Tree Girth Protocols   

American Forests has proposed that their measurement protocol 
for measuring circumference be changed.  The existing standard
states:  "When measuring the circumference of a tree on a slope, 
measurements are normally taken at the high and low side of the 
slope and then averaged. However, in some cases an especially steep 
slope may prevent the low side of the trunk from being measured. In 
this situation, the measurement should be taken at 4 feet above the 
mid-point of the trunk."  The proposal is to change the protocol to 
measuring at 4.5 feet above the ground surface on the upslope side
of the tree.

Re: High side, low side, and everything in between   Edward Frank
  Jan 17, 2006 06:27 PST 


The idea of the original position of the acorn may seem quaint, seeing as
the acorn is long gone by the time the tree is being measured. But the
advantage of this concept, and I believe the overwhelming point, is that
this position on the tree does not change over time. It is the same
regardless of how tall the tree grows. It is the same no matter how fat the
tree gets. It is a constant reference point. As a tree grows wider on a
steep slope, the reference point used for measuring on the high side
continues to creep upward. Would height also be measured from the high
side? With trying to measure at the original growth elevation -
extrapolated as mid slope. The starting point for height remains the same
over time, the starting point for girth remains the same over time, and both
measurements use the same base reference point. The change in reference
point for girth by measuring on the upslope may not be that much, not may it
affect the girth measurement drastically, but still it is not a constant.

Ed Frank


RE: Girth   Robert Leverett
  Jan 16, 2006 06:13 PST 

... material deleted 

Those of us who have measured literally thousands of trees do
appreciate the simplicity of choosing the uphill side versus mid-slope,
but too often the uphill side has accumulated material that partially
burys the trunk. In surburban environments where houses and yards are
next to hillsides, residents push their leaves and other organic debris
over the edge and down the embankments. Material quickly piles up
against trunks on the uphill side, partially burying them. Smaller trees
are affected less, but the big ones can suffer greatly. The differences
can be substantial.


RE:tree measuring moves forward
  Jan 16, 2006 19:48 PST 


I am sure that my USFS upbringing will show soon here, but the decision of
where you measure DBH on a tree might bear a little more discussion. Myself,
I can't see but what measuring 4.5 feet above "the highest level attained by
the root collar" wouldn't be most appropriate. I know that the USFS way was
determined by pure practicality (it's easier to stand on the up hill side of
the tree to measure it), but does have two's usually close to
the highest level attained by the root collar (certainly reasonable to begin
measuring tree height where root stops), and doesn't fly in the face of
countless MILLIONS of trees measured over a century or more, at the DBH from
highest side of tree.
I disagree on the "acorn" precept, as that point is often eroded away long
before we humans come on to a scene (in the context of old trees).
Just a few thoughts for discussion.

-Alaska Don
High side, low side, and everything in between    Robert Leverett
   Jan 17, 2006 06:01 PST 


   You make some interesting and worthy arguments (as always) for
measuring circumference on the high side. While I still prefer
mid-slope, I do see the logic of the high side with respect to the root
collar idea. However, it seems to me that the convenience idea, though
compelling from a management viewpoint, has been the source of
significant errors over the years as with the clinometer only methof of
height measuring. That's another story. With respect to circumference,
if the high side still has root collar and the basic idea is to measure
trunk at some standard height to get above the root collar, then we wind
up at varying heights above the root collar by standardizing on 4.5 feet
from either mid-slope or the high side. That seems odd as I think about
it. It would seem more logical to measure at a standard distance above
the root collar. In fact, why not measure at the highest point of the
beginning of the trunk regardless of position around the tree.
Presumably this would always be on the high side. Just wondering out
loud. If we did this, on a large tree that's growing on a steep slope,
we wouldn't so often find themselves 7 or 8 feet above where the tree
contacts the ground on the low side. Taking a circumference measurement
there, has always seemed odd to me. I feel like I'm cheating the tree.
And, if I'm doing it in the heat of the summer, later I have to go
inside and have one of those tall frosted glasses of a stout beverage
that you and I used to dream about as we floundered around in the old
growth. Of course, one tall glass leads to another, but after while,
pentance has been appropriately done to the tree for cheating it.

   Some general observations about ENTS and the champion tree lists come
to mind, not relating to anything you've said, Don. Just starting to let
my thoughts wander. Over the years I've been pretty vocal at voicing my
feelings about the limitations of the National Register of Big Trees. It
has been plagued with problems, but still has a good purpose that I
support. As for ENTS, I just don't see much point in us throwing our
hats into the ring in any competing way with the national Register or
the state lists. As for myself, I have no objection to taking
circumference measurements at 4.5 feet so we can do our own comparisons
as well as support the champion tree lists. I certainly would do it to
support ENTS members like Will Fell, Scott Wade, and BVP who run state
lists, but I hope we don't get involved with competing with those lists.
I'd much rather that we support the lists in the background and do our
own thing in the foreground.

    I really like Will's TDI system for a variety of comparisons to
include within a species and across speices and plan to regularly use
the system. However, I also admit to liking big point totals like Scott
mentioned. There is an excitement to a 450-point tree. Yeah, baby!

    When tackling the measuring of a really big tree like the
Sunderland, Pinchot, or Pine Plains sycamore, I like to take many
measurements. The standard 3 always seem so inadequate. For example,
Will brings up an excellent point about considering the cross sectional
area of the crown that is at a particular height threshold. That concept
really excites me. As he points out, it clearly distinguishes trees such
the giant Sag Branch tuliptree from very tall, skinny trees that are
hardly even noticed by non-ENTS types. For a behemoth like the Sag
Branch tuliptree, I'd think that as a minimum for historical
documentation, we'd want:

    1. Circumference at just above the root collar,
    2. Circumference at the traditional 4.5 feet,
    3. Circumference at the traditional 4.5 feet at 90 degree position
around the trunk,
    4. Circumference and height at the point of major branching,
    5. Total height,
    6. Maximum crown spread,
    7. Average crown spread,
    8. Longest limb extension,
    9. Longest linear distance within crown spread (maybe),
   10. Cross sectional area of crown projected onto a horizontal plane
at ground level
   11. Cross sectional area of crown projected onto a horizontal plane
at intervals of 25 feet starting at 100 feet.   
   12. Trunk volume,
   13. Limb volume,
   14. Diameter of biggest limbs at trunk
   15. Derives statistics such as height to diameter ratio from the
above basic measurements.

   Well, I've rambled enough. Time to listen to your thoughts and those
of others.

Fw: High side, low side, and everything in between   Edward Frank
  Jan 18, 2006 17:27 PST 


I may be about ready to jump ship with regard to the position in which to
measure the girth. Your arguments seem to make sense, but I will wait for
other dissenting voices to chime in first.

I think height should be measured from the "a la acorn" position from which
the tree forst sprouted - in effect for most trees the projected center of
the tree - on slopes that would mean mid-slope. I can't see any other
point as the start for height meaurements.

What does everyone else think about the point of meaurement for girth?

Re: Fw: High side, low side, and everything in between
  Jan 18, 2006 18:35 PST 

I think that the point for measurement will vary in the size of tree and
slope steepness.

On extremely steep slopes (60-80%) in West Virginia it is not uncommon for
the base of the downhill side large diameter trees to be six feet below stump
height (ground level) on the uphill side. In trees like this the taper is
minimal and I would probably want to get a circumference measurement at about
18 to 24 inches and compare the circumference to 4.5 feet (DBH).

I think that for some tree species there may be a sliding scale of the best
place on the bole to determine circumference. 4.5 feet as a measuring point
is a standard determined years ago by the timber industry to calculate the
board foot volumes in standing trees.

Although it is measuring trees at CBH is easy to accomplish, sometimes I'd
rather measure a tree six or seven feet up. With an old sycamore that has
lots of root swell or an oversized cull with a massive cat face you can do lots
of numeric fibbing if you stick with.

RE: Fw: High side, low side, and everything in between
  Jan 18, 2006 19:45 PST 

I prefer the "acorn" for both measurements. Many trees that are "Big" still have root flare above 4.5', no matter where you measure. For the hobbiest, it is easier to remember that height and girth are measured from the same spot. Science and forestry are different and can measure from wherever the grant or lumber agent wants.

