Immersion As soon as you step into a forest, you step into a different space. Depending on the type of forest, the trees may be growing together so closely that their tops almost touch. Outside, the sun may be shining brightly, but here, you are in the shade. The leaves are busily absorbing sunlight to make food. What little light makes it through the canopy is mostly green, so it feels as though you are slipping into an underwater world. The forest is refreshingly cool. Years of discarded leaves and needles have turned the ground into a huge sponge that absorbs rainwater as it drips through the leaves and then slowly releases it into the forest floor. Above ground, you breathe in damp air, while below ground, the trees tap into the pockets of moisture captured by their maze of roots after the last rains fell. Fallen branches and trunks lie strewn on the forest floor. Rain-saturated rotting wood and downed logs steam as the sun hits them. The trees, both living and dead, are actively creating the cool, shady, moist conditions they most enjoy. Let your eyes adjust to the quality of light around you and listen as the breeze brushes through the branches. It sounds like traffic on a distant highway, water cascading over rocks, or waves breaking on the shore. Individual trees creak and groan as they rub against one another, each producing a slightly different sound depending on how slowly or quickly, how densely or airily their wood has grown. You might even hear a hollow tree humming as though it's experimenting with the beginnings of a tune. Leaves and needles whisper and sing. Dry leaves hanging on young beeches chatter in the brisk spring air while they wait for the larger trees in the forest to leaf out. Unfolded aspen leaves produce a muffled muttering as the breeze turns them one way and then the other. The stems of most leaves are round to keep the tops of the leaves oriented to the sun, but the stems of aspen leaves are flat, allowing the leaves to twist in the wind so both sides can bathe in the light. Vortices of air form around and detach from the tips of conifer needles, producing a melodic chorus--known in Japanese as matsukase or the "song of the pines"--that varies in pitch as the breeze builds and dies. Small branches buffeted against one another twang like wire strung taut between fence posts. On a hot day, the popping of pinecones opening and ejecting their seeds punctuates this symphony of sound. If you are one of those people who has trouble slowing down to listen, you might pick up on the soundtrack of the forest when something quite different draws your attention. As Jane took photographs of a particularly pleasing pattern of lichens on bark in Big Thicket National Preserve in Texas, she heard a rustling. Quite a loud rustling, it seemed to her, but when she investigated, she discovered it came from a small brown grasshopper perfectly blended into the leaf litter below. If she had not been stopped and silent at that moment, she would never have noticed it, even though it was right at her feet. It froze as she bent down to inspect it. Jane is no entomologist, so she had no idea what kind of grasshopper it was, but a search back home revealed it to be the delightfully named "mischievous bird grasshopper"--also known, somewhat less delightfully, as the Carolina locust. As humans, we rely heavily on visual images and are not particularly skilled at interpreting sounds, especially in unfamiliar territory. In forests where bears are about, birds scratching in leaf litter can sound especially large and menacing. Later in her trip, Jane, who lives in the Pacific Northwest, heard a quiet mewing sound in Highlands Hammock State Park near Sebring, Florida, and became convinced it must be a panther kitten calling for its mother. It turned out to be a gray squirrel hiding behind a branch. A mysterious nocturnal scuffling around her campsite in Paynes Prairie Preserve State Park just south of Gainesville revealed itself in the comforting light of morning to have been an armadillo snuffling for insects in the thick layer of leaves under the live oaks. Because we rely so heavily on sight, the merest flicker of movement quickly commands our attention even if an animal is being as quiet as it can be. In the beech-magnolia forests of southern Texas and the baldcypress swamps of northern Florida, these movements often come from green anoles scattering at the sound of your approach. Jane watched one skittering across a boardwalk in the Okefenokee Swamp Park in Georgia. On the boardwalk it was a dull brown, but as soon as it reached the grassy vegetation on the other side, it turned a bright, almost luminous, green. She had witnessed the so-called American chameleon in action. Stopping to listen hones your senses until even stationary patterns register: a black-and-yellow salamander by the side of the trail, an orb-weaver spider suspended between branches (careful you don't walk into its web), a striped chipmunk standing on guard next to a small crevice at the base of a tree. As you walk through the forest, many eyes will be watching you. If you take the time to stop and listen, every once in a while, you might discover some of the creatures that have you in their sights. While you're standing there, taking in the forest, close your eyes. Smell is not exactly our strongest sense, but we become more aware of smells when we are not distracted by what we can see. Some of the aromas you are detecting are being produced by trees as they pass chemical messages amongst themselves. What kind of messages might these be? Trees, as you have probably noticed, cannot run from danger, so they have other ways of defending themselves. You might get a whiff of a cyanide compound in black cherry bark that smells like bitter almonds. This warning scent lets browsers know not to mess with this tree. Oaks go even further, using airborne messages to summon reinforcements that help them combat pests. When caterpillars start