Hey Tom, what did Nick say again?
Watch that clinometer usage...
How Tall is that Tree?
If a tree is not laying on the ground so you can use a tape measure, how can you be sure how tall it is? Foresters have historically used a variety of methods and tools to answer this question. Readings from an Abney hand level, hypsometer, transit, Biltmore stick and clinometer are accurate enough to show the approximate length of the trunk and about how much wood will be harvested.
These techniques may also be used to satisfy the needs of modern research, which looks instead at the height of the entire tree. When the highest point of the tree is visible and directly over the base of the tree, and the tree is growing on level ground and not leaning, they tell you how tall that tree is. On trees that lean or spread, other techniques are used, because canopy researchers demand greater accuracy, and insist on repeatability.
The Middleton Oak, at a plantation with the same name near Charleston SC, was measured with a clinometer at 85 feet tall. Technicians of various experience, under the direction of Dr. Robert Van Pelt of the University of Washington, measured this massive tree using the Eastern Native Tree Society Laser Method. (See
http://www.uark.edu/misc/ents/measure/tree_measuring_guide.htm ) Their readings were all just over 67 feet; the tape measure that I dropped from the top read 67’4”. (Wake County’s Capital Trees Program also hosted a workshop on the ENTS method on July 22nd, and its members were impressed with its accuracy.) Dr. Van Pelt and the ENTS have measured the total volume of that oak at 4,820 cubic feet. A tuliptree that reaches100’ taller measured only 3,990 cubic feet.
American Forests, keeper of the National Big Tree Registry,
http://www.americanforests.org/resources/bigtrees/register.php is looking at total volume as a future category for champion status, but for now is relying on the traditional formula of height plus circumference plus one-quarter of the average spread. What is new is the requirement that only trees measured within the last five years are eligible. Advanced climbing gear makes it easier to get to the top, and using the ENTS method with the laser rangefinder (<$200) makes it easier to measure accurately without climbing.
There will be a call for a lot of remeasuring, so it is more important than ever to get the height right. Trees in NC in search of a national champ include winterberry, Ilex laevigata, American and Bigleaf snowbells, Styrax americanus and grandifolius, the Kelsey locust Robiniae kelseyii, Bigflower pawpaw, Asimina obovata, and Sarvis holly, Ilex amelanchier. Also, a recent survey showed 42 deceased NC champs, so big tree hunters are needed to nominate replacements. For a free copy of the summer issue of American Forests magazine containing the Registry, and a copy of the ENTS measuring guide, email
[email protected] .