The Arbornaut, page 6
Aberdeen University required a research thesis to achieve the master of science degree in ecology. I was immediately smitten by Scottish birches, reminders of an upstate New York childhood, which grew in the Highlands and were the toughest trees I’d ever seen. Gale-force winds and the prospect of snow almost any month of the year is daunting even to the most robust buds and foliage. As a result of this extreme environment, trees at the tops of hills were much shorter and scrawnier than in the valleys. I was curious about the phenology of birch along their elevational gradient, ranging from warm and almost subtropical in the sheltered valleys to freezing cold with arctic winds at the top. So I decided to survey seasonal variation of their leafing and flowering patterns at different elevations, which required an active schedule of hill-walking (as the Scots called it). My advisor, an enthusiastic tropical botanist, wisely spent much of his winter months in Malaysia conducting research on tropical trees. (He waxed lyrical about the mysteries of rain forests, so much so that his stories ultimately inspired me to find my own way to that part of the world.)
Over the course of a year, I befriended a crusty old forester who seemed to know the location of every single birch tree in the country. I met Richard when my Aberdeen class visited the western Highlands and toured some of the forestry plantations he managed for the shire. After that, he hosted me for some of my birch-spotting expeditions, and probably saved my life on several occasions as we tried to find patches of trees at the highest elevation. Almost every weekend, I took the public bus over to Skye or Inverness or Loch Ness, buying fish and chips in its traditional newspaper wrapping at a petrol station en route, and then met up with Richard to observe birch foliage in remote parts of the Highlands. I traveled light—a sleeping bag, a mountaineering tent, and a tiny stove that could boil a cup of tea in five minutes. Richard had his own gear, but best of all, he had an internal compass when it came to navigating in the hills. On occasion, we encountered a whiteout, which amounted to a dangerous blizzard when fierce winds whipped up the snow and enveloped the entire landscape in a white cocoon. Many hikers have died under these conditions, but Richard managed to guide me down from my high-elevation birches, walking blindly and numb with cold, but always reaching a valley where we could pitch our tents. Over time, I probably hiked several thousand miles in Scottish hills and examined hundreds of birch trees, taking careful notes about their leafing and flowering status, but mostly gaining a huge appreciation for their tenacity. It always felt great to remove my rough wool socks from my leather hiking boots after a long day of frigid hill-walking and squeeze my toes to make sure frostbite had not set in.
In addition to monitoring the phenology of birch canopies over the western Highlands, I was also curious whether individual trees leafed synchronously between bottom and top; perhaps the microclimate was warmer in the sheltered understory as compared to the windswept canopy? In the valleys, tree height reached thirty feet, but near the hilltops, only ten or fifteen feet. My advisor, Peter Ashton, thought this question was a great detective opportunity to study the whole tree instead of just the base like conventional foresters. He helped me collect a few old poles and planks, and together we crafted a rough, albeit hazardous, scaffold to survey the tree crowns about twenty-five feet high. I did not appreciate it at the time, but our makeshift framework launched my inaugural ascent into the canopy and lifelong career as an arbornaut. My first canopy research started with stunted Scottish birches and a rickety scaffold! I dragged the contraption to different hillsides using Peter’s family station wagon, looking like a dumpster diver who had rescued some old timber and metal struts, but in fact these discarded bits of construction allowed me to measure buds in tree crowns. The scaffold methodology only lasted two months, after which time some university maintenance people, upon finding the pieces carefully stowed in a corner of the botany parking lot, dutifully dragged the metal contraption off to the university dump. But that was enough to provide me with up-close insights into a birch tree’s seasonality from top to bottom, confirming that lower branches greened up before the upper canopy, thereby utilizing sunlight before the overhanging branches shaded them.
