New England's Roadside Ecology

Features Focus

This chapter offers deeper explanations and additional information on common aspects of the natural areas you will find in this book and throughout New England. The features here include the good, the bad, and the ugly: the amazing systems and interrelationships that organisms form to survive; explanations of how some life forms can have detrimental effects on other life forms in the quest to survive; and details of how even when life forms don’t survive, life emerges from death in new and interesting ways. These are the clues to what has happened and continues to happen in our regional ecosystems.

As you browse the hikes and explorations in this book, look for “Features Focus” in the chapter heading, which will list the noteworthy aspects of the site that are covered in more detail here.

Basal Fire Scars

Tree wounds known as basal fire scars can be seen on many trees in natural areas of our region. Such a scar occurs at the base of a large trunk and is evidence that the tree survived a burn. These were spots where piles of leaves, sticks, branches, and other material had accumulated, providing fuel that burned long enough to kill the cambial tissue under the bark of the tree. The fire didn’t burn through the bark, but a few years after the cambial tissue died, the bark fell away from the trunk and created the scar.

An uphill basal scar occurs when trees are growing on a slope. As forest debris moves downhill, tree trunks stand in the way of this flow. This material piles up on the uphill side of an obstructing trunk, while the tree’s downhill side remains clear. If a fire is sparked and burns upslope, it runs right past the clear downhill side of a tree, but when it hits the combustible pocket on the uphill side, it burns there far longer. As with any basal scar, the heat then kills the cambial tissue beneath the bark and a scar eventually forms on the tree’s uphill side. Any slope with a number of trees that have scars like this on their uphill side has likely been burned in the past.

Beech Bark Scale

This disease is the result of an exotic scale insect that came to the New World on a load of European beech logs shipped to Nova Scotia in the late 1800s. The scale insect resides on the bark and feeds on the sap of beech trees, covering itself in a white, waxy coating to protect it from desiccation. It appears as a little white dot on the bark of beech trees. Eventually, as the number of scales on a tree increases, they compromise the tree’s bark, allowing Neonectria fungi to invade. These fungi eventually weaken the trunk of a beech to the point where it will just break off, in what is called beech snap, killing the aboveground portion of the tree, but not its root system. Because beech is our only native interior forest tree that root-sprouts, as the trunk of the tree dies, it is replaced by root sprouts that also will eventually succumb to the disease. After a number of outbreaks, the beech trees in a stand become replaced by a dense understory of root sprouts. These form what is known as a “beech hell.” Historically, beech trees were the most common representatives of northern hardwood old-growth stands, but this disease has dramatically changed the composition of this type of old growth.

Unfortunately, we have a number of introduced, exotic pathogens impacting our native trees. I am hopeful that, due to the workings of coevolution, the vast majority of our native trees will be okay, given time. The only exception is the beech. Studies show that somewhere in the range of 2 to 5 percent of beech trees are resistant to the impact of this disease. However, as beech hells develop, they expand outward, increasing the area of a forest understory that they dominate. Due to the dense network of roots and deep shade that develop in a beech hell, nothing else can establish within them. This means that through time, the number of seedlings from resistant trees will likely decrease as beech hells increase their dominance of the understory. Without intensive management, not only will resistant beech decline, but the total plant diversity in these stands will wither, making this a serious situation for our regional northern hardwood forests. Yet there is one hope. If one of our native species adapts to prey upon the scale insect—a potentially easy target since it is sedentary—the impact of this disease could decline and the beech would be given a fighting chance.

