The
Forest Unseen
The
Forest Unseen
A Year’s Watch in Nature
David George Haskell
VIKING
VIKING
Published by the Penguin Group
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First published in 2012 by Viking Penguin, a member of Penguin Group (USA) Inc.
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Copyright © David George Haskell, 2012
All rights reserved
LIBRARY OF CONGRESS CATALOGING IN PUBLICATION DATA
Haskell, David George.
The forest unseen : a year’s watch in nature / David George Haskell.
p. cm.
Includes bibliographical references and index.
EISBN: 9781101561065
1. Old growth forest ecology—Tennessee. 2. Old growth forests—Tennessee. 3. Natural history—Tennessee. 4. Seasons—Tennessee. 5. Nature observation—Tennessee. 6. Haskell, David George. 7. Philosophy of nature. I. Title.
QH105.T2H37 2012
577.309768—dc23 2011037552
Printed in the United States of America
Designed by Nancy Resnick
No part of this book may be reproduced, scanned, or distributed in any printed or electronic form without permission. Please do not participate in or encourage piracy of copyrighted materials in violation of the author’s rights. Purchase only authorized editions.
For Sarah
Contents
Preface
January 1st—Partnerships
January 17th—Kepler’s Gift
January 21st—The Experiment
January 30th—Winter Plants
February 2nd—Footprints
February 16th—Moss
February 28th—Salamander
March 13th—Hepatica
March 13th—Snails
March 25th—Spring Ephemerals
April 2nd—Chainsaw
April 2nd—Flowers
April 8th—Xylem
April 14th—Moth
April 16th—Sunrise Birds
April 22nd—Walking Seeds
April 29th—Earthquake
May 7th—Wind
May 18th—Herbivory
May 25th—Ripples
June 2nd—Quest
June 10th—Ferns
June 20th—A Tangle
July 2nd—Fungi
July 13th—Fireflies
July 27th—Sunfleck
August 1st– Eft and Coyote
August 8th—Earthstar
August 26th—Katydid
September 21st—Medicine
September 23rd—Caterpillar
September 23rd—Vulture
September 26th—Migrants
October 5th—Alarm Waves
October 14th—Samara
October 29th—Faces
November 5th—Light
November 15th—Sharp-shinned Hawk
November 21st—Twigs
December 3rd—Litter
December 6th—Underground Bestiary
December 26th—Treetops
December 31st—Watching
Epilogue
Acknowledgments
Bibliography
Index
Preface
Two Tibetan monks lean over a table, cradling brass funnels in their hands. Colored sand spills from the tips of the funnels onto the table. Each fine stream adds another line to the growing mandala. The monks work from the center of the circular pattern, following chalk lines that define the fundamental shapes, then filling in hundreds of details from memory.
A lotus flower, symbol of Buddha, lies at the center and is enclosed by an ornate palace. The four gates of the palace open out to concentric rings of symbols and color, representing steps on the path to enlightenment. The mandala will take several days to complete, then it will be swept up and its jumbled sands cast into running water. The mandala has significance at many levels: the concentration required for its creation, the balance between complexity and coherence, the symbols embedded in its design, and its impermanence. None of these qualities, however, define the ultimate purpose of the mandala’s construction. The mandala is a re-creation of the path of life, the cosmos, and the enlightenment of Buddha. The whole universe is seen through this small circle of sand.
A group of North American undergraduates jostle behind a rope nearby, extending their necks like herons as they watch the mandala’s birth. They are uncharacteristically quiet, perhaps caught up in the work or stilled by the otherness of the monks’ lives. The students are visiting the mandala at the beginning of their first laboratory class in ecology. The class will continue in a nearby forest, where the students will create their own mandala by throwing a hoop onto the ground. They will study their circle of land for the rest of the afternoon, observing the workings of the forest community. One translation of the Sanskrit mandala is “community,” so the monks and the students are engaged in the same work: contemplating a mandala and refining their minds. The parallel runs deeper than this congruence of language and symbolism. I believe that the forest’s ecological stories are all present in a mandala-sized area. Indeed, the truth of the forest may be more clearly and vividly revealed by the contemplation of a small area than it could be by donning ten-league boots, covering a continent but uncovering little.
The search for the universal within the infinitesimally small is a quiet theme playing through most cultures. The Tibetan mandala is our guiding metaphor, but we also find context for this work in Western culture. Blake’s poem “Auguries of Innocence” raises the stakes by shrinking the mandala to a speck of earth or a flower: “To see a World in a Grain of Sand / And a Heaven in a Wild Flower.” Blake’s desire builds on the tradition of Western mysticism most notably demonstrated by the Christian contemplatives. For Saint John of the Cross, Saint Francis of Assisi, or Lady Julian of Norwich, a dungeon, a cave, or a tiny hazelnut could all serve as lenses through which to experience the ultimate reality.