Field observations also showed that birch leafed out at least one month later at the higher elevations as compared to the valleys. Not surprisingly, trees on the hilltops were so dwarfed by the rigors of climate that they did not grow taller than ten feet, so their buds burst simultaneously throughout the crown. But in the sheltered valleys, where trees grew to at least twenty-five feet, budburst in the understory occurred two to three weeks earlier in spring as compared to the canopy. Although I did not appreciate it then, at the end of summer, temperate forests take a cue from seasonal day length to prepare for their winter “hardening.” When the days grow shorter, trees strategically prepare for the cold by winterizing their entire machinery, so woody cells are not left with excessive water that might otherwise expand to burst the cell walls with those first freezing nights. Recently, as the onset of climate change creates increasingly great oscillations in extreme weather, the environmental cue of seasonal temperatures is proving less reliable, wreaking havoc on Mother Nature’s systems. But the sun, whose light through the millennia has provided regular cycles of day length, also called photoperiod, remains a constant, signaling trees to shut down their operations for the winter and then ramp them up in the spring. If plants relied entirely on temperature, not sunlight, as indicators for seasonal changes, they would most certainly have suffered extreme confusion and more widespread mortality, especially during recent times with the rapid onset of warming trends.
From that short Scottish summer, I stumbled onto a novel observation that inspired future research. Aphids attacked the birches en masse just after all the new leaves appeared. The carnage was shocking—leaves were sucked, disfigured, and scrunched into dry, shriveled corpses. This was my first confrontation with six-legged foliage enemies, technically referred to as herbivores. As I observed with horror, aphids did not actually chew foliage but instead sucked their juices, leaving a rattling skeleton of dried leaf carcasses. Aphids infested 85 percent of foliage in the valleys, but only 35 percent in the exposed, windswept hills. So if you are a birch, maybe a good defense against insect pests is to live at the top of the mountains, where weather is too extreme for your enemies? I could have spent a lifetime in Scotland, studying the fate of Betula in valleys versus hilltops to understand the interactions of leafing, weather, and aphids. As with many aspects of ecology, one year was not enough to draw firm conclusions. And as I would later learn from tropical trees, even several decades were not always enough to accurately answer ecological questions.
Despite an entire year of miserable weather, I loved field research on Scottish birch. This was my first academic experience where gender was not a disadvantage, because Aberdeen’s ecology course and faculty were extremely inclusive. We not only had equal gender representation in our class of twelve, but also students from five cultures. After hearing my Scottish advisor tell stories about his tree research in Malaysia, I became infected by his tropical bug. Peter Ashton was a world expert on a major family of trees called Dipterocarpaceae. These tall denizens dominated many forests in Southeast Asia, and he had written much of the definitive biology of these important trees. He told amazing tales of forays into Malaysian jungles, surrounded by flora and fauna unknown to me—ranging from sun bears to leaf langurs, hornbills, and slow lorises—and unexpected encounters with several species of deadly cobras. Hearing Peter’s stories of sultry heat and dehydration in Malaysia while sitting in a Scottish pub with the cold North Sea winds rattling the windows was more than enough to inspire my daydreams about working in a tropical habitat. By amazing coincidence, several weeks later I met an Australian botanist spending his sabbatical at Cambridge University. Along with Belize, Australia was one of only two English-speaking countries with tropical forests. I learned from this chance encounter that the University of Sydney offered generous scholarships to international students.
Suddenly, my sights were set on the Australian tropical jungle, even though I was woefully unprepared. I applied to the program, was accepted, and joyfully purchased the cheapest ticket available, flying from London to Sydney for $200 via People Express airline. I mailed the Aberdeen diploma back home. Mom cried when I called her from a pay phone. The notion of her only daughter moving even farther away from Elmira, New York, in pursuit of leaves was more than she could bear. We had a close mother-daughter relationship but somehow never shared life-changing decisions such as college choices, boyfriends, or what I wrote on college essays. My parents offered unconditional love and trust but left the choices completely up to me. I can’t imagine how my mom would have reacted if she knew it would be thirteen long years before I lived on American soil again. I boarded the plane in London with forty pounds of books in a carry-on bag, trying to avoid paying for excess luggage. Dressed in wrinkled khakis and hiking boots, I was greeted with frowns from the stewardess who noticed my heavy science library. Most females boarding the plane had makeup kits or extra jewelry as carry-on, but I proudly carted botany books as I headed halfway around the world to study enormously tall plants.
