Composition and Dynamical Status of Heathland Communities in Iceland in Relation to Recovery Measures

ACTA PHYTOGEOGRAPHICA SUECICA 75 EDIDIT SVENSKA V AxTGEOGRAFISKA SALLSKAPET

Elfn Gunnlaugsd6ttir

Composition and dynamical status of heathland communities in Iceland in relation to recovery measures

UPPSALA 1985

ACTA PHYTOGEOGRAPHICA SUECICA 75 EDIDIT SVENSKA VA XTGEOGRAFISKA SALLSKAPET

Elfn Gunnlaugsd6ttir

Composition and dynamical status of heathland communities in Iceland in relation to recovery measures

Almqvist & Wiksell International, Stockholm UPPSALA 1985 Doctoral thesis at Uppsala University 1985

Suggested citation: Gunnlaugsd6ttir, E. 1985. Composition and dy namical status of heath/and communities in Iceland in relation to recovery measures. Acta phytogeogr. Suec. 75. Uppsala. 84 pp.

ISBN 91-7210-075-3 (paperback) ISBN 91-7210-475-9 (cloth) ISSN 0084-5914

Svenska Vaxtgeografiska Sallskapet Box 559, 75 1 22 Uppsala

Editor: Erik Sjogren Technical editor: Gunnel Sjors

Phototypesetting: Textgruppen i Uppsala AB Printed in Sweden 1985 by Borgstroms Tryckeri AB, Motala 1985

Acta Phytogeogr. Suec. 75 Abstract mion drucei (B0cher 1954) de Molenaar 1976 described from Greenland; the wind-exposed heathland association Racomitrio Gunnlaugsd6ttir, E. 1985. Composition and dynamical status of languinosi - Thalictretum alpini ass. nov. and a related commu heathland communities in Iceland in relation to recovery mea nity are assigned to the Racomitrio - Thalictrion alpini all. nov. sures. -Acta phytogeogr. Suec., 75, Uppsala. 84 pp. ISBN The two above-mentioned alliances are assigned to the order 91-72 1 0-075-3 (91-72 10-475-9) Sedo - Poietalia glaucae de Molenaar 1976. The grassy heathland associations, namely the Agrostio capillaris - Hylocomietum Changes in species composition and cover were studied in perma splendentis ass. nov., the Racomitrio canescentis - Gentianetum nent plots in uneroded areas and deflatedones being restored by nivalis ass. nov. and one related community, are provisionally protection from grazing, fertilization with mineral fertilizer (NP, assigned to the alliance Equiseto - Galion borealis Tx. 1969. The NPK, NPKS), and sowing of alien grass seed. The native grass Dryas octopetala - Betula nana community and the Kobresia species Agrostis vinea/is, A. capi/laris, Festuca pruinosa and F. myosuroides - Sa fixlanata community are provisionally assigned vivipara increased after fertilization as did several small herbs, to the class Carici rupestris - Kobresietea bellardii Ohba 1974. for example, Cerastium alpinum, Lychnis alpina and Armeria The species composition of the Icelandic heathland communi maritima. The first and biggest effect of fertilization only lasts ties deviates from that of related ones described for neighbouring 2-3 years but some minor effects are discernable up to at least countries. Some Icelandic communities are characterized by 20 years. combination of species, which are not found elsewhere. This The year-to-year analyses of the permanent plots did not reveal might be explained by different climatic conditions, different any successional trend. On the other hand, fluctuations do occur; bedrock and edaphic conditions, erosion, or any combination of they may be due to fertilization and fluctuating unfavourable these factors. weather conditions. A real succession from the vegetation-poor status of deflated areas to fully revegetated ones needs probably Key-words: Phytosociological classification, multivariate 50-100years, or more. methods, permanent plots, vegetation dynamics, deflated areas, In addition, the vegetation in two of the areas was described fertilization, vegetation restoration. and classified, and the vegetation of the permanent plots was as signed to the units obtained. Vegetation types were interpreted as syntaxonomical units according to the Braun-Blanquet ap proach, and the associations and communities described in this Elfn Gunnlaugsd6ttir, Institute of Ecological Botany, Uppsala study have been provisionally assigned to higher units in this sys University, Box 559, S-751 22 Uppsala, Sweden. tem: The open sward assocation Armerio - Silenetum acaulis Ha The Akureyri Museum of Natural History, Box 580, Is-600 dac 1972 em. is provisionally assigned to the alliance Sedo - Thy- Akureyri, Iceland.

