Flora and Vegetation of Iceland

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(EA-Plant Sciences. Askell Löve)

FLORA AND VEGETATION OF ICELAND

       

CONTENTS

	Page
Topography	1
Climate	3
Flora	4
Vegetation	6
Moist Soils	6
Dry Soils	14
Bibliography	23

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EA-PS. Love: Flora and Vegetation in of Iceland

       

LIST OF FIGURES

		Page
Fig. 1.	The main nunatak areas during the maximum glaciations	3a

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EA-PS. Love: Flora and Vegetation of Iceland

       

PHOTOGRAPHIC ILLUSTRATIONS

        With the manuscript of this article, the author submitted 8 photo–

graphs for possible use as illustrations. Because of the high cost of

reproducing them as halftones in the printed volume, only a small propor–

tion of the photographs submitted by contributors to Encyclopedia Arctica

can be used, at most one or two with each paper; in some cases none. The

number and selection must be determined later by the publisher and editors

of Encyclopedia Arctica . Meantime all photographs are being held at The

Stefansson Library.

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EA-Plant Sciences

(Askell Love)

       

FLORA AND VEGETATION OF ICELAND

       

TOPOGRAPHY

        Iceland, the largest plinth on the submarine ridge crowing the Atlantic

between Scotland and Greenland, has a surface of about 104,785 square kilo–

meters. Its southernmost point lies at 63°19′ N. latitude, its northernmost

isle at 67°07′ N. latitude, its westernmost point at 24°32′ W. longitude, and

its easternmost skerry at 13°16′ W. longitude, the Arctic Circle touches the

northeastern part of the mainland. The shortest distance from Iceland to

Greenland is about 300 kilometers, to the Faeroes it is about 420 kilometers,

to Scotland about 800 kilometers, and to the Norwegian coast about 970 kilo–

meters.

        Iceland is built up mainly by basic eruptives from the Tertiary, Pleisto–

cene, and Holocene, subsequently molded by abrasion, faults, and other denuding

agencies. The principal rocks are basalt and palagonite breccia, attaining a

total thickness of perhaps 4,000 meters. The oldest layers are at least some

200 meters below the present sea level, but the rocks underlying the basalt

formation are as yet unknown. In Paleocene times about half the total thick–

ness of the basalt was formed, and in the Eocene a lignite formation up to 50

meters thick accumulated, indicating a long period without great change. The

plant remains of this formation seem to suggest a climate of perhaps similar

character to that at present found in the temperate areas of North America

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EA-PS. Lõve: Flora and Vegetation of Iceland

and southern England, although the remains have, so far, not been thoroughly

studied from modern viewpoints. It is suggested that during the Eocene the

mean annual temperature of the island was about 7° to 10°C higher than at

present.

        Originally the plateau was built up of horizontal lava layers, but in

preglacial times a broad central zone of submergence, now filled up by the

palagonite , was formed. It is in this district that almost all the present–

day volcanoes are found. In the west and east, large areas are formed entirely

by the old basalt layers.

        In the basalt districts in the northwest, north, and east, only two

topographical levels above the submarine shelf are discerned: ( 1 ) the coastal

and the valley plains from sea level up to an altitude of about 100 meters,

and (2) the tableland from about 600 up to about 1,000 meters. In the central

part of the country, however, at least three such levels are found: ( 1 ) the

coastal plains up to about 100 meters, ( 2 ) the Inland plateau or tableland

from 300 to 600 meters, and ( 3 ) the plateau horsts from 1,000 to 1,800 meters.

Above the plateau horsts some isolated volcanoes reach up to 2,118 meters (in

the case of Oraefa jökull). The present glaciation is mainly connected to tea

plateau horsts and volcanoes, as its limit is generally above 1,000 meters.

        The Icelandic coast line is more than 6,000 km. in length. The coast in

much indented except in the south, but practically no coastal archipelago is

found. Although lowlands are fairly plentiful in the west, southwest, and

south, they are estimated to occupy not more than one-fifteenth of the country

as a whole.

        At the present time, about one-seventh of the island is covered by perma–

nent ice, but during the Pleistocene glaciations only snail areas were

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unglaciated; exceptions were in the mountainous coastal regions in the north–

west, east, and between Skagsf jördur and Skjalfandi in the north — i.e., the

so-called Eyjaf jördur district, the history of the glaciations in Iceland has

not been very closely studied as yet, but according to some geologists rather

large nunatak areas did exist within the above-mentioned areas during the max–

imum glaciation; it is to be presumed that on them persisted both plants and

small animals (see Fig 1.)

        Although no c h alk formations are found in Iceland, some real calciphilous

plant species occurs They are mainly restricted to the basalt regions.

        According to geologists, the connection between Iceland and other countries

was disrupted in the late Miocene, and since then the country has been an iso–

lated island. This is, however, mainly an assumption.