In those days, a flight from London to Sydney took almost twenty hours and required a stopover for fuel. I sat awake, anxiously wondering what lay ahead. A gang of Australian blokes became drunk in the back of the plane and thought it was quite humorous to ask girls to take off their shirts as a toll to access the bathrooms. I was not amused and, in fact, started to realize I was about to immerse in a new culture. “Stone the bloody crows,” those drunken Australians taught me to say when something crazy happens, which simply translates to a more vivid version of “Holy cow!” Our flight touched down to refuel in Kuala Lumpur, Malaysia, a place I knew of only as my Aberdeen advisor’s winter tropical ecology retreat. This country’s forests are among the tallest, dominated by dipterocarps, the most economically important family of trees in the world, yet I had never heard of them throughout undergraduate botany training.
Was I really cut out for graduate school in the “Lucky Country,” as Australia was affectionately called? I did not even know what a tropical forest looked like firsthand, though I could still recall images in a National Geographic magazine I read during childhood. I did not relish the venomous snakes in a teeming mass under every canopy depicted in those glossy pages, and certainly was not an enthusiastic beer drinker like all the boisterous Aussies at the rear of the international flight. But even if I flunked out of the University of Sydney, it would be a small consolation to see a koala and add a new continent to my expanding bucket list of botanical wonders.
My Favorite Birches
(Betula papyrifera, B. pendula, and B. pubescens)
THE MAJESTIC WHITE OR PAPER BIRCH (Betula papyrifera) grows in the backyards of upstate New York and graces many New England forests and roadsides. Its characteristic white bark peels easily and forms an important resource for canoe-making by the Onondaga, Cayuga, and Seneca tribes native to my upstate New York region. A famous American naturalist, Donald Culross Peattie, paid tribute to birchbark canoes with the following statement:
To any American of an older generation (now, alas, even canoes are being made of aluminum) there was no more blissful experience than the moment when on his first visit to the North Woods he stepped into a Birch bark canoe weighing perhaps no more than fifty pounds, but strong enough to carry twenty times as much. At the first stroke of the paddle it shot out over the lake water like a bird, so that one drew a breath of the purest ozone of happiness, for on all the waters of the world there floats no sweeter craft than this.
Who doesn’t love the sight of graceful paper birches swaying in a breeze? But watch out—they are shallow-rooted and fast-growing, often the first to fall in a ferocious storm. Their roots penetrate about two feet at most below the surface, and birch can’t tolerate living under the shade of others. Hence, they are classified as early successional, meaning they grow quickly in the early stages of forest development but die out when overtopped by taller trees such as beech and maple that comprise later successional species. It is possible to play detective and age a New England forest by determining which species occupy the canopy and classifying their status as early versus late successional.
Betula timber is harvested for veneer, plywood, furniture, and firewood. Native Americans used this species not only for canoes, but also for baskets, baby carriers, torches, moose- and bird-call whistles, and mats. Medicinally, birch was used to treat skin ailments and dysentery, and to promote milk production in nursing mothers. In the spring, birches were often tapped because their sap makes flavorful beer, syrup, wine, or vinegar. During childhood, we enjoyed many crackling family fires fueled by their papery-edged logs. Like most temperate trees, Betula has its share of insect pests. The bronze birch borer threatens the trunks, while outbreaks of leaf miners defoliate the canopies, and several fungal species cause canker diseases. Peeling birchbark has long been a temptation for children, but when stripped from living trunks, the beautiful white bark never grows back. Instead, ugly black rings take its place, so it is always best to remove shavings of white bark from a fallen log.