Re: Fw: High side, low side, and everything in between   Edward Frank
  Jan 19, 2006 13:22 PST 


I will post a longer note tonight or tomorrow. Everyone is voting on the
question, and it is not time to vote yet. If the consensus is mid-slope
that is fine, but I think that Don has raised a couple of valid points and
that the issue deserves discussion before being dismissed. I have been
thinking about what are the underlying assuptions of the girth measurement.
I have posted in the past about girth. I summarized many of the recent
discussion on the issue, citing heavily Will Blozan's Tree Measuring
Guidelines on the website at: Feb 2005. An
earlier discussion of the issue was posted on the web from Nov 2003:

In addition I have posted discussions relating to defining the tree base
position (mostly my comments - but anyway) from Sept 2005 on the website
at: If we as
a group are going to have standards and protocols for our measurements. And
I believe everyone agrees that we must, then it is incumbent on each us to
understand the basic assumptions and strengths and weaknesses of our choices
and likewise thos eof opposing viewpoints. With as large of a group as
this, there will always be differences of opinions even about such basic
concepts as girth measurements. We can agree to disagree at the end, but I
think the discussion would be worthwhile. (Even in light of recent
diatribes on my part.)

Ed Frank
Trunk Flare   John A. Keslick, Jr.
  Jan 19, 2006 13:42 PST 

First I do not know if it is flair or flare. Either way the flare at the
base of a tree trunk is trunk tissues and not root tissues. So I think, the
trunk flare should be measured as trunk. That area is the toughest area.
If you run a chain saw into the trunk flare it will dull your saw. Woody
roots do not have that much lignin. I just saw a beaver was chipping at the
trunk flare of a tree in my back yard. That's a tough job. Further
dissections of trees would make this feature clear.
Its obvious when a root decay causing fungi which is discriminate to root
tissues rather than trunk tissues decays the woody roots yet leave the trunk
Here is an example:

RE: Trunk Flare   Robert Leverett
  Jan 20, 2006 04:33 PST 


   You've raised the bar for us in these discussions. Again you
demonstrate that the expert testimony of a tree biologist is needed
before we make judgments on what is trunk tissue versus root tissue on
the basis of outward appearance. What is your take on the term root
collar? What biological validity does it have? Standing back from a tree
with a fairly large trunk, I look for that pont where the curvature
changes abruptly. Shortly or immediately thereafter is where I notice
what I would have called the beginning of roots. It does appear to be a
transition zone.

High side, low side, and everything in between:let's stay between   MICHAEL DAVIE
  Jan 19, 2006 18:22 PST 

Hey everybody-
About girths: personally, I'd like to have the gavel banged on this one. We
already have tons, years worth of girth data, taken nearly exclusively at
midpoint. It would be very confusing to change teams midstream or switch
horses in the middle of the game, whatever. There are merits and faults of
each position, just as there are between different crown measurements, but
there isn't a clear precedent within ENTS for crown measurement, so that
seems more fairly debatable. I'm not exactly sure why this is coming up.
While it does not always do every tree justice to measure at midslope, no
girth measurement really does a tree justice; until we can 3-d laser-scan
the totality of each tree, there will be shortcomings we'll have to live
with. I don't believe midslope is inherently superior or inferior, it is
simply an indicator of girth at a particular height. We can always have more
measurements at other heights, the more the better to really document an
individual. But as a standard, midslope is fine and it is the precedent
I'm resting my case, thanks for listening.
High side, low side, and everything in between:let's stay between-Mike's   Robert Leverett
  Jan 20, 2006 05:27 PST 


I can appreciate your point. When is enough, enough? I guess that I
tend to see all the talking about measuring circumference at mid-point
versus other locations and the strengths and weaknesses of each location
as akin to talk about a game on the morning after. It is just the
chatter that goes with the profession/avocation/hobby. However, your
point is well taken. We do have all these measurements taken at
mid-slope. After all, if whe shifted the location, what would we do, go
back and re-measure every tree in our datbases? Yikes! No way.


Re: High side, low side,
and everything in between:let's stay between-Mike's
  Jan 20, 2006 15:54 PST 

I really really don't want to stifle opinion or debate, I just wasn't
understanding the object of the hash/re-hash of that subject. I was getting
scared someone was going to start pushing to change a pretty entrenched
standard. Omigod. I wouldn't know what to do. But it's not like the eleventh
commandment or anything, and that's one of the great things about this
group, the analysis and discussion of methods and reasons. Hope I didn't
sound crabby or anything.

RE: High side, low side, and everything in between:let's stay between, I'm with   Will Blozan
  Jan 22, 2006 12:01 PST 

Hey Mike and ENTS,

We all (give or take a fraction) have been measuring at midslope for
decades. Midslope does not change appreciably over time and as such provides
a permanent and repeatable reference. On some trees such as BVP encounters
and we may run across in the east the midslope will be underground on the
top side of the slope. BVP measures such trees at ground level on the top
side. I can't say I have ever encountered a tree in the east like this but
have instead run into logs or other debris against the trunk. But still, a
rare occasion.

It mnay be argued that the midslope rule will inflate the girth on trees on
a slope. I agree, but that is partly due to the response of the tree and the
relatively close distance to major anchor roots and trunk systems. That is a
biological component of trees on a slope and need not be ignored.

Truth is, functional diameter (smaller than indicated by the flared portion)
is the most accurate and it likely does not differ much from the portion of
the trunk a few feet above the midslope. Unfortunately, functional diameter
is beyond the realm of everyday ENTS surveys. And also, the 4.5 feet is such
an arbitrary rule based solely on convenience. If people were two feet tall
we would measure at 1.5 feet up.

My gavel falls in favor of midslope.

Girth Measurements   Edward Frank
  Jan 25, 2006 00:36 PST 

Will and others favor that girth should continue to be measured
at mid-slope. The fact that we have years of measurements taken at
mid-slope is a compelling reason for keeping the same methodology. The
problem of trunk basal flare will affect measurements taken either at
mid-slope or on the upslope side. There is the fact that the difference
in methodologies would only affect a handful of trees. The decision to
continue to measure girth at mid-slope is a reasonable one. I will
support the decision of the group and frankly do not disagree with the
final result.

The recent proposed change of circumference measurement methodologies
 by American Forests offered an excellent opportunity for have our group 
re-examine our procedures. 

People visiting the website will want to know why ENTS chose to measure
girth at 4.5 feet above the base of the tree from the mid-slope point on
a steep slope. Why was this chosen instead of the upslope side of the
tree as used by the USFS? Why is out methodology different from the USFS
and the revised methodology of American Forests? I ask that someone
writes a statement for publication on the ENTS website that addresses
these questions and explains why this methodology was chosen to measure
girth, explaining the logic and benefits of measuring girth at the
mid-slope. (I also want to preempt these arguments for use on Scott
Wades PA Big Trees website.)

Ed Frank
RE: High side, low side, and everything in between:let's stay between, I
  Jan 25, 2006 07:00 PST 

I "feel" that the upslope measurement came from the timber industry/Forestry side in order to better represent the volume of a tree in board feet. It is usually easier to measure here as it is usually level ground due to debris, but you still have to walk around the tree to run your tape, so how is it easier. If you can locate the high point, you should be able to locate the mid point.

Measuring height and cbh from the same point makes more sense to me, and creates a standard point to measure from that does not change much over time.

I will be measuring trees tomorrow for the website, and I will try both to see what the difference really is. Depending on species, it may not be enough points to really worry about. I have measured trees on slopes where if I used the upslope method, I cannot reach up that high when I am on the downhill side.

Circumference conventions   Robert Leverett
  Jan 25, 2006 08:12 PST 


     Over the years, circumference measuring conventions have received a
lot of attention on the ENTS list, but alas to no firm conclusions.
Colby Rucker had many posts, and as you know, Colby and I were on a
special AF committee studying the rules by which champion tree
contenders are measured. Over the past seevral years, I think I've had
at least a three dozen posts, but with the same basic message - a call
for flexibility and not worrying about being too close to the champion
tree list conventions for a variety of reasons. Since you are in a mood
to thrash the subject around, I'd be delighted to trot out my old
arguments, give them a new dressing, and present them again, plus
discuss the context for the current circumference measuring conventions.

