The Pisgah Forest: Harvard’s Living Laboratory

The Pisgah Forest: Harvard’s Living Laboratory

Hemlock saplings take root on a downed log - the next generation of trees growing off the last.

One irony of ancient forests and wilderness areas – known for their absence of human imprint – is that their names conjure up associations with people. In the Sierras, the Mariposa Grove of giant redwoods will be forever associated with John Muir. Gates of the Arctic, one of America’s largest wilderness areas, is inextricably linked to Bob Marshall, the wildlands advocate who mapped this spectacular section of the Alaskan Brooks Range before he founded The Wilderness Society. Closer to home, Walden Pond and the Maine Woods are tightly associated with Henry Thoreau, Acadia with the Rockefeller family.

And then there’s Pisgah, a magnificent forest in southwestern New Hampshire with a social history as tumultuous as its natural one, which is saying quite a lot given that the forest was saved from the logger’s axe twice, flattened by the 1938 hurricane, and examined in minute detail by three different graduate students.

To those who know this forest intimately, Pisgah will always be associated with Richard Fisher, the founding director of Harvard Forest. Fisher grew up in the small town of Berkshire, Massachusetts, in the late 1800s, shortly after the relentless press of deforestation had crescendoed and the New England landscape was in the early throes of what Henry Thoreau termed “succession.” A few artists, romantics, naturalists, and scientists began searching the region for nature untouched by human hands – drawn to the deep woods of northern Maine, the White and Green Mountains, the Catskills, or Adirondacks, where they could take in scenes of raw nature before the waves of logging and fire swept through. But wilderness zealots also spread out through already settled lands, searching for pockets of ancient woods in less inhabited corners, where they expected that rough terrain and thin soils may have left a few stands untouched.

One such forest lies along the Massachusetts and New Hampshire border. Here, rugged hills rise above Brattleboro, Vermont and stretch beyond the Connecticut River toward Mount Monadnock, through the border towns Hinsdale, Winchester, New Hampshire, and Winchendon, Massachusetts. In his never-ending search for local wildness, Henry Thoreau pursued rumors of big trees and ancient groves in this region. Twice he climbed Monadnock for its rugged splendor, and on at least one occasion, he diverted his return to Concord through the well-rivered borderlands to gaze toward ancient forests and beyond the mill towns that were expanding to destroy them.

Growing up in this area, Fisher would have been familiar with these tales of immense trees. An English major at Harvard College in the late 1890s and a passionate consumer of Thoreau’s writing, he spent summers on his uncle Abbott Thayer’s small hill farm in the town of Dublin, New Hampshire. It was from his uncle that Fisher first heard of Pisgah Mountain and the ancient groves of pine and hemlock in the Ashuelot region, west and south of Keene.

Fisher graduated from Harvard in 1898 and went to work for Hart Merriam in the Division of Economic Ornithology and Mammalogy, predecessor to the U.S. Fish and Wildlife Service. Through his travels and work – from the redwood country of northern California throughout New England – he became convinced that forest management must be guided by a deep understanding of nature and the cultural processes that shape it through time. When he returned to Harvard to lead the new forestry school in 1903, Fisher increasingly focused his attention, and that of his students, on Pisgah Mountain. In that rough massif lay dozens of untouched and unnamed old-growth groves. The stands were diverse, ranging from immense beech, oak, maple, and birch on the slopes above North Round Pond to isolated patches of pitch pine on the most extreme rock ridges and outcrops.

He described Pisgah this way in a letter to friend Harry James:

“The stand in question is perhaps the best sample remaining of absolutely primeval forest such as once covered the whole tract and still covers various areas aggregating perhaps 600 or 700 acres. Personally, I do not know of any other absolutely authentic original forest, except for small areas, left in central New England. Furthermore, the remoteness and wildness of the region makes this particular example uncommonly valuable and interesting, not to say secure. The trees are for the most part white pine and hemlock, the largest of which range from 200 to 300 years old. Some of them are approximately 140 feet tall and three feet in diameter at breast height. If there is to be any surviving specimen of the original forest preserved for the enjoyment and study of the present and future generations, I do not know where it could be secured except here.”