This book is a biologist’s response to the challenge of the Tibetan mandala, of Blake’s poems, of Lady Julian’s hazelnut. Can the whole forest be seen through a small contemplative window of leaves, rocks, and water? I have tried to find the answer to this question, or the start of an answer, in a mandala made of old-growth forest in the hills of Tennessee. The forest mandala is a circle a little over a meter across, the same size as the mandala that was created and swept away by the monks. I chose the mandala’s location by walking haphazardly through the forest and stopping when I found a suitable rock on which to sit. The area in front of the rock became the mandala, a place that I had never seen before, its promise mostly hidden by winter’s austere garb.
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p; The mandala sits on a forested slope in southeastern Tennessee. One hundred meters upslope, a high sandstone bluff marks the western edge of the Cumberland Plateau. The ground falls away from this bluff in steps, alternating level benches with sharp inclines, descending one thousand feet in elevation to the valley floor. The mandala nestles between boulders on the highest bench. The slope is entirely forested with a diverse collection of mature deciduous trees: oaks, maples, basswoods, hickories, tuliptrees, and a dozen more species. The forest floor is ankle-twistingly strewn with jumbled rock from the eroding bluff, and in many places there is no even ground, just heaved, fissured stone overlain with leaf mulch.
The steep, challenging terrain has protected the forest. At the bottom of the mountain, the fertile, level soil on the valley floor is relatively free of rocky encumbrances and has been cleared for pasture and crops, first by Native Americans, then by settlers from the Old World. A few homesteaders tried to farm the mountainside in the late nineteenth and early twentieth centuries, a task that was as hard as it was unproductive. Moonshine stills gave these subsistence farmers extra income, and this mountainside got its name, Shakerag Hollow, from the way townspeople would summon the distillers by waving a rag that was then left with some money. A jar of strong liquor would take the place of the money some hours later. The forest has now reclaimed the small agricultural openings and still sites, although the locations of the old clearings are marked by rock heaps, old pipes, rusted washtubs, and daffodil patches. Much of the rest of the forest was logged for lumber and fuel, especially at the turn of the twentieth century. A few small pockets of forest were left untouched, shielded by inaccessibility, luck, or the whims of landowners. The mandala sits in one such patch, a dozen or so acres of old-growth forest embedded in thousands of acres of forest that, although it has been cut in the past, is now mature enough to sustain much of the rich ecology and biological diversity that characterize Tennessee’s mountain forests.
Old-growth forests are messy. Within a stone’s throw of the mandala, I see half a dozen large fallen trees in various stages of decomposition. The rotting logs are the food for thousands of species of animals, fungi, and microbes. Downed trees leave gaps in the forest canopy, creating the second characteristic of old-growth forests, a mosaic of tree ages, with groups of young trees growing next to thick-trunked elders. A pignut hickory with a trunk a meter wide at its base grows just to the west of the mandala, right next to a crowd of maple saplings in a gap left by a massive fallen hickory. The rock on which I sit is backed by a middle-aged sugar maple, its trunk as wide as my torso. This forest has trees of all ages, a sign of the historical continuity of the plant community.
I sit next to the mandala on a flat slab of sandstone. My rules at the mandala are simple: visit often, watching a year circle past; be quiet, keep disturbance to a minimum; no killing, no removal of creatures, no digging in or crawling over the mandala. The occasional thoughtful touch is enough. I have no set schedule for visits, but I watch here many times each week. This book relates the events in the mandala as they happen.
January 1st—Partnerships
The New Year starts with a thaw, and the fat, wet smell of the woods fills my nose. Moisture has plumped the mat of fallen leaves that covers the forest floor, and the air is suffused with succulent leafy aromas. I leave the foot trail that winds down the forest slope and scramble around a house-sized piece of mossy, eroded rock. Across a shallow bowl on the mountainside I see my landmark: a long boulder, cresting out of the leaf litter like a small whale. This block of sandstone defines one edge of the mandala.
It takes me just a few minutes to traverse the rocky scree and reach the boulder. I step past a large hickory tree, resting my hand on its gray strips of bark, and the mandala is at my feet. I circle to the opposite side and take my seat on a flat rock. After pausing to inhale the rich air, I settle in to watch.
The leaf litter is mottled with browns. A few bare spicebush stems and a young ash stand waist-high at the mandala’s center. The muted, leathery colors of these decaying leaves and dormant plants are eclipsed by the glow coming from the rocks that frame the mandala. These stones are tumbled remnants of the eroding bluff, smoothed into irregular, lumpy forms by thousands of years of erosion. The rocks range in size from woodchuck to elephant; most are about as big as a curled-up human. Their radiance comes not from stone but from mantles of lichen that blush emerald, jade, and pearl in the humid air.
The lichens’ growth forms mountains in miniature, sandstone crags with variegated patches of moisture and sunlight. The highest ridges on the boulders are spattered with tough-skinned gray flakes. Dark canyons between rocks have a purple sheen. Turquoise glistens on vertical walls, and concentric circles of lime flow down gentle slopes. All the lichens’ hues are paint-stroke fresh. This vibrancy contrasts with the winter-weighed lethargy of the rest of the forest; even the mosses are muted and frost-bleached.
