Thresholds for sport and science
  Oct 03, 2003 06:51 PDT 


   Statistics matter. Then there are "lies, damn lies, and statistics". It depends of how carefully they've been developed, who uses them, and for what purposes, i.e. to inform, mislead, or evangelize. Unfortunately, in today's sound bite world, they are often used to trivialize. But not so, ENTS.

   For big tree thresholds, some of us are always experimenting with combinations that seem to tell us something about species maximums. But how fine-tuned do we want to get and when the potential combinations go through the roof, where do we call it quits? Do fractions matter? Sometimes they do.

    Let's consider some sports analogies. If you are a major league baseball player, a seasonal batting average of 3 hits for every 10 trips to the plate puts you in pretty exclusive company. An average of four hits for every ten trips makes you a legend. The addition of an average of one hit in ten trips to the plate pinpoints the limits of hitting. Big players, little players, tall players, short players, all players bow to the limit. The .300 is a threshold, .350 is another.

    For baseball fans, that average of one additional hit in ten is no minor matter. Real baseball fans would never mistake a .300 hitter for a .400 hitter, if there were any today (Ted Williams was the last and he had exactly one seasons over .400). So a difference of 0.100 in seasonal batting average is of monumental importance to baseball owners, players, and fans. Small differences can be incredibly significant when a limit is being approached.

    So what are some of the upper limits for eastern trees and corresponding thresholds? Well, it sounds like an age of 420 years is one for chestnut oak, courtesy of Ed Cook and Neil Pederson. What would some chestnut oak thresholds be - ages that stratify old chestnut oaks into the commonplace, the unusual, and the extraordinary. I don't know. I suspect Neil does, or at least he has a good idea. Neal?

Thresholds for sport and science continued   Robert Leverett
  Oct 03, 2003 07:54 PDT 


   Seeing tree dimension and growth through limits and thresholds is
admittedly more sport than science, unless the reasons for the limits
and thresholds are studied. What is genetic, what is climate driven,
disturbance driven, nutrient and moisture availability driven, etc.

   There are plenty of sufficiently favorable growing spots harboring
white pine in eastern Massachusetts, but eastern Massachusetts white
pines just doesn't quite match the western Mass population when it comes
to growth. Why isn't there an exception here or there? Maybe there is
and I haven't found any of them. But there is an east-west gradient.

    What is it about the area in Vermont that Russ Richardson told us
about earlier that produces white pines of extraordinary growth
potential. Is the spot on which they grow really that different from
surrounding lands? Historically, around Blandford, VT. white pines of
extraordinary grew. If left alone for 150 years, would we see them once

     Well, there are lots of fascinating reasons to collect data and
that is exactly what I'm headed out the door to do today on a day off
with my wife accompanying me. What will the agenda? Buy apples, measure
trees. Stop at the antique store. Measure trees. Swing by Joann Fabrics,
then go measure trees. Seek out a used book store. Measure trees. I'm
sure everyone has the picture. A full report will be rendered tonight.


Re: Thresholds for sport and science   Colby Rucker
  Oct 03, 2003 09:14 PDT 


I suppose, for baseball, we have to consider the conditions which affected
the stats for a particular player - expansion, wartime, fences, walls,
rabbit balls, leagues, strike zones, etc.

For trees, some obviously have greater natural "talent" for longevity than
others, but the stats are subject to various habitat conditions. It all
gets pretty involved, but we can start with a few positives and negatives.

Short trunks are usually a positive, bringing the essentials - roots and
leaves - closer together. With less trunk surface to be clothed in new
wood, there's more energy for broader crowns (more leaves) and greater root
development. Also, there's less loss from windthrow. In England, ancient
oaks and pollarded trees are good examples. Most of our eastern oaks are
tall, and hit the wall when a fixed leaf area no longer produces enough
nutrients to add sufficient sapwood on a demanding trunk. The dense, narrow
sapwood conducts less water, and becomes subject to fungi clogging the
vascular system, especially bleeding canker.

Rapid growth early on takes surface area to the critical stage sooner, with
fewer rings to be counted. Of course, for some species, this overwhelms the
competition, and provides the necessary elbow room for long-term survival.
Where black walnuts and tuliptrees can kill off the competition, they
achieve great structural stability, significant crowns and extensive root
sysytems, and their capacity for longevity can be utilized.