A grip kerfis: Gr6�ursveit mela og orfoka lands, Armerio - Silenetum acaulis Hadac 1972 em., hefur veri� skipa� i groourfylki� (e. Gunnlaugsdottir, E. 1985. Hei�agr6�ur a islandi, tegundasam alliance) Sedo - Thymion drucei (B0cher 1954) de Molenaar setning hans og grMubreytingar me� tilliti til uppgrre3slu. Acta 1976, sem lyst hefur veri� fra Grrenlandi;gramosapembusveitin phytogeogr. Suec., 75, Uppsala. 84 pp. ISBN 91-72 10-075-3 ni Racomitrio lanuginosi - Thalictretum alpini (ny sveit) og (9 1 -7210-4 75-9) skyldu gro�urfelagi hefur veri� skipa� i groourfylki� Racorni trio - Thalictrion alpini (nytt fylki). IJessi tvo groourfylki heyra Rannsoknir a tegundasamsetningu og pekju groours hafa fari� til. gro�urlendisins (e. order) Sedo - Poietalia glaucae de fram i fOstum reitum a orkfoka landi sem og ouppblasnu. Fylgst Molenaar 1976. hefur veri� me� gro�urbreytingum, par sem uppgrre�sla fer Tvrer gro�ursveitir heyra grashei�inni til, p. e. Agrostio fram fyrir tilstilli fri�unar, abur�ardreifingar (NP, NPK, NPKS) capillaris - Hylocomietum splendentis (ny sveit) og Racornitrio og saningu innflutt grasfrres. canescentis - Gentianetum nivalis (ny sveit) asamt skyldu gro�ur Spretta innlendra grastegunda svo sem tytulingresis (Agrostis fe lagi og hefur ollum veri� skipa� i groourfylki� Equiseto - vinea/is), halingresis (A. capillaris), tunvinguls (Festuca pruino Galion borealis Tx. 1969. sa) og geitvinguls (F. vivipara) jokst mjog eftir abur�ardreifmgu Dryas octopetala -Betula nana gro�urfelaginu og Kobresia na sem og voxtur og fjoldi ymissa smajurta t.d. musareyra ( Ce myosuroides - Salix lanata gro�urfelaginu hefur til brMabirg�a rastium alpinum), ljosbera (Lychnis alpina) og geldingahnapps veri� skipa� i gro�urflokkinn (e. class) Carici rupestris - Kob (Armeria maritima). Einnig hafa lagplontur teki� breytingum. resietea bellardii Ohba 1974. i Fyrstu og mestu abur�arahrifm vara a�eins 2-3 ar, en dauf slenski heit�agroourinn er mjog frabrug�inn skyldum gro�ri abur�arahrif eru sjaanleg i 20 ar a. m. k. i grannlOndunum. Grooureiningar hans eru einkenndar af hopum Arlegar gro�urgreiningar (e. vegetation analyses) i fostu tegunda, sem hvergi annars sta�ar vaxa saman. Orsakanna er reitunum syna ekki fram a sokn (e. succession) groours ar fra a� leita i frabrug�inna voorattu, berggrunni, jar�vegi, uppblrestri ari. Aftur a moti hafa gro�ursveiflur (e. fluctuations) att ser og afoki, e�a samverkan allra e�a einhverra pessara patta. sta� vegna abur�ardreifmganna og/e�a ohagstre3s arfer�is. Sokn gro�urs fra gro�urvana, orkfloka landi til algroins �a Lykilor�: Flokkun i gro�urfelog, reikniaafer�ir moo morgum pvi sem nrest algroins lands tekur 50- 1 ()() ar ooa meir eftir breytistrerOum (e. multivariate methods), fastir reitir, gr6�ur a�stre�um. breytingar, orfoka land, aburOardreifmg, uppgrreOsla. A� auki hefur groori tveggja rannsoknarsvre3anna veri� lyst og hann flokka�ur i einingar gro�urfelagsfrre3i. Einnig er gro�ri fOstu reitanna skipa� i pessar einingar. Grooureiningar Elin Gunnlaugsd6ttir, Institute of Ecological Botany, Uppsala nar (e. vegetations types) eru skilgreindar sem einingar i flokku narkerfi bygg�u a kenningum Braun-Blanquet og grooursveitum University, Box 559, S-751 22 Uppsala, Sweden. (e. associations) og gro�urfelogum (e. communities), sem her er The Akureyri Museum of Natural History, Box 580, Is-600 lyst, hefur til bra�abirg�a veri� skipa� i �ri einingar pessa Akureyri, Iceland.

Acta Phytogeogr. Suec. 75

Contents

1. General introduction 5 1.1 Aims 5 1. 2 Research plan 5 1.3 Physiography 6 1.4 Climate 6 General characteristics 6, Climate of the studied areas 9, Growing season 11 1 . 5 Vegetation history 12 General 12, Vegetation history of the studied areas 13

2. Ma terial and methods 14 2.1. Introduction 14 2.2 Permanent plots in N and S Iceland (P-data set) 14 2.3 Line transects at Assandur (S-data set) 14 2.4 Systematic plot system for analyses of heathland vegetation near Gunnarsholt (H-data set) 14 2.5 Comparison of the sampling methods 14 2.6 Soil samples 15 Sampling 15, Chemical analyses 15 2.7 Data analysis 15 Introduction 15, Multivariate treatments 15

3. Statistics on species occurrences 17 3.1 Introduction 17 3.2 Relation between number of taxa and number of plots 17 3.3 Relation between cumulative number of taxa and number of plots 17 3.4 Phytogeographical observations 17

4. Phytosociological classification 20 4.1 Introduction 20 4.2 Procedure 20 Interpretation of results 20, Site and vegetation characters 23 4.3 Other calculations 24 4.4 Assigment to higher syntaxa 24 4.5 Plant communities 25 Synopsis of the vegetation types 25, Homotoneity of the vegetation types 27, Alpha diversity of the vegetation types 28