Living laboratory

Pisgah furnished Fisher with a grand laboratory for the investigation of nature in the raw. Fisher and his students commenced their studies in the old-growth areas, and were soon tallying its assets. They were struck by many features: the immense height, mass, and age of the trees; the variation in tree size and species, both in individual stands and across the landscape; and the abundant evidence of natural disturbance – wind, ice, insects, pathogens, and even small fires. Most striking were the features not found in typical New England forests: There were windthrow mounds ten feet high, immense dead snags that reached up so far they were lost in the canopy, and the fallen carcasses of trees up to four feet in girth that seemed to molder on the ground for decades.

Fisher’s reconnaissance trips fostered an understanding of the New England landscape that stood in sharp contrast to the simple, deterministic view of nature that would dominate ecology for much of the twentieth century. Pisgah helped shed light on the tension that naturally exists in the forests of central New England, where the conifers of the far north meet the hardwoods of New England and are regularly buffeted by natural disturbances and climatic extremes. In his paper, “Evolution of Soils,” Fisher, drawing on lessons from Pisgah, wrote:

“The original upland forest ... contained many species of hardwood together with hemlock and white pine, the hemlock a more or less constant element and the pine variable in numbers and distribution. Although this forest over huge areas was apparently stable in percentage composition of species, there is evidence for believing that on smaller areas, and over periods of several centuries, there was a tendency to fluctuation in dominance between softwoods and hardwoods. The natural adaptabilities of species to site were intermittently upset by lightning, fire, windthrow, ice storms, and sometimes insects or disease. Thus a declining group of pine and hemlock would be replaced by one of hardwoods, and vice versa. This tendency is indicated both by the frequent groupwise distribution of the softwood and hardwood elements in the stand and by the relative management of the size or age classes.”

With a solid grasp on the structural patterns in this natural landscape, the Harvard group sought a temporal framework for interpreting the relationships among all of these features. Exactly how ancient were these trees, and what initiated their establishment? How frequently did these different disturbances occur, and what was their role in determining the age, type, and placement of individual trees? How much did the various disturbances vary across the landscape? And do forests develop slowly and progressively, or episodically and in fits and spurts? Though the academics could hazard guesses based on information like the sizes of trees or their degree of decay when fallen, they were rightfully insecure about these speculations. What they needed was to really dive into and disassemble the forest.


Saving – and Studying – a Stand

The opportunity for just such a breakthrough came with some calamitous news. In 1919, the sons of Ansel Dickinson, long-time principal of the New England Box Company, announced plans to log the old pine and hemlock on their 5,000-acre holding on Pisgah Mountain. New England Box held tracts across the region that it logged heavily, but the family had mined small pockets of old growth judiciously. Fisher had worked closely with the company on occasion, and there is no evidence that he attempted to reverse their thinking about Pisgah. But the Dickinsons’ decision did motivate him to launch a comprehensive study of all the old stands and to count and measure the tree rings on every stump produced by their initial harvests in order to reconstruct the history and dynamics of the old-growth forests. Their decision to log also prompted him to raise funds to purchase and protect the most magnificent of the old stands.

Fisher’s focus lay on a 50-acre tract that wrapped over one of the higher ridges in the region and across a narrow valley. Here stood the forest he described in the letter to his old chum Harry James with pines and hemlock three or four feet in diameter and more than 140 feet tall. To save this stand he sought funds from Harvard alums, like James, and forged a campaign with Philip Ayres, president of the Society for the Protection of the New Hampshire Forests. The effort ultimately led to Harvard University’s peculiar ownership of a small parcel in the midst of what later became the largest state-owned property in New Hampshire – the 13,000-acre Pisgah State Park.

By the time Richard Fisher died of a heart attack in 1932, at the age of 54, his interpretation of the Pisgah landscape had been reinforced with solid data. Three of his students – W.C. Branch, Robert Daley, and Thomas Lotti – spent two years ferreting out and studying all of the ancient stands and following the loggers’ fresh trail through the areas that had been cut. They studied 68 old-growth patches that either escaped logging or were located and sampled just before the axes and saws arrived. In 28 harvested stands, the ages and growth histories of the immense trees were recorded by laying a strip of paper across each fresh stump and then marking the tree pith and every 10 years of growth out to the bark and outermost ring. The students examined each site for evidence of past disturbance by laying out a few transects across the entire landscape and sampling at points along them to evaluate the variation in sites, forests, and history. Though their story would not become widely known until Al Cline and Steve Spurr mined it for their classic paper “The Virgin Upland Forest of Central New England” in the early 1940s, the students’ joint thesis became a treasure in the Harvard Forest Archives and lore to all who worked and studied there. Cline and Spurr captured the major message from their work:

“The primeval forests, then, did not consist of stagnant stands of immense trees stretching with little change in composition over vast areas. Large trees were common, it is true, and limited areas did support climax stands, but the majority of stands undoubtedly were in a state of flux resulting from the dynamic action of wind, fire, and other forces of nature. The various successional stages thus brought about, coupled with the effects of elevation, aspect and other factors of site, made the virgin forest highly variable in composition, density, and form.”


