Tough little trees on the fringe.

You can't help but love these gnomic creatures striving to survive at the limits of their natural range.

The last place I expected to meet a yellow birch that August afternoon was near the windy summit of Picket-on-a-Reef, a cusp of ancient gray rock jutting 1,750 feet above Bonne Bay in western Newfoundland. Yet there it was, miles north of where it should be, anchored to an unstable talus slope at the treeline and overlooking a glacial rockyard where only cinquefoil flourished.

Years later, the encounter still resonates in memory. For one thing, that little birch saved me from a broken leg or worse. And it taught me something we never learned in forestry school--that forests are as mobile as clouds. Conventional textbook dendrology was too preoccupied with tidy range maps, useful products, and "normal" dimensions to teach us about the little trees of the fringe.

Now, whenever I think of that birch--or of Monterey pine bending to Pacific gales at Big Sur, dwarf aspen gilding the high Sierra, or a crabbed tamarack silhouetted against a Labrador sunset--I see the tough little outriders of forests to come. The great trees of the heartland I admire; the gnomic trees of the hinterland I love.

For weeks Bill Whiffen and I had been working our way up Newfoundland island's 300-mile-long Great Northern Peninsula by pickup, by canoe, and on foot. Our job was to collect data for the provincial government's western region before heading back to university.

At 49 degrees 25 minutes North, Bonne Bay isn't exactly arctic. Yet its 2,000-foot hills look decidedly boreal. The Labrador Current can clog the nearby Strait of Belle Isle with polar ice any June, and snow lingers in the high ravines of the Tablelands all summer. No wonder we hadn't seen a temperate species since leaving Bay of Islands weeks before.

Bill and I climbed Picket-on-a-Reef partly out of youthful curiosity, partly from Sunday boredom. The reef did indeed have a surveyor's picket, its red pennant long since reduced to a pink tatter. After a mug-up, we rested in pale sunlight on crowberry mats that smelled of resin. Around us spread the burly mountains, blue fjords, and matchbox villages of Canada's future Gros Morne National Park.

The sky clouded over. A gust of wind rattled the picket in its cairn. We took the hint and started down. Descending the steeper west face, I turned for a last look at the Tablelands--and lost my footing.

A curious thing, the brain of a keen university student fresh from Dendrology 200--it works automatically. While loose rock clattered down, my mind scanned the sturdy bush I'd instinctively grabbed onto, noted its curly bronze bark and fine-toothed, ovate leaves, and announced, "Betula alleghaniensis Britton." I paid myself no heed. "Yellow birch, alias bronze, curly, or swamp birch," the inner voice went on, "geographic range centered on Lake Ontario, reaching south to Alabama and west to Minnesota with northern outlyers on Anticosti Island and southern Newfoundland; at maturity averaging 70 feet tall by two feet in diameter. . . ."

By the time my feet hit solid rock I was taste-testing a twig for telltale wintergreen: ID confirmed. But how could such a big species grow so small?

For many heartland forest species, my part of Canada is the northeastern rim of the world. Here--long before they reach the ocean and quite apart from human interference--they falter in their post-glacial expansion. Butternut and silver maple, accustomed to softer air and richer soils, drop out in southwestern New Brunswick. Black cherry, its blossoms repeatedly nipped by frost, gets only as far as eastern Nova Scotia. Beech, sugar maple, and eastern hemlock have invaded all three Maritime provinces, but apparently arrived too late to cross the newly formed Cabot Strait into Newfoundland. Red and white pine, red maple, and yellow birch did so; white elm and black ash got only a toehold in the southwest corner.

Except on good lowland sites, these temperate species seldom attain full stature here. Cape Breton Island's sugar maples glow as richly as New England's in October, but for commercial purposes they are "one-log trees." Even so, it's the mingling of temperate and boreal species that has created the distinctive Acadian Forest region, named after early settlers from western France.

When it comes to colonizing unfriendly territory, temperate interlopers are no match for their northern neighbors--especially black and white spruce, tamarack, and to a lesser extent balsam fir. Aggressive, opportunistic, and tenacious, they form the forests of our hilltops, bogs, and seashores.

In doing so, they've evolved a myriad of survival tactics. To escape untimely frost, they flush late and bud early. To conserve energy, they limit stressful flower and seed production. They hug the ground to escape drying winds and absorb solar warmth. And they exquisitely balance biomass production with nutrient availability. In living on the edge they became nature's bonsai trees.

Despite such tactics, the price is high. For example, black spruce and tamarack invade acidic bogs that starve them of nitrogen and sometimes even oxygen. Often they seem scarcely alive, like hibernating woodchucks. Many times I've counted 100 or more annual rings on a one-inch cross section. (The wood is as hard as nails.)

