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    Flora and Vegetation of Arctic Alaska, Yukon, and Northwestern Canada

    Encyclopedia Arctica 6: Plant Sciences (Regional)

    Flora and Vegetation of Arctic Alaska, Yukon, and Northwestern Canada

    Unpaginated      |      Vol_VI-0449                                                                                                                  
    EA-Plant Sciences

    (A. E. Porsild)





    Introduction 1
    The Flora 3
    Types of Vegetation 6
    Rocky Barrens or Fell-fields 8
    Tundra 12
    Strand Vegetation 17
    Vegetation of Fresh Water 18
    Bibliography 20

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    EA-Plant Sciences

    (A. E. Porsild)






            Floristically the North American Arctic, here taken to include the

    total land area lying north of the tree line, may be divided into four major

    provinces, namely ( 1 ) arctic Alaska and Yukon, ( 2 ) the arctic Archipelago,

    ( 3 ) continental parts of arctic Northwest Territories and Ungava, and ( 4 )

    Greenland. The present description however, embraces only arctic Alaska–

    Yukon and the arctic parts of Mackenzie-Keewatin to which has been added

    the western and central islands of the Arctic Archipelago. It does not

    include arctic Ungava, the easternmost islands of Ellesmere, Devon, Cornwallis,

    Somerset, Baffin, or the islands of Hudson Bay. In this area the writer today

    recognizes 872 species (and varieties of well-defined geographical range) of

    vascular plants distributed among 60 families and 194 genera.

            Although the two areas under discussion are separated by a rather strongly

    marked phytogeographical boundary - the Mackenzie Valley - they have many

    features in common. Approximately one-third of the species which make up the

    combined floras are widely distributed, circumpolar species. Common to them

    both, as the most striking feather, is the total absence of trees. There are,

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    to be sure, a number of ligneous or woody plants - such as willow, dwarf

    birch, and various kinds of heath and berry bushes - but even these become

    low and dwarfed north of the tree line, and are generally restricted to

    places where protecting snow cover is assured during the winter. In the

    interior of the mainland some of the these species still are a dominant component

    of the vegetation, but when we reach the seacoast or cross to the arctic

    islands their numbers dwindle rapidly. The few woody plants that occur there

    become low and creeping, with their stems partly buried in the moss, while

    some of the berry bushes cease to produce fruits, or disappear entirely.

    the climate of the entire region is arctic but there are, nevertheless, strong

    regional differences; thus the Bering Sea shores, and also the Canadian Arctic

    east of Hudson Bay, has a maritime polar climate whereas the Mackenzie and

    Keewatin districts, and also the Arctic Archipelago, all have distinctly con–

    tinengal types of climate with relatively warm summers and very cold winters.

    This is well illustrated by the course of the 50° F. isotherm for the warmest

    month, July, which in western Alaska first parallels the Bering Sea coast,

    then swings abruptly eastward across the north slope of Alaska. From the mouth

    of the Mackenzie, it follows the Arctic coast east to Bathurst Inlet whence, by

    the cooling influence of Hudson Bay, it is deflected in a southeasterly direction,

    bisecting the west coast of Hudson Bay between Chesterfield Inlet and Churchill.

            Even locally the proximity of the sea strongly affects the temperature

    and thereby also the vegetation. Thus, at Nome on the south coast of Seward

    Peninsula, the mean temperature for July is 50° F. whereas Kotzebue, at the

    head of Kotzebue Sound and only 1 1/2 degrees farther north, but sheltered by

    Seward Peninsula, has a 2-degree warmer July mean. Of much more importance,

    however, is that the average numbers of days without killing frost is 52 at

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    Nome but 93 at Kotzebue. The mean annual precipitation at Nome is 18 inches

    whereas at Kotzebue it is only slightly over 6 inches. Barrow, on the other

    hand, has an extreme polar climate; the mean for July there is 40° but the

    number of days without killing frost is only 17, At Coppermine, and at

    Cambridge Bay on Victoria Island, the mean for July is 10° F. higher and the

    number of days without killing frost almost seven times as high as at Barrow.

            Except for the distinctly moister southern part of the Bering Sea region,

    precipitation throughout the area is light, averaging perhaps about 10 inches

    for the year. All records, however, are from stations situated along the

    coast, and there is reason to believe that the annual precipitation of the

    interior mainland as well as that of some of the larger islands is consider–

    ably less. Most of the precipitation falls as snow during the winter but is

    swept off the ground by frequent gales, so that the plant cover, moreover, is

    exposed to the drying effect of the wind. The light precipitation is to

    some measure compensated by the fact that 40 per cent falls as rain during the

    months of June, July, and August. Of far greater importance, however, is that

    owing to the presence of permafrost a few inches below the surface, moisture

    derived from melt water as well as from rain is prevented from penetrating to

    depths beyond the reach of plant roots. Without permafrost many areas in the

    Arctic would be a lifeless desert.



