FLORA of GLACIER NATIONAL PARK, MONTANA. by Paul 0
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FLORA OF GLACIER NATIONAL PARK, MONTANA. By Paul 0. Standley. iirrsoDucTioir. Glacier National Park lies in northwestern Montana along the main range of the Rockies. It embraces an area of 1,534 square miles, nearly all of which consists of masses of high mountains. ♦ On the north it adjoins British Columbia and Alberta; eastward stretch the prairies of the Blackfoot Indian Reservation, aqd to the west lie the mountains and heavv forests of the Flathead Valley. The Continental Divide runs along the crest of the chief mountain ridge. The drainage of the west (Pacific) slope of the park is conse- quently into the Columbia River, while on the east (Atlantic) slope it is partly to Hudson Bay and partly to the Missouri River. From one point, Triple Divide Peak, the drainage is partly into each of the three systems. The highest peaks of the region reach an altitude of but little more than 3,000 meters (10,000 feet), but the elevation of the surrounding country is comparatively low (950 meters on the west slope and 1,440 meters on the east slope), so that the mountains are quite as imposing in appearance as many of those in the southern Rockies which have a much greater elevation. The rocks of the park are stratified and of Algonkian age. They consist chiefly of shale, limestone, sandstone, and argillite, their pre- vailing colors being rich reds and dull greens. In many places the stratifit ation is very regular and certain strata can be traced with the eye for many miles, but in other places the strata are folded and con- torted in an interesting fashion. Besides the stratified rocks, a con- spicuous feature is an intrusion of diorite—an igneous rock—which can be followed for a long distance along the Garden Wall as a well- marked band of black. The whole region of the park is extremely rugged (see plate 33), the mountains usually having sharp summits and precipitous sides. The main ridge is broken only infrequently by passes, whose altitudes range from 1,800 to about 2,100 meters. The slopes of the mountain masses have been plowed by ancient glaciers, and numerous lateral valleys have been cut, along which streams now run. In many of the valleys lie large or small lakes whose waters are wonderfully trans* parent and beautifully colored in blue or green. Fed directly by 235 236 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. streams from the snow fields and present glaciers, the water of these lakes is ice cold. High up on the peaks, in glacier basins, are often found miniature jewel-like lakes of intense colors, frequently sur- rounded by the ice walls of the glaciers themselves. Most spectac- ular of them is Iceberg Lake, on the east slope, which all summer long is full of huge blocks of floating ice which have broken off from the overhanging glacier. In some of these small alpine lakes the water is milky white from the particles of rock, finely ground by glaciers, held in suspension. One of the most striking features of the park is found in the glaciers which have given it its name. These lie in depressions at the head of some valley or hang high up on steep rock slopes. None of them are very large—Blackfoot Glacier is about three miles wide—but there are over 60 of them in the park. Each one possesses all or most of the features of the largest glaciers, and in a small glacier one can see the processes of glacial action much more readily than in a large one. Streams of water flow away from each of these ice masses, often falling abruptly over high cliffs, carrying down chunks of ice and rock which are heard constantly crashing upon the rocks below. The streams themselves, which abound everywhere in the park, are one of its many attractive features. To most people another source of interest is the profusion of animal life.1 Deer, elk, moose, mountain sheep and goats, bears, and many smaller animals are found in varying abundance. Sheep and goats are particularly plentiful and may be seen by the visitor in any of the higher regions, sometimes even in the vicinity of the hotels and chalets. The streams and lakes are well stocked with trout and other fishes. The winters are long in northern Montana. Snow falls by middle September or even earlier; indeed, at high altitudes, it frequently falls even in midsummer. At low elevations it remains until late in the season. In 1919, although the snowfall had been extremely light the previous winter, numerous snow banks remained at middle or even at low altitudes the first of July. Because of the short summers, the tourist season is limited; it extends from June 15 to September 15. GENERAL FEATURES OF THE F10BA. All the national parks of the West possess many attractions for anyone interested in plants, whether from the esthetic or from the scientific standpoint, and for the study of plants none offers greater advantages than Glacier Park. The flora is rich in number of species, and the vegetation is luxuriantly developed. All through 1 See Wild animals of Glacier Park: The mammals, by Vonion Bailey; The birds, by Florence Merriam Itailey. Department of the Interior, National Park Service. 1918. STANDLEY—FLORA OF GLACIER PARK 237 the summer there is a lavish display of color, which attains its climax about the first of July. The flowers follow close upon the retreating snow banks, and thus even when they are somewhat faded at lower altitudes they may be seen in all their vernal freshness on the high slopes. The growing season is so brief that plants must bloom and fruit quickly. At high altitudes, and to some extent at middle ones, there are no "spring," "summer," or "fall" flowers, for nearly all plants are in bloom at once, asters and goldenrod mingling with violets, springbeauties, and anemones. At low altitudes, however, there are marked- differences between the spring and autumn floras. The flora of Glacier Park is in general typical of the Rocky Mountain region, but like that of any restricted area it shows certain special characteristics. The Continental Divide, which traverses the park, is to a certain extent a barrier to plant migra- tion, and there are noticeable differences between the plants of the east and west slopes. The differences are 'most conspicuous in the case of the trees, and will be discussed in detail further on. In general, the flora of the east slope is like that of the central Rockies, while the flora of the west slope shows a marked relationship to that of the northern Pacific coast. It is noteworthy that a large number of coastal species reach the eastern limit of their range (in the United States at least) in Glacier Park. Many char- acteristic plants of the mountains of Alberta and British Columbia reach their southern limit in this region, and several such plants collected in Glacier Park have not been found elsewhere in the United States. Of course, more thorough exploration of the mountains of western Montana may show that some of these have a wider range than is known at the present,time. The forests of the park are of chief interest to those who come from the East. Like all western forests, they are composed almost wholly of coniferous trees belonging to a comparatively small number of species. The only broad-leafed tree which occurs in much abundance is the aspen. The forests of the east slope are only moderately heavy, but those of the west slope, especially about Lake McDonald, are very dense and are composed of large trees. The forests of the west slope are similar to those of the Pacific coast, although they are not so extensive or luxuriant. Since there is practically no cultivated land inside the park, few introduced plants are to be expected, and in the present list there are included only 61 species of foreign origin. Most of these have been found only about B el ton and the east entrance, where they have become established along the railroad. A few foreign plants are thoroughly naturalized in the park, however, and some are abundant, such as timothy, sheep sorrel, fanweed, red, white, and alsike clover, 238 CONTRIBUTION'S FROM THE NATIONAL HERBARIUM. and the common thistle (Oirsium lanceohium). None of these, with the possible exception of the thistle on the west slope, is sufficiently plentiful to constitute a prominent element of the flora, XIFE ZONES. In the study of the vegetation of any region it soon becomes apparent that many of the species are restricted in their distribu- tion. Some plants, of course, grow only in water or in wet soil, and others only in dry or well-drained situations, but most species are not generally distributed even when such habitats are disre- garded. In the mountains, as one ascends the slopes, it is noted that the character of the vegetation changes, either gradually or abruptly, certain plants disappearing and new ones taking their places. Very few plants that grow on mountain tops grow also in the foothills or valleys or on the plains. In general, it is found that the vegetation is divided roughly into belts or zones, which are sometimes well marked, but often of indefinite limitation. As a general rule the trees and scrubs are more definitely distributed in belts than are the herbaceous plants. This zonal distribution of plants is the result of varying conditions with regard to temperature and moisture, as influenced by exposure and elevation.