Once, while cruising timber on Newfoundland's Bonavista Peninsula, our compass lines intersected so many thickets of scrub spruce that I wore the knees out of two pairs of tough army pants in a single summer. No wonder hares and voles, ever mindful of death that swoops down from the sky, like these forests.

Among the worst habitats for trees is the North Atlantic coast. Fog, gales, blizzards, ice storms, and salt poisoning assail any tree that ventures there. It may also have to cope with an overdose of seabird guano. Nevertheless, from Maine to Labrador, headlands and islands wear manes of pigmy white spruce and balsam fir. I've seen seaside thickets so dense and wind-pruned one could clamber across them without falling through.

Sometimes even a forester can't tell the species. That happened to me once on Nova Scotia's Scatarie Island. The dark, leathery needles looked like balsam fir, but without seeing a cone, I couldn't be sure. Then, beneath the hedge I saw another forest--delicate little balsam firs rising green as grass, symmetrical as Christmas trees. No matter that soon they too would by sheared by the elements. DNA does not forget.

Still, what possible advantage can such places offer?

The short answer seems to be freedom from multi-species competition. A longer answer involves the immense perspectives of arboreal time and global change.

Unlike individual trees, forests are practically eternal. The conifer line stretches back to a time when dinosaurs were new, when the sun rose over an Atlantic not much wider than today's Gulf of California and set over a West without Rockies. Broadleafed forests, though more recent, witnessed the demise of dinosaurs, and the birth of the Mississippi.

We are dealing here with organisms from a time inconceivably remote. Is that why we sometimes feel a sense of awe in their presence? Like the mysterious arboreal "ents" in C.S. Lewis' sci-fi classic Out of the Silent Planet, they are friendly enough but almost from another world.

To be even more shamelessly anthropomorphic, my guess is that seashore conifers are waiting to reclaim part of that world. They are first in line to green the vast cod pastures of the sea. If this sounds fanciful, what are we to make of ancient pine and beech stumps that Grand Banks fishermen sometimes hoist from the deeps--with soil still clinging to the roots?

To me, colonizing the continental shelf is no more far-fetched than the stupendous feat of reforesting upper North America. Geologists tell us that 16,000 years ago the great Laurentide ice sheet was at its maximum. Its tentacles sprawled from the Pole down to Seattle, Missoula, Des Moines, Cincinnati, and Manhattan and out over the continental shelf. America looked like today's Antarctica.

By 8000 B.C. the ice was mostly gone. It left a sodden landscape, a continental gravel pit shimmering with uncountable new lakes, rumpled with strangely worn mountains, alive with tumbling rivers seeking new channels to rising seas. Southward stretched hundreds of miles of sparsely treed taiga flecked with the gray and white of caribou, and somewhere near the Gulf of Mexico was the temperate zone. Northward the land was treeless.

Sometimes I imagine a time-lapse video taped from outer space around that time. A shimmering blue-green tide follows the defeated glaciers northward, ascends the cool alpine valleys, creeps around the Great Lakes, and finally over-spreads the Hudson Bay Lowlands like ink on a blotter. At the leading edge are lichens and mosses; then come sedges, rushes, and other flowering plants, and finally willows, poplars, and conifers. Seed by seed, they clothe the desolation.

Sphagnum moss is remarkable for its thirst and its ability to colonize shallow acidic ponds. Since biomass production outstrips decomposition here, undecayed peat accumulates. When it rises above the water table, shrubs like leatherleaf (Chamaedaphne) and bog laurel (Kalmia) seed in from the edges. Tamarack and black spruce follow. In time, the bog becomes a forest.

From the air, these swirling patterns of bog reclamation--moss green, tan, tea, and indigo--resemble watered silk.

A few centuries from now, should supposed warming trends continue, Labrador black spruce may invade the shores of Baffin Island and Georgia baldcypress may dip their knobby knees in Long Island Sound.

But what if we get another global freeze? Then the oceans will dwindle as in past eons and the little trees of Mount Desert Island and Scatarie will have another chance at the continental shelf.

Ugly? Useless? The little trees on the fringe have been called such names. The ugliness is only bark deep. As for utility, they refresh our air and water, soften Earth's desolate places, and warn of climatic upset. As a DNA bank they could prove invaluable. Most importantly, they helped reforest half a continent.

Not bad for useless.

Some years ago a Hallmark greeting-card survey revealed America's favorite image to be that of a blasted tree on a windy hilltop. That Lincolnesque icon of lonely strength speaks to us all. Yet it tells only half the story. The other half is that trees and forests are mercurial shapeshifters, tireless travelers marching to the slow drum of climatic change. Ancient as dinosaurs, modern as the new face of Mount St. Helens, they're forever poised to green our world anew.

Gary L. Saunders, with 26 years in extension forestry in Nova Scotia, is the author of six books and numerous natural-history articles.