Part 4

Elevation exerts an additional restriction on the distribution of tree species. Since climatic conditions vary with change in elevation—lower temperatures resulting in shorter growing seasons, and increased wind exposure resulting in greater loss of moisture through evaporation—we would expect to find the forest composition change as we ascend a mountain slope. In Glacier, eastern valleys average 240 meters higher than western, and thus even if they had more moisture they would not sustain the redcedars and hemlocks. All plants have range limits, some narrow, some broad; and they excel where their particular set of preferences as to moisture, soil, sunlight, and wind exposure are best met. On sites that do not meet their optimum requirements, they face being crowded out by species better adapted to the prevailing conditions.

Physical features of the land determine vegetation also. Certain trees prefer the moist areas along a streambed—the great black cottonwoods, for example. And on steep hillsides, avalanches prevent the growth of climax trees, permitting instead only shrubby, pliant growth—mountain-ash, mountain maple, alder, menziesia.

Forest communities are named for their dominant tree species. Thus, an area in which Douglas-fir dominates is called a “Douglas-fir forest.” Glacier does have forests in which Douglas-fir is the climax species; these are chiefly dry areas, below 1,800 meters, with south and west exposures. But we usually associate the park with its Engelmann spruce-subalpine fir forests, found extensively between 1,200 and 2,100 meters, and with the western redcedar-western hemlock forests in the McDonald valley.

Because forests mature slowly and change is usually imperceptible, we are tempted to think of them as static and eternal. But since a forest is a community of living things, it responds to changes in the environment. Subtle physical or climatic changes, such as a rising or falling water table or a slight increase or decrease in annual precipitation, will favor some species of trees and hinder others, eventually altering the composition of the forest.

Other changes are more dramatic. Most notable of these is fire.

From Fire to Forest

Heat lightning, glimmering soundless behind the western peaks. Then the first low rumble. At first the flashing had been from cloud to cloud, but now, as the storm nears, the first ground-spears appear, lighting up the night. Here is a big storm, many-celled, engulfing more and more territory beneath its angry bulk. Lightning dances into the dry August forest. In their towers the lookouts stay awake.

Close strike and a flare-up! The ridge snag burns like a Roman candle, sending bright embers down. Valley, ridge, and peak blink on and off with blue light as the storm roars like night-firing artillery.

Passing overhead, the low cloud belly brings a sudden lash of rain. But it is not enough: tomorrow will mean long hours of fire watch.

The next day dawns clear, a morning of heavy dew. The ridge strikes did not ignite the forest. Inspecting the storm path, aircraft and lookouts find no evidence of fire.

But two days later, in a morning of high wind, thin smoke plumes rise upward. Smoldering in the thick duff of the forest floor, a lingering hot spot explodes with the fanning wind. It quickly spreads from a hectare to ten while the quadrants are called in and the hot-shot crews dispatched; then to a hundred, bringing in the smoke jumpers and mobilizing the vast fire-control network. A thousand hectares, perhaps ten thousand might burn this week of big fires.

In the resulting skeleton forest, the scene of devastation is almost overpowering: life seems forevermore excluded from this blackened ruin. But fire is nothing new to forest communities. We may think fire demonic because it takes from our life span this block of mature forest, a sight we will never again see in this place. But nature does not operate in terms of human time scales. This forest is simply pushed back closer to its starting point, to begin again its long progression toward a climax vegetation cover.

Forest Succession

Through a series of complex vegetation stages, each characterized by different herbs, trees, and shrubs, the forest slowly returns to the type of vegetation best suited to the physical and climatic conditions of the site; this is called a climax community. The fact that most of Glacier’s forests are in some stage of recovery from fire accounts in part for the mosaic of forest cover found here.

The forest of Huckleberry Mountain on the Camas Creek road was consumed in the 1967 fire. By 1969, among the charred, lifeless trunks of the former forest, lush grass and sunloving fireweed, thistle, and paintbrush were growing. And by 1974 lodgepole pine seedlings along the road were a meter or two high. Lodgepole is a fast-growing tree that requires full sun to germinate. Forest fire is necessary for the regeneration of these trees: the intense heat causes the tightly closed cones to open, releasing the seeds that will establish the forest. So young pines developed among fireweed, spiraea, willow, and mountain maple shrubs.