            Arctic Alaska and Yukon — largely unglaciated during the Pleistocene —

    presents the greatest variety of plant habitats; its flora is rich in isolated

    and endemic species and, undoubtedly, is very old. Through its former land

    connection across hypothetical Beringia, there has been a free interchange

    of species so that almost one third of the present flora of 604 species of

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    vascular plants is of Asiatic affinity. The much smaller number of Cordilleran

    species may have reached the area by way of the Mackenzie Mountains. In the

    Eastern Arctic practically all mountains areas were covered by huge ice caps

    during the Pleistocene. In consequence, the alpine flora of the Eastern

    Arctic is youthful, poor in species, and usually entirely lacking in rare or

    endemic species. In Alaska and Yukon, on the other hand, although some of

    the high mountains may have had, or even now have, isolated ice caps, such

    glaciations as existed was largely limited to cirques and valley glaciers;

    during the Pleistocene many of the large mountains massifs undoubtedly acted

    as refugia and, indeed, today harbor the richest floras of rare and endemic

    species (5; 14; 16). Such discontinuous vertical distribution of plants is

    very noticeable on the Seward Peninsula and, indeed, in most places in arctic

    Alaska and Yukon wherever mountains or hills exceed one thousand feet in

    elevation. Below this level the coastal flats are occupied by a wet, marshy

    tundra that everywhere is inhabited by practically the same assortment of

    species. The most notable change in the flora, when one travels inland,

    away from the seashore, is the increasing ration of fruticose species over

    herbaceous ones.

            On the hills, on the other hand, above the one-thousand-foot level, a

    very different and much more varied flora is encountered; here we find most

    of the rare and interesting plants for which the region is famous, notably

    those of Asiatic affinity or at least of bilateral Beringian range. The writer

    (11) selected 88 species that, in the Bering Sea region, appear to be

    restricted to levels above one thousand feet. By grouping these species

    according to their general distribution it is found that, roughly speaking,

    three-fourths are either Western-Cordilleran, Bering Sea endemics, or essen–

    tially Asiatic species transgressing into western America, whereas but one-

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    fourth are widely ranging, circumpolar, or North American species that are

    common across the continent from the Atlantic to the Pacific coast. A

    further breakdown discloses that 17 species are circumpolar or essentially so,

    3 are essentially North American species, known from the Atlantic to the

    Pacific coast, 16 are western American or Cordilleran, 15 endemics of the

    Bering Sea region, and no less than 37 are Asiatic or Beringian bilateral

    species transfressing into western America.

            The Arctic Archipelago was formerly though to have escaped glaciations.

    Recent investigations, however, indicate that at least the southern islands

    have been severely glaciated and that all but the higher parts of the Archi–

    pelago was submerged in Pleistocene time, (13; 20). The climate is decidedly

    high-arctic, and the flora, consequently, is comparatively poor in species.

    The total number of vascular plants species known to occur in the Archipelago

    has recently been increased to 308, of which 226 occur in the western part

    and no less than 214 in Banks and Victoria islands alone (13). Almost

    one-half are widely distributed arctic species. The presence of a compara–

    tively large number of isolated and endemic species offers some curious

    phytogeographical problems.

            The arctic Canadian mainland is characterized by a distinctly continental

    and very dry climate which, together with the absence of mountain barriers,

    accounts for its strikingly uniform and monotonous plant cover. Of the 651

    species known to occur north of the tree line, 70 per cent are widely distri–

    buted circumpolar arctic or North American species. A considerable number

    of nonarctic forest species reach far north of the present tree line and,

    together with tree stumps in situ and peat deposits, may indicate past

    oscillations in the tree line. In terms of postglacial chronology, the flora is

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    youthful, as indicated by unstable, preclimax plant communities and by

    the general paucity of endemic and isolated species. To the west, the

    Mackenzie Valley forms a strongly marked floristic boundary which has been

    crossed by comparatively few species of Cordilleran or bilateral Beringian




            Land surfaces in the Arctic may be divided into three principal tyles

    of landscape: ( 1 ) the ice desert, ( 2 ) the rock desert, and ( 3 ) the tundra.

