Back to the Business of Defining OG    Leverett, Robert
   Aug 07, 2002 13:42 PDT 

Apart from big tree news, I would guess that most of the members on our ENTS list are very interested in definitions of old growth forest. From time to time on the list, we've talked about OG characteristics and the processes that shape forests over time, (centuries worth of time). But most members may not realize that OG definitions have proliferated over the last several years. There have been moves in the right direction, but also administrative definitions have proliferated. More specifically, there are definitions that have been crafted by academics, by the managers of national forests, by states bureaus of forestry, nature organizations like TNC. The list goes on. Is this proliferation creating confusion? Yes, definitely!

A couple of weeks ago Jess Riddle asked me a question about sources of information on OG definitions. He was asking for some help on a research project he'll be doing in the Chattahoochee NF (I think). That really set me to thinking. Rather than me just popping off, maybe the group of us could weigh in and lend a hand to one of our star performers.

To anyone who is not up on the subject, I should point out that the term old growth is used so commonly now, that in the public's mind, OG is a definite reality. But not all ecologists accept that there is such a thing as old growth. So there are plenty of issues to discuss. For instance, is OG an actual definable state of natural forests, a convenient abstraction, conceptual, or just the pure fantasy of us Tolkien types?

Our list is very well qualified to discuss the topic. We currently have as members, all of whom I hope will participate to the extent their time permits:

1. Dr. William Martin, Eastern Kentucky University - one of the very icons of old growth forest ecology and an important sources of early OG definitions,

2.    Dr. Charles Cogbill - an independent forest ecologist who is credited with developing a working definition of old growth used here in the Northeast,

3. Dr. Lee Frelich, Director of the Center For Hardwood Ecology, UMN - an expert on forest disturbance regimes and everything else to do with forest ecology,

4. Dr. Rick Landenberger, West Virginia University - a research scientist who has struggled for years with old growth issues in the mountaineer state and was one of the first scientists to create a website on the eastern OG,

5. Dr. Lynn Roger, famous black bear biologist from Minnesota - Lynn came to understand the association between black bears and old growth white pines yeares ago,

6. Dr. John Okeefe, Director of the Fisher Museum at Harvard University's Harvard Forest - John has access to the extensive archives and stays current on old growth issues,

7. Dr. David Orwig,Research scientist at Harvard Forest - Dave gets down and dirty with the old growth and has a wealth of experience studying it while pinned down under mountain laurel,

8. Dr. Alan White, Professor and forest ecologist at the University of Maine -Alan and colleague Dr. Mac Hunter wrote one of the important papers on old growth forest definitions,

9. Dr. Robert Van Pelt, Research scientist at the University of Washington and tree measurer and modeler extraordinaire - Bob studies old growth forms from high in the canopy,

10. Will Blozan, former science technician at the GSMNP, co-founder of ENTS, and now arborist, tree measurer, and climber, extraordinaire - Will has paid his dues and belongs in this discussion, if anyone does,

11. Dr. Larry Winship, forest ecologist professor at Hampshire College - Larry has designed courses around old growth forest ecology,

12. David Yarrow, Director of the New York Old Growth Forest Association - David is a rising star in the OG arena,

13. Neil Pederson, Columbia University, a PhD candidate -Neil is also a rising star,

14. Matt Therrell, University of Arkansas, co-founder of ENTS, and PhD candidiate - Matt has made amazing OG discoveries,

15. Matt Largess, Arborist, and new old growth sleuth - Matt is out there hunting and finding,

16. Dr. Tom Diggens, formerly Hamilton College and now at Youngstown State in Ohio - Speak to us, oh Oracle of Ohio, where be thou now?

17. Bruce Allen, forest ecologist and researcher with the Savanna River Ecology Labs and expert on Congaree Swamp NM - Bruce sweats everyday in the OG,

18. Professor Gary Beluzo, Diretor of the Environmental Science Dept, HCC, and my sidekick - Gary stomps the steep ridges with me measuring, GPSing, and eating plenty of goodies on our return,

19. Tamra Raven, Restoration Ecologist and former Vice President of the National Council For Women - Tamra definitely belongs in these discussions,

20. Don Bertolette, Restoration Ecologist with the Grand Canyon NP - Don got his masters degree from UMASS, studying old growth identification via satellite imaging,

21. Dr. Mary Byrd Davis, an old growth researcher and legend - Mary is my colleague and the source of THE inventory of eastern old growth sites,

22. Dr. David Stahle, Director of the Tree-Ring Laboratory at the University of Arkansas and co-founder of ENTS - The Lord of The Rings is a living legend. What else can I say.

22. Old Burl-belly, himself.

Beyond Jess Riddle's recent question, Gary Beluzo and I just received our special permit from the Department of Environmental Managment. It has been renewed so we can complete the inventory of old growth forests on state lands - a project we have been doing for the Commonwealth of Massachiusetts. As a consequence, OG definitions have floated to the top of my agenda.

Hopefully, others who have dropped of the list or haven't yet join will come aboard. Among the ones we extend a special invitation to include:

Dr. Tom Wessels, Dr. Rick Van de Poll, Dr. Marc Abrams, Dr., and Dr. Don Leopold.

Stay tuned.

RE: Back to the Business of Defining OG   Lee E. Frelich
  Aug 08, 2002 09:02 PDT 
Bob et al:

Well, I am going to stick with the O.G. my recent book, that I also used in
a chapter of an upcoming book on old growth that the Canadian's will be
publishing next year:

Old growth is a forest that meets some threshold (could be age, logging
status, tree size, etc.), determined by some political process.

