ENTS,
For those on the list who shy away from our
discussions of tree
mathematics, you might not want to read this post  then again,
you
might, at least for information purposes  especially the
newcomers to
the list. Will Blozan, Jess Riddle, John Eichholz, and myself
have
finally decided (more or less) to embark upon the perilous
journey of
writing a guide book to simple and intermediate tree mathematcis.
I'm
sure Ed Frank will be involved. Such an ENTS undertaking without
Ed's
participation is unthinkable. I expect a few others to sign on.
We will probably title the book something like
"Dendromorphometry
the Science of Measuring Trees". Hopefully, some of the
big guns on
ENTS will join us, or at least review the work as it proceeds.
The big
guns of whom I speak are the stellar PhD scientists on the list,
i.e.
Drs. Bob Van Pelt, Lee Frelick, Don Bragg, Tom Diggins, Larry
Winship,
Dave Orwig, John Okeefe, Roman Dial, etc. There are other
potential big
guns, but we don't often hear from them. So I'm including only
those who
post and/or who I know.
There are many topics that need to be included
in the planned book.
Obviously, the ENTSengineered methods for measuring tree
height, crown
spread, and trunk volumes would be included. A full discussion
of other
common treemeasuring techniques would also be included with
pros and
cons provided for each method. We would discuss which shortcuts
work and
which ones don't. An appendix would provide a review of the
geometry and
trigonometry that we commonly use to include derivations of some
of the
formulas that we use. We would provide a review of the accuracy
of the
instruments that we use and how to get the most out of each
type. There
would be lots of pictures and diagrams.
Folks, this is a work that needs to be
done. There is so much stuff
out there in the way of measuring and calculating techniques
that make
hidden, simplifying assumptions about trees that are just not
fulfilled
much of the time. For example, I was looking at the internet,
searching
for crosssectional area determinations and found the following.
I omit
the referenced table.
============================================
Crosssectional Areas of Trees
Dr. Kim D. Coder
The University of Georgia
December 1996
Many tree appraisal, measurement, and structural mechanics
systems
require crosssectional areas at some given height or point
along a stem
or branch for completing calculations. Table 1 presents these
crosssectional areas in square feet and square inches across
wholeinch
diameters from 1 to 75.
Values were determined by:
Crosssectional area (square inches) = 0.785 × DIAMETER^2
Crosssectional area (square feet) = (0.785 × DIAMETER^2) / 144
===============================================
Those
who live and breath tree dimensions and formulas, will quickly
recognize that the 0.785 factor comes from the area of a circle
formula:
A = PI * D^2/4 where PI
= 3.141593 and PI/4 = 0.785.
So what's my point? The assumption being made
is that the
crosssectional area of the trunk at the point of interest is
that of a
circle. So, all that the user of this method gains is the
division
3.141593/4 being reduced to the constant 0.785. The table that
accompanies the formula gives the crosssectional area for
diameters of
1 to 125 inches.
This simplified formula and accompanying table
is an example of one
of the shortcuts I alluded to, but in the age of electronic
calculators
and computers, it is hardly needed. What IS needed is a better
way to
determine the crosssectional area of a tree when it isn't
circular or
almost circular. Making the assumption of circularity is
something we
all do, but there are times when we clearly shouldn't. And our
distinguished president of ENTS, Will Blozan, has risen
magnificently to
meet that challenge. Will and associates have engineered a
method by
where they climb the tree to the offending trunk section. These
pesky
trunk sections, often where fused trunks part company, simply
refuse to
act like a selfrespecting cylinders and challengingly stick
their
tongues out at Will. Honest, folks, I've seen it happen. Will
then
encloses the trunk with sticks that form an enclosing a
rectangular box.
He then measures distances from the rectangular frame to the
trunk. We
then enter his offsets into an Excel spreadsheet and use a
series of
trapezoids to calculate the blank space. We arrive at a pretty
accurate
crosssectional area of the trunk at that point.
Now who, but thoroughly obsessed Ents, would
go to so much trouble to
measure the crosssectional area of a tree trunk? But, alas, we
can't
help ourselves. We must do it. It is our calling. So, we'll
justify our
obsession by writing a book.
Bob
Robert T. Leverett
Cofounder, Eastern Native Tree Society