    The first, which in the form of glaciers, ice caps, or perennial snow fields,

    occupy 86 per cent of the interior of Greenland, and also some smaller moun–

    tain regions in Baffin, Devon, Ellesmere, Axel Heiberg, besides several

    islands of the Sverdrup group, in the area under discussion occurs only as

    local glaciers in the Brooks Range. The rock desert - the dominating land–

    scape in heavily glaciated northern Keewatin, northeastern Mackenzie, and

    the arctic islands - in Alaska and Yukon is found only at high elevations

    in the mountains. In arctic Cnada the rock desert is everywhere interspersed

    with lakes and ponds, or with small or large areas of tundra. The tundra,

    finally, occupies a wide belt between the edge of the forest and the high–

    arctic rock desert and is endowed with the richest flora. Like the rock

    desert it may be divided into several distinct plant communities such as

    marsh, grassland, and dwarf-shrub heath.

            The present treatment deals mainly with the vascular plants. The cryp–

    togamic flora of the arctic landscape is very incompletely known outside

    Greenland, and its ecological aspects are practically unknown. Among the

    terrestrial cryptogams, bryophytes and lichens are both very significant

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    ecologically in the composition of arctic vegetation.

            Thus far comparatively little progress has been made in the study of

    arctic plant communities in North America. In the heavily glaciated parts

    of Keewatin, Mackenzie, and the Arctic Archipelago, the comparative youthful–

    ness of the flora and vegetation is evidenced by unstable plant communities,

    whereas in unglaciated Alaska and Yukon, and in the coastal plain east of the

    Mackenzie, climax conditions may have been attained in the lowland “niggerhead”

    tundra which is so characteristic a feature of the coastal plain landscape.

            Four major types of vegetation may be recognized in arctic North America,

    each capable of subdivision into a number of more or less distinct ecological

    associations, the composition and interrelation of which again depend on the

    physiography of the landscape.

            Rocky barrens or fell-fields

            Vegetation of rock desert

    Vegetation of unstable screes and frost-activated (congeliturbated) soils

    Vegetation of gravelly river flats, flood plains, and fans


            Dwarf-shrub heath

    Lichen and moss heath


    Copses and thickets

    Marsh and wet tundra

    Snow-flush herb mats

            St r and vegetation

            Brackish meadows and marsh subject to floods

    Vegetation of sand dunes and gravel beaches

    Vegetation of rocky shores

            Vegetation of fresh water

            Vegetation of ponds and lakes

    Vegetation of brooks and rivers

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    Rocky Barrens or Fell-fields

            Vegetation of Rock Desert . The fell-field, or rocky barren, has been

    defined ( [ ?] 19 ) as having so scanty a vegetation that the ground is

    only partly covered. To this should be added that the winter snow cover is

    generally deficient. Fell-field vegetation is found at high elevations and

    also in high latitudes and is the dominant vegetation type in the rock desert

    of northern Keewatin and Mackenzie, the greater part of the Arctic Archipelago,

    and the highest mountains of Alaska and Yukon.

            Most striking features of the rock-desert landscape are the flat-rock

    tables and ridges of pre-Cambrian crystalline rocks of the heavily glaciated

    Laurentian Shield or peneplain that has been left almost completely denuded of

    soil, and the extensive, flat, or slightly rolling rock-strewn plateaus of

    severely weathered Paleozoic or pre-Cambr ian sediments predominant in the

    western and northern islands of the Archipelago. But although soil is every–

    where scarce, these wastelands, nevertheless, are not completely lacking in

    vegetation. Over large areas the rock surfaces of the acid pre-Cambrian rocks

    are covered by black, brown, and gray species of the crustaceous lichens ( Rhizo–

    n , Licidea , Lecanora , Buellia , and others), or by the much larger black

    and green foliose lichens, sometimes called “rock tripe” ( Gyrophora and Umbil–

    ) that all lend a rather somber and depressing color to the landscape.

    Some of the Silurian and Paleozoic rocks of the arctic islands, on the other

    hand, almost completely lack lichen cover.

            On loose rocks and gravel grow a number of fruticose species among which

    may be mentioned the coral-like Stereocaulon , black and gray Alectoria , and

    yellow, gray or brown species of Cetraria and Cladonia . On cliffs, below

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    ledges providing nesting sites for gulls, hawks, falcons, or ravens, or on

    isolated boulders that, in the Arctic, are favorite perches for snowy owls

    and other birds, the dung-loving orange or vermilion lichen ( Calopaca elegans )

    often grow in great profusion and lend a touch of color to the otherwise

    bleak landscape

            Flowering plants, however, are not entirely missing in the arctic rock

    desert, for the rock-strewn barren flats or cliffs that from the air may look

    entirely devoid of vegetation, on closer inspection from the ground may dis–

    close small or large patches, or “islands,” of vegetation composed of mountain

    avens ( Dryas integrifolia ), yellow arnicas, several species of locoweed ( Oxy–

    tropis arctica
    , O. pygmaea , O. Maydelliana , and O. arctobia ), or saxifrages.