That's what old growth actually is, regardless of what anyone wants it to be.

The question then becomes what threshold do you use? I advocate using
primary forest status as the threshold--in other words the forest has never
been logged. It doesn't matter to me whether the forest has been burned,
blown down or been through some other natural disturbance in recent times,
because I view old growth as an ongoing process of natural disturbance and
recovery. A primary forest leveled by wind still has all the components
necessary to recover to big tree status. For example, the big blowdown in
northern Minnesota's Boundary Waters. About 100,000 of primary boreal
forest was leveled to a greater degree than any other wind blown forest I
have ever seen in my life. It is truly flat at this point. The stands
within it may now be young, but the forest is old. The genetic heritage of
the tree populations and their adaptations to local conditions goes back
5000-6000 years. Isn't that old? Why salvage it at this point and bring a
6000 year heritage to an end just because people with small minds can only
see stands of trees as being old, rather than the forest itself? Why set
old growth aside so that there is an area where natural processes are
supposed to dominate, and then remove it from the system because a natural
process (wind) happens? We are fortunate that the MN blowdown is in a
designated wilderness and will not be salvaged.

Of course there are some regions with no primary forest, and they need to
take the best second growth they have and help it recover to the extent
possible to old growth condition.

The only other criteria I have ever seen that is worth anything for an old
growth threshold is that the trees are relatively large and old for the
species and site conditions. These criteria will satisfy those who can't
accept young stands as part of old growth, but one still needs to recognize
the need for future old growth--that is naturally regenerated stands that
will get old in time. At least this sort of criteria doesn't exclude dwarf
forests and forests of short-lived tree species from being included in old
growth. An example if balsam fir in northern MN. It only lives 40-50 years
and doesn't get very big by human standards, but it has the same gap-phase
replacement processes as a hemlock forest, and can develop all-aged forests
that are stable for hundreds of years at the stand scale. It can recover
from windthrow just like hemlock. Only the human time scale would prevent
us from calling this fir forest old growth (i.e. if the trees aren't older
than people, or large from our perspective, then they can't be part of old

After thinking about it for several years, I came to the conclusion that
definitions that are very specific (i.e. certain number of trees of a
certain size or age per acre, etc.) are not scientific at all and in
addition, do more harm than good by causing much old growth to be
overlooked, or salvaged because of natural disturbance.

I am going to be out of the office for the next week. It will be
interesting to see people's response to this post when I get back.


Re: Back to the Business of Defining OG    John Knuerr
   Aug 10, 2002 05:11 PDT 
Tom Berry uses the concept of microphase/macrophase to analyze impact. For
example, when there were few cars (microphase) their impact on people,
cities, the environment was relatively small. Our human nature gets us
enamored with the technology in its microphase, there is rapid adoption of
the technology and then we have the effects of the technology in its
So, the equation of human impact across our history on this planet has to do
with how many of us there are and the extent and type of technology that is
RE: Back to the Business of Defining OG   Heidi Roddis
  Aug 08, 2002 10:40 PDT 
I agree with Lee. To me, the age of the community and lack of human disturbance are the key defining factors. However, it is very difficult politically to get governments to adopt such broad definitions. It is also difficult to get people to recognize that a naturally stunted forest such as the Manual Correllus State Forest on Marthas Vineyard is "old growth."

It is far easier to get people to recognize and protect large, impressive old trees than to bring them to a level of ecological understanding where they appreciate the natural integrity of a community undisturbed by people for very long periods of time. Most people have no knowledge of the interactions between plants and soil organisms, or the role of fungi in forest ecosystems. It is hard to see and appreciate the intricacies of natural ecosystems. Not that these difficulties in public perceptions deter me in the least. We should advocate for protection of old growth systems even if the political processes to achieve protection are cumbersome, slow, and difficult.

Heidi Roddis
Re: Back to the Business of Defining OG    TJ Sullivan
   Aug 08, 2002 11:18 PDT 

With my limited experience in comprehending the natural world, I can still
understand and accept both of your thresholds for old growth (primary forest,
and sites with old trees relative to species and environmental conditions).
But I wonder if we are shooting ourselves in the foot by allowing the term
Old Growth to be used at all. Since the majority of the public and
politicians view OG as being stands of big old trees growing on never
disturbed sites, they may use this far too overly simplified vision in trying
to apply conservation and management techniques to various forests.

From a management standpoint, and perhaps a public understanding one as well,
wouldn't it be better to break the forest down into simplified yet
descriptive categories? Here are a couple ideas for starters:

Category 1) Primary Forest -or first forest as I recently heard it referred
to by Michael Kudish. This one is easy to imagine and define. It coincides
directly with your first threshold. Whether it is a stand of giant red woods
or a mountain top community of dwarf bilberry these forests are invaluable to
our understanding of how these communities are supposed to function.

Category 2) Recovered Forest. This one is probably a lot trickier to define
since we still have so much to learn about how forests truly function. But if
a forest shows little to no recognizable sign of past human influence, acts
as if it has not been touched by human influences and is currently untouched
by human influences then lets leave it that way.

Category 3) Recovering Forest. A forest that shows signs of previous human
impact but the presence of exceptional individuals of various species in
cunjunction with overall forest health indicates a high probability for
recovery in the not too distant future. The question here is, do we help it
along or let it recover on its own? Personally I would like to see both
approaches tried and compared directly to the forests in categories 1 and 2.