       

CLIMATE

        Iceland is situated in the region where the cold Polar Current and the

warm Gulf Stream mingle. The climate seems best considered subarctic in most

parts of the island. The mean temperature of July, the warmest month, varies

from approximately 7.2° to 10.6°C. (45° to 51°F.), but the winter temperatures

are not very low, the lowest January mean on record being −6.1°C. (21°F.), and

the highest l.4°C. (34.5°F.). The mean temperature during the year varies

from about 0° to 5°C, (32° to 41°F,). Frost may, however, be experienced in

every month of the year in all localities. In all places the weather is very

stormy, and the precip it ation is considerable in the southern and western parts

of the country, The snow lies in the northern lowlands for as much as 3 1/2

months in an average year, but only for 1 to 1 1/2 months in the southern parts

of the country. Solifluction is more common in the southern than in the northern

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lowlands, but permafrost exists only in the inland plateau, mainly in the

northern and eastern parts of the country, where precipitation during the

w inter months is relatively small. In some years the arctic drift ice will

affect the spring and summer temperatures, at least in the northern parts

of the country, but in most years it will only be found for a short time off

the north coast. Nevertheless, only in one year out of every five has the

coast been completely free from drift ice daring the last 150 years.

       

FLORA

        The flora of Iceland is not yet thoroughly investigated, as large areas

have never been studied by a trained botanist, and only a few collections of

lower plants have been made by specialists. The number of species known is,

therefore, by no means complete, and some of the species and their lower units

are not as yet fully determined. The total number of species known at present

seems to be about 3,600, bacteria excluded. Of these, about 770 are freshwater

or marine diatoms; about 300 are other freshwater and aerial algae; the marine

algae recorded are only 200 (exclusive of diatoms); about 1,000 species of

fungi are known from the island; the lic eh he ns known number about 350; the

bryophytes collected are about 450; 33 species of pteridophytes are known;

and about 550 spermatophytes, including Taraxacum and Hieracium . Of these

figures, however, only those of the spermatophytes, pteridophytes, and marine

algae are based on really detailed studies in many parts of the island.

        It is assumed that a large part of the Icelandic flora has survived the

Pleistocene glaciations in the nunatak areas of the coastal refuges. This

suggestion is not only based on geobotanical studies of the present flora, but

also supported by studies of the flora of the interglacial layers observed in

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some places in the southwest and north. According to preliminary calcula–

tions, at least 55% of the present flora of higher plants belong to the group

of glacial survivors; about 30% may have been introduced by man during the

last 1,000 to [ ?] 1,200 years; but the remaining 15% might perhaps belong to

the first-named group or have dispersed from other regions in postglacial

though prehistoric times. Among the lower plants, the percentage of glacial

survivors is estimated to be still higher.

        Although the Icelandic flora is rather young, it includes some endemics.

Those known at present among the higher plants are: [ ?] Ophioglossum vulgatum

var. islandicum , Sesleria varia subsp. Islandicum , Roegneria ( Agropyron )

doniana var. stefanssonii , R. borealis var. islandica , Dactylorchis maculate

subsp. islandica , Silene maritima subsp. islandica , Papaver radicatum subsp.

islandicum and subsp. stefanssonii , Euphrasia rotundifolia , E. davidssonii ,

Galium pumilum subsp. islandicum , and several Hieracium and Taraxacum micro-

species. If we exclude the last-named apomictic groups, less than 2% of the

flora of higher plants are so far known to be endemic types. However, this figure

will certainly become higher when closer studies of all the species are per–

formed.

        Although the great majority of the Icelandic higher plants belong to the

group of circumpolar or at least circumboreal species, a rather high percentage

belong to groups present in Scandinavia or Eurasia but not in northeastern

America. There are also some species which belong to the group of “west-arctic”

plants, occurring in eastern North America, Greenland, and northern Scandinavia,

but not in Asia; and some species of this group are not met with in Scandinavia,

their area of distribution reaching from North America to Greenland and Iceland

only. The most remarkable of these plants of more restricted range are:

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EA-PS. Lõve: Flora and Vegetation of Iceland

Elymus mollis ( E. arenariu m s var. villosus ), Leucorchis ( Habenaria ) straminea ;

Platanthera ( Habenaria ) hyperborea , Salix cordifolia var. callicarpea , Cakile

edentula subsp. typica , Saxifraga aizoon subsp. neogaea , Epilobium latifolium ,

Galium brandegeei , and Plantago juncoides var. glauca . Of the mosses, at

least Bryoxiphium norvegicum belongs to this group.

       

VEGETATION

        As a whole, the vegetation of Iceland is characterized by the low number

of species withstanding the wet and relatively cold climate. Typical alpine

species are met with at sea level in the southwestern portions of the country

as well as about the outer parts of the fjords in the other regions, but in

the inner parts of the fjords in northern Iceland and the inner lowland in

the east, the climate is more continental and real alpine species are not found

at the lowest altitudes. The tree limit is at 200 to 300 meters in southern

and western Iceland, but in the northern and eastern parts it may reach up to

500 or 600 meters.

       

Moist Soils

        Submarine Shelf and Littoral Zone . The vegetation of the submarine

shelf is not very complicated and its characteristic types are almost the

same as in northern Norway and southern Greenland. Farthest from the coast

only the formation of crustaceous algae is met with, followed toward land

by the Lithothamnion, the deep-water associations of the Floridion (mainly

Polysiphonetum arcticae), the Desmarestion, and different associations of

the Laminarion, the Laminarietum digitatae, and the Laminarietum hyperboreae.