5. Synopsis of plant communities - description and phytosocio- sociological affinities 29 5.1 Gravel flat vegetation 29 (1) Armerio- Silenetum acaulis Hadac 1972 em. 29

Acta Phytogeogr. Suec. 75 4 Elfn Gunnlaugsd6ttir

5.2 Racomitrium lanuginosum heaths 33 (2) Racomitrio lanuginosi - Thalictretum alpini 33, (3) Empetrum nigrum - Racomitrium lanuginosum community 38 5. 3 Grassy heathlands 3 8 (4) Agrostio capillaris - Hylocomietum splendentis 39, (5) Festuca vivpara - Racomitrium canescens community 44, (6) Racomitrio canescentis - Gentianetum nivalis 45 5.4 Dryas octopetala-heaths and related dwarf shrub heaths 46 (7) Dryas octopetala - Betula nana community 47, (8) Kobresia myo- suriodes - Salix lanata community 49 5.5 Comparisons with other vegetation types 50 Syntaxonomical comparison 51, Life-form spectra and species groups 52

6. Soil factors and vegetation 54 6.1 Introduction 54 6.2 Statistical comparison of various phytosociological units 54 Comparison between the lower units of the Racomitrio lanuginosi - Thalictretum alpini 54, Comparison between the lower units of the Agrostio capillaris - Hylocomietum splendentis 55, Comparison between the associations and community of the Equiseto - Galion borealis 55, Comparison between alliances 56 6.3 Ecological evaluation 56 6.4 The relation between taxa density and soil pH 57

7. Vegetation dy namics 58 7.1 Introduction 58 7.2 Data analysis 58 7.3 Results 58 Classification 58, Ordination 60 7.4 Interpretation of the ordination diagrams 60 Dynamic approach 60, Static approach 62 7.5 Species behaviour 62 7.6 The alpha diversity index (a) as an indication of floristic dynamics 65 7. 7 Discussion 65

8. Discussion and conclusion 67 8.1 General 67 8.2 Vegetation dynamics 67 Effects of mineral fertilizer 67 8.3 Aspects of nature conservation and vegetation development 68 8.4 Evaluation for agricultural use 68 8.5 Restoration treatments and recommendations for the future 68

References 70

Plates 78

Acta Phytogeogr. Suec. 75 1 General introduction

1.1 Aims and near the deserted Melakot farm in the deflated lava-field Eldivi3arhraun, S Iceland (Fig. 1). The main purpose of the investigation was to study As the permanent plots of each area are few and changes in permanent plots in heathland vegetation the vegetation of these areas had not been described caused by mineral fertilizer in order to reveal the earlier, the investigations were expanded in two of duration of the fertilizer influence on the vegetation the areas, namely in the deflated Assandur area and and if the use of the mineral fertilizer will speed up in the uneroded heathland in the vicinity of the the process of succession. The changes in the soil Gunnarsholt farm. The expanded survey of the ve chemistry caused by the mineral fertilizer were also getation of these areas facilitated the phytosocio investigated. logical classification and enabled the vegetation in The second main aim was to classify the plant the permanent plots to be assigned to phytosocio communities in several heathlands involved in the logical units. In addition, the overall survey pro succession studies and to establish the vides information on the status of the vegetation at phytosociological status of the vegetation of the the time of the analyses, which is necessary for the permanent plots. Furthermore, attempts were made long-term successional studies in the areas. In the to relate the plant communities to certain kinds of case of uneroded heathland it also provides an idea utilization and to evaluate the agricultural and of what kind of "original" vegetation is left, a vege nature conservation status of the communities tation where soil is still eroding from its edges. judged from their species assemblage. In the present context the word heathland is used In the third place it was intended to compare the in the sense of Specht (1977 p. 4). The heathland in plant communities distinguished with related com cludes dwarf shrub heath, mossy heath (dominated munities in neighbouring countries and to incor by e.g., Racomitrium lanuginosum, R. canescensor porate them into the phytosociological system ac Hy locomium sp lendens), grassy heath and open cording to the Braun-Blanquet approach with sward with grassy vegetation of deflated areas de regard to their climatic and edaphic conditions, as rived from heathland. well as their utilization. Heathlands are wide-spread in Iceland. The dwarf shrub heaths and the open sward heaths are to be found both in the lowland and in the highland. 1.2 Research plan The mossy heaths, e.g, the Racomitrium heaths, generally belong to the highland vegetation but are The investigations began with vegetation analyses also found in the lowlands of SE, S, SW, W and NE of several plots. Most of them are situated in wind Iceland. The grassy heathland is most common in eroded, deflated areas (i.e., areas where the top soil the lowland of S Iceland (cf. Steind6rsson 1964b). has been almost totally removed by the wind ero The data of the vegetation analyses have been sion), where the vegetation is under restoration (cf. processed using multivariate methods. Three data Gunnlaugsd6ttir 1982a). The permanent plots were sets are involved, based upon three different located to three areas of N Iceland, namely the methods of vegetation analysis (see below): the first deflated areas of Assandur and Hei3arspor3ur and for the analyses of the permanent plots (P-data set), the dwarf shrub heath in the H6lssandur area. Per the second for the analyses of the Assandur area (S manent plots were also located to several eroded and data set) and the third for the analyses of the uneroded areas in the vicinity of Gunnarsholt farm uneroded heathland near Gunnarsholt (H-data set).

