Tree Measurement Reflections:  Will, Bruce, and Beyond  

TOPIC: Will, Bruce, and Beyond

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Date: Fri, May 9 2008 2:05 pm


I don't think I want to involve myself further in the ongoing exchanges between Will and Bruce. So, in terms of the title of this email, this is the beyond phase. There are general points from their conversation that need to be addressed, and I'd like to do so in a non-confrontational way. I will add emphasis to some key points, but that is as far as I will go. So to all who may read this communication, please don't interpret my comments as being directed at any particular person, persons, or situation. I simply want our ENTS members, and others who may read this communication, to get my perspective, especially the folks who are not tree measurers and are wondering what the fuss is all about.

Some questions come immediately to mind. Relative to tree measuring accuracy and methodology, are we making mountains out of mole hills in our attempts to distinguish ENTS methods from the more traditional ones taught and used by timber specialists? Is the clinometer-tape measure tree height measuirng method good enough for scientific work? If not, whose job is it to challenge that particular method and the results reported in studies that utilize it? Where, exactly, does ENTS fit in within the spectrum of researchers, professional foresters, amateur tree hunters, etc.? These are some of the questions that occur to me as a consequence of the discussion between Will and Bruce. I will address these questions and I welcome the contributions of others, especially the research scientists on this list. I also hope webmaster Ed Frank will weigh in as member with a strong scientific background and a commitment to reporti ng accurate data on our website.

First Question: Are we making a mountain out of a mole hill?

This is a fair question, especially to serious mided scientists. In answering the question, Dr. Don Bragg may have said it best. I quote from a recent email he submitted:

"There is definitely a need in the scientific community for the maximum dimensions of trees to be accurately measured and available for use. The use of champion tree data to help certain aspects of research programs can be quite pervasive, even if not well recognized. For example, a lot of forest simulation models (the popular gap models, for instance) define parts of their optimal growth equations using species-specific maximum heights and diameters. A number of height models use champion tree heights as an asymptote to fix the upper height possibilities of a species, while other models use parameters like maximum tree age to define response functions. I believe the evidence is strong that we can use champion trees to help better define the shape of height:diameter functions that are used in many vegetation simulators. Other issues related to relative tree size include the ecological role of supercanopy species (e.g., eastern white pine) in manag ed landscapes, or vertical structure of forests and their relationship to ecosystem function, etc. Most people using the champion tree data do not likely pay close attention to the source of the data, and its reliability. This, in turn, could have dramatic results on the outcomes of their simulations."

In the past, Dr. Tom Diggins also made eloquent arguments for getting the numbers right for tree height measurements. He pointed out that accurate measurements were necessary to differentiate the exceptional sites, needing protection, from the ordinary ones. Zoar Valley, NY. was the example he gave.n I could give other examples to include Mohawk Trail State Forest, Cook Forest, and other exemplary sites that have not received their just due. So, our insistence on accuracy is not a trivial issues unless accuracy doesn't count, which is hardly a credible scientific position. My conclusion is that we are not making a mountain out of a mole hill. Perhaps other Ents would care to weigh in on this question.

Second Question: Is the use of the clinometer and tape measure method of measuring tree height good enough for scientific work?

It depends on the trees being measured and how the method is applied. If the method is used with crown point cross-triangulation on trees where cross-triangulation can be successfully applied, then the clinometer-tape measure method will be give results comparable to the accepted ENTS sine top-sine bottom method. In the days before lasers, the cross-triangulation method is what I used, what Will used, what Dr. Lee Frelich used, etc. But the method is difficult to apply on in-forest measuring situations and on broad-crown trees. If cross-triangulation is not used, then measurement errors can go through the roof for tall, broad-crowned trees. To give an idea about the magnitude of error, if you set a 100-foot baseline to the trunk of a tree and shoot to a crown point a t an angle of 45 degrees that has a horizontal distance from you of 80 feet, you are going to make a measurement error of 20 feet. That is going to happen and your profession, your professional associations, your
job title, you degrees, your publications, and your overall field experience aren't going to save you. To put the needed emphasis on the point, if the spot in the crown that you are shooting has a different horizontal component of distance as compared to the length of your baseline, you ARE going to make an error in height. You can minimize the error by using the method that Don Bertolette describes. When in the Forest Service, he used a method of error control that employs one leg of a horizontally configured right triangle to stand for the hypotenuse distance from eye to directly beneath the crown point. This method requires the measurer to position himself/herself in such a way that the high point is on a line that is 90 degrees from th e line from measurer to trunk. To say it in general terms, the high point is off to the side of the tree relative to the measurer. Don's method provides a pre tty good adjustment and if implemented correctly can eliminate a big chunk of tangent-ind
uced error. I note that Don's description of the method was both enlightening and heartening to me to confirm that there were people out there who weren't just blindly using an error-prone measuring process.