munching on them, the trees pump bitter tannins into their leaves. They also send chemical messages over the air waves. Parasitic wasps fly in when they receive the oaks' airborne invitations and lay their eggs in the caterpillars. When the eggs hatch, the wasp larvae eat their way out of their hosts, putting an end to the caterpillar buffet. In a coniferous forest, you will pick up on that piney scent so popular with companies that make room and car deodorizers. It smells like a mixture of sap, candied orange peel, and sugar. It reminds me of summer holidays spent on the coast of the Mediterranean where the pines smell just the same. Many conifers native to northern climes suffer when they are planted in lower latitudes where the weather is too hot and dry for them. When conifers don't have enough to drink, they become stressed because lack of moisture weakens their defenses against bark beetles. They release olfactory alarm signals to warn their companions, and these are the tangy scents that smell so strongly of beach vacations (to me, anyway). These piney scents come from bitter-tasting essential oils called "terpenes." In spring, pines pump more terpenes into the tender new growth deer prefer to eat and less to old growth that deer tend to avoid. In addition to acting as a deer deterrent because they taste bad, terpenes have antimicrobial and antibacterial qualities that clean the air in the forest, making it pleasant for us to breathe when we decide to indulge in a bit of forest bathing, which is basically like taking a refreshing shower in forest air. Terpenes are also an essential component of conifer resin. When you see drops of resin oozing down a tree, you know the spruce, fir, or pine is actively defending itself, flushing out intruders such as bark beetles and filling the holes they bore with sticky sap so the beetles cannot crawl inside. I can tell you from experience that if you want to take the weight off your feet or get extra support when crossing a rocky patch in the trail, it's not a good idea to lean on a sticky conifer as it's almost impossible to get the resin off your skin and clothes. Out on the trail, you can try rubbing sticky skin on tree bark to remove as much sap as you can. You'll find some of the dust on the bark sticks to the sap. Now your skin will be dirty, but at least it won't be sticky any longer. Your clothes, alas, will need to wait for more intense treatment when you get home. Conifers use terpenes in other ways. On hot days, the trees increase their production of terpenes until they rise in the heat to float above the forest, where they attract water molecules. The gathering water molecules form clouds that shade the forest like an enormous sun umbrella. If there is enough moisture around, the trees might even summon up a raincloud or two. It is terpenes that put the "smoky" in Tennessee's Great Smoky Mountains as clouds collect over the forested hillsides. Not all the scents floating around you are defensive. Some are associated with reproduction. Many forest trees are wind pollinated. Alders hang their catkins in the breeze and pines release puffs of pollen from the pinkish-red pollen cones growing at the tips of their branches. The wind provides an efficient distribution service, dusting neighboring trees with male pollen that fertilizes female reproductive organs to start the next generation. You will get dusted, too. If you suffer from allergies, what is a cause for celebration for the pines and Douglas firs will make you reach for a paper tissue or an antihistamine. Some forest trees, however, need to attract the attention of insects to make reproduction happen. Insects get a light coating of pollen as they crawl into the trees' flowers in search of pollen and the co-opted carriers then drop off some of the dusty grains at their next floral stop. In forests in the American South, black tupelo trees, magnolias, and black cherries all vie for the pollinators' attention. In the swamp forests of Georgia and central Florida, bees produce highly prized tupelo honey after visiting the flowers of white tupelo trees. Flowers are eye-catching, but to get ahead of the game, these trees also make their blooms fragrant to let pollinators know energy-rich food is on offer. Scientists at the University of Tel Aviv have discovered that at least one plant, the evening primrose, increases the concentration of sugar in its nectar when bees buzz by. Perhaps some of the sweet forest aromas you smell are coming from trees keeping an ear open for passing pollinators and stepping up sugar production to lure in customers. If you are out on a mild, damp fall day, you might become aware of an earthy smell that comes not from the trees but the forest floor. This smell is released as springtails and millipedes, bacteria and fungi break down rotten wood and discarded leaves and process the nutrients they contain, making them available to the next generation of forest dwellers. The earthy aroma intensifies after a rain when the force of raindrops hitting the ground splashes bacterial spores up into the air. The smell is most intense after a dry period when spores have been collecting in the soil. We, as humans, are exquisitely attuned to it. We even have a special name for it: petrichor. Perhaps we find it so attractive because it smells like plenty, the promise of new life about to begin. When you first stepped into the forest, you might have thought you were the most active organism around, but as you can see, the forest itself constantly reacts to and shapes its environment, from the air above it to the earth below. But now it's time to get that hike underway. Excerpted from Forest Walking: Discovering the Trees and Woodlands of North America by Peter Wohlleben, Jane Billinghurst All rights reserved by the original copyright owners. Excerpts are provided for display purposes only and may not be reproduced, reprinted or distributed without the written permission of the publisher.
