The Mosaic Forest: An Interview with Howie Neufeld

by Nathan Poole Issue: Fall 2016 Special Issue on Forests

Howie Neufeld and I met here at Appalachian State University in the Fall of this year at a conference entitled, “The Value of a Tree.” As the title suggests, it was something of a catch-all, with presentations from a wide range of specialists, including a Luthier (violin maker), a trail-builder, a timber industry representative, and a US forest service employee. Though he is a professor and biologist with a tremendous wealth of specialized and practical knowledge on the life of forests and their various “values,” Howie managed to awaken and unite the room with his presentation by introducing us to his favorite trees—and not all of them were real, I should mention, at least not the one growing on Pandora (the fictional universe of Avatar). After his presentation on November 14th, 2016 we began the following conversation.

Nathan Poole: Has the public's definition of forests changed in America, and is that change related to our lack of experience with old growth, or climax stage, forests? 

Howie Neufeld: Roderick Nash, in his seminal work, Wilderness and the American Mind, documented the changing attitudes by people toward wilderness, many of which were forested areas. For Europeans colonizing America, the forest was a forbidding place, filled with danger, as opposed to the view today that pristine forests are ecosystems that must be preserved for either recreational or ecological reasons. This switch-over in thinking occurred during the early to mid-1800s when the transcendentalists abandoned a solely utilitarian perspective and began viewing forests as areas in need of preservation, the beginnings of a more ecological tone. As Thoreau said, “in wilderness is the preservation of the world.”

Of course, this shift resulted from a complexity of issues, among which is that as the country developed, forests were increasingly logged and converted to farmland, and the realization soon set in that as vast as they appeared to be across the landscape, they were, in fact, a very finite resource worthy of conservation and preservation. Furthermore, an enhanced societal infrastructure removed some of the fear of these forests, and it became safer to go into them and to appreciate their beauty, and this in turn, led to the use of forests for recreational purposes. People like John Muir made wilderness preservation the cornerstone of their life’s work.  

With the development of ecology as a bona fide field of scientific inquiry in the late 19th century, and the establishment of a guild of prominent nature writers and poets, such as Ralph Waldo Emerson, Henry Thoreau, John Burroughs, John Muir, Walt Whitman, and even Teddy Roosevelt, the public began to consider forests as vacation destinations. Their fragile nature led to wilderness preservation movements, spearheaded mainly by John Muir and which gained momentum when Teddy Roosevelt took the unprecedented step of protecting millions of acres of land, which eventually led to the establishment of the National Park Service in 1916.

The idea of a climax, or old growth forest, gained popularity from the writings of the ecologist Frederick Clements, who viewed forest succession as a developmental process somewhat analogous to a developing organism, that a co-evolved collection of species moved inexorably from early successional status after a disturbance, such as logging or a severe storm, to a climax state dominated by shade-tolerant, slower growing species.

This concept guided ecologists for quite a while, especially in their characterization of forests, which are traditionally named after the climax state that eventually dominates a site given enough time, such as the beech-birch-maple forests in New England, or the oak-hickory forests in the Piedmont of North Carolina. But in the early 20th century, Henry Gleason, a botanist at the New York Botanical Gardens, challenged this view, emphasizing that communities were not a co-evolved complex, nor a ‘super-organism’, but rather a mix of species whose composition was determined by the individual physiological and ecological tolerances of each species, a theory known as the Individualistic Hypothesis. These ideas were further supported by the work of Robert Whittaker, from Cornell University, whose detailed community analyses in the Santa Catalina Mountains out west and the Smoky Mountains in the east confirmed Gleason’s ideas.