The lodgepole forest near the western entrance to the park has been developing since 1929, when fire destroyed the redcedar-hemlock forest in the area between Apgar and West Glacier. Beneath the scattered spires of old larch that survived the burn, the lodgepoles have now grown up, forming a canopy that shades the forest floor. Because lodgepole live only about 80 years and will not germinate in shade, this forest will not exist long. Shade-tolerant Douglas-fir, white pine, Engelmann spruce and western redcedar seedlings are now taking hold. But the physical characteristics of this area—the climate, terrain, and soil—are ultimately most favorable for western redcedar and hemlock; and unless other disruptions intervene, this area will eventually again become a dense redcedar-hemlock forest.

But this will not happen quickly. The soil after hundreds of years of collecting debris will again become rich and moist. Young hemlocks will germinate on and near decaying logs. When old larches, firs, and pines fall, the slow-growing redcedars and hemlocks will take their places in the canopy.

Forest succession is a more complicated story than this; it is a fascinating study involving herbs, shrubs, small and large trees, and animal populations. From location to location it will vary; only in its broad outlines is it predictable. It is based on the observation that, given time, a forest—or any other plant community—will progress until it reaches climax—that is, the stage that will perpetuate itself.

■ How then are we to think about fire? Increasingly, experts are concerned not so much with fire suppression as with fire management. For suppression has at least three disadvantages: it allows the accumulation of unburned fuels that can result in “fire storms” when they are finally ignited; an undiversified climax forest is more vulnerable to disease than is a mixed forest; and a dense forest canopy discourages shrub growth, an important food source for deer, wapiti, moose, and smaller animals.

As the well-being of the deer herd depends on the predators that thin its numbers, so the long-term well-being of the forest depends on fire to rejuvenate it periodically. We must realize that wilderness is identified with fire, landslide, avalanche, windfall, and flood. Nature not only has learned to cope with these agents of change—she depends upon them for maintaining the delicate balances between landscape and life. There is in the business of nature, after all, more than the pleasing of man’s eye.

Spruce Morning

Of all times to get a rock in my boot! I had just started out, the morning was still cool in this eastern valley, and the heavy pack was not yet biting into my shoulders. Sitting down beside the trail, I leaned the pack against the base of an old spruce and began unlacing.

I could hear the scratching of the red squirrel descending to investigate, but I didn’t look up until it let go with long indignant chatter at finding its territory invaded. I plunked out the pebble and began relacing my boot. Cautiously the squirrel came down, pausing frequently to scold, its lower jaw quivering with rage and exposing yellow rodent teeth. Neighboring squirrels joined in and soon the trees danced with flicking tails.

Down the squirrel came, almost to the ground, then raced back up the tree, stopping at each lateral branch to deliver a vocal broadside. Finding no danger to themselves, the other squirrels soon quit the uproar and went about their morning business. I was beginning to suspect that I was committing some graver offense than the mere exercise of squatters’ rights—perhaps I threatened its cache of fir cones. Then into the corner of my vision shot another form, streaking soundless as a shadow; the squirrel also saw it—but too late. With a thin terrified squeak, the rodent started to go higher; but the pine marten was above it. The squirrel quickly reversed itself, sending bits of bark showering down.

As the squirrel leaped from the tree in desperation, the marten overtook it in mid-air; they came down together. Clamping the limp creature firmly in its jaws, the marten strode up the incline of a fallen spruce. Before it hopped off onto a shelf of higher ground to disappear, it looked briefly back at me. I fancied I could read, fixed in its eyes, a certain recognition of my having distracted its prey.

A breeze made me shiver, snapping me back from that swift vision of luxuriant fur, that blinding grace which flashed its orange throat-patch through the trees, and I realized I was sweating. For a moment I had been that squirrel, eyes wide with terror, seeing fate bear down, and powerless before the natural order of things.