Letting Nature Take its Course

As they studied the growth rings of the massive trees, researchers learned that part of the forest on Pisgah had gotten its start in the wake of a catastrophic disturbance in the 1600s. In 1938, history came full circle when a great hurricane swept the region, uprooting nearly three billion feet of timber from Long Island Sound to northern Vermont. On the Harvard tract in the Pisgah Mountains nearly every large pine and hemlock was laid flat.

In the storm’s aftermath, Ward Shepard, Fisher’s successor at Harvard Forest, declared the event a regional disaster and helped promote a massive, federally orchestrated timber harvest and clean-up. The New England Timber Salvage Administration was formed, which organized the single largest forest salvage operation in United States history. Fortunately, it also drew Shepard to Washington, D.C. to help administer the program and the ensuing timber effort in World War II. Shepard’s departure left the Harvard Forest in the decidedly more capable hands of Fisher’s old student and acolyte, Al Cline.

In his desire to focus federal resources on New England forestry, Shepard had advanced the argument for the region-wide timber harvest by appealing to concerns over human safety. His most strident appeal painted a fear-mongering vision of firestorms sweeping the damaged land and roasting villages, homes, and citizens. Rather than reflecting on the insights from Pisgah and Fisher, namely that hurricanes had shaped New England for millennia and that the forests would regrow rapidly, Shepard cast the 1938 storm as a national forest calamity and emergency. As a consequence, the salvage operation garnered support from federal, state, and local sources and crews began arriving from across the country and Canada. Ultimately, a remarkable 50 percent of the downed timber was harvested. But the environmental consequences of the post-hurricane logging frenzy were severe. The New England landscape was left cut over, scraped over, and smoldering from slash fires, which occasionally escaped into intact forests. The zeal to sanitize the land and thwart the flame even threatened the virgin forest that Fisher had fought so hard to save.

The most critical challenge arrived as pressure mounted to liquidate the voluminous material lying on the ground at Pisgah. Fortunately, with Shepard diverted, Fisher’s insights were heeded at this critical moment. Acting director Al Cline was no visionary leader, but he revered Fisher, grasped the broad implications of his research, and subscribed to his philosophy of management. Cline faced intense pressure from federal, state, and local authorities, who argued that Harvard had a civic duty to protect the region from devastating fires, a moral duty to demonstrate appropriate management, and an economic responsibility to contribute its valuable old-growth timber to local mills and markets. Despite his well-known role in overseeing salvage operations on the three Harvard tracts in Petersham, and as a member of the town and state timber salvage commissions, Cline stood resolute behind the writings of Fisher and his students when it came to Pisgah. In the face of intense political and social pressure, he refused to allow any cutting on Harvard’s small virgin tract.

“Even in their prostrate position, these veteran trees are an impressive sight,” Cline wrote. “In the small openings among the fallen trunks and branches, the new generation is already becoming established. In accordance with the purpose of acquisition of the Harvard tract, no salvage of the down timber was permitted. It remains a place where one may study nature undisturbed by man.”

Cline reasoned that the forest, in its uprooted condition, provided an invaluable natural laboratory in which recovery and the slow development of the next old-growth forest could be studied in great detail. His bold decision proved prescient. Though no longer filled with immense trees, this virgin forest came to attract even more research following the hurricane than it had received in the three decades under Fisher.

By the late 1940s, Steve Spurr was a Yale graduate student and returned to Pisgah to evaluate the forest’s recovery. His observations complement the photographs of the place and underscore its unique qualities relative to the rest of the New England landscape.

“Conditions following blowdown on this virgin timber tract differed very greatly from those on second-growth areas. The tangled blowdown of heavy timber (largely hemlock and white pine) was four to ten feet thick over most of the area. Under this criss-cross of logs, the soil was moist and relatively undisturbed except around the uprooted stumps. The boles of the fallen trees covered over 30 per cent of the area, and inasmuch as most of these were suspended several feet from the ground, they affected practically all of the surface.”

