Crown Spread   Edward Frank
  May 01, 2005 08:40 PDT 
One of the questions I wanted to address with Will at Cook, but did not get
the chance is how to measure the greatest spread, (especially with tree
that may be tilted- I see a 100 foot tree tilting out over a river with a
horizontal offset of 70 feet to match its 70 foot height as measured from
the base).

Is the longest spread measured from the base of the tree?

What about trees that are slanted?

I don't think it can be measured from where it diverges from the trunk,
because that is an arbitrary decision especially with trees that quickly
break up into multiple large braches/trunks.

Attached is a small graphic. When you map a cave at each survey station
you note the passage width and the passage height. What is also important
is to draw a cross-section of the passage to give meaning to the numbers.


When we consider in Will's formula whether to use the greatest spread or
average spread, there are good points for both. The biggest advantage for
longest spread is that it might actually get measured. On the other hand,
I think average spread is a more meaningful number as it represents the
mass of the canopy as a whole rather than just a single branch.

Ed Frank
RE: Maximum spread   wad-@comcast.net
  May 01, 2005 09:34 PDT 
Ed

The way I measure spread is to go from drip line to drip line, no matter the shape of the tree. Often, the lowest branches are not the widest spread. At high noon, I guess it would be the shadow cast by the tree with the sun directly above it. I typically pace the spread, as it doesn't make a lot of difference in champion points. It is somewhat subjective as to what the shortest and longest spreads are. I imagine two people would come up with a different interpretation on most trees. I did use my range finder on the Laffayette sycamore to estimate the length of the one limb that stretched out over the creek.

Scott
Crown Spread    Edward Frank
   May 31, 2005 18:30 PDT 

ENTS, Bob, Will,

How are we going to deal with crown spread in our data sets? Average crown
spread is used by American Forests in their big tree calculations. This is
the method outlined in Will's Tree Measuring Guidelines. Some of our tree
data already has this measurement, but overall crown spread is not measured
often.

In Bob's excel spreadsheet to link to the database Max spread is listed.
This is the only place I can see that it is used.

In the ENTS dimension Index (Blozan Index) we discussed this winter longest
limb seems to be preferred for this usage. I really like this dimension
concept, although I would favor average crown spread as being more
representative of the "canopy" of the tree than length of a single limb. I
again repeat the questions I had posted May 1 concerning how to measure
longest limb (especially with tree that may be tilted- I see a 100 foot tree
tilting out over a river with a horizontal offset of 70 feet to match its
70 foot height as measured from
the base).

Is the longest spread measured from the base of the tree?

What about trees that are slanted?

I don't think it can be measured from where it diverges from the trunk,
because that is an arbitrary decision especially with trees that quickly
break up into multiple large braches/trunks.

Where we do have crown spread information in the database, if what format
is it typically measured? Is this the measure we want to use, or should
we opt for another format? Should we continue to examine all three
measurement options before deciding on one?

I am just wondering what we are doing. It would be better to pick one
method and try to collect data for that method, rather than sometime
getting one reading, sometimes another, and most of the time ignoring it
entirely.

Ed Frank
RE: Crown Spread    Robert Leverett
   Jun 01, 2005 05:35 PDT 

Ed:

   Crown spread measurements, let alone a satisfactory definition of
same are often problematic. Crown measurements really do make sense for
isolated trees that one can stand back and view. But for trees grown in
competition with one another where crowns often overlap and visibility
of crown spread is very limited, good crown measurements are often so
difficult that taking shortcuts is the rule rather than exception.

   Circumference is a pretty good surrogate for crown spread - except
where the crown has become broken. Trees with big trunks produce big
crowns and for forest-grown trees I'm usually content to allow
circumference to stand as a surrogate for crown spread.

In terms of our interaction with American Forests, I have long felt
that the AF rules for crown spread are flawed. However, when I do take
crown measurements, I like to find the longest limb projection using the
base of the trunk as a center point of a circle. This is not equivalent
to measuring the longest limb, which can be much more difficult to
measure.

Viewing the tree at a distance, I like to measure the longest
horizontal distance across the crown as a vertical projection to the
ground to capture what the eye sees. I then like to go 90 degrees around
the tree and repeat the process. If access is not a problem, I like to
circle the tree at the perimeter of the vertical projection of the crown
spread to the ground and shoot to the trunk as a series of radii and
then average the radii. An alternative that Will Blozan and I have often
discussed and occasionally used is to position two measurers on opposite
sides of the tree at the perimeter of the crown and shoot the distance
from one measurer to the other. Rotating around the tree and repeating
the process probably gives the most accurate determination of average
crown spread. The abbreviated method where only one measurer is involved
is akin to measuring the spokes of a bicycle wheel where one might
imagine spokes of varying lengths.

   I no longer have the inclination to want to express the various crown
spread measurements I make take as a single figure. Stated a little
differently, I no longer have a desire to include a crown measurement as
part of some formula or process that seeks to reduce a tree's crown
spread to a single composite number. But if I must choose one of the
above measurements as some kind of preferred measurement, I think I
would vote for the longest horizontal spread taken across the full crown
as a vertical projection to the ground to capture what the eye sees
looking at the tree from a distance.

   This does leave the issue open as to where ENTS fits into the
champion tree picture. When I am measuring a tree for someone to report
to the state or AF, I use the state/AF rules and don't think much beyond
that. If I am asked what significance the measurement has in terms of
classifying a tree, I usually say "not much".

   When we ENTS types measure a great tree such as one of the giant
northeastern sycamores, we can't take too many measurements. We want to
try to measure the single greatest limb length, the single greatest
horizontal crown projection from the trunk, the greatest crown
projection at right angles to the longest, and the spoke method. If the
tree is of lesser stature, and we "must" take a crown measurement, as
noted above, I prefer the longest vertical projection of the crown as
taken across the full crown. That's just my preference.

   I'll button up now and give others a chance to contribute. Will?

Bob                
RE: Crown Spread   Edward Frank
  Jun 01, 2005 15:41 PDT 

Bob,

It seems to me that the crown is the most important part of the tree. It
is where the photosynthesis takes place that provides the energy for growth
and reproduction. The weight of the leaves is itself enormous. The trunk
is the supporting pillar that holds the branches and the leaves. We
measure both the height an circumference of the trunk. We don't have a
practical way to measure the roots. If the canopy is the most important
part of a tree, we should have some way to represent its size numerically.
There should be field measurements that can be taken and compiled in our
dataset to represent this canopy size.

I am not sure if the measurements under discussion adequately provide that
information, but they are what we have at the moment. What can be done,
given the problems of measuring crown spread in the field, to make the
crown measurement easier and more frequently collected? Ideally it could
be calculated as a volume based upon average crown spread, live crown
ratio, and some solid shape characterizing the shape of the crown in a
particular tree. This isn't practical at the moment, but I think where
practical measurements should be taken. What measurements should we focus
on getting if we are taking crown measurements? And are they supported in
your database?

Ed Frank