Plant-and-Animal Communities

The mink, a solitary predator associated with low-elevation watercourses, preys on anything it can catch and subdue.

I like to begin with St. Mary, a lake the whitecaps love to run. From the far passes the several winds gather and collect, arranging long lines of white waves for the race downlake. Past the purple scree of Mahtotopa and Little Chief they go, white as the headdress of Going-to-the-Sun Mountain, colliding, collapsing along the promontory snares about the Narrows. Onward they press, spreading out and setting sail for the straight rush to the final shore where a line of cottonwoods sings with a sound like applause.

Across the lake the timbered ridge starkly contrasts the finger of prairie that claims the north shore. This is a flower-glad place, a meeting-ground for mountain and prairie plants. Along the road the grassland holds the conifers back, allowing only scattered clumps of aspens.

Finally, at Rising Sun, beneath the shadow of Goat Mountain, the prairie ends and wind-seasoned Douglas-firs announce the coming forest.

There’s excitement now, with the prairie heat gone, the wind scent raw with fir and high meadows, honed by waterfall and tall, dank rock. Our mountain thirst is never extinguished, and a road that tightens down to cliff face and sudden turn brings back to our blood the ancient need to go to the highest place.

There is sword-edged Citadel, and the snow-flanked spike of Fusillade holding court like a queen in this valley of peaks; then the dome of Jackson and the Gunsight notch. Our eyes are kept high, transfixed at last by looming Heavy Runner and the distant promise of Reynolds.

Looking for mountain goats, we scan the walls around the sweep of Siyeh Bend, catching a glimpse of the trail that crosses the scree to hidden Piegan Pass.

Beargrass heads lean out above the road like old men conferring on the view. The purple trumpets of penstemon crowd the rocks, and spots of Indian paintbrush lead like a blood-trail to the higher slopes.

Intoxicated now, feeling the fresh full force of the wind from Logan Pass, we race on. We hardly notice the struggle of the forest in Reynolds Creek far below, how it thins and loses strength in its own hard climb. We sweep past it on the broad magnificence of this pass.

Level but a moment, the road dips to a shelf on the headwall above Logan Creek and swings over the great sculptured cliff of the Garden Wall. For several kilometers this masterpiece of a road glides down a constant grade, squeezed between rock face and space, twisting into tight drainages—a road for storm lovers, wet with spray and snow-seep, its quick turns concealing sudden winds.

Mighty, snow-robed Heaven’s Peak appears, taking our attention from the Pass-group mountains and the hanging valleythat spills Birdwoman Falls. Northward is the great array of peaks encircling distant Flattop, jumbles of mountains and glaciers. How are we to notice the forest far below?

Not until we have passed the Loop and are moving past the blackened snags of a recent burn do we realize the stature of this forest. The long road down will take us into a valley much deeper than any on the eastern side. Near Avalanche Creek are trees we have seen nowhere else in the park—giant western redcedars, western hemlocks with their nodding tops, monstrous black cottonwoods with bark so deeply furrowed that it looks hewn by hatchet.

We take a long ride down the valley, past the low pyramid of Mt. Stanton, final peak in the Livingston Range. Near the outlet end of Lake McDonald, birch and aspen again appear in numbers, and the road enters a crowded stand of lodgepole pine.

Our memories cluttered with mountains, waterfalls, and snowfields, we do not quite realize the significance of this 80-kilometer journey. We have crossed the boundaries of several different plant-and-animal communities, spanning a range of climate that would be encountered on a 5,000-kilometer north-south journey at sea level.

At first glance the various trees, wildflowers, and animals seem randomly distributed, scattered about like the distant mountains. But mountainous terrain represents an organized high-rise approach to life. From the lowest, most protected valley to the highest wind-and-ice-cut summit, the life-forms align themselves, each according to its own climatic tolerance.

Here too can be seen the great cycles of nature: fire and regrowth, the building of soil and its erosion, the incessant duel of the eaters and the eaten.

In the following sections we will spend some time in these various communities, from prairie to tundra.

There is something about spring on the prairie that gets me up before dawn. I like to watch the seasons change their guard over the landscape, from the wintry cold of pre-dawn dark to the spring-scented morning air to the hot summer-foretaste of the noon May sun.

