| Forest
Structure and Old Growth Definitions |
Colby
Rucker |
| December
26, 2002 12:15 PM |
Bob,
It's a bright morning, and last night's heavy winds have left
the ground bare and frosty, with no trace of yesterday's snow
and rain. From the news, I'll guess that you had quite a
snowfall; I hope that you're pacing yourself shoveling out the
walk and driveway.
I was looking at a stack xeroxes given to me some years ago by
Dan Boone. Dan is a gifted plant taxonomist and naturalist. He
was in charge of Maryland's Natural Heritage division until
ousted for being too strident about preservation. Since then, he
has been quite active in locating areas in Maryland (mostly in
Garrett, our westernmost county) that mimic old growth. The
xeroxes all concern old growth forest structure and habitat.
The definition of old growth is not unlike the chart that Herb
Schwartz got from a Maryland forester, and breaks forest
succession down into four stages: reorganization, aggradation,
transition, and steady state. My woods has passed aggradation,
which is that most desired for woodfiber production. Having
passed through a long period of natural thinning, and the
development of a rather uniform canopy of mature trees, many of
the largest tall trees are being lost each year to old age,
lightning and windthrow.
It would be easy to suggest that continued loss of large trees
and the attainment of a steady state condition will mean the
woods has become old growth, but I would disagree. There are two
reasons why this will not happen so easily. Whether derived from
old-field or selective logging, the stand has a disproportionate
amount of tuliptree, northern red oak and other fast-growing
species, and those specimens usually have tall straight trunks
free of limbs for a great distance. In time, an uneven aged
stand with a discontinuous canopy will develop, but
structurally, a stand where the oldest specimens originate from
a second growth condition is quite different from old growth.
Of course, it is doubtful that Maryland has any old growth left,
so it may be argumentative as to what it would look like. This
is particularly true for a hardwood forest. I am inclined to
believe that the local woodlands which I knew as a boy provided
some clues. The many ancient trees which had been spared by
logging were often heavy limbed, crooked, or hollow. Of course,
the area had been subject to usage since about 1650, so all
sorts of logging, clearing, grazing and burning had taken place,
but the first colonists commented on the openness of the woods,
and the large size of the trees, which they attributed to
burning by the Indians.
Whatever the effect of those early influences, the woods I
recall seemed to have been composed of trees which often
branched at a modest height, and did not attain the considerable
height of specimens which have developed over the past one
hundred years. Although it might be argued that activity by the
early colonists opened the woods and promoted the development of
low limbed, broad crowned trees almost like the deer park at
Cedar Park, I think the structure was a natural condition
typical of old growth.
Considering the age attained by the chestnuts, white oaks,
chestnut oaks, sour gum and beech once prevalent at Chase Creek,
there were few opportunities for young trees, and successors to
lost specimens were likely old themselves, with crooked trunks
and uneven crowns. Occasional windthrows of a large tree often
took others with it, opening a considerable area to the
sunlight, which led to the development of groves of very tall
straight tuliptrees, northern red oaks and other species, so not
all the trees were crooked or hollow, but the woods was quite
different from a second-growth stand grown old.
Besides the differences in structure and distribution of
species, there were undoubtedly differences in soil chemistry,
fungi and other complex associations. Some of these elements may
have been altered by microscopic introduced species, or simply
became incompatible with the second growth condition. Such
elements may become reestablished, but it seems uncertain what
the lag time might be.
So time is an important element. It seems that nearly all
vestiges of the second growth forest must pass away before a
forest structure more typical of old growth can exist. If
"steady state" is defined as simply the fourth stage
of succession in which there is a balance between growth and
loss, that seems simplistic, suggesting that "old
growth" can be regained in "perhaps two centuries from
the initial disturbance." For some species, this might be
true if the disturbance were a severe wind event in an old
growth stand, but it cannot be the time required to convert
second growth to old growth.
On sites where the growing conditions are extremely poor and
past logging hardly profitable except for charcoal, the limited
number of competing species may provide an opportunity for a
more rapid return to an old growth condition, but I cannot see
that hardwoods on the better sites can return so easily. Part of
the problem may be an arbitrary comparison with photogenic
stands of tall, straight conifers. People associate old growth
with big tall trunks, which is why they call Belt Woods
"old growth." At that site, many of the white oaks are
240 years old, but most of the sour gum and beech are small, and
crooked or hollow trees are essentially non-existent. Someone
played forester ninety years ago, and then didn't have the heart
to cut the results.