I should emphasize that the average height error made from repeated use of the clinometer-tape measure method without controls is a current topic of research in a study headed by Dr. Lee Frelich. Other study members include Dr. Don Bragg, Will Blozan, and myself. With Lee and Don as key study participants, any questions raised about scientific credibility of the study will be put to rest. The study will include close to 800 sample trees measured and compared through the ENTS sine top-sine bottom versus the tangent method. Lee will get the paper published.

Third Question: Whose job is it to challenge the status quo with respect to tree measuring?

Well, anyone with the acknowledged credentials and/or experience can do it, but I readily acknowledge that challenges will be taken more seriously if all the proper scientific checkboxes are marked. Those boxes are filled for ENTS. For anyone who reads this communication, Drs/professors Robert Van Pelt, Lee Frelich, Don Bragg, Roman Dial, Tom Diggins, Larry Winship, and Gary Beluzo use the sine top-sine bottom method and acknowledge its higher level of accuracy relative to the conventional tangent method. I doubt any of the foregoing individuals want to get into a credential comparing contest with colleagues who stick to the old methods, but I have no question that they well understand the source and magnitude of measurement errors common to the tangent method and stand firmly behi nd the ENTS methods. As a group, ENTS is a highly credible resource for measuring trees. We will quickly be recognized as experts on tree measuring by anyone with an open mind and common sense who is
adept at Internet research. Our website is a gold mine of good information. However, we do recognize the need for an authoritative text on tree measuring to lend added credibility to ourselves as premier tree measurers. So Drs. Frelich, Bragg, and Van Pelt and Will Blozan and myself will be writing that text. I will soon begin on the draft for others to review, correct, expand, clarify, etc. Lee will find a publisher. The book will probably be titled "Dendromorphometry - the Art and Science of Measuring Trees in the Field." It will be an extremely important work and should satisfy those looking for a credible book reference to tree measuring. In the interim, we will continue to do our job through the ENTS Bulletin (a highly credible source) and via the Internet with essays and diagrams.

On our tree measurement essays and diagrams offered on our website, I think it is not an exaggeration to say that they speak for themselves. There isn't much in our diagrams that one can logically disagree with. If so, let those who disagree come forward and present their case. From my perspective, our diagrams clearly show the common sources of error in tree height measuring and the arguments we make can be followed by anyone with rudimentary math skills. However, the ENTS website has much, much more than just the tree measuring guide. Many of my past e-mails captured by Ed and posted to the website quantify sources, magnitudes, and rates of change of errors in tree height measurements. Some folks probably hit the delete key when they sense a formula deluge coming, but fun to read or not, there is definitely a large body of material available to include tables and spreadsheets. Unfortunately, it is scattered. However, with respect to the mathematics, I respectfully point out
, it ain't rocket science, folks. Still there is always room for disagreement. If anyone cares to present alternative measuring models, we invite them to do so. But they should include detailed diagrams that we can all examine. Generalizations don't count nor do assertions such as "we've always done it with clinometer and tape measure" carry weight. The "experts" once thought the Earth to be flat.

In terms of ENTS tree measuring credibility, as recognized by outside parties with standing, Pennsylvania's DCNR and Massachusetts's DCR have recognized our expertise for a number of years. We have put on many tree measuring workshops in both states. The prestigious Biltmore Estate recognizes our tree measuring expertise, as does the Great Smoky Mountains National Park. In authorizing Tsuga Search, the NPS paid us the highest compliment. But that isn't all.

In the past several years, I have been contacted by at least a dozen academics who have sought information about the ENTS method of measuring tree heights and offered no counter arguments. They accepted our methods. I have personally instructed a couple dozen professional foresters in our techniques and I received highly positive responses from every one. Within ENTS and affiliated personnel, there is the acceptance of stellar performers like Dr. Robert Van Pelt. Now, who out there in academia seriously wants to challenge Bob? Really? And then there is Dr. Lee Frelich. Lee will not waste his time on non-performers. If we weren't superb at our craf t, the Director of The Center For Hardwood Ecology at the University of Minnesota wouldn't waste a minute of his time on us. That is a simple statement of fact. Lee abandoned the clinometer and tape measure technique just as Will and I did and for good reason. It was pe rfectly clear to him that the sine top-sine bottom technique got
around the problems of the clinometer and tape measure approach even when applied with crown point cross-triangulation.