Hoarfrost surrounds these patches of pasqueflowers, blue goblets on downy stems. On this windless night, frost has formed everywhere, reclaiming for a time its vast winter range, sparkling over the green handiworks of spring.

But the god of the growing grasslands is the sun, and it now proclaims itself, stretching out to make the mountains shine. With its assault the frost collapses, becoming bright beads on grass tip and leaf joint by which a beetle might refresh itself.

Spring is best perceived ant-level, at its ground beginnings, where the bright yellow-green tips of new grass shoots reclaim the winter-blighted land. I look closely at a drag line of spider silk; a necklace of dewdrops slides down, collects to a moment’s greatness, in which I briefly see a curved horizon, the morning sunburst, and myself, before it falls away.

Getting up from my prone position, my belly damp from the prairie earth, I startle a whitetail jackrabbit; bounding high, it zigzags off. The commotion disturbs a distant badger, which faces about from its diggings to confront danger in whatever form it might take. It swings its snout to scent the air. Somewhat uncertainly, it returns to the business of hunting, then hesitates, swings about once more and waits, myopic, patient.

Satisfied at last, the spurt of the now distant rabbit lost in its brain, the creature snorts a defiance at the mystery and resumes its morning gopher hunt.

Overhead a marsh hawk skims past, its flight erratic as a butterfly’s. Far away a magpie rattles at the passing hawk and takes flight, briefly flashing black and white.

■It is easy to see only pieces in the natural puzzle—a badger throwing dirt, horned larks dipping into wind, black ants dragging the rosette of a dead spider—and be satisfied with the scattered scenes. But at last, to make it meaningful, we must complete the picture. There is that special joy in discovering larger schemes: green plants utilizing sunlight; a rabbit building its days at the plants’ expense; the falcon tearing the rabbit meat for its young; magpies picking at the fallen falcon; and then, in the end, all returning to the earth.

Here on the prairie, as in every plant-and-animal association, the ancient drama repeats itself over and over; the distant tundra is a drastically different stage with different actors, but the cycle is the same. Life depends upon the interaction of all itsmany forms. Unseen bacteria are as necessary to the land as green grass; the meadow vole and the coyote are as much a part of the prairie as the grasses.

The secret of life rests in the wonder of photosynthesis. Only green plants can manufacture food from the earth’s raw minerals. This is the vital first step upon which the great pyramid of animal and plant life is built. Using energy from the sun, green plants combine water and carbon dioxide to synthesize sugar, and give off oxygen as a by-product. The caterpillar takes its energy from the plant tissue, converting to protein the sugar and minerals in its body. The caterpillar is then food for a spider or other predator. A yellow warbler may take the spider and in turn be ambushed by the prairie falcon. Thus the energy produced by the plant travels through the food chain. When the prairie falcon dies, scavengers—including insects and other invertebrates, birds, and mammals—redistribute its wealth among themselves; the rest is decomposed by bacteria. Thus, eventually, the nutrients on which the plants depend return to the soil.

When we look at any living organism, whether it is plant, herbivore, carnivore, parasite, scavenger, or decomposer, we are soon made aware of its associations with other living things, each puzzle piece leading us to another and another. We begin to see a picture whole—the fox, meadow mouse, grasshopper, bunchgrass, and sparrow hawk—all interlocked.

Geologically speaking, grasslands are a recent development. As the Rocky Mountains were being uplifted, the prevailing warm, moist climate began to change. The rising mountain mass intercepted moisture-laden winds that blew in from the Pacific, creating a rain shadow that lengthened eastward as the mountains rose higher. A continental climate, characterized by severe winters and dry, wildfire summers gradually took shape, extinguishing the great forests that had grown across the continent’s interior. Herbaceous plants, which had been evolving amid the forests, inherited the land.

Unlike trees, grasses die back to the ground each winter, hoarding their life-germ beneath the protecting soil. Growing not from the tip but from the joints, grasses regenerate quickly after fire or grazing. Suspension of the normal metabolic processes enable the grasses to go dormant and thus survive periods of severe heat and drought.