    For a short time each summer these flowers transform these cases of the rock

    desert into incredibly gas miniature rock gardens.

            A number of plants that grown on windswept, stony soil develop tussocks

    or dense, flat, hemispherical cushions, that by their shape provide protection

    against evaporation and mechanical abrasion by wind, drifting sand, or snow.

    Examples of such plants are the moss pink ( Silene acaulis ), Diapensia lapponica ,

    Loiseleuria procumbens , a number of saxifrages, Draba Bellii , and many others.

    In rock crevices grow a number of species that, like the foregoing, are all

    strongly xerophytic. Among them are several saxifrages ( Saxifraga nivalis

    and S. reflexa ), tufted fescue ( Festuca brachyphylla ), several sedges including

    Carex rupestris , and the rock ferns Woodsia ilvensis , W. glabella , and

    Dryopteris fragans .

            On gravelly slopes or in shelter of rocks where some soil has accumulated,

    the showy, white-flowered avens ( Dryas ) forms large, flat cushions, often many

    feet in diameter, sometimes to the exclusion of other species. In such places

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    we may also find mats of crowberry ( Empetrum ), clumps of the purple-flowered,

    broad-leaved willow herb ( Epilobium latifolium ) or the vetch Hedysarum

    , whose showy purple flowers are scented like sweet clover. Other

    colors are added by the lilac-flowered vetch ( Astragalus alpinus ), by yellow

    arnicas and locoweeds ( Oxytropis ), by blue campanulas, bluish-white anemones

    ( Anemone parviflora ), white chickweeds ( Stellaria and Cerastium ), or by the

    large-flowered and very fragrant Pyrola grandiflora . In the southern part of

    the arctic rock desert occur a number of dwarf shrubs, including several species

    of willow, Lapland rho do dendron ( Rhododendron lapponicum ), dwarf azalea ( lois–

    eleuria procumbens
    ), Labrador tea ( Ledum decumbens ), and bilberry ( Vaccinium

    ). These are always low and prostrate with their stems bent and

    gnarled. Furthermore, their shape is often contorted by wind action so that

    the prostrate crown grows away from the root by which it is anchored. Some

    of them grow espalierlike against south-facing rocks or cliffs from which they

    obtain added warmth. The roots of these dwarf shrubs are spread horizontally

    in the upper layers of the shallow soil, avoiding the permafrost. The majority

    are evergreen, and in the structure of their leaves possess special features,

    such as hair covering and concealed stomata to prevent loss of water.

            Vegetation of Unstable Screes and Frost-activated (congeliturbated) Soils .

    Unstable rock screes and stone creeps, together with soil sorting and heaving,

    usually result from frost action in the soil and are features of high-arctic

    climates such as are found in high latitudes or at high elevations. The un–

    stable soil conditions of these habitats make them unsuitable to many plants,

    especially such as have woody stems or horizontal thizomes, whereas those with

    superficial runners, strongly developed taproots or adventitious root systems

    are able to persist. A number of xerophytic species, particularly in the

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    families ( Cruciferae and Compositae ( Erysimum pallassii , Lesquerella arctica ,

    Smelowskia calycina , Draba spp., Arabis spp., Crepis nana , Artemisia spp., and

    Taraxacum spp., to mention only a few) by their growth form seem especially

    well adapted to slide-rock habitats. In the strongly frost-activated soil of

    polygon fields in Banks and Victoria islands, avens ( Dryas integrifolia ),

    cinquefoil ( Potentilla rubricaulis ), and the locoweed ( Oxytropis arctica ) are

    extremely common and frequently comprise 90 per cent of the plant cover.

            Vegetation of Gravelly River Flats, Floodplains, and Fans . Floodplains,

    river flats, and fans are inhabited by plants whose growth form, like that of

    the scree plants, permit them to endure unstable soils, but they must also be

    able to withstand water erosion and inundation. Because the soil movements

    are less violent and water is abundant, a few woody species, notably willows

    and several hemicryptophytes with sell-developed rhizomes may grow here as well.

    [ ?] The broad-leaved willow herb ( Epilobium latifolium ), the vetches (Hedysarum

    alpinum and Astragalus alpinus ), besides several grasses and sedges, are ubiquitous

    in these habitats.