Nonetheless, I acknowledge the need for submission of official peer-reviewed ENTS paper and articles in peer reviewed journals. Lee has frequently pointed out the need, as have others. So we are moving in a direction to remedy the weakness. Followers of ENTS can expect multiple papers in the coming several years.

Fourth Question: How credible is the American Forests National Register of Big Trees as an accurate source of tree height information?

The answer is that the document is not credible. Over the last 13 or 14 years BVP, Will Blozan, Michael Davie, Colby Rucker, when he was still with us, myself, and others have literally shredded the credibility of the National Register as a source of reliable species height information. The frequency and magnitude of errors in that document are off the charts. Errors of as much as a whopping 67 feet of height on a single tree have been made. That's a whole tree, folks! Yet people still use the Register for research. In so doing, they risk compromising the credibility of their study conclusions. The National Register is simply NOT a credible document and its inadequacies led in part to the intense ENTS focus on tree height accuracy.

Fifth Question: Should Will Blozan's tree measurements be considered authoritative?

Will is a close friend of mine, so my objectivity on this issue can validly be questioned, but please hear me out. I may also be the best person to render a verdict. I'll present my case below and let the rest of you be the judge. I'll then present a challenge to those who doubt Will's measuring skills. Let me begin by saying that with no false modesty, I don't usually lose arguments on tree measuring methodology, at least none I can remember. I place myself up there with the best of them on tree mathematics as exercised at the practical level. I also have a pretty good eye for judging tree height. But compared to Will Blozan in eyeballing a tree's vertical stature, I'm not remotely in his class. He has an exceptional ability to judge tree heights as well as do the ground-based measuring to as fine a level of accuracy as any of us get. As an enhancer to his measuring skills with laser and clinometer, Will gets direct feedback about tree h eight and crown structure by climbing and tape dropping trees. As a consequence, he has an accumulating database of comparative measurements to calibrate his eye and accuracy that is not matched by any of us restricted to ground-based measuring. Because of his natural abilities and his vast reservoir of experience, I'll state categorically that Will achieves a level of accuracy that is matched only by our West Coast partners and perhaps some folks in the tropics, Australia, and Tasmania. He is that good. If anyone wishes to call into question Will's abilities based on their experience using just a clinometer and tape measure, 

I cordially invite them to the fall ENTS rendezvous in western Massachusetts in mid to late October. At the rendezvous, we are tentatively planning an intensive equipment comparison and tree measuring technique workshop. That is what this year's fall ENTS affair will be about plus a field trip, probably to the Catskills in NY. However, if Will should receive challenges, we would make time for a tree measuring contest. I would entertain up to 10 challengers. I would select 10 trees to be measured. I would get an independent arborist to climb and tape drop each tree with the results known only to the arborist and Dr. Lee Frelich, if he is willing to serve in that capacity. Will would measure the trees by the ENTS sine top-sine bottom method. Will's competitors would use the clinometer and tape method by the protocol they normally employ. For example, if a measurer's common method is to establish a 100-foot baseline and shoot the angle to the top of the tree from that distance, that would be the method applied to all 10 trees. Any challenger who matches Will's accuracy would be paid $100 by me - personally - out of my pocket. If this looks a little like showboating, well, maybe it is, but that is how confident of Will Blozan's tree measuring s kills I am. I'll put up to $1,000 of my hard earned money on the line.

I'll conclude with some pertinent observations. Before the days of the laser rangefinder, both Will and I measured several thousand trees using the conventional clinometer and baseline method. We quickly abandoned that method in its simplest form for obvious reasons. We employed an increasingly sophisticated method of crown point cross-triangulation, drew a lot of diagrams, and eventually wrote a book with a surveyor friend entitled "Stalking The Forest Monarch - A Guide To Measuring Champion Trees". At the suggest of Bob Van Pelt, we moved to the laser-clinometer combination expressly to solve the accuracy problem that we had so valiantly struggled with using just the clinometer and tape. I independently developed the mathematics according to an account I gave in an email on the subject of sine-based mathematics. So, it isn't as though we weren't well versed in the risks of the tangent-based method. We'd been there, done that. We understood the process only too well. When a better method came along, we jumped on it. Neither of us were slaves to convention, pushed by anachronistic techniques given credibility by wide spread, long term acceptance in academic and professional communities. As with other advancements, to promote improvements in tree measuring methodology in the field, somebody had to make a break from the group. However, in fairness to others, the break apparently occurred in more than one location. The West Coast folks were first and for their contribution and foresight, we are most grateful. But I've gathered from a conversation I had with BVP in North Carolina, the sluggish establishment hasn't embraced the better techniques out there either. According to Bob, they consider our methods to require too much work. That kind of says it all.