Arctic flora

“ On mountain-ranges situated within the Temperate Zone, such as the European Alps, and much more on those nearer the Equator, the day temperature in summer is very high wherever the sun strikes, and while plants may have to withstand at night a temperature comparable to that borne by the Arctic flora, they must endure by day the most intense insolation.
Neither in the Arctic nor on the high hills does plant life cease merely on account of low temperature. Species belonging to many families venture even beyond the limit of perpetual snow. ”

“ In those periods when a warm climate prevailed in the Arctic regions, the temperate flora must have been, like the modern Arctic flora, circumpolar. When obliged to migrate to the south, it had to follow the lines of the continents, and so to divide into separate belts. Three of these at present are the floras of Western Europe, Eastern Asia, and Eastern America, all of which have many representative « 228 » species. They are separated by oceans and by belts of land occupied by plants which have not been obliged to migrate. ”

“ Plant-development under different Temperature Conditions.—In the arctic regions the ground, frozen in winter to unknown depths, may thaw to only three to five feet during the summer, notwithstanding the great length and continuous sunshine of the arctic day. The shallow-rooted arctic flora develops very rapidly under the influence of the continuous daylight and heat, in the course of from five to eight weeks. ”

“ Further, the periods of Arctic warmth permitted the passage round the northern belt of many temperate species of plants, just as now happens with the Arctic flora; and when these were dispersed by colder periods they marched southward along both sides of the sea on the mountain-chains. ”

“ The Arctic flora is by no means abundant, but it is peculiarly interesting. In Greenland, besides numerous mosses, lichens, algæ, and the like, flourish three hundred kinds of flowering plants, all of which are natives of the Scandinavian peninsula; and Dr. Joseph Hooker remarks that they exhibit scarcely any admixture of American types, though these are found on the opposite coast of Labrador. It would seem probable that in the warm period which preceded the Glacial Age, the Scandinavian flora spread over the entire area of the Polar Regions ”

“ The area of the Arctic flora comprises Greenland, in the western hemisphere, and extends considerably to the south of the Arctic Circle, especially on the coasts, where it reaches the parallel of 60° N. lat., and even overpasses it.
In Greenland the vegetation is more truly of an Arctic character than even in Iceland. The valleys are covered with marsh-plants and dingy mosses; the gloomy rocks are encrusted with lichens; while the grasses on the meadow-lands that border the fiords and inlets are nearly four times less varied than those of Iceland. ”

“ It has been pointed out that in spite of a superficial similarity, wide disparity exists between the sets of conditions prevailing in the two kinds of habitat just mentioned. In the Arctic the winter is continuously dark and the summer continuously light; and in summer the sun is never far above the horizon, so that the temperature remains low, though it rises amply far enough above freezing-point{197} to allow of plant life. ”

“ The Scottish mountain-sides and Irish moorlands still to a great extent retain a natural flora, save that the greater number of grazing animals which they now support, as compared with the times when wolves and other enemies roamed unchecked, leaves its impress upon the vegetation.
Viewing the plant world as a whole, its primary divisions, from the point of view of ecology, are governed by the factor of rainfall. It is true that the plants of the Tropics differ profoundly from those of the Temperate regions, and those again from the plants of the Arctic. ”

“ Arctic. On our loftier hills, indeed, the heat is on occasions oppressive.
Again, the mountain climate, with its heavy rainfall and long cold period, tends to the formation of peat; and the acids thus engendered in the soil, as well as the low temperature prevailing during most of the year, render difficult the absorption of water by the roots of plants. The conditions under which alpine plants, then, live may be summed up as follows: a long cold winter, a short summer; great exposure; scarcity of food-supply. ”

“ If, however, our modern flora is thus one that has returned from the south, this would account for its poverty in species as compared with those of the early Tertiary. Groups of plants descending from the north have been rich and varied. Returning from the south they are like the shattered remains of a beaten army. This, at least, has been the case with such retreating floras as those of the Lower Carboniferous, the Permian, and the Jurassic, and possibly that of the Lower Eocene of Europe.
The question of the supply of light to an Arctic flora is much less difficult than some have imagined. ”

“ It seems as if the polar water is specially favourable for the development of pelagic plant life, which makes the flora, and consequently also the fauna, flourish as soon as the ice covering disappears and the water surface is exposed to the full sunlight of the long Arctic day. At the same time the temperature of the water uses, and thus the conditions for the chemical changes of matter and nutritive assimilation are much improved. ”

“ We have to explain how an Arctic flora, consisting of plants specifically identical with those which inhabit lands bordering the sea in the extreme north of America, Europe and Asia, could get to the top of Mount Washington. Now geology teaches us that the species living at present on the earth are older than many parts of our existing continents ”

“ The alpine floras of Europe and Asia, so far as they are identical with the flora of the Arctic and sub-Arctic zones of the Old World, are fragments of a flora which was diffused from the north, either by means of transport not now in action on the temperate coasts of Europe, or over continuous land which no longer exists. The deep-sea fauna is in like manner a fragment of the general glacial fauna. ”

“ But just as the Eskimo live under conditions which would be wellnigh prohibitive to inhabitants of more temperate regions, so many of the higher as well as the lower plants creep northward far beyond the Arctic Circle, where, awakening from a nine months’ winter sleep, they break from the still half-frozen ground to brighten the brief summer with their leaves and flowers and fruit. The flora of Greenland, for instance, which we generally think of as an ice-bound and inhospitable land, numbers some 400 species of Seed Plants. ”

