#2)  Re: Redbud puzzle

Postby bbeduhn » Mon Nov 17, 2014 11:13 am

I'd lean toward the smallest point below where the two trunks (or branches) split, above where the third trunk (branch) shoots off.  Redbud, dogwood, and even live oak are puzzling in this regard.  I found a fat redbud very similar in nature and called it a multi but I'm not certain about that.
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#3)  Re: Redbud puzzle

Postby edfrank » Mon Nov 17, 2014 11:42 am

Will,

I would agree with Brian.  Any guidelines are going to have some trees that will becuae of their character have inflated girths.  The little burls/epicormic growths will make this tree larger than it would be otherwise, but the best representation is below the lowest side branch.  My opinion.

Ed
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#4)  Re: Redbud puzzle

Postby Will Blozan » Mon Nov 17, 2014 11:49 am

Nice to see we are all on the same page... Now take a look at the National Champion.

http://www.americanforests.org/bigtree/cercis-canadensis/

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#5)  Re: Redbud puzzle

Postby bbeduhn » Mon Nov 17, 2014 12:07 pm

Even measured correctly, you would almost certainly hit a burl.  Of course, that's small potatoes compared to measuring a veritable grove of trees like the redbud national champ.
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#6)  Re: Redbud puzzle

Postby edfrank » Mon Nov 17, 2014 12:21 pm

The national champ looks like a cluster of trees that have grown together, while your example is arguably a single trunk tree with lower branching.
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#7)  Re: Redbud puzzle

Postby Will Blozan » Mon Nov 17, 2014 4:21 pm

Maybe it is time to revisit Colby Rucker's Rule of 73...

The Rule of 73

Colby B. Rucker

July 2003

Trees are often compared by measurements of the trunk circumference taken at breast height (4 ½ feet, or 54 inches above grade).  National and state big-tree registries use this measurement, often known as cbh, by adding one point for each inch of cbh to points for height and average spread in their periodic lists of champion trees.  When a fork, burl or low-branching habit causes the trunk to have its smallest girth at some point below breast height, many of the big-tree registries have allowed that lower girth to be entered as cbh.  This has given such trees an unfair advantage over competitors that have a similar lower girth but taper to breast height, where their circumference is less.

I felt that some simple formula was needed to allow a fair comparison between trees with a low “waist,” and those that taper in a typical fashion.  An old list of national champions provided the elevation of 35 circumferences of trees measured below breast height.  I found that those trees averaged eight feet in circumference.  I then measured actual mature trees of ten species, which also averaged eight feet in girth at the same height.  After taking circumferences at numerous elevations, I devised a formula to fit the actual flaring contours of the trunks measured.  That formula, which I call “The Rule of 73,” is as follows:

Measure the smallest trunk circumference at or below 54 inches.  Add one-half the elevation (in inches) of the circumference to 73.  Apply the sum as a percentage of the measured girth.  The product is the hypothetical circumference at breast height.

As an example, in 1988 the Liberty Tree measured 31’ 7.5” (379.5”) in circumference at 24” above grade.  One-half of 24 is 12, which added to 73 gives 85.  85% of 379.5 is 322.6.  By the formula, the hypothetical cbh is 322.6”.  The actual 1988 measurement of the tree at breast height was 26’ 11”, or 323.0”.  Although some trees have greater or less taper than is typical, the accuracy of the Rule of 73 is often quite surprising.  Since the rule is based on percentages, it is applicable to trees of various sizes.  Also, because of the nature of percentages, hypothetical circumferences (from breast height to grade) do not increase by fixed increments, which would produce a conic structure.  Instead, circumferences increase by gradually greater increments, which produce a concave curve, which corresponds to the flaring base of a typical tree, as may be seen below.

Column “A” shows the elevation above grade in inches.

Column “B” shows the hypothetical circumference.

Column “C” shows the increase in inches over the girth just above.

Column “D” shows the increase as a percentage of the girth just above.



A            B              C             D

54        100.00

52        101.01        1.01        1.01

50        102.04        1.03

48        103.09        1.05        1.03

46        104.17        1.08

44        105.26        1.09        1.05

42        106.38        1.12

40        107.53        1.15        1.08

38        108.70        1.17

36        109.89        1.19        1.09

34        111.11        1.22

32        112.36        1.25        1.13

30        113.64        1.28

28        114.94        1.30        1.14

26        116.28        1.34

24        117.65        1.37        1.18

22        119.05        1.40        

20        120.48        1.43        1.20

18        121.95        1.47        

16        123.46        1.51        1.24

14        125.00        1.54        

12        126.58        1.58        1.26

10        128.21        1.63

8         129.87        1.66        1.29

6         131.58        1.71

4         133.33        1.75        1.33

2         135.14        1.81

0         136.99        1.85        1.37

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#8)  Re: Redbud puzzle

Postby dbhguru » Mon Nov 17, 2014 4:46 pm

Will,

  This comes at a good time. I'm glad you resurfaced Colby's Rule. We need to think very seriously about this rule for American Forests. Bless Colby. He was a treasure.

Bob
Robert T. Leverett
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Friends of Mohawk Trail State Forest

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#9)  Re: Redbud puzzle

Postby edfrank » Mon Nov 17, 2014 4:52 pm

Will, Bob,

I am always uncomfprtable where a formula like this is used to calcualte an equivalent diameter or other parameters.  I personally would rather see the raw numbers - in this case the measured girth and the height at which it was measured, than see a diameter equivalent number used.  I want to see actual measurements where ever possible.  But that is just my opinion.  

Ed
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#10)  Re: Redbud puzzle

Postby dbhguru » Mon Nov 17, 2014 4:56 pm

Ed, Will,

 The start of a great discussion. Since you two are part of the National Cadre, as are a few others on the BBS, I hope we all can give the subject a good airing. I'll toss out some ideas tomorrow. Gotta get ready to go to upstate NY tomorrow to check out a new old growth site.

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