Plant-and-Animal Communities (continued)

Tundra

Porcelain-cold, the November sun dawns in the southeast sky. The ledges, ice-encrusted, layered with sleet from a recent squall, whistle the cold morning wind aside. Rattling down, a slide of rock plunges off the final ledge, seconds passing before the hollow sounds of impact clatter back. Like an apparition of winter itself, white beard bent sideways by the wind, a mountain goat steps to the precipice edge. Looking out across the vast white void, its long belly hair and pantaloons streaming with the ceaseless wind, this strange animal, product of some unfathomable ingenuity, hesitates but a moment; dropping down from step to invisible step along the sheer rock face, fracturing the ice glaze as it goes, it turns a wall and disappears. A nimble, eight-months-old kid follows.

Blinking and twisting in the dull light, the shower of shattered ice clinks softly downward against rock, fading away like the short summers of this place.

But while the wind chants winter, life has made a passage here, and also waits, hidden in seed and root and den.

The nanny and her kid have bedded down now, looking across the deep, snowy basin below. Their ledge shines with the first spear of sunlight.

Far below the pass that connects Mount Siyeh to the snow-giants Matahpi and Going-to-the-sun, three male white-tailed ptarmigan emerge from their night's huddle within a snowbank and step out to peck at an exposed mat of willow. Ptarmigan, the only birds on the winter tundra, wear white plumage in this season, helping to camouflage them in the snow, just as their mottled brown summer plumage makes them difficult to detect among bare rocks. There are few predators here to hunt them now, but they move with habitual slowness; quick movement can be fatal when summer brings numerous eyes to scan the slopes. With legs and feet heavily feathered and sharp claws to scratch for food beneath the snow, the ptarmigan live at truce with winter. When blizzards rage between the peaks, they nestle together in snow dens, beyond the reach of the winds. Ptarmigan hens winter lower in taller willow thickets, but the males prefer to take their winter as high as possible.

Now they crouch behind the wind-deflecting rocks, dozing in the meager warmth of the morning sun.

Near the snowless summit crags, a flash of brown fur zigzags among the rocks. That would be a pika. Only for a moment does it show itself, so quickly does it move.

Also called the rock rabbit, the diminutive pika belongs to the order of hares and rabbits. Resembling a small guinea pig, this sturdy creature spurns hibernation as a way to beat the challenge of winter. Instead, it spends the summer laying in a store of hay for the lean season, spreading cut grass to cure upon the rocks and tending its "haystacks," on which its survival hangs.

Winter is a great peril to small mammals. Their small bodies, because of large surface area in relation to volume, retain heat poorly, and their high metabolic fires consume calories quickly. Great amounts of energy are required to sustain an active animal in rough terrain, placing further demands on the animal's capacity to survive the cold. The pika may need to stack as much as 25 kilos of hay; to keep its furnace burning during winter it will have to fuel its stomach almost hourly.

Small animals of cold climates often show distinctive body adaptations. On the pika the small, rounded ears lie flat along the head, the tail is inconspicuous, the legs are short; heat loss from exposed surfaces is thus reduced. Fur insulates the soles of the pika's feet while at the same time providing good traction on steep rock faces.

Hidden below these rocks are the hibernating marmots and the sleeping ground squirrels. Beneath the snow the mice, shrews, and pocket gophers struggle on with their lives. But above ground, directly confronting this arctic climate, are the pika, the ptarmigan, and the mountain goat.

A triumph of adaptation, the mountain goat faces the winter day without benefit of either the pikas den or the ptarmigan's snow roost.

The nanny and kid descend from their ledge to search out browse at treeline with other members of a loose band—yearlings, young males, other nannies with kids. At the fringes of the band a solitary adult billy only grudgingly associates with other members of his kind; for this is the season of rut.

Not really goats at all, these relatives of the European mountaineering chamois are insulated from the wind by coats of long, hollow-haired fur overlying wooly underfur. They are stocky, stiff-legged, and deliberate, able to negotiate the walls and pinnacles with their superbly adapted hoofs. The unique design of these hoofs gives the animal great traction and stability on precarious crags. Opening towards the front, the cleft between the two hoofs spreads each outward as the animal descends a slope, helping to grip the rocky surface. In addition, the large, rough, and pliant sole of each foot conforms to the bare rock, increasing traction.

There is little need for the goat to leave its steep sanctuaries; it can subsist on lichens and mosses if browse is not available. It depends on the inaccessibility of the cliffs for its security. Accidents, avalanches, and rockfall are greater enemies than predators. Golden eagles sometimes attempt to knock newborn kids from ledges and a young goat quickly retreats under its nanny when an eagle soars by. With the protection of sharp spike horns and a terrifying terrain, adult goats seldom fall victim to cougar or grizzly.

It will be a long time before the snow releases this land and wapiti, bighorn, grizzly, and cougar wander back into these high basins. In this winter minimum of life, the spring songs of rosy finches, water pipits and white-crowned sparrows seem an impossible extravagance.