Chestnut Blight

Chestnut blight may have had the greatest single impact on the ecology of North America’s eastern temperate deciduous forest in thousands of years. Around 1900, the chestnut blight fungus was accidentally introduced to North America with the importing of Asian chestnuts. These trees from Asia had coevolved with the fungus to the point that it was a mild parasite in its land of origin, but to the American chestnut, the new arrival was lethal. It is estimated that at the time of the introduction, American chestnut was one of the most common forest trees east of the Mississippi River. One out of every four trees was a chestnut in some Appalachian stands. These trees were also massive, with trunks up to 14 feet in diameter. They produced the most consumed nut in North America. American chestnut was truly the signature tree of the temperate deciduous forest, but in only 30 years, it was almost completely eradicated by the blight. Trees less than 10 inches in diameter had the ability to stump sprout after their trunks were girdled (when cambial tissue beneath bark is destroyed in a ring around the trunk) by the blight, but larger trees died outright, prompting massive salvage efforts for the highly sought-after wood.

Although the chestnut blight was a devastating blow, I am confident that in time—possibly hundreds or thousands of years—the American chestnut will come back. Whenever there is a strong selection pressure such as the chestnut blight’something that kills off a large percentage of a population—the surviving individuals are the ones that have some level of resistance. That doesn’t mean they are not impacted, but they can reach reproductive age. Since 2012, I have encountered five stands of American chestnuts that display resistance and are reproducing with seedlings and saplings in the understory. These resistant trees will eventually succumb to the blight, but will also have decades of reproductive time before they do. Since the only trees reproducing have some degree of resistance and have to cross-pollinate to make viable nuts, each succeeding generation should have greater resistance than its predecessor. In time, we can hope they will coevolve with the fungus as they did in Asia.

Glacial Impact

Between around 90,000 and 20,000 years ago, a massive glacier called the Laurentide Ice Sheet covered most of northern North America, including all of New England. The ice was more than a mile deep in many places, and as the ice sheet advanced for tens of thousands of years, it scraped, gouged, eroded, and shaped many of the landscapes of our region. Exposed ridgelines, U-shaped valleys and cirques, and polished granite are just a few of the New England features that were created by the glacier. In fact, the massive weight of the ice even pushed the continental crust of our region hundreds of feet down, into the planet’s mantle.

Then, 24,000 years ago, the Laurentide Ice Sheet began to melt and recede northward as the global climate warmed. The glacial ice sheet had collected all sorts of materials while it was advancing, from clay and sand to boulders and pebbles. As the glacier melted, these sediments and debris—called glacial till—were widely deposited across the landscape.

Evidence of the Laurentide Ice Sheet’s advance and recession are visible on explorations throughout this book.

Grafting

Many of our New England trees growing within 10 to 15 feet of each other become root grafted. This can happen within species, between species, and more strikingly, even between broad-leaved trees and conifers. If two trees have been root grafted and one is cut down, its stump can sometimes manage to survive from the energy of the other tree through the graft connection. Less often, trees can also graft trunk to trunk instead of through their roots. This occurs when the trees are growing very close to each other and repeatedly rub together and through their bark, allowing their cambial tissues to graft.

Great New England Hurricane of 1938

While it is not really a feature, but rather a natural event, the Great New England Hurricane of 1938 had a huge impact on the ecosystems of New England, and visibly affected five of the sites covered in this book. It was a very powerful—possibly category 4—storm that was unusual because of the high speed with which it traversed New England. It made landfall near New Haven, Connecticut, around 3 p.m. Traveling at over 40 miles an hour, the hurricane was moving into Canada to the west of Lake Champlain a bit after 9 p.m. Because of its fast advance, it was also called the Long Island Express Hurricane. Its traveling velocity enabled the storm to maintain itself as a hurricane well into central Vermont, 200 miles from where it made landfall, causing a long path of forest blowdowns and widespread infrastructure damage. When the storm was in western Massachusetts, the Blue Hill Observatory just south of Boston—roughly 100 miles away—clocked 121-mile-an-hour sustained winds and one gust at 186 miles per hour.

Tragically, the storm was not predicted to make landfall in New England, so people flocked to the shore in places like Rhode Island to see the impressive surf. A storm surge of over 20 feet in many places rose within minutes of landfall. Close to 700 people died in the storm, the majority washed out to sea by the surge.