In the 1960s, a modification of climax theory known as the Mosaic Theory worked its way into the lexicon, through the writings of F. Herbert Bormann, a prominent forest ecologist at Yale University. He and Gene Likens, from Cornell University, were studying forest ecosystem processes at the famous Hubbard Brook Watershed in New Hampshire, and Bormann proposed that random processes, such as disease, or violent weather, or simply the dying of old trees, would periodically impact climax forests (old-growth forests as they are known today), and create pockets of disturbance. Successional processes would be stimulated in these areas so that from a landscape viewpoint, old-growth forests would be seen as a mosaic of successional states interspersed within the larger region of old-growth forests. This viewpoint emphasized the dynamic nature of forests and helped abolish the idea that forests always end up in a static state once the late-successional trees come to dominant. Over time, these pockets of early successional states migrate over the landscape such that if you were to view the forest through a sped-up timeline so that a century was a minute, you would see this mosaic of shifting forest successional stages wandering across the landscape in a very dynamic and somewhat stochastic manner.

Bormann’s and Liken’s ideas had been built upon the concepts of succession outlined by Eugene P. Odum and his brother Howard T. Odum, two of the 20th century’s most prominent ecologists. E.P. Odum, especially, promulgated a set of hypotheses about ecosystem changes through succession that stimulated many later researchers, including both Bormann and Likens, and although some of Odum’s hypotheses were later disproved, his writings stimulated ecological research for decades.

NP: What animal species are sensitive to the age of a forest? If perhaps the timber will come back, seeming much the same as before, what are the unseen things that we have lost after, say, a clear cut has regrown into an early successional forest?

HN: Although I’m not an expert in this area, I can add a few thoughts here. The Southern Appalachians are the center of diversity for salamanders, with some estimates showing that the density is so high here (one or two salamanders per square meter of forest) that in an acre of forest the biomass of these small and relatively innocuous creatures can exceed that of deer! But salamanders have very specific habitat requirements, among which is the presence of dead wood for them to hide under to avoid desiccation and predation. When a forest is logged, much of the dead wood is often removed, and although the trees may re-establish a forest within a few decades, the accumulation of dead wood lags far behind. What then appears to be a fully functional forest is actually very depauperate of salamanders for several decades compared to what used to be in the forest before being disturbed.

With regard to understory herbs, we see a similar, but longer-lasting pattern. These plants dominate the diversity of forests (e.g., there are many more species of herbaceous plants in forests than trees) and they are very sensitive to disturbance. Studies have shown that areas cleared for agriculture and then abandoned and allowed to reforest, may not recover their herbaceous species diversity even after 1,000 years, a millennium! This means that some types of disturbances may have lasting and essentially permanent effects that are not easily reversible, if at all.

For larger animals, there are other subtle changes that can affect the faunal diversity and abundance. The most prominent of these is the break-up of forests into smaller tracts. Whenever you fractionate forests into smaller units, you change the ratio of edge to interior area and the average distance of the edge to the interior, both of which can impact forest composition and functioning. For example, many invasive species, especially vines, are prone to dominating edge habitats, and so small forest fragments are more affected than larger intact ones.

Furthermore, if forests are broken up into long, narrow units, as opposed to remaining in more circular shapes, this too brings edge habitat and its associated weedy plants closer to forest interiors, which in turn alters the composition and suitability of those forests to animals. For example, some species of birds require large tracts of undisturbed forest and are negatively impacted when edge habitat encroaches into their forests.

Fractionation also isolates forests into separate patches, and the migration of animals between patches is inhibited because they cannot traverse the inhospitable areas that separate those patches. This can result in the loss of genetic diversity and for some species, such as butterflies, put them at risk of extirpation (elimination) because of their failure to be able to migrate to more favorable habitats.

The loss of top predators, such as the wolf, has had enormous impacts on forests. The hunting and elimination of wolves, for example, has allowed deer populations to explode in much of the eastern United States, and their impact on forest regeneration has been devastating. In Yellowstone, the loss of wolves has been found to impact aspen regeneration because there are no controls on browsing by the elk. In Pennsylvania, large deer populations remove vegetation from the understory up to a height of about 8’, and they also browse native herbs and tree seedlings to such an extent that the forest can no longer regenerate in a satisfactory manner. In some places, such as northern New Jersey and central Pennsylvania, deer have browsed favorable tree seedlings and leave only the unpalatable species, such as sugar maple (which for some reason they don’t like to eat) and this shifts the composition of the understory into a mono-culture of maples. That in turn, alters the trajectory of succession and affects the future composition of these forests after the overstory trees die from old age.