Spurr also drew a major conclusion that has since been verified many times over the decades: he correctly recognized that natural disturbances often advance the development of mature forests, rather than generating the scarred and rather weedy early successional conditions produced by salvage harvesting.

“In this case where no logging followed the blowdown of old growth pine and hemlock, the following stand represents essentially a later successional stage than the preceding one, being characterized by hemlock and beech,” Spurr wrote. “In other words, the blowdown accelerated rather than set back successional development by felling the overstory and releasing the tolerant understory.”

Spurr’s work was built on in the early 1960s by David Henry, a young master’s student, and his advisor at the Harvard Forest, Professor Mark Swan. Their paper, “Reconstructing Forest History from Live and Dead Plant Material,” published in Ecology, advanced Fisher’s arguments that ecological interpretation was strengthened by historical understanding. Following that burst of activity, interest in Pisgah seemed to wane.


Research Renaissance

When I arrived in Petersham in 1983, I was surprised and disappointed to learn that only a single permanent plot existed at Pisgah, despite three-quarters of a century of research. (Spurr’s plot data remained in the archives, but the field markers were lost through the years.) That solitary 20 by 20 meter area was established in 1967 by David Henry. After nearly two decades of neglect, it was barely defined by a few wire stakes. With the help of Peter Schoonmaker, who conducted his Ph.D. research at Pisgah, we added 12 similarly sized plots across the Harvard tract and reanalyzed all of the historical data. Schoonmaker found all of the former old-growth stands across the greater Pisgah area and studied how they had survived the hurricane and the ensuing 50 years. He then turned to the 25-acre Harvard tract and spent nearly two years establishing permanent transects and examining landscape-level variation in the forest and site. To complement these efforts, Schoonmaker applied pollen analyses to swamp sediments and small boggy hollows in order to explore the deep history of the area.

The results of this work would have fascinated Professor Fisher, but it wouldn’t have surprised him. Fisher would certainly have anticipated the rapid way that the forest regrew after what appeared to be catastrophic destruction. And now, eight decades later, the new woods have emerged as a maturing forest landscape. What has surprised everyone – and would have shocked even the first director – however, is that, while hemlock has recovered superbly and emerged as the dominant tree, there is but a single white pine on the entire 25-acre tract. Pine, which once reigned here as the largest and most visible species, has disappeared. Natural processes alone caused this remarkable change, confirming how kaleidoscopic our forests really can be.

Over time, the general appearance and broad composition of the regional forest remain relatively steady, but the details regarding the size of trees and types and distributions of individual forests may change considerably. The dramatic shift in composition has major consequences for the ecosystem. White pine grows faster and larger than most other species, and its longevity allows it to reach superlative heights and girth. This meant that Fisher’s old-growth stands at Pisgah had among the greatest amounts of standing timber of any forest in New England. In contrast, the new stand – with its smaller and slower-growing hemlock and beech and much shorter-lived birches and red maple – will never support such massive trees or staggering amounts of wood. The rapidly regrowing forest will become increasingly impressive and may one day assume old-growth qualities, but it will never be the one that Fisher saved.

Another aspect of Pisgah that never fails to amaze those of us who visit it frequently is the persistence of the immense downed trees, root masses, and associated pits and mounds of earth. Despite, and in large measure because of, the ravages visited by the hurricane, the forest continues to support features once common but rarely seen in New England today. A 2012 trip to identify and core these downed trees revealed an even greater surprise: every one of the remaining immense prostrate logs is a white pine. The branches and trunks of all of the other species that once constituted this ancient forest have decomposed, leaving only pine, whose old-growth wood is extremely resistant to the action of insects and microbes. These downed trees will persist well through the centennial of the hurricane as a legacy of the ancient stand and the storm. Although this new forest is dominated by hemlock, pine will remain an important but subtle part of the forest for decades to come.

David Foster is an ecologist and director of the Harvard Forest. He is author of Thoreau’s Country – Journey Through a Transformed Landscape and editor of Hemlock: A Forest Giant on the Edge, from which this article is excerpted.

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  1. Jason Berard → in Thetford, Vermont
    Apr 25, 2014

    Thanks so much for this article on the Harvard Forest. My great-grandfather, forester Paul M Reed worked there in the mid-20’s and assisted with a few publications, I think.

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