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