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Branching Out

By Ellen Bergan, Land Stewardship Assistant

I crane my neck to look up the tree trunk rising above me. Pale furrows in the bark run in ski track patterns down the tree’s otherwise darker exterior. “Nope, definitely red oak.” I say, shaking my head. “The bark’s not scaly enough at the base to be a scarlet.”

I look over at Chris Fox, Land Stewardship Director and my tree ID accomplice, as he nods in agreement. We continue walking over the forested ridge as we finish up our annual monitoring visit of this Sycamore property, calling out the names of trees as we go.

Tree identification has become a pastime of Chris’s and mine while doing stewardship fieldwork, helping keep our minds occupied while trekking miles of off-trail property. As I’ve become more familiar with the native tree species of our southern Indiana forests, learning to recognize the particular bark, leaf, or habitat that characterize certain tree species, the way that I see our forests has also changed.

The trees I pass are no longer passive pillars of wood; rather, the forest is a collection of unique individuals, ones that I can recognize and call by name. I am by no means an expert in dendrology (the study of trees), and scientific names still escape me, but there’s a comforting familiarity to the forests I walk through now.

Names, after all, are a foundational building block of relationships, allowing us to forge connections to both each other and the natural world. In her book Braiding Sweetgrass, writer and scientist Robin Wall Kimmerer discusses the disorientation and disconnection that can come with not knowing the names of the plants and animals around you. She calls the resulting isolation “species loneliness,” describing “a deep, unnamed sadness stemming from estrangement from the rest of Creation, from the loss of relationship.”

The roles of names and relationships in nature was an introduction into the importance of how we view the world around us — and the complexities of trees and our connections to them go far beyond species identification. The roles trees play in our lives and communities, how trees form communities of their own, and how much we can learn from trees themselves give invaluable insight into the relationships among ourselves and nature.

Dear Tree… Love helps everyone grow big and strong. Do you have a favorite tree on Sycamore’s preserves? Send them a love letter to letters@sycamorelandtrust.org.

ROOTED IN COMMUNITIES

For many of us, communities center our identity, acting as a source of support and belonging and emblematic of our connections to each other. Sometimes, our arboreal neighbors become integral parts of these communities.

When officials in Melbourne, Australia, created a program that assigned email addresses to the city’s trees for citizens to report damages, they did not expect the trees to, instead, become recipients of thousands of personal letters from human admirers. These messages ranged from poetic declarations of love and appreciation — expressing endless gratitude for the shade, oxygen, and natural grace provided by the trees — to queries about dendrology and discussions of global events. People posed existential questions to the trees, or asked if, like them, the trees were tired of neighborhood construction or city traffic.

“Dear Moreton Bay Fig,” one person wrote.

“You are beautiful. Sometimes I sit or walk under you and feel happier. I love the way the light looks through your leaves and how your branches come down so low and wide it is almost as if you are trying to hug me. It is nice to have you so close, I should try to visit more often.”

The program became a stunningly sweet demonstration of the relationships people create with the trees around them. With every letter, people expressed that trees meant more than landscaping ornaments; they were a part of the community and played a recognized, cherished role in the lives of its human members.

The place of trees in our communities stretches back much further than modern-day emails, however. In the forests of the eastern and Midwest United States, looming “wolf trees” act as physical placemarkers of human communities.

Wolf trees, characterized by their large circumference and low, broad, and often gnarly branches, are results of the forest clearing that came with European colonization. Most of Indiana’s forest was cut down for timber and to clear land for farming. A few trees were allowed to grow in these open areas, often along property lines or to provide shade for livestock in pastures. Surrounded by open space and ample light, they had the opportunity to spread their branches into a sprawling canopy. As farmland and settlements have been abandoned, wolf trees have come to stand out as exceptionally large and wide[1]spreading anomalies within the returning younger forest.

We can see these wolf trees in our backyards, such as the white oak with its swooping lower branch along the trail at Sycamore’s Touch the Earth Natural Area, or this girthy beech nestled within the bottomland woods of Trevlac Bluffs Nature Preserve. These gnarled, elder giants are points on a map of the past, reminders of communities that used to inhabit that space.

While we have incorporated trees into our own communal systems, trees have long been sustaining active communities of their own. Complex ecological connections among trees show that they are capable of forming and sustaining relationships, communicating, and protecting one another. This “wood-wide web,” as it’s been called, is actually a subterranean network of mycorrhizal fungi.

Mycorrhizal fungi act as extensions of the plant root system and, in a symbiotic relationship that is hundreds of millions of years old, give trees water and nutrients from the soil in exchange for carbon. But that’s just the beginning.

Scientific research shows that the web of fungal threads links nearly every tree in a forest to each other. Trees use these underground connections to communicate and share resources, a sort of arboreal altruism. The fungal network acts as a messaging system, allowing trees to send news and distress signals through chemical compounds and electrical impulses via their roots. If a tree is under attack, it can send out chemical alarms to prepare its neighbors for danger. If a tree is under stress, other trees transfer water, carbon, and other nutrients to help it, sometimes even nourishing stumps for centuries after the tree was felled.

If a tree is sick or dying, it can dump its remaining resources into the network for other trees to use. There is even evidence of kinship among trees. Older trees, sometimes dubbed “mother trees,” share nutrients with their nearby seedlings to give them a better chance of survival.