These are the communities of the depths, the Laminarietum saccharinae form–

ing most of the vegetation nearest the coast. Above this sublittoral zone

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the Corallinion is met with, followed by Polysiphonetum urceolatae, Rhodomenion,

Chondetum, and Monostrometum. The comes the real littoral zone, dominated by

the Fucion and some communities of filifrom algae, the Ulotrixetum, Codioletum,

Bangietum, and Porphyretum. In the inner fjords of the west coast the Zoster–

etum occupies relatively large areas of muddy clay in the sublittoral zone, al–

though it became very much decimated by disease during the period 1930 to 1940

as in other parts of the North Atlantic. At one place only, in somewhat brack–

ish water in the sublittoral zone, the Ruppietum maritimae was observed.

        Immediately above the littoral zone the Verrucarion and other lichen com–

munities are met with on stones and rocks, but on sandy and gravelly coasts

where the winter storms drive in masses of wracks ( Fucus app.) the outposts of

higher vegetation are hapaxanthic species of Polygonum , Atriplex , and various

Cruciferae. On the sandy and gravelly beaches above this zone, there occurs

more or less open vegetation characterized by Cakile edentula , Arenaria peploides ,

Potentilla anserina (in the northernmost parts P. egedii ), Mertensia maritima ,

and Tripleurospermum maritimum . This zone seems to merge into the next which

consists of Festucetum cryophilae, Puccinellietum, and Agrostidetum, intermixed

with Polygonum heterophyllum , Silene maritima , Cochlearia , Potentilla anserina ,

Thymus arcticus , Plantago maritima (in the northernmost parts P. juncoides var.

glauca) , Galium verum , and other more or less typical coastal plants.

        In sheltered localities around the inner parts of some fjords, a closed

marsh is apt to be formed in places flooded by the sea during some time of the

year. The vegetation of these marshes seems to be exclusively the Puccinellie–

tum maritimae mixed with a few individuals belonging to the general Carex ,

Juncus , Scirpus , Triglochin , Potentilla , and Plantago .

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        Some parts of the coast, especially in the basalt regions, are formed

of steep cliffs, often populated by sea birds during the spring. Such situa–

tions are very rich in vegetation, the most frequent communities being com–

posed chiefly of Festuca , Poa, Cochlearis , Sedum rosea , Angelica archangelica ,

and Ligusticum scoticum . On the cliffs thems le el ves, many speci e s of lichens

and mosses from their varied and often colorful communities. On the more

grassy parts of the cliffs, Potentilleto-Bistortion vivipari and communities

belonging to the Ranunculeto-Oxyrion or the Geranietum silvatici are often

mixed with the Festuceto-Poeticum.

        Lakes and Pools . The vegetation of the lakes and pools is different in

eutrophic and oliotrophic water, but the difference has not yet been very

closely studied in Iceland. In deep lakes only Characeae and other algae

are met with, but in shallow lakes the vegetation belongs to the Littorellion,

including species of Isöetes , Littorella , Subularia , Callitriche , Myriophyllum,

Hippuris , and some other plants. The associations belonging to the Potamion

euro-sibiricum are common at least in the eutrophic lakes. Its typical repre–

sentatives are various species of P e o tamogeton , Sparganium , Ranunculus , etc.

        The shores of the lakes and shallow pools are almost entirely covered by

the Equisetetum fluviatile and Caricetum rostratae-Lyngbyae, follow [ ?] ed by at the

d r ier margins by Caricetum fuscae (with the moss Drepanocladus exannulatus )

and other marsh communities.

        Running Water . The vegetation of running water is almost the same as in

the lakes when the current is slow; but in rivers and streamlets with a strong

current, there are rather few higher plants — except, of course, at the banks.

Nostoc spp. And other algae together with such mosses as Fontinalis , Hygrohyphnum

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EA-PS. Lõve: Flora and Vegetation of Iceland

and Rhynchostegium are frequent in the rivers, but in glacier streams no mosses

or higher plants are to be found.

        Springs . The vegetation of springs and of the banks of small streamlets

in both the lowland and the highland is extremely rich in mosses. Most of the

vegetation of the springs seems to belong to alpine associations. Examples

are ( 1 ) Mniobryo-Archangeletum and ( 2 ) Mniobryo-Epilobietum hornemanni, which

are not restricted only to the highlands, ( 3 ) Philonoto-Saxifragetum stellaris,

which is common almost all over the country, and ( 4 ) some communities belonging

to the Cratoneureto-Saxifragion aizoides in the northern and eastern parts of

the country. These last include the Cratoneureto-Crepidetum paludosae, the

Cratoneureto-Saxifragetum aizoides, and some other communities occupying small areas and involving

Cratoneuron glaucum , Bryum ventricosum , Equisetum variegatum , Epilobium alsini–

folium , and some other species.

