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TOPIC: Use of Tsuga Search data
http://groups.google.com/group/entstrees/browse_thread/thread/db9804774e510f01?hl=en
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== 1 of 1 ==
Date: Tues, Jan 1 2008 9:54 pm
From: dbhguru@comcast.net
ENTS,
Thanks to Will and Jess, we're awash in high quality data on old
growth hemlocks. Attachment 1 is an Excel workbook with 8
spreadsheets that examines a number of OG hemlocks from a trunk
modeling standpoint. Spreadsheet DataAndModels compares the actual
circumference of the hemlocks at as close to 100 feet up the trunk
as Will's data permits to that predicted by several trunk models,
more specifically, the paraboloid, cone, and three mixes of
paraboloid and cone (5050, 6733, 3367).
Spreadsheet SummaryOf Models provides a convenient summary of the
DataAndModels spreasheet. I think I have presented these results
before. Spreadsheet 100FtAnalysis is an excerpt from DataAndModels
for the cone and paraboloid only. Spreadsheet PctConeVSPara is an
excerpt for the cone and parabolid mixes. The last two columns of
this spreadsheet show total measured volume and big tree points as
applied to only circumference and height for each hemlock. I didn't
have crown spread data, but do believe that circumference can be
treated as a surrogate for crown spread.
Spreadsheet PtsVSVol regresses volume against points as the
independent variable to produce a bivariate linear regression
equation with a regression coefficient of 0.82. That's not shabby.
Obviously, the idea here is to see how well weighted points can be
used to predict trunk volume.
Spreadsheet HgtAndCirVSVol regresses volume against height and
circumference as independent variables with a regression coefficient
of an impressive 0.89. The last two spreadsheets show the results of
the two regressions.
The regression tests show that using height and circumference
separately to predict volume is measurably better than using the
weighted points approach. Since the weighted formula is less
successful at predicting trunk volume than a direct multivariate
linear regression of height and circumference onto volume, we are
left to ponder the validity of the formula extended to the three
dimensions of height, circumference, and spread as a predictor of
tree bigness  to the extent that bigness is defined primarily
around trunk volume.
Bob
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TOPIC: Excel Workbook
http://groups.google.com/group/entstrees/browse_thread/thread/743348eb8e4d5167?hl=en
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== 1 of 1 ==
Date: Wed, Jan 2 2008 10:08 am
From: dbhguru@comcast.net
ENTS,
If anybody has opened the Excel workbook I sent earlier as an
attachment to an email, and are confused by it, I apologize. Please
feel free to ask questions about it and I will happily clarify.
Communications such as the Excel workbook are often presented by me
without any strong expectation of responses from fellow and lady
Ents , although I'm happy when I get responses. My main purpose with
the technical emails is to provide a continuous stream of
infromation and data that will become available to researchers when
Ed posts the communications threads to the ENTS website. For me, it
is easier to present material on these technical subjects in bits
and pieces via th email process. However, I hope that some of the
material will stimulate interest in others to join the measuring
mission of ENTS.
In presenting technically oriented emails, there is usually a set
of priorities that I am attempting to implement. The first priority
is to produce a more accurate statistical description of a forest
site and/or individual tree. Rucker analysis and its spinoffs does
that. The description priority is usually suffiicient to justify the
effort. The second priority is to perfect our measuring craft, push
the envelope as it were, but always in a direction of our own
choosing. Development of formulas meets the second priority. We
don't have the market cornered on tree measuring, but at this point
we're by far the best show in town within the geographical East. I
don't want us to lose that edge. The third priority is to build
databases of scientifically useful research data. I have faith that
the Tsuga Search database and my reports on MTSF will eventually be
courted by serious scientific researchers. The fourth priority is to
provide a means of distinguishing exemplary forest si
tes and individual trees through measurment methods that highlight
differences. In the past Tom Diggins has spoken eloquently to this
point. The exemplary status of Zoar Valley, NY, was virtually
invisible to the local DEC people. Their techniques were (and still
are) too crude to reveal the exemplary features of Zoar. About all
the DEC representatives have done has been to add up board feet and
to misrepresent the true nature of the resource at Zoar Valley (Ooh,
my bad).
The above having been said, I still plan to produce a set of
examples to help interested Ents explore the value of formulas,
methods, and protocals.
Bob