Acta Phytogeogr. Suec. 75 6 EHn Gunnlaugsd6ttir

1.3 Physiography dates back to the finiglacial and postglacial epochs (Sremundsson 1977). The investigated areas in N Iceland are: Assandur The uneroded 6500-7000 years old lava-fields (ea. 20-25 m a.s.l.), Hei3arspor3ur (ea. 360 m are covered by a thick loessial, silt-loamy soil with a.s.l.) and H6lssandur (ea. 215 m a.s.l.). There are layers of tephra. On the other hand, the young lava also several investigated areas in the vicinity of field Su3urhraun has very thin silt-loamy soil in its Gunnarsholt farm, in the country of Rangarvellir, fissures, or is without any soil. The deflated lava S Iceland (Fig. 1) at 100-160 m a.s.l., namely the fields are more or less covered by the same kind of lava-field (named Vesturhraun) near Gunn soil, often intermingledwith sand and loose blocks. laugssk6gur, the fenced area near Akurh611, the The bedrock itself commonly rises through the re Rey3arvatnshraum lava-field, the Gari, the mains of the soil. Eldivi3arhraun lava-field in Keldnagir3ing near The soil types of the investigated areas are not Melakot, all of which are deflated. Also the widely found in Iceland. Johannesson (1960) gave uneroded heathlands Brekknahei3i, Steinkross a strongly generalized classification of Icelandic moar, Steinkrossbrun, the heath! and near Kot soils. He classified the soils of the Assandur area as farm, the Dagver3arnesm6ar heathland and the aeolian sand of flats and dunes, with lag gravel as Su3urhraun and Brejarhraun lava-fields are in major associate soil type (his mapping unit 14). This cluded (Fig. 2). soil type covers ea. 1.9 OJo of Iceland. Nevertheless, All these areas lie within the zone of volcanic ac the alluvial gravel flats of the Assandur area fits bet tivities which passes through Iceland. (For the zone ter with his mapping unit 16, i.e., sand, see, e.g., Jakobsson 1979.) Erosion damage of soils fluvioglacial, a lowland soil type, which covers ea. and vegetation is greatest within this zone. The soil 2.4 OJo of the total area of Iceland. there is usually well drained and rather coarse, The soil of the dwarf shrub heath in H6lssandur partly because of the mechanical weathering of the and in the uneroded heathlands in the vicinity of bedrock and partly because of the tephra deposits Gunnarsholt is silt- loam, 15 to 100 cm thick, on (and other wind-borne deposits). The coarseness of gravelly or stony material (his mapping unit 5), a soil the soil makes it more sensitive to wind erosionand type which covers 2.5 OJo of Iceland. it retains nutrients poorly. With the exception of The soil type of the deflated areas, namely Assandur, the areas are lying on basalt lava bedrock Hei3arspor3ur, the Vesturhraun lava-field near of varying age. Gunnlaugsskogur and the Rey3arvatnshraun, Gari The bedrock in the Hei3arspor3ur area is formed and Eldivi3arhraun lava-fields, is classified as lava of postglacial basaltic and andesitic lavas where the major associated substrate is aeolian sand (Sremundsson 1977) about 7100 years old (his mapping unit 22), a soil type covering ea 7.9 OJo (l>orarinsson 1960). of Iceland. In my opinion the soil of the above In the vicinity of Gunnarsholt farm there are mentioned areas is better assigned to his mapping postglacial basalt lavas (Kjartansson 1962) from the unit 11, i.e., silt loam, 5-15 cm on lava, even if the volcano Hekla. The underlying bedrock in the Gari, areas here are deflated. The last-named mapping the Steinkrossm6ar and the Eldivi3arhraun lava unit covers 1.7 OJo. field is 5500-6000 years old; the bedrock of Furthermore, it might be of interest to recall that Steinkrossbrun and Brejarhraun is 5500-6500 only 27 OJo of the Icelandic soil types are covered by years old; the underlying bedrock near Kot farm, vegetation (J6hannesson 1960). the Rey3arvatnshraun and Vesturhraun lava-fields together with the bedrock of the area near Akurholl and the heath Brekknahei3i is 6000-7000 years old, 1.4 Climate and finally, the extremely irregular and blocky General characteristics Su3urhraun lava-field is about 1000-5500 years old (Jakobsson 1979). The climate of Iceland has been classified as boreal The Assandur area is unconsolidated gravel flats, in S Iceland and arCtic in N Iceland (Waiter 1979). formed by the glacial river Jokulsa i Axarfir3i. It Boreal climate (sensu Waiter) has a daily average

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 7

Fig. 1. Map showing the location of the investigated areas (•) in Iceland, the meteorological sta tions ( •) and other places refer red to in the text.

Fig. 2. The investigated areas near Gunnarsholt farm . The uneroded heathlands are: (1) Brekknahei5i, (2) Dagverd arnesm6ar, (3) Steinkrossm6ar, (4) Steinkrossbrun, (5) the level heathland near Kot farm and (6) the Su5urhraun and Brejarhraun lava-fields. The areas of soil deflation are: (7) the Vesturhraun, (8) the Rey5arvathnshraun lava-fields, (9) the Gari and (10) the Palsteinshraun lava-field.