With such a mind-set, most people simply can't imagine the
complexity of an intact ancient woodland containing numerous
trees with hollow trunks and broken tops. The simplistic
attitude regarding "den trees" doesn't touch the
complexity of a truly old stand. A tree severely damaged by
wind, fire or lightning decays to the boundary of the active
sapwood. A fire may scorch these boundaries, but the dried
surface decays little. In time, fungi enter through crevices,
and decay reoccurs perhaps two to four inches within, leaving a
dry shell within the hollow. This may take another hundred
years, but greatly increases habitat greatly for flying
squirrels, white-footed mice, lizards and snakes, spiders and
millepedes, etc. We might ask, where were house spiders before
houses, and chimney swifts before chimneys?
If there's a point to all this rambling, it's to suggest that
the lure of ecoforestry is likely to be limited to the
aggradation stage, avoiding the losses in board feet of the
transition stage, and by any definition, incapable of accommodating
the so-called final stage of steady state.
That limitation demands that we think more about what is meant
by old growth. Admittedly it means many different things to
different people, so no one definition is possible. What does
seem possible is that we recognize that allowing a woodland to
return to steady state does not mean that the final plateau has
been reached. It seems that there is much that continues to
develop. Of course, any return to the past is compromised by
chestnut blight, the wooly adelgid, and introduced species, not
to mention passenger pigeons or global warming. That said, the
past is always a moving target.
Despite all the uncertainties, we should continue to look for
exemplary examples of the "highest," most complex
attainment of "old growth" within "steady
state." Does a perfect site exist anywhere? Probably not;
as we learn more about the complexities of the ancient forest,
the more elusive our goal will be. That is as it should be; to
be satisfied with any arbitrary definitions of
"perfection" is just not good enough.
Colby |
| Re:
Forest Structure and Old Growth Definitions |
Robert
Leverett |
|
Dec
29, 2002 11:56 PST |
Colby:
Lee Frelich has perhaps the best working
definition of old growth. It is incredibly simple and 100%
functional. For Lee's purposes, it is whatever the group he is
working with says it is. Lee Frelich, Charlie Cogbill, Don
Leopold, Mac Hunter, and other forest ecologists who study
forest processes have considered different definitions and
concepts for years. None have found a point in the development
of a forest in which the forest suddenly transitions to
something we all agree is old growth from something we agree is
not. There are no thresholds. This leads some foresters and
forest ecologists to conclude that old growth is a figment of
our imaginations. I would use a different term. It is a
convenience. I am comfortable using the term old growth because
its fills a niche and its absence would leave us with a hole
that would need to be filled by a term identifying largely the
same thing. In a nutshell, the term old growth
signifies/identifies a range of forest/forest habitats that
we're trying to protect for historical, scientific, ecological,
and aesthetic reasons. This could well include habitats that
were shaped by Indian fires over centuries if not millennia.
In terms of judging tree form, there is
little doubt that Native Americans shaped forests in much of the
inhabitable regions of the East. But areas in large mountain
ranges such as the Blue Ridge in VA,NC, SC, TN, and GA, the
Alleghenies in WV, Whites in NH, and most certainly, the
Adirondacks in New York were much less impacted by Native fire
management, except of course in especially fire prone areas.
Consequently, the dominant tree form in mountain forests was,
and still is, the forest-grown form. So the forest-grown forms
of a second-growth forest do not invalidate that as an old
growth form. In the Smokies, there are tens of thousands of
acres of forest with trees between 250 and 500 years of age.
This forest looks much as it did when logging began in earnest
around 1900 to create a large areas of second-growth. About 35%
of the Smokies are first growth forest. This compares to about
8% of the Adirondack Park forests and 17% of the acreage of the
Forest preserve. That makes the Smokies remarkable as a
concentration of old growth for a region of over a half million
acres. The Porcupine Mountains may have an even higher
percentage of first growth forest.
In terms of the impact of the Cherokee
on the Smokies, well it was probably very small. The Cherokee
numbered around 40,000 to 50,000 at the height of their power,
but these numbers were spread over a region of around 40,000
square miles. The high mountains were not the abode of the
Cherokee. They lived in the river valleys. So vast areas of
mountainous terrain were for all practical purposes untouched
with the exceptions of narrow corridors and some summits called
balds.
With respect to the hoopla over old
growth, much of what passes for first or primary forest in the
East is a mix of primary and old second growth or old second
growth. But the distinction is not necessarily all that
important. As Barbara McMartin notes, where logging in the
Adirondacks was limited to light cutting of spruce, the forest
today looks no different from adjacent areas of first growth
forest. Making distinctions and looking for shades of gray is no
longer relevant.
