Part 14

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.

The Water Communities

Snowfields begin again their summer-long melt. The alpine stream, vocal again, collects its water from a thousand places. Miniature gorges drain the meadow, gurgling with the sparkle and rush of meltwater in the lengthening spring days.

Gathering volume, the stream seems to hurry faster; at the first rock staircase, it begins to sing. I follow the gully downward, drawn like the water. There is excitement in the growing dash and roar, a wind-gust sweeping spray into the air. A rainbow appears, holding steady to the swirling cloud of spray, then doubles and abruptly disappears.

At the first great plunge the water lunges outward over the lip. Like glass at shattering, long shards lance out. But the wind feathers the sharp edges as they fall.

The close thunder of a waterfall beats at your head, and your mind must shout to think. Here is water, a most amazing and most important substance. Perhaps some of this same water was once part of the ancient sea in which was laid down the mudstone of this ledge; was once drunk by dinosaurs; has coursed the globe countless times; and has flowed in this very stream before. In solid, liquid, or gaseous form, it goes through its own cycle. Together with sunlight, water makes possible and maintains all life on Earth.

Ouzel Music

A glacier might cling to a winter snow a hundred years and turn it to ice, a blue tool to rasp and pluck at rocks, before letting it go. Lingering summer snowfields might delay its passage for a time. But the water always wins at last, becoming, in one decisive instant, liquid again, and beginning its long journey to the sea. Plants and dry air will intercept some of its molecules, sending them back into the atmosphere to bloom as fog and cloud; but as rain, snow, or dew, these are soon commissioned to the land again.

Water is so familiar to us that we seldom think about it. We know that fish swim in the lower lakes, and we are vaguely aware of the bewildering assortment of life-forms abounding in a pond. But life begins in the streams.

Even cups of cold meltwaters, scooped out of a rivulet only a few meters away from its snowbank source, contain some life. Snow algae, which grow on the snowbank surface, often sufficiently dense to give the snow a distinctive red complexion, are released into the meltwater. In summer, small invertebrate life can be discovered in the standing pools of even the highest cirque.

But conditions are not good for the development of complete aquatic food chains in the streams and lakes of higher elevations. Alpine lakes, or tarns, support little visible life. Often flanked by high ridges and peaks, many tarns receive scant direct sunlight during the day. Since these lakes occupy basins that capture tremendous amounts of snowfall, the snowbanks persist in the mountain shadows, and summer makes little progress in warming the water. Iceberg Lake, for example, is seldom free of floating ice, and its temperature never rises above 4° C in summer, even at the surface.

Moving out of the cirque lakes, water is soon churning again, dashing downward many hundreds of meters to the valleys below, in rapids, cascades, and breathless waterfalls. Not surprisingly, few plants and animals are adapted to life in fast-moving water.

Algae can be found covering streambed rocks and stranded, water-polished tree trunks. Securely attached by holdfasts, these small plant forms survive the rigorous stream flow that would destroy the larger vascular plants. Several species exist, from microscopic forms to branched filamentous algae whose long hairlike strands wave in the current.

A surprising number of insects live on the stream bottom, finding a measure of protection from the current in the jumble of rocks. Underwater beetles live under the gravel or among the debris at the stream-edge, or cling to stones and sticks. Scurrying and creeping among the rock-crannies are the larvae of stoneflies, mayflies, and caddisflies. These and the small fish that venture up from lower lakes are the food of the water ouzel, a creature that loves the places where the waters thunder.

■ The noise of the water is overpowering. A slip into this boiling rage would mean quick death. Looking 10 meters across the dim, mist-slippery, water-scoured canyon, I see a young water ouzel peering out of its unique nest, on the lookout for its parents. Clouds of spray keep the nest of living moss continually wet; but this bird is waterproofed with an oily plumage and keeps its vigil at the nest opening. Peering into the torrent below, then upstream and downstream, it awaits patiently the delivery of the next meal.

With the approach of one of the adults, three other heads crowd the opening, begging yellow mouths agape. Flying low, the ouzel parent zeros through the heavy spray, alighting on a slippery boulder below the nest ledge. Preparing to fly up to the nest with its load of insect larvae, the ouzel spots me across the water. At its sharp jigic, jigic alarm, the bills of the young snap instantly shut. Nervously the bird regards my close presence, dipping its entire body rapidly up and down, as if keeping time with the surging torrent.

Discovering no danger, the dusky blue-grey bird bobs more slowly. The other adult, returning from an upstream forage, alights on the same rock, occasioning a new outcry from the fledglings. Each in turn, the parent birds fly up to feed their young, beating their wings to maintain their position at the perchless nest. Not pausing to regard me further, they split the stream between them again, one flying upstream and one down, to continue the hunt. Blinking and shaking the collected mist from its bill, the single young sentry renews its watch.

In Shallow Waters

Life abounds in the shallow lakes and ponds. Calm, protected John’s Lake offers a fine example of how a complex aquatic plant-and-animal community can exist in balance in a confined space. The water teems with the microscopic algae, protozoans, and rotifers that sustain the barely visible zooplankton. Dancing, flitting, hopping, and swaying through the water, these zooplankton in turn support the larger plankton-eating animals.

Dragonflies and damselflies shoot past, crackling their wings, and perch in the bog grass. Looking into the shallow water, you will see a wealth of small animal life. A spotted frog swims into view, floating to the surface beside a lily pad so that its eyes protrude above the water.

The ribbonlike form of a leech swims across the bottom toward deeper water. Looking closer, you see that the water swarms with bizarre shapes—water boatmen propelling themselves with oarlike appendages, a gliding mayfly nymph, then a predacious diving beetle surfacing, grasping a bubble of air beneath its shiny brown wing plates and disappearing downward again—the bubble’s edge shining silver—into the brown bottom debris. Suddenly a whirligig beetle sets the surface to spinning, wrinkling the view below.

Everywhere in the water there is animal life, forms that are attached, free-swimming, crawling on the bottom, and clinging to or swimming on the surface film. The gray, slimy encrustation on a sunken log looks like a covering of lichen but is really a freshwater sponge, a colonial animal that feeds by filtering minute plankton from the water. Another attached creature is the barely visible hydra; this twig-shaped predator, related to marine jellyfish, captures water fleas and other small animals in its several poisonous tentacles.

Water beetles, backswimmers, water boatmen, and many other creatures move about more or less freely in the water, propelling themselves along with jerky movements. Suspended between surface and bottom are the zooplankton, the tiny water fleas, cyclops, daphnia, and others, which feed by filtering minute algae. On the bottom and below live scavenging worms. Water striders skate on the surface film.

Along the shore, frogs, salamanders, garter snakes, and water shrews are hunting. Dabbling and diving ducks patrol about, tipping or submerging for the bottom plants. Moose tracks circle the muddy shore. Because it produces vegetation abundantly, John’s Lake sustains a great diversity of animal life.