The incident got the other squirrels singing again; but the confidence was gone, and soon it was quiet. What dreams do squirrels dream, I wondered, looking around. I saw that place more clearly then, having been caught between a marten and its prey. I saw each spruce: its age, its condition, the onslaughts it had borne; the beargrass coming up in an opening; and down the trail a meadow that was yellow, white, and red with sulphur plant, mariposa, and Indian paintbrush. Bees, flies, spiders, and butterflies worked that little garden tucked among the crowding trees. Countless forms of life beneath the soil and bark, in tunnel, crevice, hole, and pocket, working unseen to sustain their lives, and somehow, when all were added up, maintaining the forest as well.

A flicker called, its loud _Klee-yer_ breaking the forest hush. Birds, mammals, plants, insects—all hide together here, their lives so skillfully embroidered that no loose thread exists that my mind might grasp to unravel and understand the work.

The forest had once been a place that obstructed my view, a great blank to stride through, a few hours of necessary blur before the high lake or pass was reached. Now I was quite content to remain awhile beneath these great-boled trees.

■ A forest, like the mountains themselves, supports various levels of life. The floor and substratum are a great processing plant where bacteria, fungi, and insects work, decomposing the plant and animal litter, recycling dead and discarded tissue back to simpler organic compounds, gases, and minerals, thereby providing sustenance for growing plants. As spiders, shrews, wrens, and thrushes seem to know, there is good hunting on the forest floor.

Just above the forest floor is the herb layer, a seasonal layer of growth including flowers, mushrooms, grasses, and other small plants.

Above that grows the shrub layer, then the understory of young trees awaiting their chance to take a place in the forest’s canopy high above. From the swaying canopy, exposed to the full force of sun and wind, to the dim, moist floor, the forest provides a wide range of habitat.

Relatively few animals live in the treetops. The almost incessant motion makes nesting too hazardous for birds. Red squirrels venture up to cut cones in the canopy, but store their booty and make their nests farther down.

In the mid-range between canopy and understory, goshawks and Cooper’s hawks nest. Woodpeckers, nuthatches, and sapsuckers forage on the tree trunks and nest in cavities they excavate or appropriate. Red squirrels and the nocturnal flying squirrels create a major traffic here, along with the martens and owls that hunt them.

The understory and shrub layers house the greatest numbers of nesting birds. Here the effects of storm and rain are minimized and protective cover is greatest. Vireos, thrushes, warblers, hummingbirds, bluebirds, flycatchers, and others can be found among the tangle of this sometimes impenetrable layer.

The most populated area, the forest floor, supports an astonishing abundance of organisms. Below the busy traffic of mice, shrews, and larger animals is a bewildering array of insects and other invertebrates. The attrition rate in the litter of the forest floor—a continual battleground difficult to comprehend—is enormous. The smaller the organism, the greater its numbers are likely to be. This humus-rich, moist soil teems with bacteria, and a handful will contain surprising numbers of small spiders, pseudo-scorpions and almost microscopic mites.

Each year some two to three thousand kilograms, dry weight, of falling material litter an average hectare of forest. All this plant and animal waste—twigs, leaves, limbs, fallen trees, feathers, hair, feces, and carcasses—is processed by the armies of decomposers that thrive on the forest floor. With the aid of larger creatures that break up the plant and animal tissue, most microscopic bacteria are able to decompose from a hundred to a thousand times their own weight every day.

Few trees die of old age in the forest. The seedling mortality rate is necessarily high, since far greater numbers of seeds germinate each year than can reach maturity. Of those that do, many fall victim to the ever-present dangers of disease, insect infestation, windfall, stream erosion, and fire. Insects alone present a formidable threat to trees, for they have evolved every means of attack—chewing and mining leaves, boring into twigs, eating cambium and heartwood, sucking sap, triggering galls. If the insect world did not police itself, aided by spiders, insectivorous birds and other animals, forests and other plantlife would quickly fade before the chewing, boring, sucking horde.