Category 4) Working Forest. Forests that are currently too used and or abused
to fit into the above categories. It is likely that we will always need
forest products to function as a society and it is unrealistic to think that
all forests could be returned to primary status in future millennia. But, I
would love to see more folks like Karl and Joe working with these forests to
restore as much of their natural processes as possible. Thus ensuring that we
humans as well as the other species we are sharing this planet with will have
the continued access to the resources we need for our survival.

My main concern with using the term Old Growth is that it tends to limit most
peoples view of what healthy forests are all about. While the sight of big
old trees makes me exceptionally happy, as far as the forest is concerned
they are just another tiny piece of the puzzle.

RE: Back to the Business of Defining OG    Leverett, Robert
   Aug 08, 2002 11:32 PDT 

Over the past couple of years, I have been moving in the direction that you have so eloquently outlined. I've just kept bumping up against OG criteria that seemed so arbitrary, so contrived - including my own criteria. However, your primary forest idea of continuous genetic heritage and the uninterrupted natural processes, including the range of natural disturbances, seems the all "natural" way to go. There is one consideration though that may apply more to southern Massachusetts than northern New England or Minnesota and that is the impacts of past indigenous populations. How should we factor the Indian influences in when attempting to identify primary forest? Where does Tom Bonnicksen's contribution fit in? Outside of high mountains and the colder climates, was indigenous influence as pervasive as Bonnicksen's research indicates? He certainly believes that Indian use of fire was pervasive and created the forest types we have throughout large geographical areas. He would explain the oak zones in Massachusetts as a consequence of long term indigenous use of fire and he would be partly right. Should we consider those areas of past indigenous impact, though the trees may be very old, to a special class of second-growth forest; i.e. a "post-indigenous" forest of mature trees that would be accepted as old growth?

We look forward to your return and your thoughts on this topic. It is going to be with us for a long time.

Re: Back to the Business of Defining OG    Don Bertolette
   Aug 08, 2002 16:55 PDT 
From an ecological restoration perspective, the issue of indigenous man
versus industrial man is crux to many considerations.
My take on it is that many consider the break to occur when man's use of
technology overtook nature's ability to respond (the forests resilience in
the face of disturbance).
For areas where industrial presence and the age range of the tree species'
mean to maximum range approximate each other, the issue comes to a head...
Re: Back to the Business of Defining OG    Will Blozan
   Aug 08, 2002 17:53 PDT 
Exactly the same conclusions I came to in 1997 after three years in the
backcountry of the Smokies. Try to put OG in a box and it will pop right on
out in your face.

Re: Back to the Business of Defining OG    John Knuerr
   Aug 10, 2002 05:11 PDT 
Tom Berry uses the concept of microphase/macrophase to analyze impact. For
example, when there were few cars (microphase) their impact on people,
cities, the environment was relatively small. Our human nature gets us
enamored with the technology in its microphase, there is rapid adoption of
the technology and then we have the effects of the technology in its
So, the equation of human impact across our history on this planet has to do
with how many of us there are and the extent and type of technology that is
Re: Back to the Business of Defining OG   Martin, Bill
  Aug 12, 2002 12:58 PDT 

Bob, Lee, Heidi, and others,

I'll chime in on this revisit of defining old growth.     An acceptable
definition is probably not possible in the near future
because participants in the exercise (including politicians) have their own
mental standard of old growth .   I guess that's what Lee means by
"political process." To many southeastern professionals I know, if the
subject forest doesn't resemble Joyce Kilmer Memorial Forest in North
Carolina in some way, it can't be old growth.     That's because they have
been in the "poplar cove" of the Joyce Kilmer where towering , huge tulip
trees are the dominating feature. This particular forest is not really very
old (as forests go) as it results from a large disturbance about 400 years
ago (or it is an Indian old field !!) that opened the way for
shade-intolerant tulip tree to get established.   Interestingly, sampling of
the area will show that another tree, silverbell, has higher density, and if
density is the criterion of vegetation classification, it's a Silverbell
forest.    So, old-growth enthusiasts of all stripes bring a different
standard to the table.   Just how old is "old"?

Here is my definition of old growth:    Old-growth forests are those forests
that possess all of the characteristics of old growth for a particular
forest type (community).    Unfortunately, these characteristics have not
been determined for most forest communities.    Is my definition ambiguous?
Sure, because forests are complex. They are not easily pigeon-holed and
this frustrates humans.    Try providing a succinct definition of life that
does not use a characteristic of life.     Certainly, the USFS approach
(particularly in Region 8) is not satisfactory because of the
characteristics used and not used across a range of types they have defined
and published.     In Region 8, of the several characteristics required to
define old growth, a few were selected to reduce the amount of judgement
required in the field by different personnel with widely different training
and expertise. .