Some trees, like staghorn sumac, spring up on a roadside cut, and die while
still dominant in their restricted domain. They seem almost eager to die.
Still other staghorns, in a better soil, do live much longer. Of course
without someone to run interference for them, they'd be overtopped on a rich
site. I saw several old, thick-barked specimens arching over a tall board
fence behind a McDonalds - their crowns had no competition, and their roots,
in good soil, were kept cool, and protected from drought.

For other species, a stressful environment is positive for longevity.
Chestnut oak grows tall in a good soil, but the roots can't withstand a wet
soil, so windthrow is common. Sand over a clay hardpan does the same thing
in time. Mossy, north-facing midslopes produce big chestnut oaks, but not
over 200 years or ca. 12' cbh. Moist soil also causes death by shoestring
fungus. On a sandy ridge, chestnut oaks withstand drought, surrounded by
dying black oaks. Of course, if the site's too bad, it would be in post oak
or blackjack. So, there's a balance. Where a steep uppermost slope
position is well drained, a short trunked tree can acquire sufficient
sunlight over the steep slope, but maintain excellent root stability.

Sour gum takes strict advantage of soil conditions. It grows best in a
loose, airy soil with a reliable source of water beneath. It's often
restricted to the transitional zone between dry oak woods upslope and
floodplain/swamp habitat below. Here, with roundleaf greenbrier and New
York fern, sour gum is an important indicator plant, often ringing hydric
soils that would otherwise be overlooked. Such habitat often provides
sunlight at the lower side, and the strong root system is among the most
reliable. With a good deal of shade tolerance, sour gum competes well for
elbow room. With its diffuse pores, it seems to escape the vascular
limitations afflicting red oaks, and withstands slow annual growth very
well. Like beech, sour gum is able to add an additional century by
relinquishing its more far-flung extremities, doing quite well with a crown
of heavy limbs ending abruptly, but thickly clothed in vigorous twigs.

The matter of reducing the responsibilities of excessive surface area is
handled in different ways. Some western conifers have extremely durable
wood, and survive via narrow strips of bark connecting roots and foliage.
In the east, exposed wood rots too quickly for this, but white cedar seems
an exception, and black locust provides some rather shaky examples.

With reduced competition, some species acquire great age. Sassafras may be
one of our oldest trees, but it's seldom seen on a site not contested by
other species or subject to "improvement" by humans. We don't see sassafras
on many longevity lists, but its capabilities are remarkable.

In Maryland, the serpentine barrens at Soldiers Delight are high in
magnesium, which prevents the growth of almost all trees except post oak,
blackjack, and Virginia pine. The lack of competition gives these species
some advantages. The forest looks a bit like a snarly apple orchard, but
the oaks, especially the post, do live over 200 years. Past disturbances
may have removed older examples, or the severe conditions may just carry a
good thing too far.

So, when we scan the stats, we can see that certain players on both scenes
had great natural capabilities, but it's good to consider where those
numbers come from. Some tree hanging on a cliff face may be older than one
on a highlty contested flat. The stats still stand, but it's hard to make
comparisons. In baseball, some sharpen their spikes, some throw beanballs.
Some punch balls through the infield, some hit for the foul poles. Trees
are just as varied, finding some advantage, some loophole, some gimmick, to
extend their playing days.

Re: Thresholds for sport and science
  Oct 03, 2003 19:19 PDT 

When I first clicked on the subject, I thought...another posting on sports.
I was pleasantly surprised to read an interesting and "very knowledgeable"
post on trees.    Somehow...someway, whether welcome or no, this "practicing
arborist" got invited into this select group. So I hope you'll afford me the
latitude to see, if not disagree, from an arborist's perspective on "urban trees".