     First, for relatively small trees on fairly level ground, the
4.5-rule for measuring a tree's trunk diameter has some good field logic
behind it. It allows timber specialists to take diameter measurements
with a D-Tape quickly. Experienced foresters can quickly swing the tape
around a tree at breast height and take a diameter measurement. Don
Bertolette told me that years ago. Although I don't know for sure, I
believe the American Forest convention of measuring circumference at 4.5
feet just follows the forestry convention of measuring diameter at a
standard (convenient) height. So for measuring efficiency in the field,
one can quickly recognize the logic behind measuring a diameter on the
uphill side of a tree and at breast height codified at a standard 4.5
feet. The problem arises when this forestry convention, applied for good
reasons, is extended into the world of tree measuring for the purpose
of crowning national and state champions where the champions are
supposed to be the largest members of their respective species. If there
is any sense to the concept of largeness, then the combined measurements
and resultant big tree formula must clearly stand up to scrutiny. It is
no longer about timber worthiness, or if it is, that should be
explained. What shouldn't happen is that our thinking about how to
create a composite formula to assess largeness and to adopt measuring
conventions be prejudiced by measuring convenience and an unconscious
bias toward timber value. When did the root flare become extraneous to
judging overall size? It thrusts itself in our faces to be acknowledged
when confronted with measuring a large bald cypress with a huge root

    This is why I advocate that we take multiple circumferential
dimensions. In modeling trees for volume, Will, Jess, and I do this
routinely, and I in the process, am quite happy taking a measurement at
4.5 feet above "something" to allow comparison to other trees for
whatever the source of the champion tree list. If it makes sense for us
to take a circumference measurement on the uphill side to fit into
American Forests new conventions, it also makes sense to measure at 4.5
feet above mid-slope to fit with our own perceptions of the best spot
and to support Scott and perhaps other state programs. In my humble
opinion, we should also measure circumference at the top of the root
flare as established on the uphill side. Finally, It makes sense to
measure the vertical distance between the point where the trunk meets
the ground on the uphill side and the corresponding point on the
downhill side. If for a potential champion (on some list), this vertical
component turns out to be say 7 or 8 feet, this would communicate
important information about the tree's mass that couldn't be gleaned
from a single circumference measurment at either mid-slope or from the
uphill side. Why keep ourselves in the dark about the structure of the
base of the tree? There is no good reason for doing that. The challenge
is to choose the fewest number of measurements needed to convey enough
information about the base of the tree to distinguish highly variant

    Although, I will respect majority wishes should ENTS eventually want
to adopt its own champion tree formula and maintain its own champion
tree list, I personally do not want to see us go down this path. I'd
much rather that we gather a broader range of tree measurements that
will allow us to make any number of comparisons, i.e. by AF measuring
conventions, by state conventions, by Will Blozan's comparative method,
etc. If we choose the latter path then we don't have to feel so
paranoid over adopting THE best set of compromise rules that we'll
revisit ad infinitum because the compromise doesn't work well for
important groups/classes of trees. For an ENTS-wide database, we could
agree that for very important trees, we will take extra measurements.
Three classes of trees come to mind.

Largest Trees:

     1. Circumference at top of root collar
     2. Circumference at 4.5 feet above mid-slope
     3. Circumference at 4.5 feet above uphill side
     4. Vertical distance between ground points on uphill and downhill

Potential Champion Trees:

     1. Circumference at 4.5 feet above mid-slope
     2. Circumference at 4.5 feet above uphill side

Other Trees:
     1. Circumference at 4.5 feet above mid-slope


Robert T. Leverett
Cofounder, Eastern Native Tree Society
Re: Circumference conventions
  Jan 25, 2006 10:38 PST 

I think you and Ed make valid points. It is true that my association with
tree measurements reflects my prior employment with the USFS, BLM and the NPS.
It also reflects my academic background, a western university (Humboldt State
University) and one closer to your environs (UMASS, Amherst), and one of the
professional organizations (SAF) that I belong to. All of these accept the
convention of measuring trees at a standard breast height from high side of
tree. It's not an emotional thing, it's just been that was for more than a

Having said that, I'm as big an iconoclast as anybody in ENTS (now that our
man Joe is lying low these days). I have no problem throwing off conventions,
particularly when they are conventions for convention's sake. If they don't
serve the purpose, then toss them.

But for a reason, for a purpose, and with strong and defensible rationale
behind the change. I'm not yet completely convinced that circumference is
that much more defensible than diameter. Neither do well when the shape is off
of circular. Personally, I think that ultimately it is mass/volume that
provides the end goal of superlatives. Volume displaced (in an infinitely
thin cross-section of the base) is the measurement you're looking for at
breast height, wherever it's measured from.

Having probably measured as many trees as anybody on this list (no, not near
as accurately, easily conceded here), I can tell you there are likely as many
trees that aren't circular as there those that are...that means that roughly
50% of any tree population aren't going to be (really) accurately measured by
a D-tape. Using circumference is less derived than diameter, but still
assumptions of perfect circles comes into play as soon as you use
circumference to calculate volume. These are small to medium errors, where the
D-tape is in continuous contact with the bark.
When trees of various species that typically have convoluted bark surfaces,
the D-tape significantly mis-measures the diameter, and not conservatively.
Here again, it's the "infinitely thin cross-section of the base" volume that
is the measurement you seek.

And what really brings home the difficulties in finding conventions/standards
is the fact that the trees most interesting to us, are those that are the
largest of their species, or kind. They are most likely to be mishapen, to
buttress and flare, to have burls, to not be perfectly circular, to not easily
AND accurately be measured at breast height (wherever measured from), because
they show their plight in surviving what the vagaries of time have thrown at
I understand the difficulty in not making emotional decisions about them, as
they were here before us, and hopefully here for our descendants...

Re: Circumference conventions   Edward Frank
  Jan 25, 2006 11:02 PST 


At this point I just want an explanation I can put on the website for the
difference in measuring protocols. I would agree that multiple measurements
of girth are better than single measurements, these measurements are
generally not done. Girth is typically measured at one point, and I am
wondering why it is measured at the point it is? How did ENTS come to adopt
that convention, and why is it inherently better than the USFS upslope
measurement taken at an upslope point? I can see advantages to measuring on
the upslope side, but am having trouble finding reasons for measuring at
mid-slope beyond the idea that we have been doing it that way for years. I
will reiterate some background information and list the merits of the
upslope measurements below:

The breast height level for measuring girth was originally used by foresters
to determine the number of board-feet in a tree. The very basal portion of
a tree trunk flares outward just above the ground where the trunk meets the
root crown of the tree. This is commonly referred to as basal flare, root
flare, or buttressing. Above the basal flare the trunk typically assumes a
more columnar shape. Girth was measured at breast height both for the ease
of measuring and in order to obtain a girth for the bole of the tree itself,
not a value inflated by basal flare closer to the ground. For average trees
and even most large trees, 4.5 is above any significant basal flare. Given
a need for standardization in their measurements, circumference at breast
height, or 4.5 feet became the accepted standard for girth measurements.
Standardization is still needed today so that comparisons of measurements
can be fairly made between different trees. While the 4.5 foot standard can
be applied to most trees to approximate the true girth of the bole of the
tree, there are times where this height is not enough to reach above the
basal flare of the tree. Some species of trees, such as bald cypress,
exhibit buttressing far up the trunk commonly exceeding 20 feet or more
above the ground surface. Very large trees throughout the country, and the
gigantic trees from western North America have basal flare extending well
above the 4.5 foot measurement height. Indeed some of the large sequoias
will have a footprint at that height that more resembles a many tentacled
octopus than it does circular column. An all encompassing variable standard
to measure the actual bole of the tree that would apply to all trees from 20
foot in height to 300 foot would be impractical to apply even if it were
developed. Therefore rather than throwing out the 4.5 foot standard out, it
must simply be recognized that for these trees the girth measurements
include a portion of the basal flare.