Although the great prairie sea washes up against Glacier’s eastern boundary, with estuaries probing into the mountain valleys on the drier, south-facing slopes, the grassland community comprises less than 5 percent of the land area of Glacier National Park. This includes the puddles of prairie west of the Divide that interrupt the dense coniferous forests along the North Fork of the Flathead River.

From the pasqueflowers that bloom in early May to the asters and goldenrod of September, these summer-long gardens of grasses and flowers lean with the wind. Here are timothy, oatgrass and the bunchgrasses—rough fescue, bluebunch fescue, and bluebunch wheatgrass. Among the grasses bloom bitterroot, blue camas, lupine, gaillardia, balsamroot, cinquefoil, sticky geranium, and wild rose.

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The Forests of GlacierFrom the lush redcedar-hemlock forest in the McDonald Valley to the subalpine fir, whitebark pine, and Engelmann spruce struggling for existence near treeline, the forests of Glacier reflect the conditions of temperature, exposure, soil, and drainage prevailing; and each forest has its characteristic association of understory trees and shrubs, herbaceous ground cover, and vertebrate and invertebrate animal life.

The Forests of Glacier

From the lush redcedar-hemlock forest in the McDonald Valley to the subalpine fir, whitebark pine, and Engelmann spruce struggling for existence near treeline, the forests of Glacier reflect the conditions of temperature, exposure, soil, and drainage prevailing; and each forest has its characteristic association of understory trees and shrubs, herbaceous ground cover, and vertebrate and invertebrate animal life.

Life ZonesMany physical and climatic factors determine the range of Glacier’s plant-and-animal communities. Boundaries between communities are seldom sharply defined, but rather merge together in broad zones of transition.With elevation gain, average daily temperature drops at the rate of 5° per 900 meters. Precipitation, wind velocity, and evaporation loss increase. Soil thins. These factors, along with others such as fire frequency, north or south exposure, and availability of moisture, combine to determine the range of each community.In the forest community below 1,800 meters, Douglas-fir, lodgepole pine, and western larch predominate. In the valleys, Engelmann spruce and subalpine fir are found. The somewhat lower and much better watered western valleys of the park support western redcedar and western hemlock.Treeline is the upper limit to which the tolerances of trees to environmental conditions permit them to grow. Because there are so many controlling factors (wind, temperature, exposure to sunlight, snow cover, etc.) treeline in the diagram is only approximate. In Glacier it averages 2,000 meters. Avalanche chutes or sheer cliff walls may suppress it to below 1,500 meters; on protected slopes it may be as high as 2,150 meters.At the eastern edge of the park below 1,200 meters, the forest gives way to the prairie community, composed mostly of soft-stemmed plants adapted to the conditions of low precipitation that prevail here in the rainshadow of the mountain range. Clumps of aspen, found in the prairie in sheltered spots, occur here in the transition zone between prairie and forest.

Life Zones

Many physical and climatic factors determine the range of Glacier’s plant-and-animal communities. Boundaries between communities are seldom sharply defined, but rather merge together in broad zones of transition.

With elevation gain, average daily temperature drops at the rate of 5° per 900 meters. Precipitation, wind velocity, and evaporation loss increase. Soil thins. These factors, along with others such as fire frequency, north or south exposure, and availability of moisture, combine to determine the range of each community.

In the forest community below 1,800 meters, Douglas-fir, lodgepole pine, and western larch predominate. In the valleys, Engelmann spruce and subalpine fir are found. The somewhat lower and much better watered western valleys of the park support western redcedar and western hemlock.

Treeline is the upper limit to which the tolerances of trees to environmental conditions permit them to grow. Because there are so many controlling factors (wind, temperature, exposure to sunlight, snow cover, etc.) treeline in the diagram is only approximate. In Glacier it averages 2,000 meters. Avalanche chutes or sheer cliff walls may suppress it to below 1,500 meters; on protected slopes it may be as high as 2,150 meters.

At the eastern edge of the park below 1,200 meters, the forest gives way to the prairie community, composed mostly of soft-stemmed plants adapted to the conditions of low precipitation that prevail here in the rainshadow of the mountain range. Clumps of aspen, found in the prairie in sheltered spots, occur here in the transition zone between prairie and forest.