■ Through the trees the light on Citadel shows the morning slipping by. As I start to get up I see a garter snake sliding out into the dusty trail, seeking the sun-warmed earth. Moving slowly, alert for danger, it probes the air frequently with its sensitive tongue. But against the lightcolored duff its dark shape offers a fine target, begging attack. A chipmunk, watching from a nearby lookout stump, twitches its tail nervously over its back, curious—perhaps suspicious—at the sight of a snake. Very slightly the snake’s head goes up, its tongue flickering. For a few seconds reptile and rodent regard each other. Then the chipmunk drops back soundlessly into its hollow stump, and the snake lowers its head onto warm ground.

Some day soon, a sparrowhawk or weasel will interrupt the snake’s morning sun-bath. The snake will fuel bird or mammal for a time, as mice, fledgling birds, and insects now sustain the snake. The chipmunk too, rummaging nearby, lives in shadows of talon and tooth.

Until that time of sharp encounter, each has its own niche, a way of life, a shaft of sun, and food enough.

A Walk in the Redcedar Forest

Climax! The word takes on a true significance here, among these broad-based trees. When you enter this forest the road noise does not follow far—as, when you walk into a cave and turn a corner, sound and light are left behind. There is a surprising spaciousness, a feeling of openness in a mature western redcedar forest. With scant understory and the canopy so far above and everywhere complete, it seems like some vast, high-ceilinged catacomb, pillared by the huge, shaggy-barked cedars and the deeply scored trunks of the black cottonwoods. The floor is strewn with fallen giants in magnificent disarray, uplifted roots still grasping fractured rock.

A rainy day is a good time to walk a cedar trail, when the dull light seems to shine from the wet moss, making the underleaves of devil’s-club and Rocky Mountain maple glow. Wind and rain, like light, penetrate with difficulty the latticework of this canopy; thin lines of fog develop over the bogs. The air is fresh with growing plants, snow-cold still when the first spring flowers appear.

Fiddleheads of unfolding lady ferns line the trail in May, pushing up from the hub of last year’s leveled, lifeless fronds. Beds of trillium shine their white, three-pointed flowers like flashlights in the dark recesses. Unlike the small, hidden calypso orchid, which bears its purple spikes and yellow throat low above the moss, the trilliums make no secret of spring growth. They are bold, handsome plants, broad-leaved and tall, with waxy white petals that tinge to purple in their month-long bloom.

Moss covers everything. Boulders are green and weightless-looking, resilient and topped with miniature forests of cedar seedlings. Ancient fallen trees are disguised with blankets of moss, sprouting hemlock here and there. The rich greens that characterize Glacier’s summers seem to begin here amid the moisture-glossed leaves of twinflower, bunchberry and bead-lily.

Later, the spiders will spin thousands of kilometers of gossamer filament among the trees. The orb-weavers will hang their webs high and low, suspended in every opening. Walking through the forest then, you will see shafts of sunlight whirling in the higher webs until they seem like tops set spinning among the treetrunks.

Indianpipes, the “ghost flowers” that need no light to grow, will break through the forest soil. Like mushrooms, with fruiting bodies that are nourished by underground mycelia, these saprophytes absorb their nutrients from a fungus that covers their roots.

Receiving an average of about 18 centimeters more annual precipitation than forests east of the Divide, Glacier’s redcedar-hemlock community hoards its moisture. Its dense growth and the surrounding mountain walls inhibit the circulation of drying winds. Mosses and ferns transpire their moisture, which you can feel; place your hand close, and you will sense a coolness like the air exuding from an ice cave. Draped from the tree limbs are long filaments of squawhair and goatsbeard, black and grey lichen strands that flourish in the damp air.

Except for the black bear, few large animals inhabit the deep forest. Grizzlies find better forage in meadows or along the forest edge. Since shade discourages shrubby undergrowth, deer and wapiti will search elsewhere for browse. In summer, wapiti, grizzlies, and mule deer bucks tend to wander up into high meadows.