Much of our understanding of forests has operated under the pretense that trees are solitary individuals, and that competition drives the survival train in ecosystems. It’s now recognized by scientists that while there is definite conflict in forests, there is also collaboration, interactions of a complex living system that operates on degrees of caretaking, nourishment, and informational exchange. Trees need their communities to survive. A single, isolated tree cannot create the moderated climatic and sheltered conditions that allow it to grow to an old age as well as a forest can. A seedling cut off from the fungal web is more likely to die than those that are networked into the complex, connected system. By communicating and working together as interdependent parts of a community, trees help one another survive and strengthen the resilience of the whole forest. When we consider the overlapping connections between our communities and those of trees, it is not difficult to blur the boundary between them. Ecologist Aldo Leopold re-imagined our place in ecological systems, arguing that we, too, are part of the greater interdependent community of the natural world. As part of this broadened community concept, we are members of a biotic team, a role that comes with a responsibility to love and respect our fellow members of the land — including the soils, lichens, rivers, and, of course, trees that reside alongside us.

And trees, as any wise, long-lived community member, have a lot to share with us — and we have much we can learn from them.

THE (TREE) CORE OF IT

Look at a cross-section of a tree in any temperate forest, and you’ll see rings expanding, in alternating light and dark bands, from the center of the tree to its bark. Each ring marks a complete cycle of seasons, one year, in the tree’s life. The abrupt shift in a previous year’s darker latewood formed in the fall to the lighter earlywood from the more recent spring creates the distinct ring boundary that separates one year from the next.

Trees grow from the inside out, where the outermost ring near the bark marks the most recent growing year, and the innermost ring, the very center of the tree, is the oldest. When we know the year of the youngest ring, we can count back to the center and know the age of the tree, as well as the exact year each ring was formed. The study of these annual growth rings to date and interpret past events is called dendrochronology.

However, the counting and dating of rings just scratches the surface of dendrochronology, as tree rings provide much more than solely an age. The widths of rings also show how much the tree grows in a year, reflecting the environmental conditions of that corresponding year. Tree rings are wider when conditions favor growth and narrower when conditions do not. The pattern of narrow and wide rings in a tree, then, can show variations in climatic conditions, such as precipitation and temperature, as well as discrete geologic or environmental events that have occurred throughout the tree’s lifespan.

Using samples from multiple trees, the climatic patterns of tree rings and their corresponding years can be cross-dated to create an even more extensive tree ring chronology, providing the data to reconstruct thousands of years of past climate. Through tree rings, we gain a window to the past, capable of seeing droughts, hurricanes, fire events, volcanic eruptions, glacial movements and avalanches, and even atmospheric air pressure fluctuations through time.

Climate reconstructions from trees also show how climate has changed throughout history, with temperature proxies revealing unprecedentedly — and increasingly — high temperatures beginning in the 20th century, far above any paleoclimatic global warming flux. Moreover, the conditions we can obtain from the past can be used to make more accurate models for predicting how climate will continue to change in the future.

Dendrochronology research on Sycamore Land Trust preserves provides a fascinating peek into the data our protected trees contain. As part of an extensive project looking at hemlock across the United States, IU dendrochronologist Justin Maxwell sampled a few trees from Sycamore properties to see how Indiana’s relict populations of eastern hemlock, disjunct from the species’s main range, are responding to climate change. Trees from our Hoot Woods preserve, one of the few remaining tracts of old-growth forest left in Indiana, extend our region’s tree ring chronology even further back in time. Last fall, a black gum tree at Hoot Woods was found to date back to the early 1600s. I remember watching in humbled awe as Justin removed the core from the immense tree, which had been here well before any Europeans had set foot on the land that would become Indiana, and may be here long after the group of us who sampled it are gone.

THE FORESTS FOR THE TREES

Exploring Indiana’s Lower Wabash Valley in the late 1800s, ornithologist Robert Ridgway wrote that the forest was “so thick that the trees had to grow upward toward the sunlight . . . it is no wonder that many species grew to a height that seems impossible to some people.” Sycamores and bald cypresses stretched 15 feet in diameter, and heavy hardwoods extended in unbroken continuity for miles. Of the original 20 million acres of forest that covered Indiana, fewer than 2,000 acres of old growth forest remain intact.

Though these forest landscapes of the past are gone, their legacy lives on through Sycamore’s work. From rare old-growth tracts to bottomland woods to rolling hardwood hills, Sycamore’s protection of Indiana forests is a promise that will last forever. These forests will never be timbered and will, at some point, begin resembling the towering landscapes that once grew here.

Trees have lots to teach us — about climate change, historical land use, and fungal ecology, but also about resilience. The connective fungal threads that sustain forests, allowing them to adapt through millennia of change, reflect the strength found in communities. When we’re cognizant of the deeply rooted interconnections between ourselves and nature, our communities become that much greater, giving us the appreciation for the natural world and our responsibility to care for each other.

The trees I pass under while working remind me that we are not alone. Their names are a rolling rhythm through the hills, calls of sugar maple, black cherry, sassafras, black oak, tulip poplar, American beech, hackberry, black walnut, eastern red cedar echoing with every footstep, a communal network expanding across species and ecosystems. The trees stand steadfast in the soil, their cambium transcribing changes in the world around them, their sun-seeking branches reaching out, connecting and rooting us in protecting the land we all share.

This article was published in the Fall 2021 edition of The Twig “The Tree Issue.”  Read more here