What most of us are really looking for
are forests that have been developing under the complete
dominance of natural processes for a long time - at least 150 to
200 years and preferably longer. During that time many natural
cycles repeatedly play out. Young trees have the opportunity to
mature and take on old-growth forms. The litter layer has a
chance to develop. Niches form to accommodate more types of
small animals and plants. The whole forest takes on a look that
most of us have been sharpening our skills at recognizing for
years.
What especially interests us about these
"old growth" forests is the richness of life and
complexity of process and of forest structure. Old growth
ecosystems are far more diverse and interesting than the tightly
controlled forests that are intentionally simplified to produce
crops. But the richness and complexity of what we label old
growth does not manifest itself well, if the forested areas are
too small. What is often preserved as old growth are small 25 to
100 acre tracts that are under assault from all sides. We may
value the small areas for historical reasons, but ecologically,
they are vulnerable - especially those in semi-urban areas. We
look to preserve relatively large, intact regions where the
forest is less vulnerable to a single disease or insect
infestation, or natural event like a fire or hurricane. The
blowdown of the Cathedral Pines of Cornwall, CT in July 1989
reminded us of how vulnerable small stands of trees are to
natural events. Having said this, even a larger forest can be
overwhelmed by outside influences such as acid rain or invasion
by exotic pests. So we cannot allow ourselves to become such
purists that we shoot ourselves in the foot. Old growth areas
will still be managed in some larger land use context.
An essential benefit of all this fuss
about old growth is the continued attention it receives in the
public eye. Attention is essential for continued protection.
There are no permanent protections! Laws can be overturned. In
addition, each new generation must be brought into the fold and
given the opportunity to discover the magic of natural forests
for themselves. Continued attention gives them appeal. However,
the growth of awareness and particularly appreciation can't be
gained at a computer keyboard and can't occur as instant
gratification or periodic diversion. Appreciation can only
develop over time. Those of us involved in old growth research
and preservation have a special obligation to the younger
generation. Old growth can't be just our trip, we have to make
room for the next generation and we have to help them see old
growth in a variety of ways.
What is truly
different about old growth ecosystems and why they hold so much
appeal to some of us. It is helpful, if not necessary, to look
at the superlatives to understand the appeal. If we consider a
system like the Great Smoky Mountains, the diversity of life,
the range of habitats, the aesthetics, the sheer expression of
nature's fecundity far exceeds that of the surrounding regrowth
and often over-worked forests. There is no substitute for the
Smokies. That's why they've been declared by the United Nations
as an international biosphere reserve. The astounding diversity
of the Smokies is why botanists from around the world visit the
GSMNP. The number of flowering plant species occupying various
niches within the 540,000 acres of the Park, now exceeds 1,800.
In fact, the number may be considerably more now. I expect it
will eventually exceed 2,000. The number of tree species stands
at 131, many of which reach their maximum sizes in the Smokies.
Great ages are common for several Smoky Mountain species. The
Smokies boast the largest diversity of salamanders known
anywhere in the world. There are 22 different species of snakes.
The Smokies are a bird watchers paradise. The super trees of the
Smokies that we in ENTS document are a reflection of the
diversity of Smoky Mtn habitat, its development over time, and
the very limited interference in that development by homo
sapiens. The Smokies are a clear statement of why we need to
maintain forest preserves and cannot afford to relax that
requirement. Elsewhere in the tropics, examples of astounding
diversity even more make the point of why we need preserves.
Well, of course, our members know this. ENTS members are the
choir. What is exciting is the possibility of ENTS partnering
with the Forest Stewards Guild and perhaps the Champion Tree
Project and American Forests to identify forests of exceptional
value. To the credit of others who have preceded us, many
exemplary forests have been identified, but many others have not
and of those that are have been identified, little has been done
to document them sufficiently or place them in a context that
will allow them to be fully appreciated. This is the job of ENTS
working in partnership with other organizations.
As a final bit of information, John
Knuerr, Gary Beluzo, and I went to the Black Stevens
Conservation Area for a couple of hours this morning to
reconfirm the champion black locust and to measure more of the
northern red oaks growing in a ravine. Three different sets of
equipment were used. The calculations for the N.. red oak
produces values from 113.6 to 115.0 feet. Based on readings from
the two most accurate instruments, the most probable range for
the tree's height is 114.3 to 115.0 feet. The use of 3 sets of
equipment and 3 sets of eyes, and a known level of instrument
accuracy helps to further confirm that we can come within about
+/- 1.0 feet of precise height using our methods at least 90% of
the time based on 3 separate measurements and within +/- 1.5
feet 99% of the time. I feel confident that given 5 or more
measurements, we can come within +/-1.0 feet 99% of the time.