        The vegetation of hot springs and solfataras is often rich in species of

algae and mosses, but as a whole it seems to be composed mainly of different

types of the Icelandic marsh and spring communities. About thirty species of

mosses, some higher plants, and several species of algae are exclusively met

with [ ?] on warm soils. Drawf forms of higher plants are typical for such locali–

ties, owing to the effect of the high temperature on the time of flowering;

but these forms are only modifications.

        Marshes . The moist soils are predominantly the marshes. Their vegetation

may most easily be subdivided into two groups, the eutropic-mesotrophic marshes

or Caricetalia fuscae, and the meso-oligotrophic marshes or Scheuchzerietalia.

In addition, there are the shrub marshes or Oxycocco-Ledetalia, which are met

with in some areas.

        The eutrophic-mesotrophic marshes are always typical infiltration ones,

i.e., they are formed mainly in places with running groundwater or those that

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EA-PS. Löve: Flora and Vegetation of Iceland

are influenced by water from rivers and streamlets. They are grouped into

two rather different types of marshes, the Caricion atrofuscae-saxatilis,

which is mainly found on basic soils in the lowlands, and the Caricion canescentis-fuscae,

which is met with on more or less neutral soils and at high as well as low

levels.

        At least five different marsh types belonging to the Caricioin atrofuscae–

saxatilis association s are known from Iceland.

        ( 1 ) In sandy or gravelly localities near rivers and streamlets the

Caricetum microglochinis marshes are met with. Their characteristic species

seem to be Carex microglochin , C. maritime , C. capillaries , C. fusca , Juncus

triglumis , and perhaps Bistorta vivipara ( Polygonum viviparum ), Epilobium

latifolium , and Pinguicula vulgaris ; the mosses most frequently associated

[ ?] are Climacium dendroides , Drepanocladus intermedius , Philonotis tomen–

tella , Oncophorus virens , and Swartzia Montana . Some lichens such as Cetraria

nivalis are frequently met with, and various species of higher plants charac–

teristic of dry and moist soils may be associated in these marshes.

        ( 2 ) In relatively dry localities, Caricetum atrofuscae-vaginatae marshes

are sometimes observed. They are rich in species and a useful indicator of

excellent soils. One of the two most characteristic species from Europe,

Carex atrofusca , is not found in Iceland, but this marsh type in Iceland is

characterized by C. vaginata , with C. dioeca , C. norvegica , C. saxatilis ,

C. adelostoma (in a few places in the northwest), Salix cordifolia var.

callicarpea , Betula nana , Bistorta vivipara , Thalictrum alpinum , Vaccinium

uliginosum , and several other species which are always found in these marshes.

Their cryptogamous flora is also rich in species, although only Blindia acuta ,

Drepanocladus exannulatus , D. intermedius , and the lichen Cetraria islandica

are always present.

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        ( 3 ) In very wet localities, often at the banks of shallow pools, Cari–

cetum saxatilis fens predominate, with the characteristic Carex saxatilis

mixed with some individuals of Eriphorum angustifolium . In the drier parts

of this association, individuals of Equisetum arvense, Juncus triglumis , Salix

cordifolia var. callicarpea , Bistorta vivipara , and various other species of

higher plants are met with. The mosses always to be found in this association

are Bryum ventricosum , Campyli u m sp., and Drepanocladus intermedius .

        ( 4 ) The marshes of the Caricetum flavae type are rather uncommon in

Iceland and perhaps totally absent in its southern parts. In only two places

in northern Iceland has Carex flava itself been observed, but in other places

the characteristic species of the association appear to be Carex dioeca ,

C. capillaries , and C. fusca , Eriophorum angustifolium , Scirpus caespitosus

subsp. austriacus , Juncus filiformis , Nardus stricta , Leontodon autumnalis ,

Pinguicula vulgaris , Thalictrum alpinum , and the mosses Drepanocladus inter–

medius and Campylium sp.

        ( 5 ) The remaining marshes of this group are the relatively common Scirpetum

caespitosi-trichophorum subarcticum, with Scirpus caespitosus subsp. austria austria–

cus and Eriophorum angustifolium Eriophorum angustifolium as the dominants, and including the mosses

Drepanocladus intermedius and Sphagnum spp. as well as a number of additional

species.

        The marshes of the Caricion canescentis-fuscae association are by far the

most common in Iceland, the main types being characterized as follows.

        ( 1 ) Caricetum canescentis-fuscae is met with in different forms, the

most common one being characterized by Carex fusca and C. canescens , with some

individuals of Eriophorum scheuchzeri , Juncus filiformis , Bistorta vivipara,

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Viola palustris , Pinguicula vulgaris , and the bryophytes Blasia pusilla , Bryum

duvalii , Drepanocladus exannulatus , Oncophorus wahlenbergii , Pellia neesiana ,

and Philonotis fontana . In all marshes of this type, iron bacteria are common.

        ( 2 ) Saliceto-Caricetum fuscae is a marsh of the relatively dry type that

is met with especially in the zone between the above-mentioned moist one and

dry grasslands or heaths. It typical species are Carex fusca , Salix phylici–

folia , S. cordifolia var. callicarpea , Betula nana , Eriphorum angustifolum ,

and perhaps also Parnassia palustris subsp. neogaea , Ranunculus acris , Bistorta

vivipara , Viola palustris , and Equisetum palustre . The moss layer is composed

mainly of Bryum duvalii , Climacia dendroides , Drepanocladus sp., and Poly–

trichum commune commune .

