Here are some better late than never hemlock statistics for
comparative purposes that come out of from my personal database.
They represent maximums of either height, girth, or volume.
Height Ice Glen
Girth Mt Tom SR
Height Blanton Forest
For height in New England, Ice Glen is the best that I've found
with at least 3 trees over 130 feet and a good dozen over 120.
MTSF will exceed Ice Glen in the number of hemlocks reaching 120
feet in height, but only because of the far greater acreage of
MTSF. Altogether, I have documented 6 sites in Massachusetts
with hemlocks over 120 feet in height, but only 2 with hemlocks
over 130. I am also aware of 6 sites with one or more hemlocks
over 12 feet in girth in Massachusetts. However, I have yet to
find a site with more than one 12-footer in close proximity.
That distinction is reserved for the 11-footers and then usually
no more than 2 or 3.
For trunk volume, the Mount Tom and Dunbar Brook hemlocks are
the largest volume hemlocks I've modeled in New England. The
Mount Tom tree weighs in at around 770 cubes and the Dunbar tree
at 727. Based on what I've seen, I would guess that 800 cubes is
about as big as you will find at 42 degrees latitude or higher
for hemlock and a tree of that volume would be extremely rare. I
think that a large number of 500 - 700 cubic ft volume hemlocks
grow between 41 and 43 degrees latitude, but this is just a
perception. I do know that as one goes beyond 43 degrees, 9 to
11-foot girths represent the maximums except where root
buttressing distorts size.
Big hemlocks in New England stems from the rarity of trees over
12 feet in girth. Pennsylvania is the turning point where 13+
footers are found more often. Above 42 degrees, 12-13 feet seems
to be the maximum with an exception here or there. In
Massachusetts, I am aware of only five 13-footers, one of which
has a huge buttress. Even the huge Mount Tom tree slenders down
quickly. Gary Beluzo's Tuntkoshala (sp?) tree and the Dunbar
Brook hemlocks have the columnar form that allows them to reach
significant volume, but we're talking between 700 and 800 cubes
for these trees. So basically, the volume ratio of the largest
of the southern hemlocks to their northern bretheren is 2:1.
Unfortunately, it is doubtful that we'll get much new data from
Connecticut and farther south due to the dieback from the
adelgid. But our existing statistics and what I regularly seeing
from the northern part of the hemlock range confirms the
species's rapid decline in all dimensional measures. By latitude
43 degrees, only the very best sites will produce hemlocks in
the 120-foot height class. I've only found one site so far.
Girths over 12 feet will be extremely rare and trees in that
girth range will usually reflect some buttressing.
Moving westward, the height rule seems to hold, but as we saw,
trees in the Porcupine Mtns are exceptional in girth for the
latitude with probably a good population reaching 12 feet. But
heights do not appear to quite reach 120 feet in the Porkies. I
would guess that there are a few 700-cubic foot hemlocks in the
Porkies. Your view on that is probably better than mine.
Now that I have finished with selling my Holyoke House, as soon
as my toe heals (dropped a stove on it and developed gout in it
- Ouch!), it will be back into the forest I go to document
Northeasten hemlocks while we still have them.