Bob
|
| Re:
Forest Structure and Old Growth Definitions |
Robert
Leverett |
|
Dec
29, 2002 17:12 PST |
Lessons from
the forest are there for anyone who carefully observes and who
can discard old concepts and ideas when they prove inadequate or
wrong. It is also important to keep in mind that processes are
playing out in forests that span a range of seconds to
centuries. Decoding the patterns and evaluating their individual
effects requires that one not focus on just one or two cycles or
limit one's view to a block of time that represents the working
lifespan of a human. Lee Frelich speaks far more eloquently to
this point since he constantly thinks in terms of patterns,
processes, and effects. That kind of focus is what it takes.
At a simpler level of understanding,
which is what I consider myself to have, so much of what can be
concluded about forest processes at the stand level can be
gathered through careful observation of what is growing in what
locations and under what conditions. Extending the observation
process to many hundreds of stands allows one to discern at
least the most apparent patterns. Careful, independent
observation was how Thoreau and Leopold made their most valuable
contributions.
However, at the landscape level, I think
a naturalist's kind of observation is a lot more difficult. It
takes a Lee Frelich to decode the far less visible macro
patterns and cycles. As a consequence, the understanding of
forest processes that ecologists like Lee possess really does
represent the cutting edge of our knowledge. Lee's comprehension
of forest processes goes far beyond the simpler ideas and
concepts of earlier eras. But alas, beyond the scientific
process, other forces are at work.
A friend of mine once counseled me that
one should always seek to distinguish institutional dogma from
fact when dealing with the forests. He had to constantly battle
dogma on his way to his master's degree. Let's face it. Aldo
Leopold's real forest education began when he cast off dogma he
had absorbed during his period of formal education. He had to
get beyond professional dogma to understand the natural role of
predators in keeping an ecosystem healthy. He learned the hard
way that more deer did not mean a better forest. Incidentally,
Joe, you've spoken eloquently to the dogma point many times in
terms of your prescription for a better forestry curricula. But
if dogma stands in the way of one's understanding of forests,
when combined with financial interest, low forest I.Q.s are
absolutely guaranteed. My introduction to the interplay of dogma
and vested financial interests relative to forest issues came in
in late 1980s.
Logging companies in the Southeast
pushed the idea that the remaining old growth on national forest
lands was decadent, and out of a mission of mercy, should be cut
to make room for new growth. Their mantra was "cut the old
ones to give the young ones a chance to grow." Presumably,
they were advocating a mission of forest mercy. But who was to
make the sacrifice and do the cutting, since there wasn't
supposed to be money to be made in cutting decadent forests?
Well, guess what? The same logging companies which were pushing
their notion of decadence were only too anxious to rush in and
do the logging. Okay, then, just how decadent was the old
growth? They weren't in the business of losing money. It was
pretty clear that the old growth had considerable economic
value. Even with heart rot, they could still make profit on the
overmature trees they intended to cut. The old growth, with its
abundance of larger diameter trees, was a windfall compared to
the high-graded, small-stemmed stuff that characterized their
private woodlands. So, was it all a ruse by them? Completely
disingenuous? Not entirely. They did have a financial motive,
but they also were victims of a dogma, albeit willingly.
Where the dogma came into play, as
opposed to purely financial interest, was in what they actually
thought was going to happen to the old-growth remnants. They
thought that the forest was going to suddenly give up the ghost.
They had absorbed the dogma that had been fed to them by I'm
sorry to say, the forestry profession. They had literally no
concept of many old growth forests as being multi-aged and in no
danger of croaking. Even though the cove forests of the southern
Appalachians are highly diverse, the mental image of old growth
carried by the owners of logging companies was that of a single
species, even-aged stand near the limits of the species natural
life. It didn't matter that one could go to any number of old
growth forests and clearly see an entirely different structure.
They had married financial self-interest to industry dogma.
In his research for his book "The
Power of Trees", Dr. Michael Perlman encountered the
absorption of that dogma and described interviews to me he had
had with timber specialists. During those days I frequently
muttered to myself, "Man, these people are seriously
deluded." That was then. What do I say today? "Man,
those people are still seriously deluded and the delusion
doesn't end at the Mason-Dixon Line."
Bob
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