From the time a tree first sprouts from the ground to form a small seedling
until it reaches old age the position of the sprouting point at the pith of
the tree remains unchanged.   This would be a reasonable unchanging point
from which to measure both the height of the tree and the basal point for
the 4.5 foot height from which to measure girth. When measuring the
circumference of a tree growing on a steep slope the ENTS standard measures
girth at 4.5 feet above the mid-slope line serving to approximate the girth
at 4.5 feet above the original sprouting point at the center of the tree.
For larger circumference trees there were potential problems when applying
this standard. The girth of larger trees as measured from the low side or
from the mid-slope slope position would incorporate large portions of the
basal flare, inflating the girth measurement significantly. This procedure
gives trees growing on a slope a numerical advantage over trees of
comparable size growing on flat surfaces. In addition for very large trees,
it may not even be possible to measure a circumference 4.5 feet above the
low side or mid-slope. The far end of a level loop may well be below the
ground surface on the upper side of the tree. There are also some practical
considerations relating to the difficulty of measuring trees on steep
slopes. A measurement standard that can not be applied fairly for all trees
or can not be applied at all needs to be reconsidered.

The newly adopted measurement standard used by American Forests and one that
had been in use for years by the USFS calls for girth measurements for trees
growing on steep slopes to be measured on the upslope side of the tree at a
height of 4.5 feet. A tree is a dynamic system, therefore while a common
measuring point is required between different trees for comparison purposes,
the point can be defined in relationship to a physical characteristic of the
tree. Measuring girth at a height of 4.5 feet on the upslope side of the
tree is one such point. This point also bears a direct spatial relationship
to the root collar of the tree which grows just below the ground surface.
The point is both dynamic, changing in physical location as the tree grows,
and clearly defined meeting the requirements of a measurement standard.
Trees with high basal flares will still reflect a portion of that basal
flare in the girth measurement, however measuring at a higher point will
lessen the amount of basal flare incorporated in the girth measurement. The
methodology also helps to simplify and standardize measurements and is
consistent with the USFS method of measuring tree circumference.

How would changing the methodology affect the existing dataset? It will
affect the existing dataset to some degree. Many trees in the list are
located in relatively flat ground. The girth measurements on these trees
will be unaffected. Only trees growing on steep slopes would be affected.
Even many of those girth measurements will not change as the original
measurements may have been above any significant basal flare. A few very
large trees growing on steep slopes will have a smaller girth measurement
using this upslopecriteria.   American Forests is planning on instituting a
10 year rule, requiring that all trees in its National Register of Big Trees
be remeasured every ten years or be dropped from the list. A similar
twilight rule for ENTS applied to our largest trees would allows us to both
see any changes in the health, or changes in size of the individual tree in
a ten year span and would alieviate any problems associated with any change
in measuring standard that ENTS might choose to adopt.

As I said in a previous post, a decision to keep measuring girth from the
mid-point of the slope is a reasonable one, given the large amount of
measurements we have taken. On the other hand I don't think it would be the
end of theworld as we know it if the standards were revised. I would like
to see someone write an essay an explanation of why this methodology was
chosen and its merits for publication on the website. Bob wrote: "it also
makes sense to measure at 4.5 feet above mid-slope to fit with our own
perceptions of the best spot and to support Scott and perhaps other state
programs."   I am asking why is this the perception of the best spot? I
have read almost all of the posts since the first one on topica, years
before I joined the organization, when first working on the website, I did
not find the answer there. The one idea that keeps comming back to me as I
read the recent arguments - essentially that the point of measurement isn't
that critical so long as it is consistent - is that the girth of very large
trees can't be measured at all using the mid-slope convention. How can we
have a standard that doesn't work for many trees? I can justify this only
by considering these very large trees as a separate measurement class - but
would it not be better to adjust the measurement point so that these trees
can be incorporated in the same group as all the other trees?

Edward Frank

RE: Circumference conventions   Robert Leverett
  Jan 25, 2006 11:14 PST 


   Excellent post! You've laid out the problems and our challenge quite
well. I agree, the area of the thin, cross sectional slice would give us
a better measure of a tree's size than a perimeter measurement treated
as the circumference of a circle or a derived measurement like diameter.
I can't count the times that I've stretched my tape around a big tree
that is irregular and observed spots where the tape is not touching the

   Nor are the trunk shapes of big trees that we measure necessarily
elliptical, or more elliptical than circular. What to do? What to do?

   Will Blozan is testing out a new microscope-telescope with a double
reticle that promises to be very accurate. If he gives the thumbs up,
I'll purchase one and then use it on the very large trees to compute at
least 4 equally spaced thicknesses and then compute an average cross
sectional area. I'll then experiment with that result.

Re: High side, low side, and everything in between:let's stay between, I   Edward Frank
  Jan 25, 2006 11:37 PST 

I don't really think for most trees that the differences between the two starting points for girth measurements will have any effect on the measured girth. I guess I am looking for an explanation as to why mid-slope is a better measurement point. So far most of the replies have basically boiled down to "It is best because it is best." I am wondering why.

RE: High side, low side, and everything in between:let's stay between, I   Robert Leverett
  Jan 25, 2006 12:12 PST 


   For some of us, trunk/root flare is important attribute to consider
in assessing tree size in comparisons to other trees. A system that
ignores the flare is missing a potentially important attribute of size,
especially other things being equal. On the other hand, a system that
over-weights flare is not the answer either. That's why I recommend the
measurement of the trunk just above the flare as well as the other
measurements. The multiple measures give us flexibility and position to
deal with all kinds of shapes.

   Now to your question. Why mid-slope? From my perspective, it has
seemed like an acceptable compromise to better capture the bulk of the
lower trunk. I think Colby saw it as the most logical spot to capture
the circumference 4.5 feet above where the tree started growing. That
made sense to him, as a compromise between high side-low side thinking.
When I think very long about circumference measurement, I invariably
drift toward multiple trunk measurements - as a standard measurement
protocol. But if I have to select a single circumference measurement,
what influences me most toward mid-slope is some of the tree shapes that
I've encountered where going to the high side would have seemed to cheat
the tree. An example follows.

   I know of a huge cottonwood growing on steep bank in Hatfield, MA.
Organic matter has piled up against the uphill side of the trunk due
largely to annual flooding. The lower side of the cottonwood drops down
to a shelf that runs level for a few tens of feet and then the land
takes a plunge into the Connecticut River. Standing on the uphill side
of the cottonwood and establishing the 4.5-foot height level places one
8.5 feet above the lower side - the top of the lower root structure, I
might add. It seems striking to be so high on the trunk when there is so
much tree below the uphill 4.5-foot level.

   So, just to summarize. For me, mid-slope has been the compromise that
I have needed to better capture the bulk of the lower part of the tree.
John Keslick Jr's recent post explaining that the flare is still trunk
tissue reinforces the lower trunk's importance to me not to be excluded.
Well that's my argument for the day. It may be lame, but I think it did
answer your question.

One more - high side, low side   Robert Leverett
  Jan 25, 2006 12:40 PST 


   One point deserves further discussion. When we deal with forest-grown
trees on sloping land, circumference measurements on the uphill side at
4.5 feet are usually better representations of trunk shape for the next
10, 20, 30, 40 feet. Thinking along these lines, there is someting to be
said for measuring forest-grown shapes on the uphill side, especially if
we're looking for a more representative single trunk measurement. I
would assume that Don Bertolette would second this thinking.

   Now, this line of argument does not hold so well for open-grown
shapes where branching often starts anywhere from just above the upper
end of the trunk/root flare to 10 to 15 feet. The trunk of the
open-grown forms often flares out significantly as the point of major
branching is approached.

   In the interest of studying the representativeness of the high side
measurement to reflecting trunk behavior, I think I will conduct a test
this weekend using my sort of trusty RD 1000. I'll measure/model a
number of trees of varying shapes that are on slopes of different
pitches to test how well the 4.5-foot uphill rule works to reflect trunk
behavior from the point of measurement up to the point of major
branching. Stay tuned. Hopefully, Will and Jess will join in. They can
provide even more accurate data with their monoculars.