The sites covered in this book that were impacted by the hurricane were on the eastern side of the storm’s path. They all received stand-leveling (the ability to level a stand of trees) winds from the southeast. Sites not covered in this book in adjacent New York State that were on the western side of the storm’s path took damaging winds from the northeast.

Math in Nature

The Fibonacci sequence is one of the most well-known patterns in mathematics. It is a series of numbers in which each number is the sum of the two numbers that precede it—for example, 0, 1, 1, 2, 3, 5, 8, and 13 are part of the sequence. Once the number 5 is reached in the series, each succeeding pair of numbers will create a ratio that slightly fluctuates around .617. This is known as the golden mean. For example, the ratio of 5 to 8 is .625, and 8 to 13 is .615. These concepts go beyond math, however. They are common patterns in nature, and can be detected in all the natural areas covered in this book.

For example, lenticels are portals for trees to absorb carbon dioxide into their bark to conduct bark photosynthesis. Visible on younger balsam fir trees in the Philbrick-Cricenti Bog exploration in New Hampshire, the lenticels are horizontal lines that appear on the bark. Looking closely at these lenticels, you will see that each one is the juncture of a clockwise and counterclockwise spiral. If you count the number of clockwise spirals of lenticels going around a tree and then count the number of counterclockwise spirals, you will always get two consecutive numbers in the Fibonacci sequence.

In fact, all interlocking right-hand and left-hand spirals found in nature are based on two consecutive numbers in the Fibonacci series. This is not just true for balsam fir lenticels, but for scales in pitch pine cones, the seed pattern in the head of a sunflower, and an endless number of natural examples. Single spirals in nature also are based on this series. Find a drawing of a nautilus shell, draw both a vertical and horizontal line through its center (dissecting the shell into 4 equal quarters), then measure the arch of the shell’s spiral in each succeeding quarter. You will consistently get a ratio of .617 by dividing the length of the shorter arch by the longer one that follows it.

Even our bodies are structured on the Fibonacci sequence. Some time when you are with a group of a couple dozen people, measure the length from their elbows to their middle fingers. Average those measurements. Then do the same for the length from their shoulders to their middle fingers. The ratio of the first average number to the second average number will be .617. The Fibonacci series abounds in nature and there is an active debate about why this is so. My guess is that it just may be an easy developmental pathway to follow.

Old Growth

Old growth is generally defined as a stand of trees that has reached maximal age without experiencing any form of disturbance during its tenure. Depending on species, in New England this means trees that are between 250 and 700 years old. Stands of old-growth trees are increasingly rare in our region, but efforts to preserve such important links to nature’s past are growing.

Pillows and Cradles

Observing the surficial ground topography of our forests, there are often visible differences—sometimes in areas adjacent to each other. The ground on one side of an old stone wall is smooth on its surface, while the ground the other side looks lumpy. The lumpy ground is the result of live trees being uprooted. The crater left by a downed tree’s extensive root system and any attached soil and rocks is known as a cradle or pit. As the roots and trunk decay over time, the soil and stones that were clinging to the root mass form a pile on the ground, known as a pillow or mound. Areas like this found years later suggest that the site has either always been forested or is an abandoned pasture. When pillows and cradles are not present, the ground is visibly even, and a stone wall is nearby, it is usually proof that at some point, the area was plowed, removing the pillows and cradles to create a hayfield or crop field.

Stone Walls and Early Agriculture

When the British first colonized New England, one of the things that amazed them was the soil. For thousands of years, soil organisms excavating material to the surface had only brought up fine materials, eventually burying the rock of glacial till under a good foot of stone-free soil.

The colonist farmers who created hayfields here needed to plow just a few times, to remove the pillows and cradles and make the ground level for harvesting with a scythe. The perennial roots of the hay then wove everything in the soil together, preventing rocks slowly moving to the surface during freeze-thaw cycles.

However, in crop fields that had no perennial roots, buried rocks began moving vertically in the freezes and thaws of the seasons. After a decade or so, these fields started turning up rocks, including a lot of fist-sized stones that needed to be removed. These rocks were cleared and added to stone walls anchored by larger rocks, or simply gathered in piles.

