| ENTS,
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 ½ 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 |
ENTS
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 |
Scott,
... 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.
Bob
|
| RE:tree
measuring moves forward |
foresto-@npgcable.com |
| Jan
16, 2006 19:48 PST |
ENTS-
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 advantages...it'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 |
Don:
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.
Bob
|
| Fw:
High side, low side, and everything in between |
Edward
Frank |
| Jan
18, 2006 17:27 PST |
Don,
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
basal
point as the start for height meaurements.
What does everyone else think about the point of meaurement for
girth?
Ed
|
| Re:
Fw: High side, low side, and everything in between |
Fores-@aol.com |
| Jan
18, 2006 18:35 PST |
Ed:
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.
Russ |
| RE:
Fw: High side, low side, and everything in between |
wad-@comcast.net |
| Jan
18, 2006 19:45 PST |
ENTS
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.
Scott
|
| Re:
Fw: High side, low side, and everything in between |
Edward
Frank |
| Jan
19, 2006 13:22 PST |
Everyone,
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:
http://www.nativetreesociety.org/measure/girth_measurements.htm
Feb 2005. An
earlier discussion of the issue was posted on the web from Nov
2003:
http://www.nativetreesociety.org/measure/tree_girth_measurements.htm.
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: http://www.nativetreesociety.org/measure/tree_base_position.htm
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
flare.
Here is an example:
http://www.treedictionary.com/DICT2003/HTMLFILES/trunck%20flares.html
John |
| RE:
Trunk Flare |
Robert
Leverett |
| Jan
20, 2006 04:33 PST |
John,
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.
Bob
|
| 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
here.
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 |
Mike,
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.
Bob
|
Re:
High side, low side,
and everything in between:let's stay between-Mike's |
MICHAEL
DAVIE |
| 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.
Mike
|
| 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.
Will
|
| Girth
Measurements |
Edward
Frank |
| Jan
25, 2006 00:36 PST |
ENTS,
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 |
wad-@comcast.net |
| Jan
25, 2006 07:00 PST |
ENTS
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.
Scott
|
| Circumference
conventions |
Robert
Leverett |
| Jan
25, 2006 08:12 PST |
Ed,
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
flare.
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
forms.
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
sides
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
Bob
Robert T. Leverett
Cofounder, Eastern Native Tree Society
|
| Re:
Circumference conventions |
foresto-@npgcable.com |
| Jan
25, 2006 10:38 PST |
Bob-
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
century.
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
them.
I understand the difficulty in not making emotional decisions
about them, as
they were here before us, and hopefully here for our
descendants...
-DonB
|
| Re:
Circumference conventions |
Edward
Frank |
| Jan
25, 2006 11:02 PST |
Bob,
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 |
Don,
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
bark.
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.
Bob
|
| Re:
High side, low side, and everything in between:let's stay
between, I |
Edward
Frank |
| Jan
25, 2006 11:37 PST |
Scott,
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.
Ed
|
| RE:
High side, low side, and everything in between:let's stay
between, I |
Robert
Leverett |
| Jan
25, 2006 12:12 PST |
Ed,
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.
Bob
|
| One
more - high side, low side |
Robert
Leverett |
| Jan
25, 2006 12:40 PST |
Ed,
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.
Bob
|
| 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
repeatability.
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 |
foresto-@npgcable.com |
| Jan
25, 2006 15:40 PST |
Bob/Ed/ENTS-
I meant to comment earlier on the topic of root/trunk flare and
wood
hardness...as 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,
harder.
Bob-
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!
-Don
|
| Re:
Circumference conventions |
edward
coyle |
| Jan
25, 2006 16:30 PST |
Don,
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 |
Jess,
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.
Bob
|
| RE:
Circumference conventions |
Edward
Frank |
| Jan
26, 2006 05:21 PST |
ENTS,
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
applies.
| |
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
upslope.
| |
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
repeatability.
|
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 |
ED,
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
flare".
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.
Bob
|
| Re:
Circumference conventions |
Edward
Frank |
|
Jan
26, 2006 10:24 PST |
Bob,
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
document.
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 |
Ed,
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.
Bob
|
| Re:
Circumference conventions |
Edward
Frank |
| Jan
26, 2006 14:27 PST |
Bob,
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.
Ed
|
| Re:
Circumference conventions |
MICHAEL
DAVIE |
| Jan
26, 2006 19:37 PST |
Hi-
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.
Mike
|
| RE:
Circumference conventions |
Robert
Leverett |
| Jan
27, 2006 05:02 PST |
Mike,
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.
Bob
|
| Back
to Ed |
Robert
Leverett |
| Jan
27, 2006 05:51 PST |
Ed,
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.
Bob
|
| Re:
Circumference conventions |
Edward
Frank |
| Jan
27, 2006 05:55 PST |
ENTS,
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 |
Ed,
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
message.
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
entirely.
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.
Jess
|
| RE:
High side, low side, What is the big deal? |
Will
Blozan |
| Jan
27, 2006 19:27 PST |
Ed,
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.
Will
|
| Re:
AF retains it's original measuring guidlines!!! |
wad-@comcast.net |
| Feb
01, 2006 08:07 PST |
ENTS
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 ½ feet above the mid-point of the trunk.
Thank you again for your participation in this important
decision.
Sincerely,
Ethan Kearns
|
|