A Mountain ProfileThis diagram represents the eastward-facing slope of a hypothetical mountain near the eastern boundary of Glacier National Park. Its life communities are somewhat different from those of mountain slopes at the western edge, chiefly because of the differential in annual precipitation.Illustration: Here, above approximately 2,750 meters, in a realm of ice, snow, and barren rock, there is little life.Alpine tundraBelow 2,750 meters and above 2,000 meters, depending on other factors such as exposure to sun and wind and steepness of terrain, exists the alpine tundra community, with vegetation similar to that of the vast, essentially level, treeless zones of the Arctic.Scrub-forestRoughly between 1,800 and 2,000 meters, the dominant vegetation is scrub-forest. Trees here are stunted; except in sheltered spots they are more or less prone rather than upright. Net growth is slow, not only because of the short growing season but also because of the pruning effect of icy mountain winds. Very few tree species can survive in this harsh habitat.Coniferous forestIn the forest community below 1,800 meters, Douglas fir, lodgepole pine, and western larch predominate. In the valleys, Engelmann spruce and subalpine fir are found. The somewhat lower and much better watered western valleys of the park support western redcedar and western hemlock. Seepage 54PrairieAt the eastern edge of the park below 1,200 meters, the forest gives way to the prairie community, composed mostly of soft-stemmed plants adapted to the conditions of low precipitation that prevail here in the rainshadow of the mountain range. Clumps of aspen, found in the prairie in sheltered spots, occur here in the transition zone between prairie and forest.

A Mountain Profile

This diagram represents the eastward-facing slope of a hypothetical mountain near the eastern boundary of Glacier National Park. Its life communities are somewhat different from those of mountain slopes at the western edge, chiefly because of the differential in annual precipitation.

Illustration: Here, above approximately 2,750 meters, in a realm of ice, snow, and barren rock, there is little life.

Alpine tundra

Below 2,750 meters and above 2,000 meters, depending on other factors such as exposure to sun and wind and steepness of terrain, exists the alpine tundra community, with vegetation similar to that of the vast, essentially level, treeless zones of the Arctic.

Scrub-forest

Roughly between 1,800 and 2,000 meters, the dominant vegetation is scrub-forest. Trees here are stunted; except in sheltered spots they are more or less prone rather than upright. Net growth is slow, not only because of the short growing season but also because of the pruning effect of icy mountain winds. Very few tree species can survive in this harsh habitat.

Coniferous forest

In the forest community below 1,800 meters, Douglas fir, lodgepole pine, and western larch predominate. In the valleys, Engelmann spruce and subalpine fir are found. The somewhat lower and much better watered western valleys of the park support western redcedar and western hemlock. Seepage 54

Prairie

The Forest CommunityA forest is organized vertically like an apartment house or office building, with layers corresponding to stories. Thecanopyis the branches and foliage of tall trees that form a roof over the community. Below the canopy are theunderstorytrees: young individuals of the canopy species; and small, shade-tolerant trees that will never become part of the canopy. Beneath the understory branches is theshrub layer, occupied by knee-high-to-man-high woody plants; beneath that is theherb layer, where most of the ferns, wildflowers, grasses, and smaller woody plants grow. Theforest flooris the zone of mosses, mushrooms, creeping plants, and forest litter (leaves, twigs, needles, feathers, bits of bark, animal droppings, etc.). The forest has a “basement,” too, interlaced by plant roots, mycelia of fungi, and tunnels of myriad animals.Each layer of the forest has its characteristic animal species, but most forage over more than one level. Some nest in one story and feed in another. The red squirrel races back and forth from the forest floor to the highest branches.The forest community also has a socio-economic organization. Every animal (and plant) takes up space and consumes a portion of the available nutrients. Each has a place in the community food chain—as, for example,herbivore,carnivore, orscavenger. Each directly or indirectly affects all the other organisms.The Forest CommunityThe role of a species in the community, like the job and social function of a person, is itsniche. Similar species of animals have different niches, thus lessening competition for food and living space. Thrushes hunt close to the ground; vireos and kinglets hunt among the branches; flycatchers snap up airborne insects. The flicker feeds upon insects, excavates nesting holes that are later occupied by other species such as squirrels and owls, and is preyed upon by the great horned owl; its niche isinsect exterminator / food for carnivores / homebuilder. The great horned owl, hunting mammals, birds, and reptiles by night, preys on species different from those hunted by the goshawk, and thus occupies a parallel niche. When it dies, its remains, like those of other animals, are decomposed and return to the soil.

