Читать книгу Olympic Mountains Trail Guide - Robert Wood - Страница 15

In mountainous regions, a phenomenon known as altitudinal zonation is present, caused by climatic changes that occur with an increase or decrease in elevation. As the elevation increases, the temperature decreases, and the climate becomes harsher, which has resulted in a classification called vegetation zones. Four such zones are present on the Olympic Peninsula—the Lowland Forest Zone, the Montane Forest Zone, the Subalpine Zone, and the Alpine Zone.

The Lowland Forest Zone ranges from sea level upward to elevations varying from 1500 to 2000 feet. This zone not only covers the lowlands surrounding the Olympics but also extends deep into the mountains by following the major rivers, gradually phasing into the Montane Forest Zone, which extends from the upper limits of the Lowland Forest Zone to an elevation about 3500 feet above sea level. The Subalpine Zone occupies the territory between the upper limits of the Montane Forest Zone and approximately the 5000-foot level. Above it, the Alpine Zone extends upward to the summits of the highest peaks.

Like everything in nature, the vegetation zones do not have distinct boundaries; instead, they blend into one another in an irregular manner. On cold northern slopes, for example, the Subalpine Zone at times extends well below 3500 feet. On the other hand, mountainsides with southern exposure often exhibit Montane Forest Zone conditions above 3500 feet. At times the Alpine Zone occurs at elevations below 5000 feet, particularly in the vicinity of glaciers.

On the peninsula, the Lowland Forest Zone has a mild marine climate, one typical of sea level at this latitude (45 degrees to 50 degrees north of the Equator). Within the mountains, this zone dominates the river bottoms and the lower foothills. The principal conifers are Douglas-fir, western hemlock, western red cedar, and Sitka spruce. Deciduous trees include red alder, bigleaf maple, black cottonwood, and Pacific dogwood. The luxuriant forest floor exhibits green mosses, flowering plants, and bushy shrubs. Included among the latter are willow, red elderberry, salmonberry, salal, huckleberry, devil’s club, and rhododendron. Low-growing plants include Oregon grape, skunk cabbage, fireweed, and many kinds of ferns. The luxuriance of this zone contrasts markedly with the dark, gloomy stands of the Montane Forest Zone on the slopes directly above. Elk herds live here the year around but particularly in the winter. Deer, bear, and cougar are also present. The bird life is varied—kingfishers and dippers on the streams, wrens and varied thrushes in the deep forests.

The Montane Forest Zone is largely confined to steep mountainsides, and the temperature is usually somewhat cooler than on the lowlands. This is a realm of dense, somber forests, mostly thick stands of tall conifers. The common trees are Pacific silver fir, western hemlock, and Douglas-fir, with a sprinkling of western white pine and western red cedar. Because the trees grow in heavy stands, and their crowns interlock, the sunlight that reaches the ground is soft and indirect, the air cool, fragrant, and moist. In fact, this canopy is so dense it intercepts the first winter snows, which often melt on warm succeeding days, never having reached the earth. On the steeper mountainsides, pistol-butted trees may be observed. Occasionally this results from ground creep, but the phenomenon is more often caused by heavy snow that bent the trees when they were young and pliable. Undergrowth in this zone is sparser than on the lowlands, but it encompasses a wide variety of shrubs and saprophytes. Vine maple, alder, and devil’s club border the streams; huckleberry, salal, and rhododendron clothe the drier slopes.

Rhododendrons bloom in late spring, bringing splashes of color to the forest along the Lower Big Quilcene Trail (Hike 80).

The conditions in this zone are less favorable to wildlife than in the other zones, thus animals are not abundant, but the chattering of chipmunks and Douglas squirrels may often be heard. Bird life is also less varied than in the other zones, but it does include the Canada jay, varied thrush, and several species of owls, including the spotted owl.

The climate is still cooler in the Subalpine Zone. This zone exhibits great variety—a mixture of subalpine trees, meadows, glacial lakes, swamps, and bogs. The forests in this zone’s lower levels blend gradually into the denser stands in the Montane Forest Zone below. In sharp contrast, in the upper levels open meadowland appears as the forest gives way to the treeless Alpine Zone.

The continuity of the Subalpine Zone forests is broken by the meadows. As in the Montane Forest Zone, the trees are chiefly conifers, but the dominant species are different—subalpine fir, mountain hemlock, and Alaska cedar. The trees are tenacious, having adapted themselves well to the harsh environment. Little groves are scattered over the grassy slopes and rises, and the ubiquitous low-growing juniper sprawls over the rocky ridges. Shrubs common to this zone include willow and slide alder on the stream banks, huckleberry and heather on the mountainsides.

Despite the difficult living conditions, a large variety of plants, animals, and birds are present in this zone. The meadows are snowbound for seven or eight months, but when the snow melts the low-growing plants bloom with a sudden rush. Although wildflowers are present in all zones, at all elevations, they reach their climax in these high meadowlands. The floral display attains its peak in late July or early August, flooding the mountainsides with color. Among the flowers are avalanche and glacier lilies in July, which bloom alongside receding snowbanks, and lupine, beargrass, and scarlet paintbrush in August.

Weather conditions in the Alpine Zone—the highest in the Olympics—are the harshest to be found on the peninsula. Lying above timberline, this is a region of tundralike meadows intermingled with snowfields, glaciers, and barren country. Much of the year this zone lies under deep snow. Plant growth is sparse because the soil is poor and the growing season abbreviated. Cold and constant wind are the rule, and night frosts sometimes occur during the summer. Because the climate is rigorous and the growing season brief, the plants have a tendency to be dwarfed, compact, and dense. Less plentiful in kind and number than the ones in the Subalpine Zone, they are all low-growing perennials, and include grasses, sedges, rushes, and a few shrubs and flowers. They blossom hurriedly, and their seeds are scattered by the autumn winds. Among them are phlox, goldenrod, bluebell, alpine lupine, and pleated gentian. Arctic willows hug the ground; anemones and Douglasia add touches of color to glacial moraines. At the extreme limits of plant growth are found grasses such as bent, timothy, and squirrel-tail, with mosses and lichens thriving in protected spots among the rocks.

Several endemic plants occur in the Alpine Zone, chiefly in areas that were not glaciated during the ice age. They include Henderson’s spiraea, Flett’s violet, and Piper’s harebell, all bearing the names of pioneer botanists who collected in the Olympics. Occurring nowhere else, these species have been adversely affected by the depredations of mountain goats, which are not native to the area.