“ With the advent of a milder temperature the Arctic vegetation has gradually disappeared from the plains. Driven up step by step before the advancing flora from more genial climates, it retired into the mountains and there to this day continues to maintain itself. The present Alpine flora of the Pyrenees, the Alps, Britain, and Scandinavia, is thus a living record of the ice age. The reindeer and his friends have long since been forced to return to their northern homes.
After this long succession of physical revolutions, man appears as a denizen of the Europe thus prepared for him. ”

“ Such distances are, as we have already seen, no barrier to the diffusion of plants; and we should accordingly expect that this great continuous mountain-chain has formed the most effective agent in aiding the southward migration of the Arctic and north temperate vegetation. We do find, in fact, not only that a large number of northern genera and many species are scattered all along this line of route, but that at the end of the long journey, in Southern Chile and Fuegia, they have established themselves in such numbers as to form an important part of the flora of those countries. ”

“ Mollusca and many other forms of life are abundant in the Arctic seas, and there is often a luxuriant dwarf woody vegetation on the land, yet in no one case has a single example of such a fauna or flora been discovered of a date anterior to the last glacial epoch. And this argument is very much strengthened when we remember that an exactly analogous series of facts is found over all the temperate zones. Everywhere we have abundant floras and faunas indicating warmer conditions than such as now prevail, but never in a single instance one which as clearly indicates colder conditions. ”

“ The existence of Arctic conditions has been proved by purely geological evidence, but it receives additional confirmation, and derives a wider importance from the testimony of fossil plants. In rocks deposited before the spread of ice from high northern latitudes, we find indubitable proofs of a widely distributed subtropical flora in Central and Northern Europe. ”

“ Again should a certain system, characterised by the presence of some particular and well-marked flora and fauna, be encountered not only in sub-tropical and temperate latitudes but also far within the Arctic Circle, we should infer that such a flora and fauna lived under climatic conditions of a very different kind from any that now exist. The very presence, in the far north, of fossils having such a geographical distribution would show that the temperature of polar seas and lands could not have been less than temperate. ”

“ Beyond the wooded region, some of the same plants, in a dwarf state, mingled with others, compose a shrubby broad belt, which ascends the hill to an elevation of 800 or 900 feet, gradually opening out into grassy slopes, and succeeded by the alpine vegetation. It is especially towards the summits of these hills that the most striking plants are found, vying in brightness of colour with the Arctic Flora, and unrivalled in beauty by those of any other Antarctic country. ”

“ The Arctic-Alpine sub-region consists of races of plants belonging originally to the general flora, and recruited by subsequent additions, which have been specialized in low stature and great capacity of endurance to survive long dormant periods, sometimes even unbroken in successive years by the transitory activity of the brief summer. It is continuous round the pole and roughly is bounded by the arctic circle. Mature seeds are highly tolerant of cold and have been shown to be capable of withstanding the temperature even of liquid hydrogen. ”

“ The changes in the types of vegetable life are apparently as extensive in high as in low latitudes. The lower cretaceous flora is almost tropical, as is shown by the predominating forms of this vegetation. Carboniferous formations obtain extensively in the Arctic regions, as they occur in the Parry Archipelago, Spitzbergen and in Siberia. During the carboniferous age there was a great extent of land near the North Pole closely resembling that of the temperate latitude of the same period, as is shown by the small number of fossil plants that are peculiar to the Arctic regions. ”

“ Its flora, though altogether Arctic, contains 386 species, none of which are peculiar to it, but many of them range quite round the Polar circle. Of those that are not so generally distributed, some, more especially on the west coast, are common to Greenland and Arctic America. Others, and a larger number, more especially on the east coast, are common to Greenland, Iceland and Norway, between which and Greenland there may have been a closer land connection than now, in Pliocene and Post-glacial times. ”

“ Even in Canada, which has a flora richer in some respects than that of temperate Europe, growth is effectually arrested by cold for nearly six months, and though there is ample sunlight there is no vegetation. It is indeed not impossible that in the plans of the Creator the continuous summer sun of the Arctic regions may have been made the means for the introduction, or at least for the rapid growth and multiplication, of new and more varied types of plants. ”

“ This relation of the arctic to the alpine flora is all the more remarkable in view of the very important differences between the arctic and alpine climates. The following circumpolar species are common, and widely diffused throughout the whole of the Alps: Silene acaulis, Dryas octopetala, Saxifraga oppositifolia, S. aizoides, S. stellaris, Erigeron alpinus, Azalea procumbens, Myosotis alpestris, Polygonum viviparum, Salix retusa, S. herbacea, Phleum alpinum, Juniperus nana. The proportion of northern forms, as regards both species and individuals, increases as we ascend to the higher regions. ”

“ The recent discovery by Lieutenant Jensen of a rich flora on rocky peaks rising out of the continental ice of Greenland, as well as the abundant vegetation of the highest northern latitudes, renders it possible that even now the Antarctic continent may not be wholly destitute of vegetation, although its climate and physical condition are far less favourable than those of the Arctic lands. ”

“ Much farther back is the separation of the species which now live both in arctic regions and on the summits of our highest mountaintops. If we compare the alpine flora with the arctic plants, a high degree of similarity at once strikes us. ”

“ Hooker, analogous and striking facts are given in regard to the plants of that large island. Hence, we see that certain plants growing on the more lofty mountains of the tropics in all parts of the world, and on the temperate plains of the north and south, are either the same species or varieties of the same species. It should, however, be observed that these plants are not strictly arctic forms; for, as Mr. H.C. Watson has remarked, "in receding from polar toward equatorial latitudes, the Alpine or mountain flora really become less and less Arctic." ”