        ( 3 ) Eriophoretum scheuchzerii forms mostly rather small marshes in some–

what sandy localities, and is frequently met with on relatively sterile, wet

soils along roadsides or in artificial holes in old marshes. Its species

are always few in number, those mostly observed besides Eriophorum scheuchzerii

being E. angustifolium and some Carices, with, in addition, the moss Drepano–

cladus exannulatus .

        ( 4 ) The fens characterized by the association Drepanoclado-Caricetum

rostratae-canescentis are always small. The characteristic species are Carex

rostrata , Eriphorum angustifolium , and the mosses Calliergon stramineum and

Drepanocladus exannulatus . In some places Carex canescens is one of the

dominating species, although it is frequently replaced by Carex lyngbyei . In

the somewhat drier parts of these fens, other Carices, Potentilla palustris ,

Salix cordifolia var. callicarpea , and Spagnum sp. are not infrequent.

        ( 5 ) The Saliceto-Caricetum rostrata-canescentis association which covers

wide areas at least in the lowland is closely related to the one last discussed. The

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dominants are: Salix cordifolia var. callicarpea , S. phylicifolia , Betula

nana , Carex canescens , C. rostrata , perhaps C. lyngbyei and C. fusca , Erio–

phorum angustifolium , Potentilla palustris , and different moss species —

especially Paludella squarrosa and Spagnum warnsdorfii .

        The meso-oligotrophic marshes are topographically determined complexes,

formed in places with a permanently high groundwater level, varying somewhat

with the seasons and the precipitation curve, but no r t or only slightly in–

fluenced by springs. They may be divided into two rather different groups,

characterized in one case by the Stygio-Caricion limosae with loose and rotten

soil and few mosses, and a very poor algal vegetation in the microflora, and

in the other by the Leuko-Scheuchzerion, which is an uncommon type of Icelandic

marsh.

        The Stygio-Caricion limosae includes all the fens listed under the Icelandic

name fl o ó i in paper previously published on the vegetation of Iceland. These

fens may be divided into at least four different marsh types: ( 1 ) The Stygio-

Caricetum chordorrhizae with the characterizing species Carex chordorrhiza ,

C. limosa , Eriophorum angustifolium , Drepanocladus exannulatus , Sphagnum sp.,

and perhaps also some of Carex lyngbyei ; ( 2 ) Stygio-Caricetum limosae, which

is a fen with Carex limosa and C. rostrata as the dominants, together with

Drepanocladus exannulatus and some liverworts; ( 3 ) Stygio-Caricetum lyngbyei

is a fen with Carex lyngbyei , C. fusca , and perhaps C. rostrata , Eriophorum

angustifolium , and Equisetum fluviatile, as well as Drepanocladus exannulatus

and some other mosses; ( 4 ) Stygio-Eriophoretum angustifoliae is a fen with

many variants, but Eriophorum angustifolium and Drepanocladus exannulatus as

the dominants.

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        The Leuko-Scheuchzerion marsh is not only uncommon in Iceland but met

with only in [ ?] very small areas. The chief type, perhaps, is that composed

of Eriophorum angustifolium , Carex rostrata , Sphagnum lindbergii , and Drepano–

cladus exannulatus , intermixed with Oxycoccus microcarpus if it is not absent

from the region in question.

        The Icelandic shrub marshes belong exclusively to the Oxycocco-Empetrion

hermaphroditi and are dominated or characterized by Empetrum hermaphroditum ,

Betula nana , Sphagnum fuscu s m , S. russowii , Polytrichum, Dicranium , Cladonia ,

and Cetraria species. The most common associations seem to be: (1) the

Sphag Sphag no-Empetretum hermaphroditum with Empetrum hermaphroditum , Betula nana ,

Vaccinium uliginosum , Sphagnum fuscu s m , Mylia anomala , and Polytrichum sp.,

sometimes mixed with a few Carices, Eriphorum angustifolium , and Oxycoccus

microcarpus ; and (2) the Cladinoso-Empetretum hermaphroditum which is drier;

with Sphagna almost absent. The characterizing species are Empetrum , Betula

nana , Vaccinium uliginosum , and various species of Cladonia ; lichens are fre–

quently dominant, especially in regions with much wind erosion.

       

Dry Soils

        The vegetation of the dry soils is classified into two main groups accord–

ing to the completeness of the plant cover. In the first group are the grass–

lands, the heaths, and the cultivated areas; in the second group are the wind-

eroded gravelly flats and sands and the clayey soils (Iceland ic flga flag .