Old-growth forests are quantitatively and qualitatively distinct from other
forests.   Of course, old-growth forests are real.    The term "old growth"
has been chosen because "virgin", "ancient", "pristine", "unique", "climax"
and other terms carry too much erroneous baggage with them.     The list of
reasons for rejecting these terms is too long and most of you know them
My own forests of interest are the Mixed Mesophytic forests of the southern
Appalachians (also known as cove hardwood, Appalachian mixed hardwood, and,
SAF-type beech-maple-basswood). I wrote about the attributes of old growth
of this type some years ago, presenting 12 characteristics.   They will not
be the same for other types and the quantiative features such as density,
basal area, and number of species may be quite different .      As several
of you have noted, these numerical characteristics are not really
satisfactory by themselves. I certainly agree and hasten to point out that
several important features of old growth are identified by what is dead ,
not what is alive.    In mixed mesophytic forests, snags and logs at various
stages of decomposition; undisturbed soils except where there is windthrow ;
soil macropores (formed by root systems and burrowing animals); pit and
mound topography (caused by windthrow of canopy trees decades or centuries
ago) are essential characteristics of these old-growth forests.     If
these features ain't there, it ain't old growth for this kind of forest.
Indeed, old-growth forests are dynamic and "busy".   They are neither
decadent,over-mature,stagnant, nor unproductive. In mixed mesophytic
forests, tree-fall gaps created by uprooting or snapping of single or
multiple canopy trees reflect the dominant natural disturbance feature of
these forests.   These gaps are created annually by wind and with episodes
of large gap formation during intense thunderstorms.   Fires and icestorms
are rare.   Every forest type has a disturbance regime that molds its
development, "busy-ness", and perpetuation.    The management issue of "how
much old growth is necessary" is answered in part by accounting for the
type, extent, and frequency of the disturbance regime for the old-growth
type under consideration. I agree with Lee's assertion that blown down,
unlogged forest in MN remains old growth because the genetic and historic
elements are still there.     Fortunately, enough of this forest exists in
the BWCA to "absorb" this short-term (in tree time) disturbance.

The "lack of human disturbance" characteristic is one that everyone likes
to gnaw on and discuss today.    A forest with any recognized logging
history shouldn't qualify because logging would eliminate some (maybe all)
of the characteristics of old growth (for the type).    However, a mixed
mesophytic forest last logged in 1810 would probably qualify as old growth
since sufficient time for recovery from that disturbance would have
occurred, the field evidence of logging is gone, AND the less destructive
logging methods of that time did not involve the machinery of today's
operations. Further, in Kentucky and the southern Appalachians, practically
every forested acre was grazed by domestic livestock from earliest frontier
settlement until well into the 20th century, but where is the evidence?
Does this grazing restrict recognition of old growth in the Appalachian
highlands as a result?    No, historical grazing is ignored because it
usually cannot be documented in the field (there are clues, but I ain't
tellin').   So, I opt for the characteristic that "there is little or no
evidence of human disturbance" for old-growth mixed mesophytic forests. The
eastern forests have been directly and indirectly hammered pretty hard by
people, particularly in the last 200 years. This means that this
characteristic has to be viewed with a more or less jaundiced eye.   Is a
2002 old-growth oak forest not really old growth because it has American
chestnut sprouts but no adult trees as a result of you-know-who?
Requiring "primary forest" as a criterion is too restrictive for eastern
forests based on these logging, grazing,occupancy,pest/disease histories.

The role of Native Americans in affecting the structure and function of
eastern forests is not clear for most of the forest types.    Separating
and weaving the strands of their role are a most interesting and challenging
research endeavors that have begun in the last 20 years.     Certainly,
today's eastern forests with their history of thousands (not millions ) of
years in their present geographic locations have also had the presence of
the native people during most or all of their development following the
retreat of ice.      There is no question that set fires were used as tools
for clearing, "wildlife management," and security purposes.   To mimic
Native Americans in forest management requires far more time and effort
devoted to research that will clarify their role.    In the meantime, there
does not need to be a rush to grab the matches and head for the oak forests
without a better understanding of fire as a disturbance regime of these and
other forest types and sites that support fire.

I share the expressed concerns about the public's lack of understanding of
forest issues in general, old growth in particular.    One major reason for
this ignorance and apathy is that university courses and faculty have
absolutely failed to make natural resource issues a part of the general
education curriculum--that exposure to the sciences and humanities required
of all.   The faculty of colleges and universtities ---the more prestigious,
the more guilty----have not and do not want to try to teach the great
unwashed who will not become one of their colleagues.   However, non
(science)-majors are the very people who will be the future legislators,
CEOs, city council members, etc.,etc. making the future decisions
affecting forests and other natural resources. Unfortunately,I do not see
the gaps in culture, understanding, and awareness narrowing..    The more
urbanized this society is becoming, the farther the citizenry is from the
forests and fields that have historically sustained and built this
country.       Do those who love the forests give up on education?    No,
we just have to work that much harder and with even more commitment, energy,
and political will.

Bill Martin
Eastern Kentucky University

Re: Back to the Business of Defining OG    Don Bertolette
   Aug 12, 2002 20:03 PDT 
Your "chime" consisted of a wonderful series of resonant chords. An
additional chord might be that of the scale of "old-growth-ness". I no
longer think of an old-growth tree, unless it is a part of a larger whole,
whether as you so well phrase it, it is a function of forest types evolving
into a sense of co-dependent community, or as others elsewhere would speak
of a forest type (the classic mixed conifer forest of California's Sierra
Nevada mountain range comes to mind). I'm reminded of Bob and my efforts
in the Deerfield River Gorge of Massachusetts, to specify a minimum area for
old-growth candidacy...methinks we were influenced by the paltry
opportunities for full-blown old-growth forest ecosystem candidacy.
I suspect there may be comments on the concept of "ecosystem"...and methinks
it as appropriate as our discussion of old-growth definition. They both are
sorely in need of better definition, but until their successors arrive, they
do it best. For me the forest ecosystem is the biotic community that has
evolved into some degree of co-dependency, and forms what I think of as
ecosystem resilience.
The point where man's impacts where within the ecosystem's resilience to
assimilate, and where man's impacts overwhelmed that resilience (ability to
return to a dynamic but co-dependent state) has a poignancy for old-growth
Re: Back to the Business of Defining OG    Robert Leverett
   Aug 14, 2002 04:05 PDT 
Bill, Lee, et al:

        Thanks for taking on the OG definitional challenge, or quagmire,
depending on one's perspective. For me the importance of discussing old
growth definitions is that we keep the subject in the spot light. This
mission is especially important as the administrative treatments of the
identification, definition, and conservation of what passes as old growth
involve more and more people with precious little experience in studying
natural forest ecosystems. At the least, it places the thinking and research
of those highly experienced in the study of old growth at a premium. Our
list can serve no better purpose than to provide a convenient forum for
experts to muse over the subject of old growth and all its permutations.