Birches produce male and female catkins, technically defined as spikes of flowers. The male catkins appear during summer, starting out as buds in the axils of the leaves, and during the following winter they emerge as erect spikes visible in the leafless canopies. By early spring, they lengthen and become droopy, eventually flowering with each male floret contained inside a four-lobed calyx. The female catkins are thicker, their florets borne without a surrounding calyx, and covered by overlapping scales tinted light yellow with an occasional tinge of red, eventually turning brown and woody. Birch fruits bear tiny nuts in cone-like heads about one and a half inches long, and release wind-borne seeds that disperse widely and germinate quickly in sunny, well-drained conditions as an early successional species.
Like many trees, Betula has relatives that exist in other regions dating back to evolutionary times when the continents were linked. Across the Atlantic Ocean where I completed a master’s thesis, Scotland is home to some birch cousins of our American species, including the ballerina of the family, silver birch (Betula pendula), with her dangling branches swaying in the breeze like a choreographed dancer. Europeans often call this beauty “lady of the woods.” Another species, and also a focus of my field research in Scotland, is the hardy Highland or hairy birch (B. pubescens), which endures the rigors of high elevations as part of its range. Despite a double whammy of extreme weather and thirsty aphids, these small, rugged trees exhibit extraordinary hardiness as the predominant canopy sentinel throughout most alpine regions of Europe, not just Scotland.
Whether in North America or Europe, a few good birch trees with some bird eggs in their branches can be inspirational to any aspiring naturalist, as was definitely the case in my own childhood.
3
ONE HUNDRED FEET IN THE AIR
Finding a Way to Study Leaves in the Australian Rain Forests
FEELING A BIT LIKE A GROWN-UP VERSION of Tom Sawyer, I eyed the target and took careful aim. Ready, set, fire. My jerry-rigged slingshot propelled its fishing line and lead weight up and over a high, sturdy branch of a coachwood tree (Ceratopetalum apetalum), some seventy-five feet overhead. Gazing up in satisfaction from the humid floor of the Australian rain forest, I hardly felt the infantry of leeches swarming up both legs and the sweat bees invading both eyes, or even spared a thought for the venomous brown snakes lying underfoot.
Believe it or not, I made that shot on the first try. The tree rigging method actually worked! Almost ten thousand miles away from any friends or relatives, teaching myself to scale trees with a homemade harness and slingshot, I was pretty scared. With the fishline catapulted over the sturdy branch almost thirty yards overhead, I next slid the nylon cord along its trajectory, and then the heavier climbing rope. I tied off one end of the climbing rope around the trunk of an adjacent tree, knotting it at least three times, which was totally overkill. I grabbed the free end of the rope and was ready to launch. Double- and triple-checking my harness and foot stirrups, I soon memorized a protocol for checking all my gear, almost like an astronaut before liftoff. After the safety inspection, I clipped my two ascenders onto the rope, making sure that the foot jumar was above the chest jumar, otherwise I would turn upside down. Squatting, I sat back in my harness and then slid the jumars up the rope, acting out the antics of an inchworm. Slowly, the ground receded and dense leafy foliage surrounded me. The dark-green leaves of the understory swallowed me up. Two of my caving friends, Al and Julia, watched from the ground, hoping I would remember all the pointers for safe use of their borrowed equipment. I hardly dared to look sideways let alone down, spinning in midair on a half-inch-thick lifeline, feeling akin to a tiny caterpillar ballooning on a silk strand through a huge expanse of green. I swayed back and forth, a bumbling first-timer with little sense of balance, flailed at the tree trunk, and grasped the rope for dear life. But as I climbed higher, moving upward became easier … practice, practice, practice. Beams of light began to flicker on my face as I drew closer to the top of the coachwood. Then mayhem broke loose around me. I had entered the sun-flecked leaves of the official upper canopy and encountered a sensory overload: creatures munching, flying, crawling, pollinating, hatching, burrowing, sunning, digesting, singing, mating, and stalking. The life surrounding me was nearly entirely invisible from the forest floor.