In areas solely used as pasture for livestock, large stones and boulders that could be problematic were removed and used in stone walls, but lumpy ground with pillows and cradles was not a problem and was left as it was.

What is the lesson for interpreting natural lands that were once agricultural? A smooth-grounded area bordered by a stone fence with telltale mug-sized rocks suggests that crops were grown there. Stone fences that lack the fist-sized rocks and have adjacent smooth topography suggest that the fence was once adjacent to a hayfield. Lumpy terrain with pillows and cradles and an adjoining stone wall was an early livestock pasture.

Stump Sprouts

Hardwoods and our regional pitch pines have a special survival technique. If they are cut or burned, but retain a stump and root system (even if the trunk is killed), epicormic buds that lie dormant under the bark of the stump will sprout when the bark is exposed to additional light. These sprouts can then grow into new trunks, accounting for a tree with multiple trunks. The original stump then decays away and leaves only a multi-trunked tree.

Tipped Trees

A tipped tree is one that is still living but instead of growing straight up, the bottom of its trunk is at an angle. Usually, farther up the angled portion of the trunk, there is an elbow and the trunk turns and grows upward. These trees were tipped by strong winds when they were young. The vertical trunk after the elbow was the lowest living limb on the tree when it was tipped. This limb then became the new trunk. Generally, only small trees, with trunks less than 6 inches in diameter, are vulnerable to being tipped like this. Larger trees get tipped as well, but as they lean over, they often develop so much momentum that they crash to the ground, completely uprooted.

Trees can also be bent over by the weight of snow and ice loading, or a neighboring tree falling on them. Trees bent in this fashion have trunks that are shaped like a bow.

A somewhat related term is “tip-up,” which refers to the often sizable base and root mass of a tree that has been completely toppled. This mass can often reach large dimensions and rise many feet into the air.

Tree Secrets

Black Birch

Black birch has bark that, as it ages, goes through distinct changes in texture. The first stage is smooth, black bark with many horizontal, white lenticels (portals for a tree to absorb carbon dioxide into its bark for photosynthesis). All trees with young bark have lenticels, though they are easier to spot on some species than others. If you find a black birch with live twigs, scrape a section of twig with your fingernail and you will see that just under the bark is a green layer of chlorophyll. If its roots are not ice bound, a tree with photosynthetic bark can do photosynthesis at temperatures below freezing, extending the tree’s growing season.

At about 50 years old, the smooth bark of the black birch starts to develop vertical fissures. Around 80 years old, the bark starts curling away from these fissures to develop rectangular-shaped plates. At approximately 150 years of age, these rectangular plates are usually shed, allowing the birch to once again have smooth-looking bark, now without lenticels. As the birch approaches 200 years old, it starts developing vertical bark ridges and begins looking more like an older red oak.

When you scrape a black birch twig to see its chlorophyll layer, smell the exposed chlorophyll. You’ll catch the fragrant scent of wintergreen, whose technical name is methyl salicylate. Large quantities of methyl salicylate can be a strong irritant, and in black birch, it wards off browsing by animals such as deer.

Black Gum

Black gum, also known as tupelo, is a southern swamp tree finding its northern range limits in southern Vermont and New Hampshire. The region’s scattered black gum swamps are refugia (areas of unaltered climate and persistent organisms) from a time when they were more widely distributed, about 8000 years ago.

Black gum swamps typically develop on fens—wetlands that, like bogs, develop peat but are less acidic. Fens are dominated by species of sphagnum moss and sedges. In the northern states of New England, black gum swamps are usually found on ridgetops—like the Vernon black gum swamp in Vermont—rather than the more commodious valley locations. The reason? Strong ridgetop winds are not as threatening to the black gum—even those perched on mucky peat—as wind is to other trees.