        For me the supreme challenge is to sort through the disturbances
that have visited a site looking for clues as to source and time. Tom Wessels
does this extraordinarily well. He calls it forest forensics and he has been
steadily building his knowledge base. One cannot have too much knowledge
about the specifics. For example, decay rates for logs and stumps of
different species in different environments is an area that is very
important. However, important or not, I can't lay my hands on one single
authoritative paper about differential decay rates. I have a few rules of
thumb, but don't know if they are reliable. A second area of knowledge is
the life cycle of tip up mounds. For different types of terrain, underlying
rock, rainfall, etc., how long will they last. I've read that they can last
for 500 years. From what I see in the berkshires, I'd place those that are
formed from falls of trees 24 inches or more in diameter at maybe a third
of that figure on sloping ground. On level ground, I'm less sure, maybe
250 - 350 years. Anyone out there have some experience in this department?


OG Characteristics - Interpretations and Misinterpretations   Robert Leverett
  Aug 20, 2002 18:13 PDT 

    The longer I stomp around the forests looking for what will qualify as
old growth under one definition or another, the more I feel uncomfortable
going into the forest with clipboard in hand tallying up OG characteristics
and then proclaiming an area OG or not based on the final tally of
characteristics. If forest type and terrain aren't factored in, forget it.
Well, I don't use the checklist approach anymore, but I suspect that a lot
of resource managers and budding OG sleuths do. They have their place to
organize and record ones observations, but there are all kinds of ways OG
checklists can fail.

    One old growth characteristic that at least few ecologists list is
"sparseness of old trees" - as opposed to abundance. Yes, that is an
interesting criteria. Where does it come from? The scenario that could make
it a reality might go something like this. An area widely accepted as OG is
dominated by densely distributed old sugar maples. The OG area is hit by a
wind storm that blows down most of the biggest and oldest maples. They decay
rapidly and are gone in 25 to 30 years. Young maple and beech fill the gaps.
There are still old trees, but they are now widely distributed. This is a
scenario that Lee introduced me to several years ago. Let's further assume
the surrounding areas are all clearly recognizable second growth. The old
growth area can be characterized as exhibiting widely scattered old trees
and declared to fit the sparseness criteria. Better that we know why there
is a sparseness of old trees as opposed to an abundance, but heck, somebody
with credentials listed sparseness of old trees as an OG criteria, so it is
available for use.

    Here is something even more bizarre. Suppose that the criteria of
sparseness is used in reverse, i.e. to disqualify an area as OG because it
has too many old trees. It never occurred to me that someone might actually
apply a sparesness test in this way, but that is just what has happened.
Most ecologists, foresters, and naturalists would likely not take this
approach, but it illustrates the weakness of the checklist approach.

    The secret is to become ever more experienced in interpreting
disturbances and that has to be learned out in the forest under the tutor of
an expert. Purchasing a copy of Dr. Lee Frelich's book is a good place to
start with reading material.

OG Definitions and Criteria   Robert Leverett
  Sep 15, 2002 15:31 PDT 
Lee and Bill:

    I have begun, in earnest, writing the long awaited report for DEM on old
growth forests on Mass public lands. I've promised Bill Rivers a draft by
the end of December. At present, I'm developing the background to the
current inventory effort and as I recall the history of my own personal
awareness, I've been revisiting the role of OG definitions and in
particular, the definition that stipulates that 50% of the canopy trees
should be half the maximum longevity for the species. DEM still uses this
definition, albeit in a relaxed form. DEM has called it the
Dunwiddie-Cogbill definition or criterion. As I recall, it was Charlie's
definition though crafted in the 80's I presume and later adopted by Peter

    Here is a tall request. Of all the OG that the two of you have studied
and are comfortable with applying the OG label, what percentages would meet
this criterion? This might be seen against different forest types,
recognizing some of the more northerly ecosystems which recycle their
forests at well under half the maximum longevity of the dominant tree
species. I'm just looking for ball park figures. For instance, for the areas
Gary and I have mapped out as old growth, perhaps 1/3 of the acreage would
meet the age criterion if strictly applied. I have come to view the
criterion as more a measure of what percentage of the areas under
consideration for OG status and meeting other criteria, beat the weather and
disease odds. The more I attempt to apply it to specific sites, the more I
see that it needs to be applied sparingly - if at all. I am tempted to
recast the criterion as: regions of old growth forest include areas in
which average tree age for the trees that make up the canopy equals
approximately half the maximum longevity for those species, adjusted to the
local site conditions, and a few individuals may approach the maximum
longevities for their represented species. I realize the latter is a
recasting of the age criterion that is more in line with a view of natural
forests as a mosaic of shifting patches of forest of different age classes
and is more in line with your thinking, Lee. However, I am not at liberty to
completely abandon the age criterion that DEM adopted for their old growth
policy, but want to at least recast it in light of current thinking.