I am drawn to the spring tundra—to the vigor and tenacity of its sparse life—where survival itself seems ceremony enough. But it is a strange world, where a man is out of perspective. Here the plant cover is carpet—high, and distance, for the lack of trees, tricks the eye. Here the wind, snow, and sun quickly burn skin, and the intense light, reflected from snowbanks, stabs at the eyes. Almost instantly, a sandwich is sucked dry of its moisture. The desiccating wind probes the ears until it seems at last to pierce your brain. Except for fearful mountain walls the only shadow is your own. Animals seem somehow remote and unknowable, as if seen through glass. A day on the tundra and you feel the want of a company of trees.

Yet once exposed, you acquire a craving for the look of tundra. Nowhere else is there such an impatience for spring—the flowers rush into bloom; the male water pipit soars, its skylark song crystal sharp in the thin air. The nesting birds are restless, for sun-days and warm days are few, precious, and quickly spent. Insects and spiders abound—flying about the peaks or crawling among the rocks.

Summer brings bands of bighorn rams up from the valley to explore the highest meadows. Though not so sure-footed as the goats, they too have hoofs adapted to climbing steep faces, and they walk the slopes not far below the goats.

Marmots, which whistle sharply when threatened, spend their days sunbathing and grazing; they must fill out their now loose-hanging fur coats with life-sustaining fat for the coming winter.

Alpine animals are blessed with mobility and can choose their weathers, retreating to burrow, den, or rock-harbor to escape the worst fury of storms. But what about the plants, rooted forever in one spot, assaulted by an untempered sun and a drying wind, and facing the almost daily threat of freeze and storm?

Alpine plants, through their design and growing habits, have adapted themselves to the rigorous demands of this climate in many ways. Most plants are perennial: there just aren't enough days or nutrients available for the growing of entire plants each year from seed. And they have the ability to grow and carry on photosynthesis at temperatures just above freezing, thus extending their season. In this zone, temperatures are rarely above 15° C; the mean summer temperature is about 10° C. But a flower such as the alpine buttercup, which is found at treeline or above, can grow through several centimeters of snow; heat given off during the plant's respiration will create an opening through which it can emerge.

Plants have various adaptations to meet the demands of the alpine environment. Yellow stonecrop, not restricted to this zone, is nevertheless able to survive here because of its fleshy succulence and a waxy covering that prevents water loss. On some plants, protective hairs covering leaves and stems help retard the burning effects of wind and sun. Often this pubescent foliage looks more grey than green, for the soft hairs mute the color.

Cushion growth is another alpine adaptation. The moss campion cushion, covered with delicate pink flowers, grows to about one-third of a meter across and only 3 to 5 centimeters high. Spreading out close to the ground, the plant avoids the major violence of the wind and hoards moisture like a sponge.

The dryad, growing abundantly on the windy sweep of Siyeh Pass, shows alpine adaptations in several ways. The energy of the mature plant is channeled primarily into reproduction: its large flower, supported by a short stem, matures quickly; and it produces many seeds, ensuring germination of a few. An evergreen, it begins to synthesize water and carbon dioxide into food as soon as the snow is gone; and its rolled leaves prevent rapid evaporation. It grows as a low and woody mat that year by year extends itself through the production of new shoots that carpet the rock. Mat growth has the advantage of retaining dead plant material and capturing wind-blown grains of soil, allowing the plant slowly to enlarge its soil base.

Compared to the forest, the heartbeat of the tundra is painfully slow. Here a plant may grow for a quarter of a century before it has acquired the reserves necessary for flowering. Contrasted with the progress on the tundra, forest succession races by with dizzying speed. Yet imperceptible as the change may be the alpine plant community also passes from pioneer to climax.

Beyond the limit of other plants, lichens thrive, encrusting rocks with their rainbow colors. A lichen is actually a primitive and highly successful association between a fungus and an alga, working together for mutual benefit. The fungus protects the delicate alga, trapping and holding moisture; the green alga, in turn, produces enough food to sustain the needs of the fungus.

Generating rock-disintegrating acids that help secure this partnership to the rock, lichens, along with physical weathering, help break down the rocks into soil particles. Collected in pockets by run-off or wind, rudimentary soil is slowly invaded by cushion plants. After centuries of colonization by these, while the meager soil is deepened and enriched and moisture retention is increased, other plants move in, climaxing at last in hardy grasses and sedges. As in the forest, pioneer species change the environment to their detriment, creating a habitat better suited to other species.

Although it will progress with geologic slowness, the rocky ground of Siyeh Pass—its plant cover presently scant and wind-rowed by frost-heave and relentless wind—will in time develop grasses and sedges, the climax vegetation of the alpine meadows.

Simplicity rules the alpine zone. Here life is reduced to bare essentials. Chief controlling force is climate; but the plants and animals that live here are well adapted. Compared to the lower realms, where both competition and predation are fierce, life here looks secure.

There is a penalty to simplicity. In the lowland, the long food chains and diversity of species, the long growing season, and the abundant food supply give the forest an adjustment mechanism and healing power not found on the critically balanced tundra. The greater the variety in a plant and animal community, the greater the stability. So in the alpine world there exists a paradox: the most durable life forms constitute the most fragile community.