The black gum is a more highly evolved swamp tree than our other regional species, with adaptations that help it survive strong winds. Black gums have very brittle wood that also tends to develop heart rot, creating trees with hollow trunks. When exposed to strong winds, their tops snap off, allowing their trunks to remain standing. Luckily, the black gum has lots of epicormic buds. These buds lie dormant under the bark of the trunk and will sprout new branches when the bark is exposed to additional light. When strong winds hit a swamp, our other regional swamp trees—such as red maple, yellow birch, spruce, and eastern hemlock—completely topple, while the black gum trunks remain standing and then resprout new branches below their snap-off points.

Northern White Cedar

Northern white cedars are interesting in a number of ways. They can grow in an array of diverse conditions, from saturated fens (wetlands that develop peat but are less acidic than bogs), to very dry and nutrient-deprived granite outcrops, to dry and enriched limestone environments. I know of no other tree species that can tolerate such extremes in moisture and pH. Northern white cedar is the oldest-growing tree species in the northeastern states, with individuals along the shore of Lake Superior dated at 1200 years. These cedars also vigorously root graft with their neighboring trees; often the aboveground grafted roots between two trees are visible. They are also hit by lightning strikes more frequently than any other species of our regional trees. If you see a spiraling scar on the trunk of a northern white cedar, it was produced by lightning. Finally, all other regional conifers have wood that rots from the outside in. That is not the case with northern white cedar, whose stumps and trunks hollow out. Since the outer wood of the cedar is highly rot resistant, hollow stumps of this species can persist for more than a century.

White Pine Weevil

White pines that are impacted by this weevil at some height—usually not more than 30 feet above ground—have their single trunk split into two or more trunks. This happens when the weevil lays its eggs on the uppermost terminal (end) shoot of a pine. The eggs hatch as larvae and drill into the terminal shoot, killing it. When this happens, limbs in the whorl (layer of branches) directly below the killed shoot take off and grow upward to replace the dead shoot. If a pine is growing by itself in full sunlight, all the limbs in the whorl below the top may grow up, giving that tree as many as five new trunks to replace the single one. If a dense stand of young white pines is being hit by the weevil, those trees only send up two of their limbs to become new trunks.

White pine weevils do not lay eggs on all white pine trees. They only choose young pines—generally less than 15 years of age—that are growing in full sunlight. These trees are targeted because the insects want a terminal shoot that is as thick as a finger, to serve as forage for their young. Older pines, or trees growing in shade, have terminal shoots that are usually only about .25 inches in diameter—too small to interest a weevil. This is a significant piece of evidence when interpreting landscape histories, because it reveals that a stand of weevil-impacted pines was the first cohort of trees to colonize a once-open site. If those trees are young enough, it becomes possible to date when they started growing by counting their limb whorls, because white pines produce only one whorl per year.

Maine

Saco Heath

A bog that has risen above the surrounding land

Location ▸ Saco, Maine

Features Focus ▸ Glacial impact, old growth, stump sprouts

Difficulty ▸ Easy

Length ▸ 1.75 miles

The Saco Heath can be accessed via State Route 112, just a few miles northwest of Saco, Maine. During rainy periods, the beginning of the trail leading to the boardwalk may have some wet patches. A good time to visit the heath is from late May to early June, when the majority of its plants are in bloom.

Saco Heath is the most southerly raised bog found in eastern North America and, as such, is a very unusual ecosystem. All bogs create peat—partially decomposed plant material. A good amount of peat is derived from species of sphagnum moss. Peat can absorb large amounts of water and, as the water-dense peat builds up, it can raise the water table along with it. In a bog like Saco Heath, the center of the heath and its water table are actually higher in elevation than the surrounding woodlands, leading to the term “raised bog.”

In 1986, the Joseph Deering family made a generous gift of the heath to The Nature Conservancy. The conservancy has done a great job of making this rare and fragile ecosystem open to the public, by building a half-mile-long boardwalk through it. Because of the boardwalk, large numbers of people can visit the heath each day and not impact the site; however, visitors need to stay on the designated trail from the parking lot to the boardwalk, which passes through a delicate swamp ecosystem.