Acta Phytogeogr. Suec. 75 8 Elfn Gunnlaugsd6ttir

1974 '76 a b d e mm 5.1° 1456 1406 ° C Hella (20ml 4.3° 1140 200 0 50 .....-1""'"""''--100 n 40 80 30 60 20 40

10 71' 20 k 00s JFMAMJJASOND

'77 '78 '79 '80 3.7° 875 1.8° 956

I' I � I� � 11 � � a � '--_.... � \ '--I- vv �

1974 '75 '76

oc mm 2.4° 455 1.5° 330 2.7°364 Reykjah 1i8(285m) 100 2.2°3 94 40 80 30 60 20 40 10 20 0 0 q r JFMAM JJASOND

'77 '78 '79 ·so

1.5° 442 1.8° 357 0.5° 433

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 9

1974 '75 mm '76

Manarbakki (17ml 3.9° 632 2.6°47 6 3.9° 418 oc 100 3.5°451 40 80 30 60 20 40 10 20

0 0 JFMAMJJASOND

'79

'77 '78 607 '80 1.10 2.8° 562 3.0° 416

Fig. 3a-c. Ecological climate diagrams for the stations at Hella, S Iceland; Reykjahlio and Manarbakki, NE Iceland (1931-1960). Weather conditions for the period 1974-1 980 are also shown. The letters and numbers in the diagrams indicate, (a) station, (b) height above sea level, (d) mean annual temperature CC), (e) mean annual precipitation (mm),

(k) curve of mean monthly temperature (1 division = woe), (1) curve of mean monthly precipitation (1 division =

20 mm, i.e., wo = 20 mm), (m) period of relative drought (dotted) for climate region concerned, (n) corresponding relatively humid season (vertical shading), (o) mean monthly precipitation >lOO mm (scale reduced to l!W) (black areas, perhumid season), (q) months with a mean daily minimum below ooe (black = cold season), (r) months with absolute minimum below ooc (diagonally shaded) i.e., with either late or early frosts and (s) number of days with mean temperature above woe.

temperature > + 10°C for less than 120 days and In the other parts of the country the climate is more than 30 days; the cold season lasting longer oceanic-arctic as the cold period is much shorter than 180 days. The arctic climate has average daily than that of the typical arctic climate. The highland means > + 10°C for less than 30 days and the cold climate may be classified as oceanic-alpine-arctic season lasts longer than 240 days. (or subarctic), e.g., around Grimssta3ir, NE The climate in S Iceland is better described as Iceland (see below). oceanic-boreal as the cold period is shorter than 180 days because of the influence of the ocean. That Climate of the studied areas type of climate prevails from Hornafjor3ur firth, SE Iceland, along the south coast and over the Climatological data are available from official lowlands ofS, SW and W Iceland to the Snrefellsnes meteorological stations in the neighbourhood of the peninsula, W Iceland. The oceanic - boreal climate studied areas. Reykjahli3 and Grimssta3ir are the type is also found locally in sheltered places in other nearest stations to the Hei3arspor3ur area and lie 7 parts of the country, but in that case with less km NW and 32 km E of the studied area, respec precipitation than in the southern part of the tively. The Gar3ur and Grimssta3ir stations lie 19 country. km WNW and 43 km SSW of the studied area in

Acta Phytogeogr. Suec. 75 10 Eltn Gunnlaugsd6ttir

H6lssandur, respectively. The Garour and Mamir exception of one station. The highest monthly bakki stations lie 12 km WSW and 27 km NNW of records are found sometimes during the period July the Assandur area, respectively. The nearest sta to October (Fig. 3). tions to the areas near Gunnarsholt, e.g., the The deflated areas studied here are usually free Vesturhraun lava-field near Gunnlaugssk6gur, are from snow during the winters, as the snow is im Hella, H�ll and Burfell, which lie 10 km W, 23 km mediately blown off these unsheltered areas. The W and 30 km NE of the area, respectively. These sta same applies to the knolls of the dwarf shrub heath tions lie about 23 km WSW, 28 km NW and 25 km in H6lssandur. The heathland in the vicinity of NNE of the area near Melakot, respectively (Fig. 1). Gunnarsholt is usually snow-free during winter, or at least with snow cover of short duration. Temperature Means of relative humidity (OJo) for the period The means of temperature for three stations are 1958-1967 are available from the Manarbakki and shown in the ecological climate diagrams in Fig. 3, Hella stations (M. A. Einarsson 1976), the annual namely for Hella, Manarbakki and Reykjahlio. The means being 81 OJo and 84 %, respectively. figures are based on data from M. A. Einarsson (1976). The means are for the period 1931-1960. Evaporation, water deficit Fig. 3 also shows diagrams drawn in the same way The Assandur, Heioarsporour and H6lssandur for weather conditions during the period areas lie in the part of Iceland with water deficit, 1974-Sept. 1980, i.e., the period when vegetation especially during the summer months, but also dur analyses of the permanent plots were made, see ing the whole year. During the summers the water later. Data are taken from Veonittan ( 197 4-Sept. deficit may be as much as 200 mm in the Assandur 1980). and H6lssandur areas, and even more in the The average annual temperature is highest at the Heioarsporour area. All these areas are situated in Hella station, S Iceland, and lowest at the Reykja the rain shadow to the north of the glacier Vatna hlio and Grimsstaoir stations, NE Iceland. July has jokull. Even the areas in S Iceland have negative the highest monthly means at all stations and the values for evaporation during the summer period lowest ones in January or February. (see M. A. Einarsson 1976), which indicates that Interpolated values have been calculated for the measurement faults may be involved. However, studied areas by using constants for temperature some of the areas in S Iceland may get positive changes with growing elevation and distance from values. the coast given by M. A. Einarsson 1976. The inter polated values for Assandur are + 9.8°C in July and Wind -2.4°C in January; corresponding values for Iceland is a windy country like all oceanic islands. Heioarsporour are + 9.9°C and -4.5°C; for the Data for 1965-1971 show that SSE winds are most