Re: OG Definitions and Criteria   Lee E. Frelich
  Sep 16, 2002 07:50 PDT 

The answer to your question depends on definition of 'canopy tree' and
'maximum longevity'. For sugar maple and hemlock the maximum ages are about
400 years and 600 years, so half of the canopy trees would have to be 200
or 300 years old or more for those two species.

Using my definition of canopy tree (any tree receiving direct sunlight,
including small trees in gaps), such stands could never possibly exist. Old
trees occupy most of the canopy area, but are numerically the rarest thing
in the forest. I always track proportion of area occupied by old trees. I
haven't found tree numbers to be of much interest.

However, when they invented the definition, they were probably thinking of
canopy trees as having some minimum size such as 25 cm or 10 inches dbh,
which has been commonly used in the literature. There may occasionally be
some sugar maple stands that would meet this definition, but you would
never find a hemlock stand with half the trees older than 300 unless you
set the canopy tree size at 50 cm. Even then a typical hemlock stand would
flip in and out of the old growth definition every several decades, because
there are periodic episodes of mortality in the larger trees.

You could get more stands to meet the definition by using tree height for
the definition of canopy tree. Half of all trees in the upper height
stratum (say 75% as tall as the tallest tree) might be over 200 years old
in many old growth stands.

I suppose you could also fiddle with the maximum longevity. You could
common maximum longevity, or the maximum age commonly found in most stands
rather than the absolute max. This would be about 300 or 350 years for
sugar maple and hemlock in your forests, so half the trees would only have
to 150-175 years old rather than 200 or 300. (on the other hand you could
use the max given by the silvics book for hemlock-998 years--and no hemlock
stand would ever qualify as old growth because you would never have more
than half the trees being 497 years old).

It is curious that they would have chosen a definition that might easily
exclude a 250 year old hemlock forest, and would also sometimes exclude
forests many hundreds of years old that undergo fluctuations in age
structure that are necessary to perpetuate the forest.

Re: OG Definitions and Criteria   Martin, Bill
  Sep 16, 2002 07:56 PDT 
After a quick read of your email, I have some questions: (1) is the age
criterion set in stone by DEM?; (2) this criterion refers to all canopy
trees, not just the dominants?; (3) who is going to determine this degree of
specificity? (4) what are the other criteria for old growth? (5) what is the
definition of canopy? I like the term "relaxed form" .   I'll bet it's
relaxed in practice.

Now,two comments:
(l) This criterion is a highly quantified one ,so I like your more general
language better.    Such a level of quantifying should not be necessary.
(2) Obviously, a forest that has recently been drastically modified by a
widespread natural disturbance may no longer qualify as old growth by this
criterion.    Does such an old-growth forest get recognized in

Bill Martin
Re: OG Definitions and Criteria   Robert Leverett
  Sep 16, 2002 15:07 PDT 

   To answer your questions, no, I don't think the age criteria is set in
stone, but DEM wants age to play an important role. The criteria is not
specific as to whether all trees that make up the canopy are included or
just the dominants. The other old growth characteristics are the ones
typically cited: woody debris, tree fall gaps, pit and mound
micro-topography, etc. The list is fairly loose though and no
quantifications. Canopy is not defined.

    What ultimately will be recognized as OG by DEM will depend on how much
science we bring to bear. If I make a strong enough case, DEM will accept
the areas that I identify. Personally, Bill, I just want the science to be
strong and represent the best thinking of the Ancient Eastern Forest
Conference Series participants. My personal preferences are not germaine.

    Definitions are on the front burner now in terms of where Gary and I
draw the boundaries.


More on OG Definitions and Criteria    Leverett, Robert
   Sep 17, 2002 05:35 PDT 

Bill, Lee, et al:

   A few more comments to add to what I previously sent. Advanced age plays an important part in DEM's old growth definitions for two primary reasons:

1. DEM has the most confidence in our (Gary's and mine) designations of sites as old growth where the distributions of advanced tree ages leave the least room for doubt. There's never any argument with them when the ages are there. DEM foresters were unable to confidently ID any of their OG sites, save two, so they understandably doubt their own abilities to recognize/judge old growth characteristics beyond an abundance of advanced age trees, as determined through coring. A high density of old stems on a site provides them the greatest amount of insurance against potential criticisms from the far right or left. I do sympathize with them. Incidentally, they really aren't trying to second guess Gary and I. They just want extra insurance for the reasons just stated.

2. The areas of densely packed old trees occupy minimal acreage. I doubt that by the time we're finished Gary and I will have inventoried over 1,000 acres of tightly packed trees of advanced age in the Massachusetts sites out of the 3,000+ acres that we'll identify as old growth. The 50-50 rule is an effective way for DEM to control what they fear might otherwise get out of hand; i.e. including acreages that are subject to debate among experts. Also, DEM has balked at large buffers and connectors between stands as proposed by Mass Audubon.

So, it is the political considerations that you and I frequently talk about that drives the age criterion. As for me, as I mentioned earlier, I just want the science to be as air tight as we can possibly make it.


Re: OG Definitions and Criteria   Martin, Bill
  Sep 17, 2002 12:20 PDT 

I have a real problem with this criterion as stated. First, canopy is not
defined.   As I understand, in a forest that is being evaluated, 50% of the
sugar maple should be 1/2 the maximum age for sugar maple (according to
whom?), 50 % of the red oak should be 1/2 the maximum age for red
oak (according to ?), etc. for all(?) species.     Is this right?    How come
no other characteristics have such a degree of specificity?       Will trees
be cored to determine the ages?   How many constitute a sample?