Contrasted to the noisy, conspicuous birds of the prairie—meadowlarks and bobolinks—birds of the forest seem elusive and secretive. Although numerous, the varied thrushes, Townsend’s solitaires, and Swainson’s thrushes are seldom seen; but when approached, they fly silently off and are swallowed by the forest shadow.

There seems to be serenity in a mature forest, as though the struggle for life is somehow suspended, the needs of the animals here less urgent, muffled. The towering redcedar forest seems to be no battlefield at all, but rather a monument to what Earth can do.

The Perpendicular Night

Behind Avalanche campground a trail leads back toward Lake McDonald Lodge. I decided to follow it one June evening, to experience the sensation of the deep forest changing into night. With the nearby mountain wall intercepting the sun, dusk comes early to this valley. On the prairie, night passes across the landscape in an even line, forthright as a waxing tide; you can almost feel the globe in its turning from the sun. There is reassurance in the night’s coming, its steady purple doming over the sky.

But here darkness seems to sprout from the earth. It collects beneath the hemlock clumps, bridges the creekbottoms. It seems to flit from place to place. You look about, uneasy, trying to catch it here or there, but always miss its infiltrations. It captures the narrow clearings when you look away; pockets of tree-darkness join together, forcing the light upward until the tree-tops seem impossibly bright and distant.

Through the trees I could see a dozen fires dance in the growing shadow, wood-smoke and camp sounds filling the air. Turning uptrail, I felt a reluctance to leave the presence of those fires—a senseless feeling, but strong. A growing forest-dread impelled me almost physically backward to those circles of firelight. I felt the need to be near a fire, to be reassured by heat and light. Fire was our greatest friend, our greatest weapon. With it we beat the long ages of ice and held the forest gloom away. There was no harm here, only silence; yet the longer I walked, with beard-moss hanging down like daggers all around, the more I craved the comradeship of fire.

_Continued on p. 104_

The Vital Predator

The merciless law of predation might at first thought seem cruel; but the predator plays a vital part in maintaining the balance of the biotic community. Without the controlling factor of predation, prey species quickly enlarge their populations. If plant eaters are not checked, the resulting excess population exceeds the carrying capacity of the range. Food supply rapidly diminishes. In a damaged range, competition and stress result, usually culminating in a massive die-off through starvation and disease.

Ironically, predators thus provide a service to their prey. First to fall to the predator are the old, the diseased, the unwary, and the young. By removing many young and old deer from a typical herd, cougars lessen competition among the deer for choice range, thus tending to keep herbivore numbers at parity with the land’s carrying capacity. Only the strongest and wariest deer survive, ensuring that the fittest will continue the species. When man upsets this delicate balance—destroying predators in the hope of increasing numbers of game animals—the result is ecological disaster. In the 1930s, in a misguided attempt to “preserve” the whitetail deer herds of the park’s North Fork area, many coyotes and cougars were exterminated. In 1935 alone, 50 cougars were killed. Relieved of the pressure of predation, the deer flourished. In a few years, however, the normally adequate range was severely overbrowsed. Suffering also from this imbalance were wapiti (“elk”) and moose, ungulates that share the winter range with deer.

Some predators are more specialized than others. The Canada lynx, for example, has oversize feet, an adaptation that helps it move across deep snow without breaking the surface. As a result, it is an efficient predator of the snowshoe hare, another large-footed animal. Relying on this adaptation, the lynx feeds almost exclusively on snowshoe hares. Consequently, its numbers inevitably fluctuate with the 10-year “boom and bust” cycle of the snowshoe.

The coyote, on the other hand, is a generalized predator, exploiting whatever prey is currently abundant. Should mice or ground squirrels be in short supply, it will subsist on anything from grasshoppers to berries until favored prey again becomes available. (Animals that normally eat both plant and animal food are referred to as omnivores.) Generalized predators are thus better equipped to survive temporary ecological imbalances, maintaining their numbers at relatively consistent levels from year to year.