        Grasslands . The vegetation of the grasslands seems to belong to the

Nardeto-Agrostion tenuis association with frequent tussocks due to frost action,

etc. The most common communities are: (1) Festucetum rubrae subalpinum with

Festuca rubra , Poa pratensis subsp. alpigena , Agrostis tenuis , Potentilla

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crantzii , Alchemilla sp., Ranunculus acris , Taraxacum spp. and many other

vascular plants, as well as mosses belonging to the general Torula , Brachy–

thecium , etc. This is also the vegetation of most of the cultivated grass–

lands without foreign grass species. (2) Agrostetum tenuis subalpinum is

also met with both in the grasslands and in the cultivated areas. Its dom–

inating species are Agrostis tenuis , Deschampsia caespitosa and D. alpina ,

Phleum commutatum , Bistorta vivipara , Ranunculus acris , Trifolium repens ,

Leontodon autumnalis , Taraxacum spp. , Alchemilla sp., etc. (3) Agrosteto–

Nardetum strictae is observed in some few places. It is characterized by

a high frequency of Nardus stricta , Agrostis tenuis , Festuca ovina and/or

F. vivipara , Anthoxanthum odoratum , Bistorta vivipara , etc.

        Heath Formations . The Icelandic heath formations are by no means

thoroughly investigated as yet. They seem, however, to be classifiable

in the Rhacomitrion, Loiseleurieto-Arctostaphylion, Phyllodoco-Myrtillion,

and Juncion trifidi. The representatives of the Rhacomitrion are f differ–

ent types of the Rhacomitrietum, dominated by Rhacomitrium hypnoides and

other mosses. These communities occupy all the recent lava fields, as well

as stony flats in some areas of the lowland and highland, and they cover

wider areas than any other Icelandic plant federation. In relatively young

lava fields they are mixed only with a few species of lichens on the bare

stones, but later on Cladonia and Cetraria species are found in the moss cover.

They are followed by some few individuals of Carex bigelowii , Lycopodium

selago , Equisetum pratense , Festuca sp., Salix cordifolia var. callicarpaea ,

S. herbacea , Bistorta vivipara , Armeria maritima , Silene acaulis , Cassiope

hypnoides , Calluna vulgaris , Empetrum hermaphroditum , as step by step the

Rhacomitrion is altered into different associations with Vaccinium uligino–

sum , Salices, and different grasses, together with various mosses and lichens.

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In the end the vegetation of the lava fields will become typically heathy.

        The most common communities of the Loiseleurieto-Arctostaphylion seem

to be: ( 1 ) the Loiseleurieto-Vaccinietum uliginosi, with Loiseleuria , Vac–

cinium uliginosum , Empetrum hermaphroditum , several grasses, and a great

many mosses and lichens. ( 2 ) The Arctostaphyletum uva-ursi, with Arcto–

staphylos , Betula nana, Calluna vulgaris , Vaccinium uliginosum , Festuca vivi–

para, Anthoxanthum odoratum , Cladonia sp., etc. (3) Vaccinietum uliginosi ,

which forms some different types of heaths, mixed with Juncus trifidus ,

Festuca vivipara , etc., and a great many mosses and lichens. ( 4 ) Empetro–

Betuletum nanae also forms heaths with Festuca vivipara and a great number

of mosses and lichens, of then with open soil between the tussocks due to

wind erosion. In some regions Empetrum hermaphroditum is almost absent from

some of these communities, but this tends to be compensated by Cladonia and

Cetraria . Rather wide areas are covered by associations with Salix cordifolia

var. C callicarpea , Festuca vivipara , or F. ovina , lichens, etc. These associa–

tions belong, perhaps, to a group which might be classified as ( 5 ) Lichenose–

Salicetum cordifoliae. Some heaths should be grouped in ( 6 ) the Empetro–

Cladinosum, that might only be a variant of (7) the Betuleto-Empetro-Cladinosum.

which is mainly met with in moraine areas with a light snow cover. It is char–

acterized by Betula nana , some small individuals of B. tortuosa, Empetrum

hermaphroditum, Vaccinium uliginosum, Festuca vivipara or F. ovina, and Cladonia,

Cetraria, Polythrichum, and Dicranum species, etc.

        The Phyllodoco-Myrtillion heaths are met with only in localities with a

thick snow cover during the winter months. As the distribution of Phyllodoce

is restricted owing to historical factors, the most characteristic species of

this federation are Vaccinium myrtillus , Betula nana , Deschampsia flexuosa ,

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Empetrum hermaphroditum , and, in some parts of the country, Calluna vulgaris

or Phyllodoce coerulea . Some of the groupings belonging to this association

are restricted to the vicinity of shrubby Betula tortuosa and are extremely

rich in thermophilous species.

        The Juncion trifidi community covers wide areas in the lowland as well

as in the highland. The most remarkable groupings seem to be ( 1 ) the Festuce–

tum viviparae, with F. vivipara , Carex bigelowii , Luzula spicata , Cerastium

alpinum , Bistorta vivipara , Silene acaulis , Viscaria ( Lychnis ) alpina , Saxi–

fraga caespitosa , and Cetraria nivalis . In some places the dominating cryp–

togam is Rhacomitrium hypnoides . (2) Juncetum trifidi is not very common in

the lowland. It is formed mainly by Juncus trifidus , Festuca vivipara ,

Luzula spicata , Carex bigelowii , Dryas octopetala , Salix herbacea , as well

as some mosses and lichens. Thymus arcticus and Saxifraga oppositifolia

frequently form part of this community even in the lowland.

