Pinus resinosa, the red pine, is a truly beautiful tree, in part because of its oft craggy homes in our region, but also because of its distinctive reddish bark. With age, the bark breaks up into flakes like puzzle pieces, and reddish is a poor description for the colors ranging from rich purple-reds to bright reddish-oranges. Red pine’s specific epithet, resinosa, is aptly chosen for its resin-rich wood, especially heartwood, and around scars it has a strong piney pungency.

Gracing cliff brows, perched on rock domes, scattered along rocky or sandy lake shores and bluffs, inhabiting coarse sandy and gravelly soils of glacial outwash, kame, and old delta terraces: these are the most common native habitats of red pine in this landscape of ours. Yet, perhaps most familiarly, it is seen in Civilian Conservation Corps–era red pine plantations along our highways and in our state parks. Scattered throughout northern New England mostly below 2,000 feet in elevation, it is not a rare tree, but it is not common on the landscape level. This scattered distribution, often in conspicuous yet wild and incorrigible sites, as well as its special relationship with fire, is what attracted me to the study of red pine some 35 years ago while a graduate student in the Field Naturalist Program. How does Pinus resinosa persist in a landscape overwhelmingly dominated by northern hardwoods, spruce, fir, hemlock, and other trees?

Red pine is a denizen of the Northern Forest, that broad belt of eastern temperate forest between the boreal spruce and paper birch forest to the north and the forests with oak and hickory to the south. The Northern Forest ranges between 42-50 degrees latitude, from Maine and Nova Scotia to the east and Minnesota, western Ontario, and northern Minnesota to the west. The southern extent of native red pine in New England pretty much stops at the northern border of Massachusetts, though there are outlier populations in Massachusetts, Connecticut, and the Appalachians as far south as West Virginia. Red pine is replaced by jack pine to the north and pitch and other pines to the south, and it is strongly associated with white pine throughout the Northern Forest. Pinus resinosa reaches its greatest importance in the forests of the Great Lakes region, where the climate is drier and more extensive glacial outwash and water-worked sandy soils occur.

Almost all the native red pine I have cored in Vermont and New Hampshire over many years have been under 200 years old. The oldest tree I have encountered in the region, 30 years ago, was just under 300 years old. The oldest Pinus resinosa listed in Neil Pederson’s “oldlisteast” online database is a whopping 500 years old, from far western Ontario near Lake of the Woods. The next ten oldest are reported at 340-433 years old, all from Ontario and northern Minnesota. Such longevity has important implications for long-term population maintenance where regeneration is episodic.

Here’s the striking facet of red pine’s natural history: throughout its Northern Forest range, red pine largely depends on fire for regeneration, because its germination requires a mineral seedbed and young plants need moderate to high light intensities to mature. More sunlight reaches the ground after a severe fire due to the death of understory and canopy trees, especially of other tree species more susceptible to scorching. While it lacks some adaptations to fire such as cone serotiny, found in at least some populations of jack and pitch pines, it is a fire-resistant species due to older trees having thick bark that guards the cambium, and to its ability to heal scorch wounds.

Through tree-ring analysis of fire scars and tree cores, my firehistory and age-structure study of six red pine stands on Resin Ridge in the Bolton Notch area of eastern Vermont shows that, from early 1800s to the 1920s, non-lethal surface fires occurred at 3-50-year intervals, while more intense fires that killed canopy trees occurred at intervals of 50-100+ years. Taking place after European settlement, this fire history likely represents an unusually high fire frequency. Visits to red pine stands throughout the region over the last 30 years, including a recent revisit to the Resin Ridge stands, show red pine regeneration is very scarce, probably in response to a lack of fires.

Pine stands are small on Resin Ridge, ranging from less than onetenth of a hectare up to two hectares, with numbers per stand ranging from 50 to 2,200. Based on a statewide survey I did on red pine in Vermont preceding my Resin Ridge study, these are fairly typical sizes. By far the largest red pine stand in Vermont is 13 hectares. In New Hampshire, Maine, and adjacent New York, there are larger stands in the more rugged, rocky country found in certain parts of those states.

The biogeography puzzle is how a species like red pine persists in a landscape where the moist, fine-textured glacial till soils are dominated by a vigorous and self-perpetuating forest composed of northern hardwood and shade-tolerant conifer species. Vermont has the nickname of the asbestos state because of its resistance to burn. Our long winters make for short burn seasons; our climate is moist with ample summer precipitation, thus precluding good drying of fuels. Plus, in contrast to red pine’s coarse needle litter, the hardwood broadleaf litter is poor fuel for carrying fire because of its sheet-layered structure and because it does not dry out in the deep shade produced by the forest canopy. In this fire-resistant landscape, however, there are islands of fire-prone habitat. The high and dry cliff brows, rock domes, steep and rocky south-facing slopes—these are the red pine redoubts where a lightning-ignited fire occurring once every 50, 100, or maybe 150 years can produce the right soil and sunlight conditions to regenerate red pine stands.

There is excellent current research on red pine in northern New England happening at UNH-Durham. Finishing her Ph.D. research in 2021, Maria Adele Fenwick studied fire regimes and stand development in rocky red pine natural communities in the White Mountains of New Hampshire. As a Ph.D. candidate, Michael J. Simmons focuses his research on the factors and interactions associated with decline of red pine forests in New England. They have both observed red pine decline in some study sites located primarily in New Hampshire and Maine. Lack of recent fire has led Fenwick to conclude that red pine stands in the White Mountains will likely be compromised if prescribed fire management is not taken.

While alien red pine scale has been implicated in the demise of some plantations in New York, southern New England, and more recently southern New Hampshire and coastal Maine, the cause of decline in northern New England is yet to be determined. I witnessed quite extensive red pine decline, including many dying or recently dead trees, on Bald Cap Peak in Shelburne, New Hampshire, during a recent field inventory. Furthermore, in Vermont I have noted over the last decade the demise of two very small red pine stands, one among northern white cedar in the Winooski Gorge in South Burlington and another on Stimpson Mountain, a rocky knob a little east of Bolton’s Resin Ridge.

And what if a red pine stand does not get burned in 150 years? Red spruce, hemlock, or even beech is usually there in the understory waiting for the red pine canopy to disappear so it can become the shady overstory. Coupled with essentially no red pine regeneration, this unburned stand maybe blinks out. In the case of the stands on Resin Ridge, I see just this scenario playing out. The canopy trees are now reaching 150+ years old, and there has not been a fire on the ridge for close to 100 years. There is attrition in the red pine canopy: windthrows, snaps of trees with rotten heartwood, and death from unknown causes. Plus, there is a century’s worth of needle-, twig-, and branch-litter accumulation: all very combustible detritus for fueling that lightning-strike fire, especially during a drought.

While tempting to think that prescribed fire management is the best solution for regenerating red pine, perhaps it is even more important to have forest managers at all levels—municipal, state, and federal—embrace a let-burn policy whenever possible, so that ignitions that occur naturally are given a chance to blaze.