The Forest Community

A forest is organized vertically like an apartment house or office building, with layers corresponding to stories. Thecanopyis the branches and foliage of tall trees that form a roof over the community. Below the canopy are theunderstorytrees: young individuals of the canopy species; and small, shade-tolerant trees that will never become part of the canopy. Beneath the understory branches is theshrub layer, occupied by knee-high-to-man-high woody plants; beneath that is theherb layer, where most of the ferns, wildflowers, grasses, and smaller woody plants grow. Theforest flooris the zone of mosses, mushrooms, creeping plants, and forest litter (leaves, twigs, needles, feathers, bits of bark, animal droppings, etc.). The forest has a “basement,” too, interlaced by plant roots, mycelia of fungi, and tunnels of myriad animals.

Each layer of the forest has its characteristic animal species, but most forage over more than one level. Some nest in one story and feed in another. The red squirrel races back and forth from the forest floor to the highest branches.

The forest community also has a socio-economic organization. Every animal (and plant) takes up space and consumes a portion of the available nutrients. Each has a place in the community food chain—as, for example,herbivore,carnivore, orscavenger. Each directly or indirectly affects all the other organisms.

The Forest Community

The role of a species in the community, like the job and social function of a person, is itsniche. Similar species of animals have different niches, thus lessening competition for food and living space. Thrushes hunt close to the ground; vireos and kinglets hunt among the branches; flycatchers snap up airborne insects. The flicker feeds upon insects, excavates nesting holes that are later occupied by other species such as squirrels and owls, and is preyed upon by the great horned owl; its niche isinsect exterminator / food for carnivores / homebuilder. The great horned owl, hunting mammals, birds, and reptiles by night, preys on species different from those hunted by the goshawk, and thus occupies a parallel niche. When it dies, its remains, like those of other animals, are decomposed and return to the soil.

Sun, Green Plants, and AnimalsThe sun is the source of energy for any plant-and-animal community. Green plants draw nitrogen and minerals from the soil, and in a process called photosynthesis use sunlight to convert raw materials (carbon dioxide and water) into carbohydrates (sugar, starch, cellulose), giving off oxygen as a by-product. Besides burning oxygen, animals depend on plants for food.Green Plants, trees and shrubs, grasses and sedges, wildflowers, ferns, mosses, algae and lichens—are fed upon by animals, which are unable to manufacture their own food.The Redback Vole, like other rodents, pikas and hares, seed-eating birds, grazing and browsing hoofed animals, and herbivorous insects, derives its energy from the seeds and other parts of green plants that it eats.The Garter Snake, feeding upon the vole, is dependent upon plants even though it does not eat them.The Great Horned Owl, preying upon the garter snake, is one more step removed from the green plants—but still dependent on them.Scavengerssuch as carrion beetles feed upon the carcass of the owl; the remains are then attacked byDecomposers, primarily bacteria, that break down the animal tissues into basic organic compounds.The Soil, enriched by the minerals and carbon and nitrogen compounds added to it by the decomposers (and by other processes such as fire) supports new green plant growth.Thus energy derived from the sun flows through the ecosystem in a food chain. A plant-and-animal community is a complex, interlocking web of such food chains.

Sun, Green Plants, and Animals

The sun is the source of energy for any plant-and-animal community. Green plants draw nitrogen and minerals from the soil, and in a process called photosynthesis use sunlight to convert raw materials (carbon dioxide and water) into carbohydrates (sugar, starch, cellulose), giving off oxygen as a by-product. Besides burning oxygen, animals depend on plants for food.