            The predominance of alpine and arctic species on erosion fans and flood–

    plains has sometimes been taken to indicate that these plants were washed down

    from adjacent mountains by glacial torrents during spring freshets, and that

    they were able to gain a foothold only because lowland species are not so well

    adapted to the edaphic conditions which are peculiar to these habitats. Per–

    haps the primary reason why alpine and arctic plants frequently dominate flood–

    plains and erosion fans, is that huge masses of overflow ice (crystocrene)

    accumulate there in winter and frequently persist until late in the summer,

    thereby shortening the season to such an extent that only truly alpine or

    arctic plants can survive.

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            Dwarf-shrub Heath . The tundra differs from the rock desert by having

    a closed or continuous cover of vegetation and in having a protective cover

    of snow in winter. The dwarf-shrub heath of the tundra is essentially a

    continental lowland plant association and reaches its best development in the

    interior coastal plain of the north slope of Alaska at some distance from the

    sea, in northern Mackenzie, and in central Keewatin. Its principal components

    are low willow ( Salix spp.), dwarf birch ( Betula glandulosa , Labrador tea

    ( Ledum decumbens , and L. groenlandicum ), Lapland rhododendron ( Rhododendron

    ), bearberry ( Arctostaphylos alpina and A. rubra ), besides white

    heather ( Cassiope tetragona ), bilberry ( Vaccinium uliginosum ), and the alpine

    cranberry of cowberry ( Vaccinium Vitis-Idaea ). Ubiquitous also are a number

    of sedges and grasses such as Carex lugens , Arctagrostis latifolia , and Festuca

    , but notably cotton grass ( Eriophorum vaginatum ) which forms huge

    tussocks that are known in Alaska as “niggerheads.” These solid, turfy

    hummocks may stand a foot or a foot and a half above the surrounding ground

    and are notorious as the chief impediment to travel across the tundra in

    summer or winter. When viewed from a distance the “niggerhead tundra” has

    the appearance of a slightly uneven grassy plain, and in mid-July, when the

    “cotton” matures, may look completely white as if the land were covered

    with snow.

            Among the smaller herbaceous plants growing on the tundra are several

    fernweeds ( Pedicularis labradorica , P. lanata , P. arctica , and P. sudetica ),

    baked-apple ( Rubus Chamaemorus ), groundsel ( Senecio atropurpureus and S .

    lugens ), Saussurea angustifolia , blue lupine ( Lupinus arcticus ), wintergreen

    ( Pyrola grandiflora ), the knotweed ( Polygonum Bistorta ssp. plumosum ), the

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    root of which is edible, yellow saxifrage ( S. Hirculus ), Spiraea Beauverdiana ,

    and many others. Many of these have brightly colored flowers and for a short

    time in early summer the dwarf-shrib heath is gay with color, but during the

    rest of the year presents a dreary and desolate aspect.

            The ground under and between the stems of the dwarf bushes and between

    the tussocks is everywhere covered by a dense carpet of mesophytic mosses

    and lichens into which the foot of the traveler sinks ankle deep at every

    step, making traveling on foot exceedingly wearisome.

            Lichen and Moss Heath . Near the timber line, in drier and better drained

    parts of the tundra, the dwarf-shrub heath imperceptibly passes into lichen

    and moss heath. The place of mesophytic species of mosses is here taken by

    gray and brown fruticose lichens of which the so-called reindeer mosses

    ( Cladonia rangiferina , Cl. alpestris, Cetraria nivalis ) and Iceland moss

    ( Cetraria islandica ) dominate to such an extent that the landscape may appear

    as if snow-covered. In time most herbs and the low dwarf shrubs become sub–

    merged in the lichen carpet, and only dwarf birch, rhododendron, and willow


            Grassland . Extensive grassland or natural meadows are occasionally found

    in the tundra regions, especially in central Keewatin, on alluvial flats

    formerly occupied by large glacial lakes. These meadows are still wet in

    spring but there is reason to believe that they will, in time, be invaded

    by tundra shrubs and eventually change to dwarf-shrub heath. The principal

    meadow-forming species are Carex saxatilis and C. membrancea , Arctophila

    , Arctagrostis latifolia , Deschampsia caespitosa , Juncus balticus , Carex

    and C. canescens , besides a number of herbaceous tundra herbs.

            Copses and Thickets . Willow and alder thickets, with their accompanying

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    flora of herbaceous species, are found chiefly on the continent, in well–

    drained soils along streams, on south-facing slopes, and on the sloping banks

    of lakes and rivers where protection against wind and consequent accumulation

    of snow is assured. The alder ( Alnus crispa ), although it does not extend far

    north of the tree line, form thickets 18 feet high with trunks up to six

    inches in diameter, along the lower courses of rivers flowing into Bering

    Sea. At some inland villages, where timber or driftwood is not available,

    alder is the principal source of fuel. The principal thicket-forming willows

    are Salix arbusculoides , S. pulchra , S. Richardsonii , S. glauca , S. planifolia ,

    and S. alaxensis . Only the last may occasionally assume tree like growth, whereas

    the rest are shrubs that rarely exceed 8 feet in height. In protected places

    with abundant snow cover, willow thickets may be found even in the arctic islands.