        Sands and Gravelly Flats . The vegetation of the sands and gravelly

flats formed by wind erosion is, in all parts of the country, primarily

characterized by the Festucetum cryophilae mixed with Festuca vivipara ,

Agrostis stolonifera , Calamagrostis neglecta , Silene maritima , Cardaminop–

sis ( Arabis ) petraea , Epilobium latifolium , and some few other species.

All of these species are met with at all altitudes, not being bound especially

to the seaside; the same is true of Elymus mollis , which is found especially

on moving sands, together with Silene maritima , Potentilla anserina , etc.

In more fixed sand, the Festucetum cryophilae is intermixed with the Elymetum,

and such species as Armeria maritima , Galium verum , Kobresia myosuroides ,

Salix lanata , Salix cordifolia var. callicarpea , and some others may be met

with in these communities more or less incidentally. The succession seems

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to proceed from Elymetum mollis through Festucetum cryophilae and Festucetum–

Agrostidetum to the closed community of the Festuceto-Salicetum lanatae. The

vegetation of the sands and gravelly flats is also characterized by some few

communities of mosses and lichens.

        Clayey flats with scattered knolls and stones occur mainly in the lowland.

Their vegetation is unusually rich in therophytes, and it is suggested that

they are the result of frost and fluctuations in water level, making it im–

possible for the plants to form a permanent vegetation cover. The vegetation

of the clayey flats may be divided into three different associations: ( 1 )

the Koenigio-Sedetum villosi, which belongs to the Koenigio-Microjunceon

arcticum and the Epilobietalia alsinifolii; ( 2 ) the Eleocharetum acicularis

islandicum, which belongs to the Littorellion of the Littoretalia; and ( 3 )

the Limoselletum borealis of the Nanocyperion flavescentis of the Isöetalia.

The first-mentioned grouping is a typical subarctic one, the second is com–

pletely European temperate, but the third seems to be a mixture of arctic

and temperate elements.

        Valleys and Slopes . The vegetation of the valleys and the slopes is

of almost the same type as the vegetation of the lowlands as regards the

fresh waters, grasslands, heaths, gravelly flats, and marshes, although

these last and grasslands are less frequent and lowland species are often

not encountered in the slope vegetation. One type of vegetation is, however,

almost restricted to the valleys and slopes, namely, the Icelandic “forests.”

These are made up mainly of Betula tortuosa with Salix shrubs as well as

Betula pubescens var. coriacea , B. callosa , Sorbus aucuparia , and Populus

tremula , the two last-mentioned species being rare. The mean height of the

forest trees reaches only 2 to 3 meters, but the highest treesm may reach

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10 or 12 meters. The groupings met with in the Icelandic forests seem to be

mainly the following: Betuletum Myrtillo-Hylocomiosum, Betuletum Empetro–

Hylocomiosum, and Betuletum Geraniosum subalpinum. In places without Betula

forests this last-named is represented by a Salicetum Geraniosum alpicolum, or

by Geranietum silvatici alpicolum. Apart from the trees, these communities

seem to be characterized by the occurrence of Geranium sylvaticum , Acetosa ari–

folia , Milum effusum , Anthoxanthum odoratum , Alchemilla sp., Angelica arch–

angelica , Hieracum sp., and in some parts of the country by Epilobium angusti–

folium and Roegneria ( Agropyron ) canina . Besides these species, a great many

of the most thermophilous ones in the Icelandic flora are met with in these

communities, which are found only in sheltered localities in the valleys.

        Higher up, the slopes become poorer in vegetation, and where the wind

erosion is too strong and the solifluction becomes too effective, the vegeta–

tion becomes very scanty — except in localities sheltered by ridges and

drifted snow. In these snow patches, the vegetation belongs mainly to the

Nardeto-Caricion bigelowii, Cassiopeto-Salicion herbaceae, and Ranunculeto–

Oxyrion. The main groupings of the Nardeto-Caricion bigelowii in Iceland are:

( 1 ) the Nardetum chinophilum with Nardus strict e a Nardus strict e a , Carex bigelowii , Salix

herbacea , Bistorta vivipara , etc., and various cryptogams; (2) Anthoxantho–

Deschampsietum flexuosae with Anthoxanthum [ ?] odoratum , Deschampsia flexuosa ,

Carex bigelowii , C. lachenalii , Lycopodium alpinum , Salix herbacea , Acetosa

arifolia , Gnaphalium norvegicum , Dicranum , Pohlia , Cetraria, and Cladonia spp.;

and (3) Caricetum Caricetum bigelowii-lachenalii with C. bigelowii , C. lachenalii , as

well as Deschampsia flexuosa , Salix herbacea , Bistorta vivipara , Sibbaldia

procumbens procumbens , and cryptogams such as Polytrichum , Drepanocladus , Cetratia , and

Cladonia Cladonia spp.