Green Plants, trees and shrubs, grasses and sedges, wildflowers, ferns, mosses, algae and lichens—are fed upon by animals, which are unable to manufacture their own food.

The Redback Vole, like other rodents, pikas and hares, seed-eating birds, grazing and browsing hoofed animals, and herbivorous insects, derives its energy from the seeds and other parts of green plants that it eats.

The Garter Snake, feeding upon the vole, is dependent upon plants even though it does not eat them.

The Great Horned Owl, preying upon the garter snake, is one more step removed from the green plants—but still dependent on them.

Scavengerssuch as carrion beetles feed upon the carcass of the owl; the remains are then attacked byDecomposers, primarily bacteria, that break down the animal tissues into basic organic compounds.

The Soil, enriched by the minerals and carbon and nitrogen compounds added to it by the decomposers (and by other processes such as fire) supports new green plant growth.

Thus energy derived from the sun flows through the ecosystem in a food chain. A plant-and-animal community is a complex, interlocking web of such food chains.

A Pyramid of NumbersNecessarily, the number of plants in an ecosystem far exceeds the number of plant eaters, and the number of prey species must exceed the number of predators. During its lifetime, a golden eagle will consume a vast number of lesser animals. The combined mass of prey animals necessary to sustain an eagle greatly outweighs the eagle itself. Ecologists refer to this proportional relationship of mass between each link in the food chain as thepyramid of numbers.The diagram represents a numbers pyramid for the alpine zone. Because of its limiting environment, the alpine zone supports a lesser plant mass than the forest zone. As a result, the carrying capacity of the alpine is less than that of the forest.1 KiloTertiary(third-order)consumersare the predators (Golden Eagle, Swainson’s Hawk, etc.) that feed upon other predators. Because of the 90% loss of energy at each level of the food chain, there will be very few hawks and eagles in comparison to the numbers of marmots.10 KilosSecondary consumersare the predators (weasels, shrews, carnivorous insects and birds, etc.) that eat herbivores. The animals at this level of the pyramid are often—though not always—larger than the animals they feed upon. But they are much less numerous, because it takes many prey animals to sustain one predator.100 KilosPrimary consumers(plant eaters, or herbivores) convert plant tissue into animal flesh. In the process about 90% of the energy stored as plant food is lost, mostly as heat energy. In the alpine community the herbivores include pikas, marmots, ground squirrels, and ptarmigan, as well as herbivorous insects.1,000 KilosProducersare the green plants at the base of the food pyramid, manufacturing food for the animals of the alpine community. Thebiomass(total weight) of each level of the food chain is ten times (more or less) the weight of the stage above it: 1,000 kilos of green plants will produce only 100 kilos of primary consumers.

A Pyramid of Numbers

Necessarily, the number of plants in an ecosystem far exceeds the number of plant eaters, and the number of prey species must exceed the number of predators. During its lifetime, a golden eagle will consume a vast number of lesser animals. The combined mass of prey animals necessary to sustain an eagle greatly outweighs the eagle itself. Ecologists refer to this proportional relationship of mass between each link in the food chain as thepyramid of numbers.

The diagram represents a numbers pyramid for the alpine zone. Because of its limiting environment, the alpine zone supports a lesser plant mass than the forest zone. As a result, the carrying capacity of the alpine is less than that of the forest.

1 Kilo

Tertiary(third-order)consumersare the predators (Golden Eagle, Swainson’s Hawk, etc.) that feed upon other predators. Because of the 90% loss of energy at each level of the food chain, there will be very few hawks and eagles in comparison to the numbers of marmots.

10 Kilos

Secondary consumersare the predators (weasels, shrews, carnivorous insects and birds, etc.) that eat herbivores. The animals at this level of the pyramid are often—though not always—larger than the animals they feed upon. But they are much less numerous, because it takes many prey animals to sustain one predator.

100 Kilos

Primary consumers(plant eaters, or herbivores) convert plant tissue into animal flesh. In the process about 90% of the energy stored as plant food is lost, mostly as heat energy. In the alpine community the herbivores include pikas, marmots, ground squirrels, and ptarmigan, as well as herbivorous insects.