Re: OG Definitions and Criteria    Robert Leverett
   Sep 18, 2002 04:30 PDT 

   No, the percentage of trees over 50% of max age are those that comprise
the canopy regardless of species. The criterion isn't applied species by
species. The "according to whom" part is left open. Presumable, DEM will
accept the assurance of Gary and I that age distribution provided we present
sufficiently convincing data. Trees will and have been cored to determine
age, but no minimum number of trees per site is prescribed. Here DEM isn't
trying to be overly demanding. For any given stand, they just want some
insurance that age was properly considered. If applied strictly, the
Dunwiddie-Cogbill definition drives the specificity of the age percentages,
but that definition includes no comparable thresholds for other old growth

    After a number of years stomping around in recognized old growth sites
from Maine to Georgia, listening to you, Lee, Mac Hunter, Don Leopold, and
others, especially including Charlie, debate the definitions question, I've
increasingly come to discount the age threshold as a valid criterion and
with this latest e-mail of Lee's, the age criterion is one big question mark
in my noodle. The age criterion was appropriate for its time to give us a
focus, but its time has passed, and truthfully, I doubt that DEM will insist
on adhering to it religiously so long as they are convinced that the science
behind the nominations that Gary and I make is sufficiently rigorous.
Practically, the maximum age for criterion that DEM wants applied might read
more like "a significant percentage of canopy trees must reach a significant
percentage of the maximum age of the represented species". This leaves a lot
of room for judgment calls and while I appreciate that, I don't want to take
advantage of the latitude.

    Now that I've begun writing the draft report, I'm forcing myself to
question every judgment call that Gary and I've made. I'm driving ME nuts
and will probably do so to the rest of you before this is over.

Re: OG Definitions and Criteria    Cogbill
   Sep 18, 2002 08:39 PDT 
Dear Bob et al.

    With all the whirlwind on old growth criteria, I feel a bit like
Huckleberry Finn at his own funeral.

    I am flattered several informal and anecdotal criteria suggested long
ago are now considered the "standard", but I'm afraid the original logic and
rigor have been lost, or at least taken out of context. To join the litany
of questions (actually testable hypotheses) on how the "50-50" age criteria
works, or doesn't work: which trees are included (number, species, minimum
size, condition, canopy position, spatial sampling pattern)? how is tree age
determined (field appearance, field-read cores/stumps, core preparation,
crossdated cores, pith date, breast-height recruitment, "corrected",
weighted)?; what are other age determinations (regressions against size,
reciprocal of the mortality rate, site history; canopy residence times,
non-parametric or classes)?; how is the age structure expressed (maximum,
mean, median, distribution parameters such as q or Weibull c shape; all
age-classes present)?; what is the maximum longevity (pathological age,
keyed to local conditions, a confidence interval on the tail of determined
ages, extreme ever documented)?; and what spatial pattern is represented
(stand size, spatial averaging, heterogeneity, broad-scale landscape "age"
structure)?. I'm afraid there is no simple answer, but there is lots wiggle
and research room.

    Much of the motivation for the "50-50" rule of thumb was to get an
simple objective indicator of the question of "how old is old enough"
applicable for a wide range of species and sites. The first approximation
was to use stand median tree age as a logistically efficient and
statistically interesting quantitative parameter. This was put in
perspective by comparing it to a local and conceptually logical constant,
the " maximum longevity". Both empirical data from sampled stands with
known histories and mathematical theory from different stand age
distributions (truncated even-aged, multi-cohort additive; "inverse-J"
thinning; negative exponential or age independent mortality; probability
density functions from Weibull hazard mortality) indicate that the median
age in relation to a theoretical "demi-tile" is an reasonable (and
dynamically responsive) estimator. Note that the theoretical maximum is
indeterminate (mathematically, not biologically), so that a statistical
parameterization of empirical samples must be used to estimate the "maximum
longevity". Thus two independent concepts have been combined: median tree
age is a good estimator for stand age structure and the "old" reference
curve is keyed to the observable maximum. The index was originally proposed
in its rudimentary form in 1982 (Maine Critical Areas Old-Growth Report, by
Anonymous) and later elaborated in 1996 with reference to the principles and
empirical data from red spruce stands (Spruce chapter by myself in the
Eastern Old-growth Book) with a conclusion of "In theory as well as in
practice, a median age of half the maximum longevity is a good index of
old-growth character." and I must add "in red spruce stands". I guess you
could quote me here and incidentally, I still like it as a generic rule of
thumb. In actuality, it is still a working hypothesis, and has never
received any discussion, critical comment, or indeed actually been peer
reviewed. Thus despite the tendency to accept it as dogma (or worse yet
"science"), everyone must be aware of its history, assumptions, and
limitations and realize it is only a first approximation waiting for
improvement.   I hope the reaction is not summary dismissal, but instead an
understanding of the underlying issues and complexities. As an aside, I am
unaware of more than a handful of sites where enough data are actually
available to determine either the stand age structure or the stand history
in enough detail to investigate these questions. Thus for now the
widespread use of this criteria is problematic and probably moot.