    Thus, on the south-facing slope at Walker Bay, on the west coast of Victoria

    Island, in latitude 71° 30′, Salix Richardsonii forms six-foot-high thickets.

            Some of the common herbs growing inside the thickets are fireweed.

    ( Epilobium angustifolium ), horsetail ( Equisetum arvense ), the anemones ( Anemone

    and A. Richardsonii ), buttercup ( Ranundulus lapponicus ), coltsfoot

    ( Petasites frigidus ), groundsel ( Senecio lugens ), wintergreen ( Pyrola grandiflora ),

    and a number of grasses and sedges. Among the latter, cotton grass ( Eriophorum

    ), blue joint grass ( Calamagrostis canadensis var. Langsdorffi i),

    and Arctagrostis arundinacea are the most important.

            Marsh and WetTUndra . Wet, grassy tundra predominates on low coastal flats

    of the unglaciated arctic coast of Alaska and probably is a climax type found

    on thick deposits of raw humus or peat that here often rests on a massive

    thickness of fossil ice. The often very great thickness of frozen, raw humus

    suggests that this lowland tundra formation is very old. It was probably

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    formed during a period with a climate wetter than the present and may be

    considered a postclimax relic which is no longer being actively formed. A

    characteristic feature of thus tundra is the presence of numerous ponds and

    lakes that have formed in places where the fossil ice below the tundra has

    melted. Such local erosion is actively going on everywhere in the tundra

    today; it frequently starts by the widening and cutting, by meltwater, of a

    frost crack or when, in some other manner, the insulating cover of humus is

    removed by water or wind erosion. Such tundra ponds usually have steep,

    slumping banks in which may usually be seen a wall of pure ice (10; 11).

    This form of tundra occurs only in unglaciated parts of arctic North America

    but has its counterpart in arctic Eurasia.

            Another feature of special interest in the low wet tundra is well-developed

    patterns of irregular polygonal ridges of peat which have formed along frost

    cracks. Another peh phenomenon caused by frost action are the conical hills

    or pingos formed in former lake basins by the local upheaval due to expansion

    following the progressive downward freezing of a lens or body of water or

    semifluid mud or silt trapped between the frozen surface soil and a lower

    permafrost layer. East of the Mackenzie delta some pingos , formed in this

    manner, are several hundred feet high (10). Around the bases of these hills

    are concentric peat ridges separated by moatlike ribbons of water.

            The flora of the wet, lowland tundra is more varied and far richer in

    species than is the dwarf-shrub tundra. In the wet tundra back of Atkinson

    Point on the Arctic Coast, east of the Mackenzie Delta, the writer (8)

    noted 150 species of flowering plants, more than a third of them grasses

    and sedges. Dwarf shrubs are almost entirely absent and represented chiefly

    by creeping willows. Fruticose lichens, too, are scarce whereas bryophytes

    are well represented.

    016      |      Vol_VI-0465                                                                                                                  
    EA-PS. Porsild: Flora and Vegetation

            Snow-flush Herbmats . An association of particular interest is found

    in places where large snowdrifts accumulate during winter. Mountain country,

    especially if the snowfall is heavy, favors the formation of large drifts,

    but even in the lowland where the snowfall is generally light, large drifts,

    favorable for the formation of snow-flush vegetation, may be formed by the

    prevailing wind in river valleys, on sheltered slopes, at the base of cliffs,

    and along lake shore . s. Such habitats are late, for the snowdrift may last

    well into the summer or, indeed, may not disappear entirely before winter

    starts. The snowdrift, on the other hand, throughout the summer provides an

    unfailing supply of water and, besides, contains a very considerable amount of

    potential plant food in the form of wind-transported inorganic dust or loess

    mixed with seeds and plant remains. The accumulation of fertile soil which is

    often found on screes and slopes is deposited in this manner.

            The principal difference between the willow thicket and the snow-flush

    association is due to the duration of the snowdrift: too deep snowdrifts

    shorten the season too much for willows. For this reason willow thickets

    usually are found on the edge of snow-flushes, thus giving the impression that

    the willows are invading the herbmat area. The assembly of species that occupy

    snow-flushes are almost entirely herbaceous, and chiefly of the hemicryptophytic

    type in which the wintering buds are placed below the surface of the soil. The tiny

    willow ( Salix herbacea ) in the East, and ( S. pseudopolaris ) in the West are

    among the few woody plants found on snow-flushes. Characteristic, and very

    necessary for snow-flush plants is their ability to persist vegetatively for

    several seasons, when thick snowdrifts reduce their growing season to a minimum.

