| Total
volume estimates (fwd) |
dbhg-@comcast.net |
| Oct
15, 2003 17:46 PDT |
ENTS:
I'm forwarding a thought-provoking communication from Colby
Rucker about calculating tree volume. Colby, Will, and I are
always talking about ways to compute tree volume.
Bob
---------------------- Forwarded Message: ---------------------
From: "Colby Rucker" ;
To: <dbhg-@comcast.net>;
Subject: Total volume estimates
Date: Wed, 15 Oct 2003 00:29:09 -0400
Bob,
I like to limit volume calculations to the main trunk and
heavier leads so
that modeling of hypothetical cuts also provides a total in
board feet.
This allows comparisons with the historic record of trees that
scaled from
12,000 to more than 20,000 board feet.
I think it's unwise to add some trifling percentage for brush to
the
carefully calculated trunk volume of some conifer. It become
apples and
oranges, and guesswork always ruins good numbers.
All that said, there are some monstrous open-grown trees that
wouldn't yield
much in board feet, but would displace a great deal in total
volume. Of
course, there's no decent way to calculate the volume of all the
twigs and
branches, but it's all wood. One interesting exception was the
Wye Oak, a
white oak that stood on Maryland's Eastern Shore. Although the
total is
somewhat of a composite, we can get a pretty good idea of volume
from the
weight of a fallen limb weighed at the feed mill across the
road.
For any kind of argument, I'll say the volume reflects the tree
as it was in
1953, with its major limbs intact. Although limbs were weighed
that fell
after that, a great deal of live wood was removed from the tree,
year after
year, in an attempt to reduce the weight and sail area of the
crown. This
suggests that the major components maintained a fairly constant
weight and
volume, despite unavoidable increases in diameter. I have not
counted a low
limb weighing perhaps ten to fifteen tons removed as part of the
state road
upgrade to auto traffic ca. 1912.
So, not perfect, but here goes anyhow:
10/6/53 Large limb fell
across road 20.0 tons (est.)
Preston, pp. 110-111.
8/29/56 Largest limb fell 30.0 tons
(est.)
Preston pp. 5, 111.
6/10/84 Largest remaining
limb fell 37.0 tons (feedmill) Balto
Sun 3/20/85
1984 Emergency
pruning 2.5 tons
(est.)
Balto. Sun 3/20/85
6/6/02 Tree fell; main
trunk 30.75
tons (crane?)
Balto. Sun 6/23/02
6/6/02 Limb wood 19.25
tons (est.)
Balto. Sun 6/23/02
Total weight of tree 139.50
tons
The estimates were probably from state foresters. The 1984 limb
appears
heavier than the 1956 limb, which was immense, and the longest.
This
suggests the estimate of 30 tons may have been somewhat low, or
the limb was
simply less fully branched. The 6/6/02 limb wood tonnage is
derived from an
estimate of 100,000 pounds for the entire tree. Leaves and
rakings were not
included. 19.25 tons seems reasonable. Although less than the
individual
weight of the three earlier limbs, much of the trunk was removed
in one
wide-load piece, with portions of the heavier limbs still
attached.
139.5 tons = 279,000 lbs. Dividing by 60 lbs./cu. ft. = ca. 4650
cu. ft.
Circumference at grade was 51 feet, cbh was 31' 10". The
bottom of the
trunk was a hollow shell, accessed via an iron port. This air
space, having
no weight, receives no volume from the 61,500 lbs. A broad void
to four
feet up, tapering abruptly to ten feet up, it amounted to about
350 cu. ft..
Thus, quite conveniently, the total volume was 5,000 cubic feet.
Colby
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