1,000 Kilos

Producersare the green plants at the base of the food pyramid, manufacturing food for the animals of the alpine community. Thebiomass(total weight) of each level of the food chain is ten times (more or less) the weight of the stage above it: 1,000 kilos of green plants will produce only 100 kilos of primary consumers.

Great horned owls are the nocturnal equivalent of Cooper’s hawks and goshawks in the low-elevation forests of the park. Large and powerful, they are capable of taking prey as big as skunks. This young bird, disturbed on its day roost, clacked its bill and fluffed its feathers in a menacing manner.

The only sizable mature stand of ponderosa pine found within the park is along the North Fork truck trail. A scattering of old ponderosas growing at the lower end of Lake McDonald suggests that at one time ponderosa forests were more extensive in this region than at present.

A black bear near treelimit. Bears will eat almost anything, from ants to carrion, grass to garbage. Color phases include brown and blonde bears. Unlike the larger, more aggressive grizzly, which ranges out onto the plains, black bears are strictly forest creatures.

The water ouzel, or dipper, a creature of fast mountain water, is admirably outfitted to cope with its demanding environment. Stubby wings, chunky body, short tail, and oily plumage allow it to walk under water, where it scavenges for aquatic insect larvae and small fish. In flying up- and down-stream, ouzels never shortcut but follow the winding streamcourse.As long as there is open water, the dipper suffers no hardship from the mountain winter. Then, when the land is shut down and lakes are frozen over, this little bird carries on in its mountain-stream habitat, plunging into the cold water to find food, and pausing occasionally to sing.

As long as there is open water, the dipper suffers no hardship from the mountain winter. Then, when the land is shut down and lakes are frozen over, this little bird carries on in its mountain-stream habitat, plunging into the cold water to find food, and pausing occasionally to sing.

Ouzels construct their nests of living moss on cliff faces or ledges where constant spray keeps the moss moist. At fledging, the four young of this nest in Avalanche Gorge tumbled one by one into the torrent below, to be collected by the adults in quieter water downstream. Within a day they appeared to have mastered the underwater gymnastics and were feeding on their own.

From their lowland wintering grounds, wapiti move up to higher elevations in spring. Summer range in the park is abundant, but winter range is limited; as a result, wapiti have a tendency to increase their populations beyond the carrying capacity of available winter range. In a severe winter many starve. But in a balanced ecosystem such loss is not waste, for the carrion helps sustain scavengers; it is an important initial food source for bears emerging from hibernation.

Cedar waxwings nest in moist areas of low valleys where fruits and berries are abundant. Although they also subsist on insects (which they can capture on the wing), their weakness for fruit is so pronounced that the birds will sometimes gorge themselves until rendered incapable of flight.

The Columbian ground squirrel is found at all park elevations, from prairie to alpine meadow. Hibernation occupies almost three-quarters of its five-year lifespan. Unlike other park ground squirrels, it lives in colonies. Although not as tightly structured as a prairie dog town, the association is beneficial to all members in that danger is readily detected.

The tundra community is encountered above Preston Park on the Siyeh Pass trail. Mt. Reynolds, a classic example of a horn, dominates the distant Logan Pass area.

Camas blooms in the prairie community along the Red Eagle road. An important staple, camas bulbs were gathered as food by Indians.

Conspicuous also are many insects—including grasshoppers; flies; ants, wasps and bees; butterflies and moths; bugs; and beetles—which fulfill important roles as herbivores, carnivores, and scavengers while also acting as pollinators for flowering plants and providing an abundant food source for other animals.

Below the ground are the tunnels. Burrowing is an important means of survival on the open prairie, and life underground is extensive. Some of the animals are rarely seen—the northern pocket gopher, for example, with a diet of underground insects, grubs, worms, and roots, spends most of its life tunneling just below the surface. Others, like the badger, leave their burrows during the day to dig for rodents. Most conspicuous of the burrowing animals in the park’s grasslands is the Columbian ground squirrel. Its alert upright stance has earned it the nickname “picket pin.” When danger approaches from the air or on land, its shrill alarm whistle passes the warning to others of its kind.