areas (heathlands) near Gunnarsholt + 11.2 o C and frequent at the Grimsstaoir station, NE Iceland,

-2.4°C; and in the area near Melakot + 11o c and whereas NE winds are most frequent at the H�ll sta -3.1oc, respectively. tion. Calm weather occurs during only 19 OJo and A characteristic of the Icelandic winter weather is 24 % of the time at these two stations, respectively. frequent thaws, short or long-lasting. The repeated The average annual wind speed is highest at the freezing and thawing, and the resulting frost move coasts and in the highland and the frequency of gales ment in the soil, implies a great stress on the plants is highest in these parts of the country (M. A. and their roots. Einarsson 197 6). It may be pointed out here that southerly winds are relatively dry in N Iceland whereas the northerly Precipitation winds are relatively dry in S Iceland. The relatively The average annual precipitation is highest at the dry winds have contributed greatly to the wind ero stations in S Iceland and is higher at the northern sion damage and the soil deflation. The desiccating coasts than in northern inland areas. The month of and abrasive effects of the winds can clearly be seen May has the lowest monthly precipitation, with the in the low, prostrate features of the vegetation and

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 11

Fig. 4. Length of growing season expressed as number of days with > + 6°C, based on data from M.A. Einarsson (1976) and Bergporsson (1973).

Fig. 5. Approximate isolines for effective temperature sum, i.e., sum of day temperatures ex ceeding + 6°C.

the dried-out soil surface in the open sward vegeta of vegetation as the length of the growing season tion. They are obviously important in preventing and the effective temperature sum in these coun plants from becoming established. tries. In the present context, the growing season is considered to be the season with higher temperatures than + 6°C. The growing season in Growing season Iceland is thus 60-160 days long (Fig. 4). Corre As the vegetation in the studied areas will be com sponding values from Norway are 110-200 days pared to related vegetation in neighbouring coun (cf. Tu khanen 1980). tries it is of interest as far as possible to compare The temperatures of the growing season are low such important factors for growth and development in Iceland. The effective temperature sums (daily

Acta Phytogeogr. Suec. 75 12 Elin Gunnlaugsd6ttir

E Fig. 6. Correlation between the :::l B ; 1200 effective temperature sum and the �

> (B) for Norway. The threshold ·� value for the growing season is w� 800 + 6°C. Norwegian data are from Tuhkanen (1980). Icelandic data are from M. A. Einarsson (1976). 600

400

200

Length of growing season 100 120 140 160 180 200 220

degrees) range from 80 to 560 (Fig. 5). Comparable 1. 5 Vegetation history values from Norway are 400-1270 (Tukhanen 1980). The daily degrees are calculated from data General given by M. A. Einarsson (1976) by using the for In these studies attention has been paid to vegetation mula for monthly degrees: of deflated areas and to uneroded areas in the W = (t-t0) neighbourhood of the eroded ones. and multiplying the results by 30. In the formula W Ever since Iceland became settled (874-930) soil

= temperature sum (heat sum); t = mean erosion has occurred but has become enormous

temperature for the month and t0 = threshold especially during the last three centuries. Indeed, it ternperature. is impossible to say how much of Iceland (which is The relationship between the effective 103 125 km2) had been covered by vegetation at the temperature sum (daily degrees) and the length of beginning of the Settlement era. Some estimate this the growing season is shown in Fig. 6 based on data to about 40 000 km2, of which there are now only from Iceland (M. A. Einarsson 1976) and Norway 20 000 km2 left. Birch woods and coppices covered (Tukhanen 1980). The Icelandic values are lower in about 20 000 km2 at the time of Settlement but at the graph; The equation for the regression line (A) present there are only 1 000 km2 left (I>orsteinsson

is y = -353 + 2.80x; n = 80, r = 0.85 and P < 1973, I>6rarinsson 1974). 0.001. The Norwegian values are higher and more The Icelandic lowland (i.e., up to an altitude of to the right in the graph, showing more favourable 350 m) at the time of the Settlement was covered conditions. The equation for the Norwegian values with coppices of Betula pubescens, B. nana and

(B) is y = -314.5 + 3.65x; n = 37, r = 0.80 and Salix spp. and with birch woods in the most p < 0.001. favoured places. Birch coppices were also found in The effective temperature sum in the Farces is suitable places in the highland up to 450-500 m similar to or higher than Icelandic values (Hansen a.s.l. Today, the highest situated remains of birch 1967). The annual, accumulated temperature (a are found at 600 m a.s.l. (Steind6rsson 1964b). related concept) in the highest parts of the Scottish In the fslendingab6k (supposed to be written in highlands (Green 1974) is found to be similar to the the 1130s), it is stated that the country was covered Icelandic values of effective temperature sum. with woody plants from the coasts to the mountains.

