(C) CLIMATE, VEGETATION
(b) Vegetation of the Alps
Six regions or zones, which are best distinguished by their characteristic vegetation, are found in the Alps. It has been a common error to suppose that these are indicated by absolute height above the sea-level. Local conditions of exposure to the sun, protection from sold, winds, or the reverse, are of primary importance in determining the climate and the corresponding vegetation.
1. Olive Region --- The great plain of Upper Italy has a winter climate colder than that of the British Islands. The olive and the characteristic shrubs of the northern coasts of the Mediterranean do not thrive in the open air,. But the former valuable tree ripens its fruits in sheltered places at the foot of the mountains, and penetrates along the deeper valleys and the shores of the Italian lakes. The evergreen oak is wild on the rocks about the lake if Garda; and lemons are cultivated on large scale, with partial protection in winter. The olive has been known to survive severe cold when of the short duration, but it cannot be cultivated with success where frosts are prolonged, or where the mean winter temperature falls below 42° Fahr; and to produce fruits it requires a heat of at least 75° Fahr., during the day, continued through four or five months or the summer and autumn.
2. Vine Region --- The vine is far more tolerant of cod than the olive, but to produce tolerable wine it demands, at the season of ripening, a degree of heat not much less than that needed by the more delicate tree. These conditions are satisfied in the deeper valleys of the Alps, even in the interior of the chain, and up a considerable height on slopes exposed to the sun. The protection afforded by winter snow enables to the sun. The protection afforded by winter snow enables the plaint to resist severe and prolonged frost, such as would be fatal in more exposed situations. Along with the vine, many wild plants characteristic of the warmer parts of middle Europe are seen to flourish. A mean summer temperature of at least 68° Fahr. Is considered necessary to produce tolerable wine, but in ordinary seasons this is much exceeded in many of the great valleys of the Alps.
3. Mountian Region or Region of Deciduous Trees. --- Many writers take the growth of corn as the characteristic of this region; but so many varieties of all the common species are in cultivation, and these have such different climatal requirements, that they do not afford a satisfactory criterion. A more natural limit is afforded by the presence of the chief deciduous trees --- oak, beech, ash, and sycamore. These do not reach exactly to the same elevation, nor are they often found growing together; but their upper limit corresponds accurately enough to the change from a temperate to am colder climate that is further proved by a change in the wild herbaceous vegetation. This limit usually lies about 4000 feet above the sea on the north side of the Alps but on the southern slopes if often rises to 5000 feet, sometimes even to 5500 feet. It must not be supposed that this region is always marked by the presence of the characteristic trees. The interference of man has in many districts almost extirpated them, and, excepting the beech forests of the Austrian Alps, a considerable wood of deciduous threes is scarcely anywhere to be found. In many districts where such woods once existed, their place has been occupied by the pine and Scotch fir, which suffer less vegetation. The mean annual temperature of this region differs little from that of the British islands; but the climatal conditions are widely different. Here snow usually lies for several months, till it gives place to a spring and summer considerably warmer than the average of our seasons.
4. Subalpine Region, or Region of Coniferous Trees. --- This is the region which mainly determines the manner of life of the population of the Alps. On a rough estimate, we may reckon that, of the space lying between the summits of the Alps and the low country on either side, one quarter is available for cultivation, of which about one-half may be venieyards and corn-fields, and the remainder produces forage and grass. About another quarter is utterly barren, consisting of snow-fields, glaciers bare rock lakes and the beds of streams; and there remains about one-half, which is divided between forest and pasture, and it is the produce of this which mainly supports the relatively large population. For nearly half the year the flocks and herbs are fed on the upper pastures; but the true limit of the wealth of a district is the number of animals that can be supported during the long winter, and while one part of the population is engaged in tending the beasts and in making cheese and butter, the remainder is busy cutting hay and storing up winter food. The larger villages are mostly in the mountain region, but in many parts of the Alps the villages stand in the sub alpine region at heights varying from 4000 to 5500 feet above the sea, more rarely extending to about 6000 feet. The most characteristic feature of this region is the prevalence of coniferous trees, which, where they have not been artificially reduced, from vast forest that cover a large part of the surface. These play a most important part in the natural economy of the country. They protect the valley from destructive avalanches, and retaining the superficial soil by their roots, they mitigate the destructive effects of heavy rains in valleys where they have been rashly cut away, and the waters pour down the slopes unchecked, every tiny rivulet becomes a raging torrent, that cuts away and carries off the grassy slopes and devastates the floor of the valley, covering the soil with gravel and debris. In the pine forests of the Alps the prevailing species are the common spruce and the silver fir; on siliceous soil the larch flourishes, and surpasses every other European species in height. The Scotch fir is chiefly found at a lower level, and rarely forms forests. The Siberian fir is found scattered at intervals throughout the Alps, but is not common. The mughus, creeping pine, or Krummholz of the Germans, is common in the Eastern Alps, and sometimes forms on the higher mountains a distinct zone above the level of its congeners. In the Northern Alps the pine forest rarely surpass the limit of 6000 feet above the sea, but on the south side they commonly attain to 7000 feet; and the larch, Siberain fir, and mughus often extend above that elevation.
