Tree size and core range   srgale-@comcast.net
  Mar 17, 2006 13:56 PST 

This question has probably been brought up before, but I’ll ask anyway.


Is there a strong correlation between the tallest/largest tree of a
species and its core range or distribution? As examples, the center of
distribution for Black Oak, based on just visually scanning its range
map, would be Tennessee, more or less, while for Pin Oak it would be
Indiana/Ohio. Intuitively I would think the center of distribution of a
species would imply ideal environmental conditions for that species,
adjusted for frequency of course, and therefore somewhere near the
center is where the tree would achieve its greatest size. Is this
basically true, or too simplistic a view? Conversely I would think the
largest trees of a species would be less likely found near the margin of
its range.

Steve Galehouse
Re: Tree size and core range   foresto-@npgcable.com
  Mar 17, 2006 15:18 PST 

Steve-

The simplest first answer is,
"...all other things being equal",
Yes.

-Don B
Re: Tree size and core range   Edward Frank
  Mar 17, 2006 18:50 PST 

Steve,

I am not a forester, but I have been reading the ENTS tall tree list. I
suppose the saving grace of Don B's answer is all things being equal. If
you look at the list of big tree, the tallest are almost all found in GSMNP
or in SC. The tallest Eastern White Pine, the tallest Hemlock. the tallest
tuliptree, and the list goes on and on... In the case of many of the
species the Smokies are not the center of the range of the species. Tall
hemlocks are near their southern limit in SC where some of the tallest
examples occur. Sites like the Smokies are wetter than other areas of the
east - which increases growth. Southern climates are warmer and have longer
growing seasons. The warmer temperatures may demarcate the southern margin
of some species, but the ones that grow there tend to be tall. In general
the farther north, the shorter the maximum height of the tree. Soil
conditions also play a role, but calling someplace being a "super site", may
actually just reflect the fact that the area had not been cut and has trees
that are old enough to grow big rather than it having some special growth
potential. For many other species the Smokies, which contain many height
champions of a variety of species, is in the center of a bull's-eye of several
forest community types: Mixed Appalachian, Oak-Hickory, Southern Hardwood,
Southern Mixed Pine-oak. The range of this wide varieties of trees tend to
extend across the entire area although their abundance varies in different
zones. The point is that I think it is coincidental that GSMNP is near the
center of the range of many species. The fact that so many tall examples
are found in the region is because of particular environmental conditions
present there, rather than because it is in the core range of a species.

Ed Frank
RE: Tree size and core range   srgale-@comcast.net
  Mar 17, 2006 19:58 PST 

Ed-

I know the Smokies are the "Mother Lode" of the eastern forests, and
many species' distributions center on the area, and most eastern forests
develop and expand from the area, but it seems like some of the big tree
records from that area reflect the relative inaccessibility of the
terrain, from a logging/clearing perspective. Do the records just show
the tallest/largest extant specimens, or the greatest historical
(potential) specimens? Not meant to be argumentative, but it seems like
certain forest associations and species development would flourish in
defined systems apart from the Smokies.

Steve Galehouse
Re: Tree size and core range   Don Bertolette
  Mar 17, 2006 20:14 PST 

Ed/Steve-

Yes, I chose the easy way out, as the array of environmental gradients that
come in to play is as complex as our member's thought processes!

But in general, (all other things being equal), environmental gradients
(topography, latitude/longitude, moisture, soil/bedrock, etc.) provide a
sensitive measure of changing environmental conditions, with the external
'boundaries' or range extensions the most sensitive, and quickest to show
change (kind of a weakest link).

An example close to home (for me!) is the interface of mixed conifer forest
with ponderosa pine forest on Grand Canyon's North Rim...as conditions over
the last century changed (some climate, some human induced), white firs
began invading the ponderosa pine ecosystem...as they move 'down'
(elevation, latitude, and moisture gradients), the northern extent of
ponderosa pines move down...because in part, of the moisture stress induced
by competing firs, and in part do to increased mortality induced by firs
providing a 'fuel ladder' where the typical low intensity ground fires in
the ponderosa pine ecosystem now encounter a means of climbing into the
ponderosa pine crowns...further 'down' (or in this case, South), a similar
change happens at the ponderosa pine ecosystems interface with pinon/juniper
ecosystem...this same kind of movement of the forest 'up' and 'down' the
North Rim has happened repeatedly over the last 10-12,000 years (palynology
or pollen analysis of ponds in this area has determined this), as much as 3
to 400 meters.