Re: Circumference conventions   Jess Riddle
  Jan 25, 2006 15:25 PST 

Ed, Bob, Don, Ents;

The problem of 4.5' above midslope being underground. Yes, not being
able to measure some trees according to protocol is a real problem,
and I know of no counterargument that dismisses that concern.
However, the magnitude of the problem in the East is much smaller than
it might appear. In measuring trees, I have NEVER encountered a tree
in the eastern U.S. that I wanted to measure where the 4.5' above
midslope was below the high side ground. That problem may frequently
occur with large western conifers, but in the East, the concern
remains theoretical. Eliminating the problem is a real, but minor,
advantage of an upslope reference point.

More frequently, coppicing precludes the measurement of the
circumference of a single stem. Using a potentially higher measuring
level will allow a few more measurements to be taken, but again the
advantage will rarely occur. In use by big tree programs, the
standard will likely exclude a few multi-stemmed trees.

Similarly, as others have pointed out, a potentially higher reference
level will reduce but not eliminate the influence of 'root flare'.

For large trees growing on slopes, keeping the tape measure high
enough on the downhill side of a trunk often presents a challenge.
Stretching as high as one can and possibly wriggling the tape a little
afterwards is usually sufficient to make the tape level around the
entire trunk. In the southern Appalachians this situation is common.
Requiring the tape to be held one to one and a half feet higher, which
would be typical for the proposed change, would add substantially to
the difficulty of taking a basic circumference. Means are available
to deal with the situation, and not doing something because it's hard
may be a path to mediocrity. However, most methods for obtaining the
circumference higher up the trunk involve to people and/or additional
equipment, so this change would significantly slow measuring and
result in the loss of a few measurements.

Circumference measuring, according to existing methods, allows for
adjustments when branching or abnormalities influence the
circumference. This flexibility allows the size of the tree to be
measured rather than allowing unusual configurations of the wood
unrelated to size to distort measurements. Measuring circumference at
a potentially higher level would increase the frequency of
encountering limbs at measurement level. Thus, the measurement would
actually be applied at the standard level less frequently.

Small species would be influenced by the proposed change less than
other species, but they would still be measured slightly higher. Many
of those species branch low, so the new level would slightly increase
the number of trees measured above major branching. This change then
runs counter to previous suggestions of measuring small, understory
species at a lower level.

Using a common definition for "ground level" between height and
circumference seems only natural. Height measurements are currently
referenced against midslope (I assume this convention results from the
fact that the tree must have physically grown from the original
position of the seed to its highest current extent).

As others have pointed out, changing our circumference protocol would
render all our previous circumference measurements incomparable. If
ENTS' goal is the long-term improvement of measurement methods, this
decision may affect far more future measurements than measurements we
have previously collected. Conversely, I think the protocol change
will have a greater effect on previous measurements than has been
suggested. The lower section of tree boles, above any root flair, are
typically concave in profile. The concavity is usually severe enough
to change circumferences by several inches over a distance of less
than two feet. Consequently, the vast majority of large trees growing
on slopes will have significantly different circumferences after the
proposed rule change. Also, the ground in immediate vicinity of large
tree bases is rarely level even in relatively flat terrain, such as
floodplains. Hence, this change would impact all but a small
percentage of the trees we have measured.

Ed Frank has clearly articulated how the midslope provides a more
stable reference over time than does the upslope. Thus, a midslope
based measurement is more truly a "standard," and provides greater

I view these arguments as a few minor points for an upslope reference,
a greater number of minor points for a midslope reference, and one
strong point for a midslope reference (repeatability). Many of the
statements above about how changing the measuring point will affect
measurement are based on my own field experience. Prior to this
discussion, I saw using upslope for the reference as clearly inferior
choice. I now see an upslope reference as a reasonable position, but
for the reasons outlined above, I believe keeping the existing
protocol will behoove ENTS.

Jess Riddle

Re: One more - high side, low side
  Jan 25, 2006 15:40 PST 

I meant to comment earlier on the topic of root/trunk flare and wood I review the comments made so far, they seem to reflect species
and their respective wood densities. The exception has been discussion of the
within tree differences of wood hardness/density. I would add to the
discussion of root versus trunk physiology, the concept of 'reaction wood'.
Reaction wood can be 'compression' wood or 'tension' wood. Compression wood
is often found in lower side of branches as they curve upward, or in a trunk
where the tree is reacting to soil slip or gravity, and begins buttressing to
add support...wood here is denser, and from the perspective of one sawing it,

The more you talk of lower trunk mass and effective ways to measure it, the
more it seems to me that its volume is what is ultimately sought. One of the
high tech devices used in the Park by archaeologists is a digital camera that
functionally scans a rock wall to capture the rock art imagery...what we need
is a scanner that is programmed to circle a tree's base and capture it's shape
in a three dimensional fashion!

Re: Circumference conventions   edward coyle
  Jan 25, 2006 16:30 PST 


You are quite correct in that trees are rarely circular in cross section.
But it is a practical measurement available to all, and directly comparable
when used by all.
I have helped measure for your idea of a 'cross section,volume
displacement'. It required mapping a tree within a triangle of known
dimension, and measuring at right angle to the sides with a very accurate
survey lazer every inch or two, recording all the data. For the final step
the data was fed into a digitizer,and a functional diameter was given.
For practical purposes, measured diameter is sufficient. Of the thousands of
ENTS measured trees only two have had their vital stats run through a
digitizer, and thankfully, BVP didn't ask for my help with that!

Ed C
RE: Circumference conventions   Robert Leverett
  Jan 26, 2006 05:31 PST 


   Your analysis is well thought through, as it always is. The desired
form that trees take for timber (forest-grown, long clear boles) lends
credibility for the uphill alternative, but that is not the case for
open-grown trees that branch low, as you properly point out.
Interestingly, American Forests seems caught up with forestry
traditions, AF's own traditions, and measuring convenience. From my
perspective, this is a lethal brew guaranteed to yield results that will
always displease a sizable percentage of the measurers. I don't envy
them their job.

RE: Circumference conventions   Edward Frank
  Jan 26, 2006 05:21 PST 


There have been a number of replies concerning girth measurements. I
want to address some points made in these posts playing as an advocate
for measuring from the upslope side of the tree. The matter in my mind
deserves discussion.

  Bob Leverett (Jan 25, 2006) wrote:
Over the past seevral years, I think I've had

at least a three dozen posts, but with the same basic message - a call for flexibility and not worrying about being too close to the champion tree list conventions for a variety of reasons.

Bob - I will agree that more measurements are generally better, but that
does not address the question of how the circumference should be
measured. I really like the proposal to take a number of additional
girth measurements for trees that are among the largest of the species
or potential champions. For these trees multiple measurements including
maximum crown spread and minimum crown spread should also be taken as
part of the measuring routine- eff

  Don Bertolette (Jan 25, 2006) wrote:
I'm not yet completely convinced that circumference is
hat much more defensible than diameter. Neither do well when the shape is off of circular. Personally, I think that ultimately it is
mass/volume that provides the end goal of superlatives. Volume displaced (in an infinitely thin cross-section of the base) is the measurement you're looking for at breast height, wherever it's measured from.

