ENTS hemlock story - in brief   Robert Leverett
  May 19, 2006 11:09 PDT 

There is a lot of ENTS history behind Will's upcoming Tsuga Search. For
the benefit of our new members, I thought I’d share some of it on the
list. First, let me say that I suspect it appears to outsiders to ENTS
that our all consuming interest in tree measuring is a bit eccentric.
But there are scientifically valid reasons for our focus on tree
measuring. Our numbers are slowly, but inexorably, filling gaps in our
knowledge base about maximum tree dimensions. The resultant
understanding spawned is turning out to have a very practical value with
respect to the threatened eastern hemlocks of the Great Smoky Mountains
National Park (GSMNP).

Several years ago, Will Blozan and I tackled the challenge of
calculating the trunk and limb volume of some of the great hemlocks in
the GSMNP. Will suspected that they were going to set some volume
records for eastern evergreen conifers. Just based on what he’d seen,
his eyes told him that. But how does one get good volume modeling data
on trees that top 160 feet, are sandwiched in among each other, and are
engulfed in rhododendron hells? Will decided that there was just one way
to get valid data. He would climb a hemlock and measure its
circumference at intervals of a yard or meter. He initially climbed what
we later named the Yonaguska hemlock and taped its height at 168.9 feet.
He took circumference measurements at intervals of 3 feet. He later
climbed the nearby Tsali hemlock – at 169.8 feet, Tsali is the tallest
hemlock we’ve ever measured. That event was televised and covered by Dan
Rather. Unfortunately of us, Will had to compete with Dolly Parton whose
DBH exceeded that of the Tsali Tree. Alas, Tsali looked positively puny
by comparison. Sadly, today, both trees are now standing dead, but not
from the adelgid, from drought. But such happens and has made us more
philosophical toward the deaths of individual trees.

On the climb up Yoni, Will was presented with a special challenge. About
75 feet up, the big tree splits into two trunks. So Will had to measure
both trunks for us to compute a total volume. In addition, the shape of
the fused area was obviously not circular. It couldn’t be ignored
because it contained a lot of wood.

Will and I developed an archetype Excel spreadsheet model to process the
data from the climb. We toyed with different trunk shapes and eventually
settled on a calculation that set the great hemlock’s trunk volume to
1458 cubic feet. Adding something for limb volume brought the tree to
over 1500 cubes. Courtesy of Will’s climbing prowess, we had entered a
new era of consciousness about the volumes of eastern trees.

Will has gone on to climb other great hemlocks and his bank of hemlock
volume data has grown. Most of his climbs are listed on the website.
What is most significant is that we now believe that 1500 cubic feet
approaches the volumetric limit of the eastern hemlock and that it
achieves this maximum only in the southern Appalachians and possibly the
West Virginia Alleghenies, which some geographers and geologists
consider to be part of the southern Appalachians and some do not.

After those first climbs, it became increasingly apparent to both of us,
but especially Will, that the eastern hemlock had been vastly underrated
as one of the largest, if not the largest eastern evergreen conifer.
Historically, the distinction of being the largest went to the eastern
white pine. More recently, it has appeared that the loblolly pines
matches and possibly exceeds the great whites in volume. That is
certainly true today. But, there are anecdotal accounts of great
colonial white pines in New England and accounts of huge pines in
Wisconsin and Michigan that exceed anything we see today for any of the
eastern evergreen conifers. Some of these accounts seem more like the
tree equivalents of big fish stories, but there are at least a few
specimens from modern times that give credence to the accounts of past
giants in the Earth.

The General McArthur pine is the most famous of the large white pines in
the Wisconsin-Michigan area. The Porcupine Mountains in upper Michigan
have had one or two even larger ones, and the Rich Mountain pine in
Tennessee was the largest of all. These pines were measured and
photographed. There is no question as to their existence. But they are
isolated trees. There are no reliable population figures on the
distribution and frequency of huge colonial pines. So, whatever the true
historical status of the white pine and the loblolly, for that matter,
we’ll never know. But we can know about what grows currently.

Though Will and I did fairly extensive literature searches on great
eastern trees of yesteryear, we failed to find a single tree
identification guide or forestry or arboriculture manual that does
justice to the eastern hemlock’s maximum size. Most sources list it as a
medium to large tree that reaches 75 to 100 feet in height and 3 to 4
feet in diameter. Absolute maximums are sometimes listed as 6 feet in
diameter and 160 feet in height. The Forest Service’s “Silvics of North
America”, refers to 76-inch DBH, 175-foot tall hemlock as among the
largest of the species. That indicates the recognition by others that
the species can reach giant proportions. But, the dimensions just quoted
sound like the former mis-measured hemlock champion of Joyce Kilmer
Memorial Forest.