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 13

There are different opinions on how literally these vegetated with birch coppices (Sigurj6nsson et al. words should be taken (D6rarinsson 1974), but the 1958) but became gradually wind-eroded, when the statement has been confirmed by pollen analyses (D. coppices became destroyed and the other vegetation Einarsson 1962). They indicate that birch overgrazed. Now most of the area is deflated, but dominated at the time of the Settlement but declined remains of older vegetation can be found here and soon afterwards; grasses became dominating in there, and it may be called a dwarf shrub heath with stead. birch coppices. This large area (MY"vatnsorrefi) is a The far-reaching utilization of the vegetation pasture land of Reykjahli3 farm in the county of which was a consequence of the Settlement became, Myvatnsveit. There is written evidence from 1505 indeed, most hazardous for its future development. (Dipl. Isl. Vol. 7) indicating that this pasture was In addition, the deterioration of the climate during poor in vegetation at that time. In the J ar3ab6k Vol. 15 50-1 890 and to some extent volcanic activity had 11 (written in 1717) the same area is said to be barren additional damaging influences. and wind-eroded. During the eruptions in The greatest changes in the Icelandic vegetation 1724-1729, named Myvatnseldar, the area became is thus the decline of birch woods and coppices, un covered with tephra (Anmilar 1400- 1 800, Vol. IV, doubtedly followed by the successive impoverish 6) with sand-drift and soil erosion as a consequence. ment of other vegetation types. One or another The flat land in the surroundings of Gunnarsholt species might have become extinct after en in the county of Rangarvellir was certainly covered vironmental conditions had become too severe by birch wood and willow coppices at the time of the (Steind6rsson 1964b). The results of these long-term Settlement. Later it became grassy heathland with changes are the soil erosion, thickening of the scattered coppices of birch and willows (Sigur loessial soil (D6rarinsson 1961) and dune building in j6nsson et al. 1958). Now there are only few places some places. with low shrubs of Salix phylicifolia and S. lanata. Some species are only found on south-facing slopes in the investigated area, species which un doubtedly were much more common in the past Vegetation history of the studied areas when the coppices dominated and the microclimate At the time of Settlement the area now named was more favourable, viz. Stellaria graminea, Assandur was most likely covered by coppices of Rubus saxatilis, Prunella vulgaris, Alchemilla Salix phylicifolia, S. lanata, Betula pubescens, B. vulgaris, Hierochloe odorata and Rumex acetosa. pubescens x B. nana, intermingled with herbs like There are large deflated areas in the surroundings Angelica spp., Geranium sy lvaticum, Alchemilla of Gunnarsholt, some of which have been revege spp., grass and sedge species, by dwarf shrub tated during the last five decades and are now used vegetation, namely vegetation types which still exist for hay-making and pastures. in nearby areas. Now there is almost only naked, The best written document on the situation on the black gravel and sand left in the Assandur area. farms in the past is the Jar3ab6k Vol. 2 (written in For centuries the Assandur area (then named 1710), where a description is given of the farms and Asengjar) was a meadow giving good yields (Sigur the utilization ofthe vegetation. The book also men j6nsson et al. 1958) which was used for hay-making tions wind erosion and describes a sand-drift, which and grazing (Jar3ab6k Vol. 11, written in 1712). It damaged or ruined the pastures of every farm in the became destroyed by debacles in the glacial river investigated area, e.g., Kot, Steinkross, Gunnars Jokulsa i Axarfir3i duringthe period of 1694-1729 holt, Dagver3arnes and Melakot. The two latter which were caused by volcanic eruptions at the farms were deserted at that time. Much land has north edge of the glacier Vatnajokull. The most been destroyed and deflated since 1712, especially far-reaching damage to the meadow, where the in during the period of cold weather with severe, dry vestigated area lies, occurred in 1694 (D6rarinsson gales (in 1860-1890). The destruction of vegetation 1974). Since then, sand-drift and soil erosion have was locally reinforced by overgrazing (sheep) as the taken place. yield became severely lowered in the unfavourable The Hei3arspor3ur area and its vicinity was weather conditions (Sigurj6nsson et al. 1958).