    Many snow-flush plants may not flower and fruit for a period of years and may

    even survive several unfavorable seasons completely buried under snow and ice.

    017      |      Vol_VI-0466                                                                                                                  
    EA-PS. Porsild: Flora and Vegetation

    Whereas the general aspect of snow-flush vegetation is similar everywhere

    in the Arctic, its floristic composition varies greatly according to geo–

    graphical position. For example, snow-flushes in Greenland and in the

    Mackenzie Delta have almost no species in common. Examples of widely distri–

    buted snow-flush plants are the alpine spear grass ( Poa alpina ), sedge ( Carex

    ), mountain sorrel ( Oxyria digyna ), dwarf buttercup ( Ranunculus

    ), and alpine club moss ( Lycopodium slpinum ).


    Strand Vegetation

            Brackish Meadows and Marsh Subject to Floods . Salt marshes subject to

    floods are found chiefly on the low continental strand flats of western and

    northern Alaska, and from the delta of the Mackenzie extend east to the mouth

    of Anderson River. Along this shelving coast large, shallow, and brackish

    bays or lagoons are cut off from the open sea by long sandspits or by narrow

    sand or gravel islands formed by sea currents and by ice-push. Rivers empty–

    ing into the lagoons speed up the silting process, which is further favored by

    the almost neglibible tide. Back of the lagoons are vast meadow-covered flats

    that, as one travels away from the coast, imperceptibly change into low tundra.

    Most common in the meadows are grasses, sedges, and rushes, among them Arctophila

    , Deschampsia caespitosa , Dupontia psilosantha , D. Fisheri , Puccinallia

    var. alaskana , and P. phryganodes , Carex aquatilis , C. glareosa var.

    amphigena , C. maritima , and C. rariflora , besides Eriophorum Scheuchzeri and

    E. angustifolium , Juncus balticus and J. castaneus . Among the more common

    herbs growing in the meadows are the chickweed ( Stellaria humifusa ), scurvy

    grass ( Cochlearia ), Chrysanthemum arcticum , the sweet-scented white buttercup

    ( Ranunculus pallassii ), the white cowslip ( Caltha natans ), and marsh fleabane

    ( Senecio congestus ).

    018      |      Vol_VI-0467                                                                                                                  
    EA-PS. Porsild: Flora and Vegetation

            Vegetation of Sand Dunes and Gravel Beaches . Along the shores, on raised

    beaches and sandspits, are extensive dunes inhabited by lyme grass ( Elymus

    ssp. mollis ), fescue ( Festuca rubra var. arenaria ), spear grass

    ( Poa arctica and P. eminens ), and Carex Gmelini — the last two do not enter

    Canada — brome grass ( Bromus Pumpellianus var. arcticua ), seabeach sandwort

    ( Arenaria peploides ), stonecrop ( Rhodiola integrifolia ), blue lungwort ( Mertensia

    ), wormwood ( Artemisia Tilesii ), Aster sibericus and several species

    of dandelion ( Taraxacum spp.). On the edge of the dune, in wet sand near the

    beach, is often found the delicate blue gentian ( Lomatogenium rotatum ), creep–

    ing buttercup ( Ranunculus gymgalaria ) and the dwarf sedges, Carex subspathacea

    and C. ursina .

            Vegetation on Rocky Shores . On cliffs and boulder beaches that are not

    too exposed to the open sea may be found dense swards of Puccinellia phryganodes

    and similar grasses that occupy crevices and crannies between rocks. Here also

    grow scurvy grass ( Cochlearia ), chickweed ( Stellaria humifusa ), and a few other

    seashore plants.


    Vegetation of Fresh Water

            Vegetation of Ponds and Lakes . Nearly all large and deep lakes in the

    Arctic are too cold for vascular aquatic plants, but they possess a rich flora

    of microorganisms such as green and blue-green algae, desmids, diatoms, and

    flagellates. Different species of these mostly microscopic plants often impart

    a distinctive colorto the waters of the lakes. This is the best seen from the

    air, when it is at once noticeable that, apart from the difference in color

    caused by the depth of the water and the nature of the bottom, the water

    itself in no two lakes is exactly alike.