Regardless, isolated statistics, like the ones quoted in Silvics and the
tree identification guides are little more than trivia. These sources do
not say where the largest trees are located or how exceptional they are.
Of course, we know that the sources don’t know, so they can’t shed light
on the practical growth limits of a species. Enter ENTS.

From what Will Blozan has discovered in the inaccessible coves of the
Smokies, giant hemlocks are not rare. So, it hasn’t been a case of
finding an isolated big tree. The Smokies have turned out to be a
treasure trove of huge hemlocks in the 12 – 16-foot circumference range
and 130 to 165-foot height class. We also know that there is a
scattering of hemlock giants in the 165-167-foot height range, and of
course, there are two accurately measured to over 169 feet in height –
Yoni and Tsali. We now believe that the absolute largest circumferences
are between 16 and 18 feet and absolute tallest between 165 and 170 feet
in terms of these dimensions and 1500 cubes in terms of volume.
Practically speaking, this is new information contributed by ENTS.
However, I don’t want to give the wrong impression.

Over the years, descriptions of big Smoky Mountains hemlocks have not
been in short supply, including reports from Park scientists. But when
relaying the size of trees, these reports have tended to either be
anecdotal or quote only a circumference measurement for isolated trees.
Even the Great Smoky Mountains most noted past naturalist the legendary
Arthur Stupka did not adequately describe the stature of the hemlocks
that he encountered in the Smokies. So up to the grand entry of ENTS, we
had isolated tidbits.

The lack of documentation of the distribution of huge hemlocks to
include their locations and their frequency of occurrence across a
diameter and height range represents a conspicuous information gap about
species maximums. The same could be said of other eastern species, but
the threat of the hemlock woolly adelgid kicked us into high gear. Back
in the early 1990s, the GSMNP recognized that there was a need to
document the great Smoky Mountain hemlock zone before the onset of the
adelgid. Part of the documentation was the identification of the
maximums and means. This was what Will Blozan was doing when I first met
him in August of 1993. The whole ENTS thing developed thereafter and the
hemlock was always an important driving force.

But once our attention turned to volumes, it became apparent that Will
could climb only so many trees before wearing out. We needed a way to
measure trunk diameter from the ground. Using a proportionality approach
developed by the late Colby Rucker, who used the scale of the Bushnell
laser rangefinder, we attempted to model a few trunks from the ground
and with some success. However, the rangefinder has limitations. Much
later, I added the RD 1000 Dendrometer/Relescope to our equipment
reperotoire. The Dendrometer is a good instrument, but has limitations
and quirky behaviors if the objective is a high degree of accuracy. Then
Jess Riddle entered the picture with a device used by his engineer
father to measure widths at a distance. Jess’s Monocular proved to be
the high precision device we needed to model a trunk from a distance
with a higher degree of accuracy. It is now the instrument of choice
although the Dendrometer is more efficient and comes in very handy. It
serves to give us a first crack where we’re just wanting to get into the

We've developed much of the mathematics and the field and computer
procedures needed to measure the variety of trunk shapes we encounter.
But even with our shortcuts, the process of volume modeling remains
labor intensive. We will continue searching for factors and models to
apply to speed the process along and to new understandings. Our efforts
are revealing facts about hemlock symmetry and lack there of and it is
in the latter category that we face our biggest challenges.

Recently, Will turned his attention to modeling the area of a main trunk
that separates into one or more trunks/limbs. For trees that split into
multiple trunks, there is often an area of fusion before the separate
trunks emerge as distinct. Will climbs to the region of fusion and
constructs a frame around the fused area. By a measurement and
subsequent computer modeling process, we can calculate the
cross-sectional area at different spots along the area of fusion. This
is far more accurate than taking a cross sectional measurement from the

Well folks, it is this modeling technology and field experience that
ENTS brings to Tsuga Search - the Great Smoky Mountain eastern hemlock
documentation and treatment project. So our measuring obsession is about
to pay handsome dividends in the most urgent and prestigious ENTS
project to date. and as more and more trees are modeled, we’ll
understand more and more about changes in trunk shape with the
progression of age. We’ll know what the maximum dimensions of the
species are throughout its range. It will then be up to Lee Frelich and
other researchers to figure out the whys.


Robert T. Leverett
Cofounder, Eastern Native Tree Society
RE: ENTS hemlock story - in brief   Will Blozan
  May 20, 2006 10:07 PDT 


Thanks for the intro. Just for the record, Tsali was the first hemlock
climbed and measured in 1998 with Brian Hinshaw and Yoni was climbed and
filmed in 1999 with Michael Davie.

The volume for Yoni will be determined in the next few weeks. Jess and I
plan to frame map the fusion section. Hopefully the bark will not fall off!
We expect the final figure to be in the low 1400's.

Yoni was 168'11" and Tsali was 169'10".