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        The characteristic groupings of the Icelandic Cassiopeto-Salicion her–

baceae are: ( 1 ) the mainly alpine Cassiopetum hypnoides which is generally

composed of Cassiope , Salix herbacea , Gnaphalium supinum , Carex bigelowii ,

and different mosses and lichens. ( 2 ) On the slopes as well as in alpine

regions, the Salicetum herbaceae boreale is characterized by Salix herbacea ,

Carex bigelowii , C. rufina (in some places only), Sibbaldia procumbens ,

Gnaphalium supinum , and different mosses and lichens. Here also is (3) the

Luzuleto-Ranunculetum glacialis, which is characterized by Ranunculus glaci–

alis , Luzula arcuata s.l., Poa laxa subsp. flexuosa , Cardamine bellidifolia ,

and other plants often found in open alpine soils.

        The groupings of the Ranunculaeto-Oxyrion so far observed in Iceland seem

to be: ( 1 ) the Phippsietum algidae with Phippsia algida , Cerastium sp., Carex

lachenalii , etc., at the margins of some glaciers and on high-alpine slopes;

(2) Saxifrago-Ranunculetum pygmaeii with Ranunculus pygmaeus , R. acris , Oxyria

digyna , Cerastium alpinum , Saxifraga cernua , S. rivularis , Sibbaldia procumbens ,

Veronica alpina s.l., Gnaphalium supinum , as well as Salix herbacea , Carex

lachenalii , and various mosses and lichens; (3) Oxyretum triviale, which is

formed mainly by Oxyria digyna , Ranunculus glacialis , Salix herbacea , Veronica

alpina s.l., and Gnaphalium supinum; (4) Ranunculetum acris [ ?] ch [ ?] nophilum with

Carex bigelowii , C. lachenalii , Poa alpina , Festuca cryophila , Ranunculus acris ,

Acetosa arifolia , Bistorta vivipara , Oxyria digyna , [ ?] Cerastium sp., Sibbaldia

procumbens , Alchemilla sp., Gnaphalium supinum , Taraxacum spp., Salix herbacea ,

and various cryptogams; and (5) Alchemilletum vulgaris chionophilum, one of

the most typical communities of the snow patches on the slopes and in the shel–

tered areas, which is composed primarily by species of the Alchemilla vulgaris

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complex, Deschampsia flexuosa , Sibbaldia procumbens , Salix herbacea , as well

as Taraxacum spp. Ver [ ?] on ica alpina s.l., Gentiana nivalis , Ranunculus acris ,

etc.

        Rocks and Stony Soils . The vegetation of the mountain rocks and the

stony soils below them is rather variable at different places. In the shel–

tered localities below the rocks, the most common communities seem to be

the Veronico-Poeticum glaucae with Poa glauca , P. nemoralis , Festuca vivipara

and F. ovina , Roegneria ( Agrop h yron ) borealis var. islandica , Cystopteris

fragilis , Sedum annum , Geranium sylvaticum , and [ ?] other species; and the Arc–

tostaphyletum uva-ursi with Arctostaphylos , Anthoxanthum odoratum , Potentilla

crantzii , and perhaps Juniperus and some other species, where the soil is

not too bare.

        The stony soils of the hillsides are characterized by rather sparse vege–

tation belonging to the Dryetum and other groupings of plants that are able

to thrive in soils with a high degree of solifluction activity and wide varia–

tions [ ?] in moisture content. In the crevices of the rocks themselves,

many thermophilous species are met with as individuals or limited associations,

examples being the Thymus arcticus-Saxifraga oppositifolia association, Sedum

roseum , the Saxifraga cotyledon-sedum roseum association in eastern Iceland,

Cystopteris fragilis , and other communities of higher and lower plants. On

wet palagonite rocks, Bryoxiphium norvegicum and other moss and higher plant

communities are met with, and on many of the basalt rocks in the mountains a

number of thermophilous species are found.

        Central Highland . The vegetation [ af?] of the central highland is mainly com–

posed of the communities of the gravel flats, the sands, and the heaths of

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the slopes and lowland, although the number of species is lower and almost

all thermophilous representatives are absent. In sheltered localities, how–

ever, different types of marshes are met with. Moreover, in the highlands,

the typical vegetation of clayey flats is absent, while it is only in the

hi g hlands of northern Iceland that the typical vegetation of the permafrost

areas, the tundra marshes, is encountered.

        The typical Icelandic tundra marshes are found mainly in almost flat

areas with a multitude of lakelets surrounded by fens of the Stygio–

Eriophoretum angustifoliae. Among these lakelets are giant tussocks up to

two meters in height and up to fifteen meters in length. The bogs between the

Stygio-Eriophoretum angustifoliae are covered with Eriophorum angustifolium-

Calamagrostis neglecta associations. On the slopes and domes of the tussocks,

however, the vegetation is clearly of the hea t h type, belonging mostly to

associations of Salix cordifolia var. callicarpea , Empetrum hermaphroditum ,

Cassiope hypnoides , Ristorta vivipara , Salix herbacea , S. lanata , Calamagrostis

neglecta , and fiferent Carices, while on the very tops of the driest tussocks

are found only communities belonging to the Rhacomitrion .

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---

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Askell Löve