Where prairie and forest meet, a never-ending struggle for dominion is waged. The isolated patches of prairie that dot the North Fork Valley near Polebridge hold the great forest of the park’s northwest region at bay.

This broad valley, floored with coarse glacial outwash and terraced downward to the deep channel of the North Fork River, presents a graphic battleground between grass and tree. Lining the upper terraces, from which they glower down on the dry, well drained grass flats like a line of warriors, are the Douglas-fir, western larch, and ponderosa pine. Seedling trees continually invade the prairie. But most perish early, their shallow roots no match for the extensive root systems of the fast-growing, moisture-greedy grasses. If encouraged by a series of wet summers, however, the young lodgepoles quickly gain stature. They had made significant inroads at Big Prairie when the disastrously dry summer of 1967 killed most of these 15-year-old pioneer trees.

These North Fork grasslands and the immediately surrounding lodgepole pine forests are an important spring range. Deer, wapiti, and grizzly—and, in the wetter areas, moose—graze or browse here. And here, low on the western slopes of the Livingston Range, are the park’s only stands of ponderosa pine, a tree that prefers warm, dry habitats. As a result, at low elevations it often merges with the prairie community.

Groves of aspen colonize the eastern prairies in areas where there is sufficient water and protection from wind. These aspen parklands are important havens foranimals. Wherever two differing communities interact, a phenomenon known as “edge effect” occurs. Here wildlife exists in abundance; the animals that favor forest cover mingle freely with those that prefer open areas. Aspen groves—supporting grasses, herbs, and shrubs beneath their thin canopies—are favored haunts for grouse, varying hare, deer, and wapiti, all of which find among the trees abundant food, shelter and concealment. Populations of insects, small mammals, and birds, which are high for the same reasons, attract a wide range of predators.

Isolated aspen groves are characteristically dome-shaped. Because aspens are capable of reproducing themselves vegetatively, the grove slowly expands outward from the parent tree. As a result, most of these groves are either exclusively male or exclusively female.

Since quick-growing aspens provide a bountiful food source for beaver, streams near these trees are often dammed by the rodents flooding lowlands and creating additional habitat in the form of willow flats. Another “edge effect” is established, attracting animals found near water. Waterfowl, marsh birds, moose, mink, muskrat, skunks, amphibians, and many others find such areas to their liking.

■Before the appearance of the white man, these eastern prairies were a paradise for animals. Once, on the summit of Rising Wolf, light-headed from the climb and the view of endless prairie, I fancied that I saw that vast, undisturbed animal panorama spread before me.

Principally there were the bison, darkening the uneven land. Pronghorn bands flashed white on ridgetops, and moose moved through the long fingers of willow that extended eastward with the rivers. Caribou and wolves inhabited the shadows. Among vast cities of prairie dogs, swift fox and grizzly roamed. There were the clamorings of sandhill crane, and white clouds of trumpeter swans.

This land, endowed with a wealth of wild grass, wore its wilderness well.

On Gunsight Pass, the rain lancing down, I found a sharpedged rock that split the continent in two. On both sides the rain rivulets ran down, a fraction of an inch determining the stream’s destination: Pacific or Atlantic.

The Continental Divide is a mighty barrier, a line of consequence that does more than determine watersheds. Its effect in Glacier is dramatic, as a look at the forests will reveal.

Obstructing the eastward flow of the moisture-laden Pacific winds, the Divide extracts a heavy annual tribute of precipitation from the air mass, forcing it to rise up the mountain chain, where it cools and condenses. Chief benefactors are the low western valleys, which respond with a lush growth of Pacific coastal-type forests.

The eastern valleys, however, deprived of abundant annual moisture and exposed to the wind and temperature ravages of the prairie’s continental climate, support a dramatically different kind of forest. Here Engelmann spruce and subalpine fir are the climax trees, contrasted with such trees as the western redcedar and western hemlock of the mild and moist McDonald valley.

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-westernhemlock 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.

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.

Through a series of complex vegetation stages, each characterized by different herbs, trees, and shrubs, the forest slowly returnsto 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.

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 loudKlee-yerbreaking 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 housethe 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.

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 undergroundmycelia, 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.

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 onp. 104

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