Forest Structure and Old Growth Definitions  Colby Rucker
 December 26, 2002 12:15 PM 

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.

Re: Forest Structure and Old Growth Definitions    Robert Leverett
   Dec 29, 2002 11:56 PST 

    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.


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."