Supple physiology allows lichens to shine with life when most other creatures are locked down for the winter. Lichens master the cold months through the paradox of surrender. They burn no fuel in quest of warmth, instead letting the pace of their lives rise and fall with the thermometer. Lichens don’t cling to water as plants and animals do. A lichen body swells on damp days, then puckers as the air dries. Plants shrink back from the chill, packing up their cells until spring gradually coaxes them out. Lichen cells are light sleepers. When winter eases for a day, lichens float easily back to life.
This approach to life has been independently discovered by others. In the fourth century BCE, the Chinese Taoist philosopher Zhuangzi wrote of an old man tossed in the tumult at the base of a tall waterfall. Terrified onlookers rushed to his aid, but the man emerged unharmed and calm. When asked how he could survive this ordeal, he replied, “acquiescence… I accommodate myself to the water, not the water to me.” Lichens found this wisdom four hundred million years before the Taoists. The true masters of victory through submission in Zhuangzi’s allegory were the lichens clinging to the rock walls around the waterfall.
The quietude and outer simplicity of the lichens hides the complexity of their inner lives. Lichens are amalgams of two creatures: a fungus and either an alga or a bacterium. The fungus spreads the strands of its body over the ground and provides a welcoming bed. The alga or bacterium nestles inside these strands and uses the sun’s energy to assemble sugar and other nutritious molecules. As in any marriage, both partners are changed by their union. The fungus body spreads out, turning itself into a structure similar to a tree leaf: a protective upper crust, a layer for the light-capturing algae, and tiny pores for breathing. The algal partner loses its cell wall, surrenders protection to the fungus, and gives up sexual activities in favor of faster but less genetically exciting self-cloning. Lichenous fungi can be grown in the lab without their partners, but these widows are malformed and sickly. Similarly, algae and bacteria from lichens can generally survive without their fungal partners, but only in a restricted range of habitats. By stripping off the bonds of individuality the lichens have produced a world-conquering union. They cover nearly ten percent of the land’s surface, especially in the treeless far north, where winter reigns for most of the year. Even here, in a tree-filled mandala in Tennessee, every rock, trunk, and twig is crusted with lichen.
Some biologists claim that the fungi are exploiters, ensnaring their algal victims. This interpretation fails to see that the lichen partners have ceased to be individuals, surrendering the possibility of drawing a line between oppressor and oppressed. Like a farmer tending her apple trees and her field of corn, a lichen is a melding of lives. Once individuality dissolves, the scorecard of victors and victims makes little sense. Is corn oppressed? Does the farmer’s dependence on corn make her a victim? These questions are premised on a separation that does not exist. The heartbeat of humans and the flowering of domesticated plants are one life. “Alone” is not an option: the farmer’s physiology is sculpted by a dependence on plants for food that d
ates back hundreds of millions of years to the first wormlike animals. Domesticated plants have experienced only ten thousand years of life with humans, but they too have shed their independence. Lichens add physical intimacy to this interdependence, fusing their bodies and intertwining the membranes of their cells, like cornstalks fused with the farmer, bound by evolution’s hand.
The diversity of color in the lichens on the mandala reflects the many types of algae, bacteria, and fungi involved in the lichens’ union. Blue or purple lichens contain blue-green bacteria, the cyanobacteria. Green lichens contain algae. Fungi mix in their own colors by secreting yellow or silver sunscreen pigments. Bacteria, algae, fungi: three venerable trunks of the tree of life twining their pigmented stems.
The algae’s verdure reflects an older union. Jewels of pigment deep inside algal cells soak up the sun’s energy. Through a cascade of chemistry this energy is transmuted into the bonds that join air molecules into sugar and other foods. This sugar powers both the algal cell and its fungal bedfellow. The sun-catching pigments are kept in tiny jewel boxes, chloroplasts, each of which is enclosed in a membrane and comes with its own genetic material. The bottle-green chloroplasts are descendants of bacteria that took up residence inside algal cells one and a half billion years ago. The bacterial tenants gave up their tough outer coats, their sexuality, and their independence, just as algal cells do when they unite with fungi to make lichens. Chloroplasts are not the only bacteria living inside other creatures. All plant, animal, and fungal cells are inhabited by torpedo-shaped mitochondria that function as miniature powerhouses, burning the cells’ food to release energy. These mitochondria were also once free-living bacteria and have, like the chloroplasts, given up sex and freedom in favor of partnership.
And life’s chemical whorl, DNA, bears the marks of yet more ancient union. Our bacterial ancestors shuffled and swapped their genes among species, blending genetic instructions like cooks copying from one another’s recipe cards. Occasionally two chefs would agree to a wholesale merger, and two species fused into one. The DNA of modern organisms, including our own, retains traces of such mergers. Although our genes function as one unit, they come with two or more subtly different writing styles, vestiges of the different species that united billions of years ago. The “tree” of life is a poor metaphor. The deepest parts of our genealogies resemble networks or deltas, with much interweaving and cross flow.
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