Don, What you measure depends on what you are trying to determine. I
like measuring circumference because it is a physical characteristic
that is actually being measured. Diameter is an interpolation based
upon the concept of circularity of the tree that doesn't actually
represent any actual physical measurement of the tree. If you are
trying to determine volume then a detailed cross-section map would be
closer to what you need to measure volume. In my opinion girth or
circumference is a perfectly valid measurement in its own right, not
just a value which is only useful in determining another value. If you
look at a tree, all of the growth and biological activity of the trunk
in restricted to the very outer portion of the tree trunk and bark. The
inner mass of wood is dead tissue which provides structural strength to
the tree, but otherwise is not involved in ongoing growth of the tree.
A tree with a solid core is little different from one that is hollow in
terms of biological production. How many of you have visited a
profoundly hollow tree, even have stood inside, and seen a healthy full
crown for the tree? There is the knowledge that the hollow trees days
may be numbered by a good windstorm, but the tree while it stands is
otherwise healthy. The linear distance around the circumference of the
tree is a fair measurement of the actively living portion of the trunk.
- eff

  Bob Leverett (Jan 25, 2006) wrote:
a) For some of us, trunk/root flare is important attribute to consider
in assessing tree size in comparisons to other trees. A system that
ignores the flare is missing a potentially important attribute of size,
especially other things being equal. On the other hand, a system that
over-weights flare is not the answer either...

b)...Standing on the uphill side of the cottonwood and establishing the 
4.5-foot height level places one 8.5 feet above the lower side - the top 
of the lower root structure, I might add. It seems striking to be so high 
on the trunk when there is so much tree below the uphill 4.5-foot level.

Bob, trunk flare is certainly a valid aspect to address when considering
the overall "bigness" of a tree. However this does not address the
question of what is the best way to measure girth. The example of the
cottonwood does not seem to apply either. I would still measure height
from the point "where the acorn grew" so I don't see how the argument

  Bob Leverett (Jan 25, 2006) wrote:
Now, this line of argument does not hold so well for open-grown
shapes where branching often starts anywhere from just above the upper end of the trunk/root flare to 10 to 15 feet. The trunk of the open-grown forms often flares out significantly as the point of major branching is approached.

Bob, I don't see how this argument favors measuring the girth from 4.5
feet above mid-slope as opposed to 4.5 feet above the upslope side.
Both would have the same limitations. In so far as measuring from the
upslope side would incorporate less flare, I think it would be better.
The existing guidelines specify of there is a branch or burl at the
measuring point that causes the girth at that height to be inflated,
then the girth should be measured at the narrow point of the trunk below
that height, and the actual height of measurement noted. That would
still apply whether the measurement was taken based upon mid-slope or

  Jess Riddle (Jan 25, 2006) wrote:
a) For large trees growing on slopes, keeping the tape measure high

enough on the downhill side of a trunk often presents a challenge.

b) ...Measuring circumference at a potentially higher level would 
increase the frequency of encountering limbs at measurement level.

c)...Using a common definition for "ground level" between height and
circumference seems only natural. Height measurements are currently
referenced against midslope (I assume this convention results from the
fact that the tree must have physically grown from the original
position of the seed to its highest current extent).

d)...Conversely, I think the protocol change
will have a greater effect on previous measurements than has been
suggested. The lower section of tree boles, above any root flair, are
typically convex in profile. The concavity is usually severe enough
to change circumferences by several inches over a distance of less
than two feet. Consequently, the vast majority of large trees growing
on slopes will have significantly different circumferences after the
proposed rule change.

e)...has clearly articulated how the midslope provides a more
stable reference over time than does the upslope. Thus, a midslope
based measurement is more truly a "standard," and provides greater

Jess, Thanks for the well thought out reply. I have taken the liberty
of numbering various point I want to address from your post. a) There
may be difficulty measuring trees from the upslope side. I will concede
this point, but measuring at mid slope may also require an awkward
stance and limit the number of measurements. b) I don't think this is
really true. The number of limbs at a 4.5 foot height would be small no
matter what point of origin would be used. The upslope measurement
would I my concept of its implementation allow for reasonable
adjustments based upon the presence of limbs, burls, or bulges just as
are encoded into the current standard. c) Common point for height and
girth. This was a point I had made originally. I see height still being
measured from the point of the original sprout, but am not sure that
girth needs to be tied to the same point. If it were a consistent
height above the current ground surface on the upslope side of the tree,
I believe that is as valid of a starting point as the point where the
acorn sprouted. d) Jess, I will bow to your opinion on the effect on
the existing database. You have measured many more trees than the small
number I have measured. If you believe it will have a larger effect on
the database than I suggested, I am sure you are right. If I want to
play Devils Advocate, then conversely the same argument demonstrates the
large amount of errors in our existing dataset that would be improved
by using a higher measuring point. e) The measurement point for girth
would be fixed by using the midslope standard. Tree girth could be
measured again and again at the same physical point over time to
determine if the girth has increased over time. That is a valid point
and one of the better arguments in favor of the mid-slope option. I
might counter and ask that while the same physical point is being
measured each time, is it the same point physiologically? Are you
comparing Apples to apples or apples to oranges? As the tree grows in
girth the taped distance is farther out from the center of the tree - so
while it is the same plane it really isn't the same point. As the tree
grows wider measuring from a fixed plane would incorporate more of the
basal flare into the measurement. Measuring from the upslope side, the
idea is that the same proportion or lesser proportion of the basal
flare, would be included in the measurement making it a truer measure
of the tree's girth. I don't know if the last argument is true or not -
but I wanted to put it out there anyway.

My goal is to have the concept of circumference measurements discussed
and as people have risen to the challenge, I think this goal has been
successful. I am still not sure what I will write on the website in
defense of the mid-slope measurement protocol.   I know many of the
arguments that American Forests will make for their revised standard.
The revised American Forests standards will be presented in the 2006
National Register of Big Trees.

Ed Frank

Re: Circumference conventions   Edward Frank
  Jan 26, 2006 05:46 PST 
Bob and Jess,

What percentage of trees are both open grown and on a steep slope? The convention described in the tree measuring guidelines state: "If a burl or other atypical growth formation is encountered at this point the least distorted girth below this point is used (B); otherwise above BH" The same would apply I think to low branches at the measurement height - this may have been addressed somewhere, but I can't find the reference.

Ed Frank
RE: Circumference conventions   Robert Leverett
  Jan 26, 2006 08:12 PST 


   What I've been saying, at least I thought I was, is that we take
circumference measurements at 4.5 feet above mid-slope and circumference
measurements at 4.5 feet on the uphill side. We also take circumference
measurements at just above the root collar from the uphill side. The
three measurements become the ENTS convention.

   There's no rule that says "we can take extra measurements if we want
to, but ONE measurement must serve as our standard". By extending our
standard to three, the first two circumference measurments would allow
us to satisfy the rules of those champion tree lists that prescribe a
particular spot for the circumference measurement. We use the applicable
rule (because we've got the measurement)when we want to interact with a
particualr list.

   The cottonwood example is relevant in this respect. Four and a half
feet above the uphill point gets one into the build up of wood that then
explodes into several large limbs. The uphill measurement is markedly
influenced by the limb formation. Going to mid-slope on the trunk puts
one under the influence of the root flare. So we run into an undesirable
situation in either case. It would seem inconsisent were we to worry
about the influence of root flare while ignoring the influence of "limb

   Open grown trees have limb flare for us to worry about. The same
trees may also have root flare. Well-behaved, straight-boled plantation
trees don't give us much to worry about, but our focus is seldom on
plantation trees.

   I may be reading more into the concerns or opinions of others that is
there, but I get the feeling that some feel we need to settle on one
circumference measurement as the ENTS convention - regardless of how
many trees don't fit well with that convention. I maintain that the ENTS
convention can be 3 circumference measurements. The benefits of
standardizing on the three are many.

   In terms of your question to one of my responses, "what is the best
way to measure girth?", Ed, do you mean: (1) where is the best place on
the tree to take the circumference measurement, (2) how do we actually
take it, if getting the tape around the tree is a bit of a problem, or
(3) how do we go about settling on where mid-slope, top of root collar,
and uphill points are? So far, I've interpreted the question in the
first way. And my answer to that one must remain, it depends on the
shape of the tree. There is no one best place that applies uniformily to
all tree shapes. For me, forcing one over the others just to say that
ENTS has a preferred way involves too may compromises. If we keep trying
to fit the proverbial square peg into the round hole, we'll be sentence
ourselves to pushing at that proverbial boulder up hill over and over.

Now, what are the objections to taking 3 measurements and calling that
the standard ENTS procedure? Time? Yes, more is involved, but the extra
time is really minimal.