    019      |      Vol_VI-0468                                                                                                                  
    EA-PS. Porsild: Flora and Vegetation

            Shallow ponds and lakes that remain water-filled throughout the summer,

    on the other hand, sustain a surprisingly rich plant life. Because of their

    shallowness, the water of these ponds warms up more quickly and becomes free of

    ice long before that of the large and deep lakes. The short season prevents

    many species of aquatic plants in the Arctic from reproducing by seed, but

    they maintain themselves successfully, nevertheless, by the production of

    wintering buds ( Potamogeton spp., Utricularia spp., and others). The most

    common aquatic plants here are pondweeds ( Potamogeton filiformis ), the arctic

    buttercup ( Ranunculus hyperboreus ), and mare’s-tail ( Hippuris vulgaris ).

    Floating and submerged mosses are abundantly represented, as are freshwater


            Vegetation of Brooks and Rivers . Small, sluggish lowland streams in the

    Arctic may sometimes be inhabited by aquatic plants similar to those of fresh–

    water ponds. Most arctic streams, however, are too cold or too turbulent for

    vascular species, but a number of marsh plants - chiefly sedges and grasses -

    inhabit protected and sheltered places on stream margins and flood plains. A

    number of dark-colored mosses ( Grimmia spp. and Hygrophypnum ) and blue-green

    and brown algae grow on the rocks of most arctic brooks, even in water that

    is but a few degrees above freezing. The brown, slimy flagellate ( Hydrurus

    ) flourished on the rocks of clear pools in ice-cold meltwater below

    snow fields.

    020      |      Vol_VI-0469                                                                                                                  
    EA-PS. Porsild: Flora and Vegetation


    1. Anderson, J.P. Flora of Alaska and adjacent parts of Canada , Parts 1 - 8.

    Iowa State College, Vols. 18, 18, 20, 21 and 23. 1943.

    2. Anonymous. Climate and Man . Year Book of Agriculture. U.S. Dept. Agric.,

    Washington, 1941.

    3. ----. Meteorology of the Canadian Arctic . Dept. Transp., Met.Div.

    Ottawa, 1944.

    4. Fernald, M. K. “Persistence of plants in unglaciated areas of boreal

    America,” Mem . Gray Herb., 2. 1925.

    5. Hult e é n, E. Outline of the history of arctic and boreal biota during

    the Quaternary period
    . Stockholm, 1937.

    6. ----. “Flora of Alaska and Yukon,” Parts 1 - 9. Lunds Univ. Årsskr .,

    vols. 37, 38, 39, 40, [ ?] 41, 42, 43, 44, and 45. 1941.

    7. Johansen, Frits. “General observations on the vegetation,” Report

    Can. Arct. Exp. 1913-18, vol.5, Ottawa, 1924.

    8. Porsild, A.E. Reindeer Grazing in Northwest Canada . Dept.Interior,

    Ottawa, 1929.

    9. ----. “Flora of Northwest Territories,” In Canada’s Western Northland .

    Dept. Mines & Res. Ottawa, 1937.

    10. ----. “Earth mounds in unglaciated arctic northwestern America,”

    Geogr. Rev., vol.28, pp.46-58, 1938.

    11. ----. “Contributions to the flora of Alaska,” Rhodora , vol.41, pp.141-83,

    199-254, and 262-301. 1939.

    12. ----. “Materials for a flora of Northwest Territories of Canada,” Sargentia ,

    vol.4, 1943.

    13. ----. “A biological exploration of Banks and Victoria islands,” Arctic

    vol.3, pp.45-54, 1950.

    14. ----. “Botany of southeastern Yukon,” Nat.Mus.Can. Bull . 121, 1951.

    15. [ ?] Porsild, M.P. “The flora of Greenland: Its affinities and probable

    age and origin,” Torreya vol. 22, pp.53-54, 1922.

    16. Raup, Hugh M. “Botanical problems in boreal America,” Bot.Rev .,

    vol.7, nos. 3 and 4. 1941.

    17. Simmons, H.G. “A survey of the phytogeography of the Arctic American

    Archipelago,” Lunds Univ. Arsskr . N.F. Afdl. 2, Vol.9, 1913.

    021      |      Vol_VI-0470                                                                                                                  
    EA-PS. Porsild: Flora and Vegetation

    18. Walker E. P. “Alaska: America’s continental frontier outpost,”

    Smithsonian Inst. War Backgr.Studies , No.13, Washington, 1943.

    19. Warming, Eng. “On Gronlands Vegetation,” Medd. om Gronl ., vol.12,

    Copenhagen. 1888.

    20. Washburn, A. L. “Reconnaissance Geology of portions of Victoria

    Island and adjacent regions arctic Canada,” Geol.Soc.Am.

    Mem . 22, 1947.


    A. E. Porsild

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