    Without revisiting the discussions of the two "old growth" definition
workshops, or more importantly the vast literature on the topic, I must
point out that we are still putting the "horse before the cart". All the
quibbling about criteria still begs the question of a real definition of
"old growth". Until we can agree (or simply state one's personal view)
about the concept and get a reasonable definition (be it verbal, conceptual,
theoretical, or typic with commonly accepted examples), there is little hope
in agreeing on any criteria which identify such an entity, or is it
entities. We also are risking tautological arguments, such as the
traditional "it is 'old growth' because I (or they) say it is". Even what I
call the Supreme Court definition, Potter Stewart's "I cannot define it, but
I know it when I see it" needs some examples and "local community
standards". Inevitably such a definition must address the history of the
area, extent and intensity of disturbance, the continuity of composition and
structures, the replacement processes, and the size and integrity of the
area at various scales. I tend to see "old growth" as a process (now there
is a conceptual definition) and doubt that specific structures, predictable
composition, or indicator species will ever be that useful as parts of a
definition. They might show up in criteria, but we first must get the
definition straight first.

Enough from the balcony, its time for Huck to float down the River, no doubt
he will return.


Charles V. Cogbill
RE: OG Definitions and Criteria    Leverett, Robert
   Sep 18, 2002 09:45 PDT 

Thanks for weighing in, my friend. I knew that if we stirred the water enough, we'd coax you out of the deep forest to give us a truly superb background on the 50-50 concept as it actually evolved. So forgive me for casting out a bit of bait. I've spanked myself thoroughly for doing it, but you were THE ONLY person who could address the history of the concept. Thanks again. I have to say that while you don't come into these discussions often, when you do, you have us all blinkling. I'm sure at least a few questions/comments will follow. I would certainly agree that many, including me, have taken the concept out of original context. It obviously developed a life of its own after being proposed.

I hope you can make it down on Sept 23rd to join Tom Wessels, myself, and a few others as we look at some ridgetop candidate old growth in MTSF. I think I mentioned the trip before, but if not, please join us. That goes for any of the rest of you who want to join us. Larry Winship, Dave Orwig, John Okeefe, Neil Pederson, etc. you all have special invitations.

Re: OG Definitions and Criteria    Martin, Bill
   Sep 20, 2002 14:12 PDT 
Bob,et al.,
Charlie's explanation and lines of questions show that old-growth forests are pretty complex.   Now you know the source of 50/50.    His example of red spruce forests plays into my offered definition: old growth forests are those forests with the characteristics of old growth for a particular forest type (community).   Characteristics include structure and process features.   The age specifics he gives are for red spruce forests , not northern hardwood, not mixed mesophytic, not white oak-chestnut oak, not northern spruce-fir, not white pine forests.     Characteristics have been developed for several communities.   Those types without defined characteristics are a field of descriptive ecology that needs to be documented and reviewed.     Where is the funding to do this rather straight-forward task?    Try the USFS and state agencies.   The pressure has not been brought to bear on this issue. Frankly, a number of bureaucrats, resource managers, ecologists, politicians are comfortable with the present form of "paralysis by analysis"   and the continued wool gathering that goes with defining old growth.    As I understand, some so-called ecologists are now challenging the existence of old growth.   Now there is a good way of dealing with an issue.   The answer is simple: get out in the field and get the data that define the disturbances, soil features, age, composition, dead material (coarse woody debris of literature fame) and all of the characteristics that need to be determined for major forest communities.   This is not a variant of the Arabidopsis or human genome projects, with a multi-million dollar price tag.    There just does not appear to be the will to do the work.

Old-growth forests, like life, are known by their characteristics.    Try defining life in one sentence that will distinguish life from, say, fire.    Enough of restating things.

Bob, try to convince the DEM that old growth is not just about age and that these forests are not just about quantity, but they are really about quality.   Quality is one word that separates old growth from successional forests of all types. (Charlie is correct to a degree: I, for one, not only know it when I see it, I know it when I smell it.)     I do understand the agency "need" for a single, quantifying feature, but I'm not very sympathetic with it    That lack of sympathy is irrelevant, so determine the possible types in Massachusetts; try to find some average (or median) age values for those types in that are realistic, reasonable and documented to the extent possible; use the ages of the dominants ,not associated species; point out the need for defining such basic ecological terms as canopy, dominants, dbh classes, community composition, uneven-aged vs. even-aged, and other items that are probably missing; and please point out that in the case of these characteristics, including age, one size does not fit all (in spite of such a feature being desirable, satisfying, and final).    How do you plan to address a case of old growth that has recently suffered a more or less catastrophic disturbance?   Is such a forest no longer old growth?     Would the answer make the "resource" appointees of the Bush administration salivate or would it provide heartburn?

OG Definitions Continuation    Robert Leverett
   Sep 20, 2002 15:39 PDT 
Bill, Lee, Charlie, et al.:

        Do I have your permissions to use these ENTS e-mail texts that
discuss OG definitions in Gary's and my pending draft report to DEM on OG?
There is no way we can be as razor sharp or elegant as the group of you by
just paraphrasing what the three of you have said. In addition, the text
threads themselves best reveal the breadth of the discussions from the
ecological to the administrative to the political.

        By incorporating the current e-mail threads and what may yet come,
DEM can see our areas of agreement and disagreement. I just want to keep the
record clear. BTW, all of you will get the WORD document form of the report.
We can't promise all the maps. At least I can't. Gary's really in charge of
the map making and speaks for the two of us. Besides being the other half of
the ecology team, Gary is our GIS guru. In addition to DEM, Harvard Forest
will get the full report. That is the agreement that Gary and I made with
David Foster, who's probably wondering when he'll see something. It's
coming, David. Honest.