In summary, let's see, above root collar, uphill side, mid-slope, etc.
and the arguments for doing one or the other. Are we pointed toward a
single ENTS choice for measuring circumference? My position is that we
are not. We are pointed toward 3 measurements and even those are
compromises. There is no one best place to measure circumference on a
tree such that the one measurement will some how stand for all possible
circumference measurements one might make. Tree forms are too varied for
that. Perhaps we should be asking ourselves, can we get by with just the
proposed 3.

BTW, I make no assumptions about how the 3 circumference measurements
would be used and I certainly don't see them feeding one composite ENTS
version of the AF formula. One compromise system is enough.       

   Now in terms of Will and Jess's TDI, that is a system of comparisons,
and a good one. As long as we don't go over board and declare overall
champions based on the TDI.


Re: Circumference conventions    Edward Frank
   Jan 26, 2006 10:24 PST 


I guess what I was asking and trying to promote discussion about was whether
or not we asa group wanted to keep the existing guidelines for measuring
girth as outlined in Will's Tree Measuring guidelines document, did we want
to change the point of measurement to upslope as has American Forests, or
did we want to devise a new methodology for measuring girth. I think there
are merits to both the existing ENTS approach and merits to the ide of
measuring girth from the upslope side. A single measurement is going to
involve compromise. The more measurements you take the better to document
the form of the tree.

Are you proposing that our guidelines be changed to require the measurement
of three different girth measurements? A protocol for taking a single
measurement to represent the girth of the tree is useful in so far as it can
be used to derive a wider variety of comparisons, such as the TDI. Multiple
measurements can not be plugged into other applications as readily, and
while they may be better for volume modeling, they are are less useful for
other types of calculations. No matter what you do there will be
compromises invlolved. What is the best compromise? We need to have a
single measurement to represent girth for some applications and what
protocols will be used to define that measurement. The consesus seems to be
to use the exisitng methodology as defined in the Tree Measuring Guidelines

Collecting more measurements on significant trees at least may be worth
doing, so long asd the core girth measurement used in these other formulas
is one of the measurements taken. I think the TDI numbers are a a
reasonable way to rank trees, and you know as well as I do that when
implemented lists of the biggest trees will be derived just as lists of the
tallest trees are derived from our existing dataset. I see no reason not to
declare overall champions based upon TDI. It is as valid of a ranking
system, if not more so, than other ones currently in use.

There are some statements and arguements made below and previously that I do
not believe to be valid. For example I do not believe that limb flare will
affect the same number of trees as does root flare. The number of trees with
low limbs growing on a steep slope is in my mind far less than the number of
trees growing on a steep slope with noticible root flare and the mid-slope
measuring point.   In any case I have specifically stated that if the trunk
at a height of 4.5 feet above the ground on the upslope side of the tree is
affected by burls, limb flare, or growth anomaly, then the girth should be
measured at the smallest girth at any point below the 4.5 foot height and
that hieght noted.

You are currently focused on volume measurements and are thinking in terms
of what measurments will provide the best volume estimates. To me volume is
not the end goal of the tree measuring efforts. Values such as height,
crown measurements and characterization, and even girth are of a higher
priority and of greater value in my estimation than are volume measurements.
I support the efforts to measure volume and read with anticipation the
results of your volume measurement experiments, but I don't see it as more
important than the other measurements being taken. I do not want to see any
changes that would emphasize volume over obtaining the most representative
or best measurements for the other parameters.

Your previous description of the cottonwood structure was not clear to me.
I understand your point now. The best point to measure would be at the
narrowest circumference below the limb flare. In order to make comaprison
between trees and areas some single standard needs to be defined.
Additional measurments can be taken to better characterize a particular
tree, but measurements that are consistantly taken at the same point in the
same manner are still needed to allow basic comparisons, even allowing that
the results of a measurements may include some flaws. So yes I do believe
we need to settle on some single measurement to represent girth, but not at
the exclusion of additional measurements as needed to describe a particular
individual tree. I would encourage that additional measurements be taken so
that we could interface with other champiuon tree lists. The only way to
affect change, upgrading the quality of the data on those lists, is if we
participate in these lists.

I appreciate the time you have put into this discussion. It has been a
enormous use in framing the discussion and highlighting the issues involved.

Ed Frank

RE: Circumference conventions   Robert Leverett
  Jan 26, 2006 12:44 PST 


   I'm with Will Blozan on retaining the mid-slope convention as the
circumference measurement - if we elect to do only one circumference
measurement as part of a standard ENTS measurement protocol. However, I
would like to see us adopt a two-measurement protocol for circumferences
by adding the uphill side measurement and updating the measuring guide
with the caveate that the mid-slope point is the ENTS preferred method
wherever one circumference measurement is used. However, I would point
out in the guide that there is no single circumference measurement that
does justice to the variety of tree forms that we encounter.

   Obviously, I am devoting a lot of time to volume modeling, but I
really haven't abandoned the idea of a limited number of tree
measurements as a primary documentation system. Not at all. For an ENTS
database, I can see a two-tiered measuring protocol. For the majority of
trees, trees of no special significance, I would propose the following
measurements be taken.

   1. Total Height (used in TDI)
   2. Circumference at mid-slope (used in TDI)
   3. Circumference at high point
   4. Maximum crown spread (used in TDI)

    For the really large trees, I propose the following:

   1. Total Height
   2. Height at the first major limb - upper side separation.
   3. Circumference at hight point of root collar
   4. Circumference at mid-slope
   5. Circumference at high point
   6. Maximum crown spread
   7. Average crown spread
   8. Vertical distance between low and high ground points

   With respect to #2, for trees that branch low and have very
conspicuous limbs, this measurement would be obvious, but it wouldn't be
as obvious for short-limbed conifers that are in the process of shedding
their lower limbs.

   If I can add an 9th, it would be likely be vertical length of the
crown area - I think. I haven't thought this one through. .

   I chose the above 8 measurements because collectively they tell us a
lot about the form of a big tree without requiring additional equipment.
Everything above is laser, clinometer, and D-tape.

   If we go beyond the above measurements, we get into trunk and limb
modeling and that's a whole different level of measuring and not
necessary to what we do most of the time.     


Re: Circumference conventions   Edward Frank
  Jan 26, 2006 14:27 PST 


A nice list of measurements to take for a particular tree. I might add to
the list a GPS location and an elevation. Other location descriptions could
be derived from maps. A description of the surroundings, associated plants,
and forest structure could also be included.    As I look at the list I am
wondering if the slope of the ground surface should not also be added to
show if the tree is located on a slope or a flat area - perhaps that would
be part of the description of the surroundings.

In your list you have the height to first major branch - upper side
separation. You also list total crown height. What do you mean by upper
side separation? Crown height would be the length from the top to the
lowest branch?

What exactly are you calling the top of the root collar? How do you
envision the circumference at the high point of the the root collar being
measured? The base of the tree is irregular in shape, would you run the
tape from wide point to wide point around the circumference? This is one
area where I see a big difference between trees growing on slopes and
similar sized trees growing on the flats - would you try a projection of the
root collar on the lower side of the tree on a slope onto the plane of the
or would you just wrap the tape around the trunk on the lower side?

I am planning a a measuring trip to mcconnells Mills SP on Saturday. I
will try to collect a suite of measurements based upon your list.


Re: Circumference conventions   MICHAEL DAVIE
  Jan 26, 2006 19:37 PST 
I'll say a little more, if that's okay...I guess the reason I said before that I thought we should stick with midslope could be elaborated on a little, since the variations are being kicked around so much. Ultimately, "breast height" is an arbitrary height to measure, as is high, low, or midslope. Every tree is different and the expression of basal flare is going to differ on each tree. "Breast height" in any postion we choose is going to indicate all flare on some trees or none on others. Many trees have no distinct point of changover to basal flare, it looks like the trunk slowly flares into the ground. Small trees have a basal flare very low, some big trees have basal flare very low, some very high, some really have none. No matter which, "breast height" will always be a flawed but useful indicator of size, and I don't think it's really that important which one is used, as long as it's consistent. But the more measurements the better, as Bob indicated, especially for the largest specimens. Ed says:" Values such as height, crown measurements and characterization, and even girth are of a higher priority and of greater value in my estimation than are volume measurements." I couldn't disagree more, really. The truer measure of actual size is the volume, and I think volume measurements are of a greater value, but I understand it's not realistic yet to measure all trees that way. The other measurements are indicators of something, but they can't really tell the whole story, and never will. They are realistic though, and helpful as well, and as to having some conventions, they do have to be realistic. I understand we have to try and make our conventions as useful an indicator of size as is possible within the limits we have.
RE: Circumference conventions   Robert Leverett
  Jan 27, 2006 05:02 PST 


   Good post! I think all of us reach a point where we get beaten down
by the 4.5-foot height above something rule and just accept it as the
standard. It's the "if you can't lick'um, join'um logic. You're
explanation that breast height will include more or less root flare
depending on the tree resonates well with me.