It's "my experience" that urban trees are mostly shortlived when compared to
forest trees. When I say urban trees, I am primarily concerned with lawn
trees, street & plaza trees and urban woodland (plant communities comprised of
spreading trees and open areas; e.g. city parks) trees. Yes, even in the absense
of litter, sufficient mulching, porosity and grade stability, many urban
trees grow quickly, but fewer stick around to enjoy their young maturity. I can crunch the numbers... cite the researchers. Though street tree
mortality averages 7 to 10 years, less than 1 in a hundred forest seedlings go on
to maturity.
Many forest trees become urban trees when prospective home owners build on a
coveted "wooded lot". Without adequate preservation, most die in 1 to 10
years. Their replacements, mostly nursery introductions (we love our exotics!),
will also be shortlived, due to poor selection, improper installation and
inadequate post-installation maintenance. For those few urban trees that live long
enough to make "elbow room" and compete successfully in the landscape, even
many of these do not come close to the old age of most of their forest
counterparts. Why? The average owner moves every 3 years. The new owner has pollen
allergies, but loves exotic turfgrass...well can fill in the blanks.
Even if every owner is a tree hugger, spreading crowns often possess spreading
"root crowns", growing into others' property and subject to their
insensitivites. Well, let's add subdivision bylaws that limit large tree removal and
"insensitive" neighbors. Nursery trees growing in the open are likely to spread
early...yes. But also are likely to develop co-dominant stems, bark inclusion,
poor weight distribution, large branch to stem ratio and subject to greater
element exposure, infrequent outer crown pruning and over-fertilizing
(especially nitrogen). Though co-dominanacy is a forest ideal, in urban landscapes, as
it pertains to stems and branches, it's often a fatal defect. Any, of which,
are weaknesses, if not defects, that often lead to failure. For those even
fewer that survive all the aforementioned urban stresses, you're still not "out
of the woods". What if drought persists for 4 or 5 years, like it has in the
East most recently? The same fast growing, early maturing, spreading
behemoth, without supplemental irrigation, suffers much from a horde of secondary
pests; insisting on having your beautiful shade tree for "lunch". Out of
concern, you may hammer fertilizer spikes into the immediate rootzone. The crown
will likely turn greener and thicker...for a while. But while resources were
translocated from the roots to the "greener" leaves, root pests seized the
opportunity, dieback soon follows, and, if not rescued, overall decline sets in. In
the meantime, it's forest counterpart, which but lays down 1/8 inch new
sapwood and 2 inches shoot growth every year, looks on in puzzlement, as it goes on
to celebrate another century of very slow, unexciting, but steady growth.
For urban trees, subject to bear the brunt of many a front, superior structure
favor longivity. I know this to be true, having observed and pruned trees for
over 30 years. Excessive individual loading, like that found in many open
environs, can and will exploit weaknesses and defects, whether caused by
heredity, environment, poor training, lack of maintenance or likely, "all the above".

Our company attempts to treat many of these stressed urban survivors.
Numerous longitudinal bisections and incremental boring samples reveal similar
many years of slow, steady forest growth,
followed by 5 years of rapid woodland growth,
followed by 5 years of slow, urban plaza growth.
So, in theory, as it pertains to urban trees, short trunks appear to favor
longivity. In reality, if not, but in my area and experience, the opposite
would appear to be true.
I did live in the U.K. for over 3 years. Yes, there are many very old,
speading oaks. But, Brits don't have our twisters, and very rarely, our hurricanes
and ice storms. Most survivors just happen to have superior structure. And,
I wonder, how many others perished while these few survived? Afterall,
Britian is but a few percent wooded!
This is but my perspective, as a "practicing arborist". I suspect you would
have nothing less! I am open to other experiences and viewpoints.
Randy Cyr
Greenville, SC          
Statistics, statistics
  Oct 04, 2003 05:51 PDT 

Colby and Ed:

After rereading my post and your informative and thought-provoking replies, I realized that I had done a poor job of explaining myself. It is true that comparisons are frequently made of things and the results expressed in statistics that aren't very comparable. Comparisons between the performance of athletes past and present is an example.

   What I was actually trying to get at was the sensitivity with which people can accept comparisions of the records of sports heros and quote numbers in refined decimals (.300 versus .400), yet the small segment of our society that deals with trees often finds such fine tuning excessive, pointless, or foolishly sentimental. My point really wasn't very profound, but I do find the attitude of such folks interesting to explore. What leads to the almost embarrassed feeling about attention given to trees as objects of beauty? Well, I suspect that one driver behind the attitude is the belief that the proper modern day perspective in which to view a tree is in its role as a commodity. If you think the tree serves best as raw material for a product, honoring it as though it were special as an individual, to include meticulously tracking its dimensions, at the least seems like a waste of energy. The proper role for a tree is as pulp for paper, veneer, industrial pallets, toothpicks, whatever.

   David Yarrow, whose father was a professor at Suny, once attempted to get support from a forestry prof at SUNY for his Champion Tree Project initiative. He was politely told, no way. The prof didn't want people (the public) thinking too deeply about trees, certainly in ways that would detract from a societal focus on trees as raw material for commodities. The prof didn't want any sentimental feelings to develop in people that would lead to preservation. Perish the thought.

   A legitimate role of ENTS is to explore the mindsets of people whose lives deal with trees. This can be fun, but also can lead to a presumptiousness that ill becomes us. We have to keep check of ourselves, or at least I should say, I have to keep check of myself.