Presumably, the GSMNP ecosystems are much more complex, and also variable
over a similar time period...
-DonB
Re: Tree size and core range   Jess Riddle
  Mar 18, 2006 16:51 PST 

Steve,

I think your point about the lack of disturbance in the Smokies is
partially correct. The vast majority of all uncut forests on rich,
fertile sites in the southeast are in the Smokies. If that were not
the case, the Smokies would probably have far fewer volume records and
national champions. However, that does not account for the abundance
of height records in second growth areas of the park or the
unparalleled growth rates in the park. Red maple, black birch, black
locust, sassafras, sycamore, tuliptree, bitternut hickory, white
basswood, and cucumbertree all reach record heights in the Smokies in
second growth forests. In the Smokies, all of those species are
towards the southern end of their range, and some of them are close to
the edge of their range.

Species are not uniform entities; populations adapt to local
conditions, so a population at the edge of the range can be just as
well adapted to its habitat as a population at the center of the
range.

Another complicating factor with this question is that the ability of
a mature individual to grow well may not be well correlated with the
species ability to reproduce in the area. For instance, a tree could
flourish on a site where temperatures are never warm enough at the
appropriate time of year to trigger germination of seeds. If that
relationship were not weak, people could not plant trees outside of
their native ranges and have them survive.

Several other factors probably weaken the correlation between position
in range and maximum size, but I'm not familiar with them. I thought
you question was interesting, and enjoyed thinking through why our
data does not support that conclusion.

Jess Riddle
Re: Tree size and core range   Edward Frank
  Mar 18, 2006 21:17 PST 

Steve, Jess, Don, ENTS

I have been thinking about this question and the replies to the original
post. What I see is the geographical range is simply where the tree will
grow and reproduce. The shape or size of the range doesn't seem to me to
have much to do with how common the species is in a particular area, nor how
big a particular species will grow in an area. The geographic center of the
continental US is somewhere in Kansas I believe. This doesn't mean that the
densest population of people is found in Kansas. The densest population of
a tree species may be in one little corner of its range, with a broad area
extending from that pocket like a tail on a comet. Big trees are not even
necessarily found where the species populations are the highest. Individual
trees grow tallest in areas with a good climatic conditions and good soils.
The best area for the tallest trees for a particular species could be
anywhere within its range. In the rest of the range the population is
reproducing -just not growing as tall. I think it is generally fair to say
that trees tend to be taller near their southern limits of their range - a
lattitudinal trend -provided growing conditions are favorable, and secondary
pockets of tall trees grow where beneficial localized soil and climatic
conditions outweigh latitude in determining tree height.

I also do not see that competition from other tree species, climatic
change, and similar edge of range effects are directly related to how tall a
tree might grow. These factors may impact how many of the species is found
in that area, but its impact on the height of individual trees is
problematic. Trees at the edge of their range, as Jess says, may be as well
adapted to their local conditions as are trees in the center of their range.
Things that affect how tall a tree grows may not be the same as factors that
determine whether the general population of the species is high, low,
diminishing, or increasing in a particular area.

Ed
Re: Tree size and core range   Don Bertolette
  Mar 18, 2006 23:11 PST 
Ed-

The simplest second answer might be...
"If all other factors were equal,
and all gradients were linear, the answer to Steve's first question could still be yes..."

-DonB

PS:Not one to keep the inquisitive waiting, I suppose the third simple answer might add the word scalar to the milieu...
RE: Tree size and core range MORE   Will Blozan
  Mar 19, 2006 08:32 PST 

ENTS,

From what I have read, some of the eastern species we track heavily, like
sweetgum, Hophornbeam, shagbark hickory, and black walnut, grow far larger
outside of our "Eastern" delineations in Mexico.

I also want to add to Jess's comments that the tallest eastern white pines
will soon be just miles from its southern range limit in GA. I predict trees
in excess of 190' within 10 years. These trees are less than 80 years old.

Will
RE: Tree size and core range   Roman Dial
  Mar 24, 2006 18:01 PST 

Steve,

Several species seem to have both current and historical max heights
near one end or the other of their geographic range.

For example, Sitka Spruce has its greatest height at the extreme south
end of its range, in California, yet the historically tallest Doug Fir
were at the north end of that range in BC.

Eucalyptus regnans was likely tallest at the north end of its range
(Victoria) but is now tallest toward the southern edge (Tasmania), since
logging removed the tall northern specimens. Many of the tallest
tropical trees in SE Asia are all near the northeastern edge of their
ranges.

These are just casual observations, but they seem to indicate that it
would be hard to generalize.

Many mammals are largest at the north end of their range (Bergman's
Rule?), but for trees it seems they are all over the place.

Roman