Invasive species, such as introduced fungi, cause disease, and have totally altered our eastern forests over the past two centuries. Dogwood anthracnose has wiped out nearly 95% of the native dogwoods, a prominent understory tree. Dogwoods were once a source of food for bear and other native animals, who now have to find alternative foods in order to survive. In addition, dogwoods are cation accumulators, meaning that they concentrate certain nutrients in their leaves to very high levels, particularly calcium. Their loss from the understory is having significant impacts on nutrient cycling in forests with consequences for other trees over the long haul.

Chestnut blight wiped out the most prominent tree species in eastern forests, the American chestnut, starting in the early 20th century, leaving only the stump sprouts that we see today, a far cry from the majestic trees they used to be. Insects such as the emerald ash borer, which is now entering North Carolina, may wipe out an entire genus of trees long treasured for their physical beauty and excellent wood. Ash trees were the main species used for baseball bats before aluminum took over, and both the Fraser fir (endemic to only seven high elevation peaks in the Southern Appalachian Mountains) and hemlock (including both the Canadian and Carolina species) are under threat because of small, aphid-like insects that are decimating their populations. The forests our children and grandchildren will experience will not resemble those we see today, which in turn, are far removed from what our grandparents saw.

NP: Is it possible now for humans to truly "manage" a forest back to a healthy, mature state? Is there an example of this?

HN: The concept of forest health is itself a matter of debate. How do you define “healthy”? Is a healthy forest one free of disease and/or insects? Is a healthy forest defined as an ecosystem that efficiently controls the cycling of nutrients and makes the most efficient use of energy inputs by growing at a maximal rate? Is a healthy forest one that is made up of a mosaic of fragments that are different successional stages, or is it a forest that has a paucity of successional stages? If a forest has invasive species in it, is it healthy?

I have already discussed the mosaic concept of an old, growth forest, which is made up of stands from different successional stages, and which shift across the landscape through time. But can we “manage” a forest back to a pristine or “healthy” state? I do believe in some circumstances it can be done, but it takes time, effort and patience. Forests have a substantial ability to recover from a wide array of natural disturbances, such as fires, wind throws, disease, and old-age.

But whether they can recover from anthropogenically-induced disturbances is another question. I brought up the fact earlier that abandoned agricultural fields allowed to regrow as forests can still be distinguished from intact forests that were never cleared for farming, even as long as 10 centuries after abandonment. This is mostly true for the herbaceous understory flora and less so for the overstory trees. Some of this failure to recover is due to the very limited dispersal abilities of understory herbs and some is due to changes in soil quality as a result of agricultural practices. Perhaps we could enhance restoration efforts in these cases by manually dispersing seeds and/or propagules into such forests, in essence, doing what nature cannot. But if soil changes are the reason for the lack of recovery, then restoration could take decades to centuries because soil formation is an extremely slow process.

In the Southern Appalachian Mountains, studies from the Coweeta Hydrologic Lab show that clear-cut forests can recover their ability to regulate water and nutrient cycling within a decade, despite the fact that their standing biomass is but a fraction of that for old growth forests, and only early successional trees are present. These forests recover quickly because these early successional trees have high growth rates and high physiological rates that compensate for their smaller stature. A good analogy is that these species act as nutrient sponges, soaking up the nutrients before they can leach out of the ecosystem, which preserves the nutrient pool for later successional trees and the maintenance of ecosystem integrity.

Early successional trees tend to be short-lived and their leaves and wood prone to rapid decomposition, and the nutrients they incorporate over the span of their short lives are quickly released back into the soils after they die, where they can be taken up by the later successional trees. These early successional trees, such as black cherry and especially black locust, which fixes nitrogen out of the atmosphere and adds it to the forest soil, are the main species that perform these functions, while in the northern forests pin cherry replaces black locust as a regulator of nutrient uptake. Herbaceous species also play a role here too, and are even more prone to rapid decomposition. These nutrient dynamics give the forest a self-regulating capability, allowing it to tolerate a great deal of disturbance without catastrophic failure caused by the losses of nutrients and/or soils.  