Back to Ed   Robert Leverett
  Jan 27, 2006 05:51 PST 


On the root collar question, I was thinking of the circumference
measurement being taken at the point of the beginning of the trunk or
end of the root collar and just running directly around the tree at that
point perpendicualr to the direction of the trunk. I wasn't thinking of
trying to follow the root flare. I was thinking that we would want to be
consistent with the other two measurements.

Deciding where the root collar ends is a toughy. For me it is a
judgment call. I think I would depend on the arborists among us to
refine the concept. Will, Michael, John, Ed, Sandy, etc., what say you?
But for the trees I had in mind when I made the proposal, it is where
the pronounced curvature ends and the individual root projections come
together. This is admittedly an irregular path around the tree,
especially when the tree is on sloping ground. Like Michael Davie
indicates, trees are very individualistic and the older and larger they
are, the more they express their individualism with flares, burls,
changes in curvature, etc. However, we all see that on many trees there
are abrupt changes in trunk curvature as the shape of the trunk becomes
distinct. The high spot of the zone of root flare to trunk change can
usually be identified. The larger white pines in MTSF fit the
description of the former. The smaller trees don't. A lot depends on
what is going on at the base of the tree to include erosion and exposure
of the root structure. Large trees growing in flood plains often have
their trunks partially buried and whatever root flare there is is
hidden. I admit to being troubled with the amount of judgment that would
enter into the top of the root flare measurement.

     Measuring the slope of the land around the tree is a good idea. GPS
coordinates when the can be obtained is a given.

     By upper side separartion, I mean the crotch on the upper side, the
vertex of the "V" where limb departs from trunk. That's an easier spot
to consistently identify than the underside start of a limb.

     In terms of total crown height, I think I had in mind the elevation
difference between the low point of the hanging foliage and the top of
the tree. I can see problems with trees that have large gaps in their
crowns due to loss of limbs. But I still think that the measurement is a
useful one to include as the vertical equivalent of the horizontal crown
spread measurement.

     A worthy ENTS project might be for us to do a formal study of these
attributes of tree shape/form. It never hurts to have plenty of data
when making pitches to adopt one convention or another.

Re: Circumference conventions   Edward Frank
  Jan 27, 2006 05:55 PST 


In order to make comparisons between objects you must have measurement
standards. In order to compare groups you must have a classification
system. A poor measurement standard, a flawed measurement standard is
better than no standard at all. It gives you a beginning point to organize
your information. You can always improve your standards and classification
system, but one is needed or your observations are simple random noise - not
useful for anything

Ed Frank.
Re: Circumference conventions   Jess Riddle
  Jan 27, 2006 19:18 PST 


I'm using the same labels you used in a previous post to refer to
parts of the discussion, and the original points are copied below this

a) I may not have been clear on this point, and as I've thought about
this issue more, the importance has grown in my mind. Yes, even with
a midslope standard, many trees are difficult to measure. Using that
difficulty and number of trees measured with the midslope reference as
standards, I think using an upslope reference would greatly increase
the difficulty on some trees and result in other trees being skipped
entirely. The latter would occur because the change would
qualitatively alter the measuring process for many trees. To
illustrate, this week I measured a 9'10" cbh hemlock growing on a
steep slope. On the downhill side of the tree, I had to stretch to my
full extent to keep the tape level. If I had measured 4.5' up from
the upslope side, the height of measurement would have been 1.5 to 2
feet higher. That increase would have made it impossible for me to
simply carry the tape around the trunk at that height. I could not
have stretched more or grown to hold the tape high enough on the
downhill side. Consequently, I would have had to use entirely
different, and less desirable, techniques, or skipped the tree

b) I still fairly certain more limbs would be encountered with a new
standard since moving along the trunk from the ground invariably takes
one towards the base of the crown. However, you're right that with
either reference the situation would rarely occur. I also assumed
that the flexibility to dodge burls and abnormalities would remain,
but I think use of that option should be minimized. When a swell on
the trunk is avoided, the resulting measurement is not consistent with
the other measurements due to the difference in height, even if that
adjustment is the best available option. Do to rarity, this point is
likely of only minor significance.

c) We may just view this point differently. However, I will add that
having a common reference point simplifies recording measurements for
volume determination. If different reference levels are used, one
tree could have two different circumferences labled as 4.5' above the
base or have to different heights. Again, this point is a minor but
obnoxious consequence of a reference change.

d) I can see the validity in that counter argument. Again, I'm not a
big fan of doing things for tradition's sake. Hence, I would just as
soon go with whichever standard will function best, and not worry
about changes to past data.

e) I find the physiological reference point argument interesting, and
I'm not quite sure how to evaluate it. However, a physically
consistent reference level provides the advantage of being able to
study growth. If the height of measurement gradually shifts up the
tree, that process will bias measurements of radial growth. By
measuring at a fixed height, the midslope standard, changes in
circumference measurements will indicate the growth of the trunk.


RE: High side, low side, What is the big deal?   Will Blozan
  Jan 27, 2006 19:27 PST 

It (midslope) is "best" because it does not change over time. A "permanent"
(leave some room for miniscule change) reference repeatable for the life of
the tree. A "root" swell or buttress will creep up the stem faster than the
radial growth "up" the slope. Why would you measure a tree at one place
(root collar, above root swell, trunk flare etc) one year and higher the
next year? Trees are dynamic; midslope is not.

4.5 feet is arbitrary to begin with. We would not be having this discussion
if diameters (girths) were measured at 8' up from midslope. It is a
reference point for the life of the tree. Good or bad, it is convention, and
will work for our purposes.

I am now fully entrenched in volume measurements. This involves many girths
for the lower trunk area up to about 8'. I collect these data points because
they are necessary for an accurate representation of the mass of the tree.
DBH at 4.5 feet is not transferable to size. It is just a measurement taken
at an arbitrary (as in easy) height that unfortunately has nothing to do
with the size of the tree.

DBH means so very little to us ENTS but is everything to AF and big tree
lists. The more I delve into volume I realize how pathetic dbh is as an
indicator of size. Worthless.

I'll stop now. It just seems too much fuss is being made of this topic. Get
more measurements if you want, but by all means get the midslope dbh for a
consistent and permanent reference.

Re: AF retains it's original measuring guidlines!!!
  Feb 01, 2006 08:07 PST 

See below, the changes were not made by a vote. Good news! 

"Big Tree Coordinators:

Thank you to all who have given me a response regarding the proposed measurement change of measuring tree circumference on a slope. This change was originally suggested in the Big Tree evaluation sent to coordinators in January of 2005. We then discussed the change in an open forum this past November at our Big Tree meeting in Charlotte. Finally the change was put to the recently formed Big Tree Committee consisting of representatives from NJ, AZ, TX, NV, VA, & ID. The committee was the first stage in the process where the response reflected a significant desire to maintain the rule unchanged. Therefore it was necessary to address the coordinators as a whole to confirm this vote. To date we have received a response from a majority of the active states. 9 to change the measurement standard and 19 to maintain the current standard, thus the standard will remain unchanged.

When measuring the circumference of a tree on a slope, measurements are normally taken at the high and low side of the slope and then averaged. However, in some cases an especially steep slope may prevent the low side of the trunk from being measured. In this situation, the measurement should be taken at 4 feet above the mid-point of the trunk.

Thank you again for your participation in this important decision.


Ethan Kearns