5. Alpine Region --- Throughout the German Alps the word alps is used specifically for the upper pastures, where cattle are fed in summer, but this region is held to include the whole space between the uppermost limit of trees and the first appearance of permanent masses of snow. It is here that the characteristic vegetation of the Laps id developed in its full beauty and variety. Shrubs are not wanting. Three species of rhododendron vie with each other in the brilliancy of their masses of red or pick flowers; the common juniper rises higher still, along with three species of bilberry; and several dwarf willows attain nearly to the utmost limit of vegetation. The upper limit of this region coincides with the so-called limit of perpetual snow, which demands further explanation.
6. Glacial Region --- On the higher parts of lofty mountains more snow falls in each year than is melted on the spot. A portion of this carried away by the wind before its is consolidated; a larger portion accumulated in hollows and depressions of the surface, and is gradually converted into glacier-ice, which descends by a slow secular motion into the deeper valleys, where it goes to swell perennial streams. As on a mountain the snow does not lie in beds of uniform thickness, and some parts are more exposed to the sun and warm winds than others, we commonly find beds of snow alternating with exposed slopes covered with brilliant vegetation; and to the observer near at hand there is no appearance in the least corresponding to the term limit of perpetual snow. But the case is otherwise when a high mountain chain is viewed from a distance. Similar conditions are repeated at many different points, so that the level at which large snow-beds shows themselves along its flanks is approximately horizontal. But this holds good only so far as the conditions are similar. On the opposite sides of the same chain the exposure to the sun or to warm winds may cause a wide difference in the level of permanent snow; but in some cases the increased fall of snow on the side exposed to moist winds may more than compensate the increased influence of the suns rays. Still, even with these reservations. The so-called line of perpetual snow is not fixed. The occurrence of favourable meteorological conditions during several successive season may and does increase the extent of the snow-fields, and lower the limit of seemingly permanent snow; while am opposite state of things may cause the limit tom rise higher on the flanks of the mountains. From these remarks it may be inferred that all attempts to fix accurately the level of perpetual snow in the Alps are fallacious, and can at the beast approach only to local accuracy for a particular distinct. In some parts of the Alps are limit may be set at about 8000 feet above the sea, while in others it cannot be placed much below 9500 feet. As very little snow can rest on rocks that lie at an angel exceeding 60°, and this is soon removed by the wind, some steep masses of rock remain bare even near the summits of the highest peaks, but as almost every spot offering the least hold for vegetation is covered with snow, few flowering plants are seen above 10,000 feet. There is reason to think however, that it is the want of soil rather than climatal conditions that checks the upwards extension of the Alpine flora. Increased direct effect of solar radiation compensates for the cold of the nights, and it the few spots where plants have been found in flower up to a height of 12,000 feet, nothing has indicated that the processes of vegetation were arrested by the severe cold which they must sometimes endure. The climate of the glacial region has often been compared to that of the polar regions, but they are widely different. Here, intense solar radiation by day, which raises the surface when dry to temperature approaching 80° Fahr., alternates with severe frost by nights, There, a sun which never sets sends feeble rays that maintain a low equable temperature, rarely rising more than a few degrees above the freezing-point. Hence the upper region of the Alps sustains a more varied and brilliant vegetation.
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