NP: Has literature ever played a role in the way you see trees, or forests, and from your perspective, what role might literature play in the future? 

HN: I think the first book that captured my imagination of the primeval and somewhat foreboding forest was Conrad Richter’s A Light in the Forest, about a settler boy in the mid-1760s, who becomes assimilated after being captured by Native Americans and then must face a future in which he is rejected by both cultures. Richter’s descriptions of how Native Americans lives were entwined with the forest in which they resided made a deep impression on me when I read it back in the early 1970s.

At that time, I also read other historical fiction novels, including Last of the Mohicans, The Pathfinder and The Deerslayer, by James Fenimore Cooper, which are set in the forests of New York state. These books instilled in me an awareness of the importance of forests to the early colonists, even if I had yet to declare forest ecology my major course of study.

Many years later, I taught an Honors course on Nature Writing with a fellow faculty member from the English Department, Howard Giskin, and we asked our students to read some of the early writings about nature by Emerson, Thoreau, Burroughs, as well as works from such 20th century writers as Henry Beston, Aldo Leopold, and Donald Culross Peattie, and from more recent writers such as Terry Tempest Williams and John McPhee. Although not all these authors wrote exclusively about forests, they did present a wide-ranging view of the natural world and how humans related to it.

Margaret Lowman’s best-selling Life in the Treetops, about her adventures as a canopy ecologist in the tropical forests of northern Australia, was a major influence on the way I envisioned the interactions between insects and trees and about the travails of being a woman ecologist in a field dominated by men. Her research was aimed at assessing the amount of tree leaves eaten by insects each year but it also incorporated how a person’s perception of trees can be altered if one climbs up into the canopy and looks down.  It’s an entirely different world up there and one that most people never experience.  Her book took me up there, both figuratively and literally (I once took a construction crane ride into the canopy of a forest in Germany). I also know that Lowman’s book has inspired numerous women who viewed her as a role model for their goal of doing ecological science research. And finally, some of the best writing about forests comes from E.O. Wilson, who is on a quest to find ways to preserve biodiversity in the face of an ever expanding global human population.

It’s hard to know what role literature will play in the future – with expanding platforms that range from print books to e-books, from online websites to video sites such as YouTube, the audience for stories about forests and trees has never been as large, nor has the writing ever been so accessible. The main question is who the audience is and what they desire to read.

As the world population continues to grow, and forests continue to be under threat from logging and land use change, I think we will see a resurgence of literature themes on preservation and conservation, for such writing is what touches people who are seeing something valuable disappear before their eyes. I think we will see poetry lamenting the thoughtlessness of deforestation, of the irreversible loss of species due to extinction, of the hubris of mankind in its zeal to dominant rather than live with nature. I can see a body of literature accumulating about what once was, rather than what is, as a message to our children about the world we grew up in and the one they will inherit. And I can envision a smaller body of literature based on the hope that we as a species will come to our senses and realize, before it’s too late, that to have a life that is well-lived and filled with a sense of awe and wonder, of grandeur, we must remain part and parcel of nature. We must realize that we are inseparable from nature and dependent on it, and that in preserving the natural world, we are in essence, preserving ourselves.



Nathan Poole

Dr. Neufeld is currently a Professor in the Department of Biology at Appalachian State University.  He currently serves as Chair of AppalAIR, the interdisciplinary atmospheric research group at ASU and is the first Director of the Southern Appalachian Environmental Research and Education Center which resides within ASU’s Research Institute for the Environment, Energy and Economics. Dr. Neufeld’s research expertise is in the area of plant physiological ecology, and has included work on desert plants, forest understory plants, and the role of anthocyanins in vegetative tissues in plants.  For over 30 years, he has been active in air pollution effects research; he was the principal investigator of a National Park-U.S. EPA sponsored research project on the effects of ozone on plants native to Great Smoky Mountains National Park, and since 1992, his research group has investigated the impacts of ozone on native wildflowers in the Park.