Acta Phytogeogr. Suec. 75 2 Material and methods

2.1 Introduction The lengths of the transects and their number were arbitrarily chosen, depending on the time available There are three different data sets as the analyses of for the investigation. the vegetation were carried out by using three differ The line transects were analysed with a perspex ent methods. The results of these methods are com frame (see Kershaw 1964), with pins of 35 or 45 cm parable, however, as the same species dominated length and points of 1 mm diameter. The hits were and the list of recorded taxa was the same. read at 1 cm intervals, one reading for the first hit in each of the three vegetation layers; the shrub layer, the field layer and the bottom layer ,and in ad Permanent plots In and S dition, the first hit on litter. The heights of the hits 2.2 N above ground were also recorded (prostrate Iceland (P-data set) unmeasurable plant parts were estimated in 0.1 cm). Additional species were recorded in the immediate The permanent plots were located in three areas of surroundings (2x5 m2) of the line transect. N Iceland and several in the vicinity of Gunnarsholt As the number of hits was high (here 400), and the (cf. 1.2 and Gunnlaugsd6ttir 1982a). Altogether 43 hits were made with small intervals (1 cm), the permanent plots were established, 36 of which were results of the readings were transformed to percent subjected to repeated analyses over a varying age cover (Kershaw 1964). number of years, all between 1974 and 1980. A total of 180 analyses were made of the 43 plots. The size (2x6 m2) and the site of the plots were subjectively chosen. Each plot lies on a homogeneous strip of 2.4 Systematic plot system for vegetation, each strip being managed in a different analyses of heathland vegetation way e.g., with application of mineral fertilizer. At near Gunnarsholt (H-d ata set) the time of the establishment of the plots, their vegetation was supposed to be "typical" of that The vegetation analysis of the uneroded heathland kind of management. In each plot percentage cover in the vicinity of Gunnarsholt was carried out using was estimated for all species and the frequency a systematic plot system (Fig. 2). The intervals be determined on the basis of recordings in 75 small tween the plot centres were arbitrarily chosen to be quadrats of 0.04 m2 size. The plant units were 200 m, and the size of the plots (2x3 m2) satisfies counted in 10 out of the 75 small quadrats. For the "minimal area" (cf. Mueller-Dombois & establishment and results see Gunnlaugsd6ttir Ellenberg 1974) for such communities. For each (1982a). taxon rooting in the plot, cover was visually estimated in percent by perpendicular projection of biomass. 2.3 Line transects at Assandur (S data set) 2.5 Comparison of the sampling The vegetation in the fenced area at .Assandur was methods analysed by means of line transects, each 4 m in length. Most of them (67) were placed at random The analyses of the permanent plots were very time and sampled without replacement. A further 12 consuming as each one included a combination of were situated in the middle of the permanent plots. cover and frequency estimations and the counting

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 15 of plants units (cf. Gunnlaugsd6ttir 1982a). The soil samples collected in the heathland in 1982 By using only cover values, changes of individual were dried at 25°C. The soil samples were sieved to species might have been missed (except for the few obtain a particle fraction of< 2 mm. The pH was dominating ones). Only through comparison of measured in H 0. The solvent for available 2 plant unit density values can we trace changes in phosphorus was 0.5 N NaHC03, adjusted at pH small alpine-arctic species in relation to manage 8.5; the samples were shaken for 30 min (Olsen et ment experiments, e.g., the fertilizations. It was al., 1954). The solvent for the potassium analyses necessary to chose the plots arbitrarily as the strips was 1.25 o/oacetic acid; the samples were shaken for subjected to the different forms of management are 30 min. small and therefore not convenient for random sampling. The line transect analyses are also time-consum 2. 7 Data analysis ing but the method is more objective. The interpre Introduction tation of the readings by grouping five adjoining figures may overvalue the percentage cover com The (estimated) cover-abundance data of the pared to the visual estimation of cover, as it was vegetation analyses have been transformed into the calculated for each of the taxa and then summed up. ordinal scale (van der Maarel 1979) for multivariate Besides, it is more time-consuming to find the ran treatments. domized points in the field than to use the systematic Readings all along the line transect were lumped method. together in groups of five adjacent ones (cf. Ker By using the systematic plot system for only cover shaw 1964) and transformed to percentage cover. estimation we save much time. It is possible to make The results of the classification of the vegetation are 2-3 times as many analyses in the same period of based on these cover percentages; additional taxa time as in the line transect method. The latter have been evaluated as I in the ordinal transforma method is therefore the most convenient for collect tion scale. ing overall information for classification of the vegetation in a certain area. Multivariate treatments

Multivariate methods have been used both for 2.6 Soil samples classification and subsequent typology of vegeta tion and for ordination, i.e. the arrangement of Sampling phytosociological entities along one- or multi-di Soil samples for chemical analyses were collected mensional schemes according to the relation be near some of the permanent plots in 1976 within the tween the entities (see van der Maarel, 1979 and strip of vegetation treated in the same way as each references quoted there). one of them. Altogether 21 such samples were col Two data programs have been used in these par lected from the 0-5 cm soil layer. Each sample con ticular studies for the classification of vegetation, sists of 10 subsamples (cf. Gunnlaugsd6ttir 1982a). namely the T ABORD program for the classification In the uneroded heathland in the vicinity of Gun and the ORDINA program for the ordination. narsholt, 48 soil samples were collected for chemical analyses. Most of the sites were sampled at random. a) The TABORD program (van der Maarel et al. Each of the soil samples consists of 20 subsamples 1978) is a procedure for clustering releves based on taken from the 0-5 cm soil layer in the same kind their similarity in combination with a procedure for of vegetation as found in the analysed plots. obtaining a diagonal structure of clusters in a table. The steps of the program are: Establishment of ini tial clusters, relocation using the similarity ratio Chemical analyses (Wishart formula), homogenization of clusters, For the analyses of soil samples collected in 1976, construction of a table, inspection of the results in see Gunnlaugsd6ttir ( 1982a). terms of optimal number of groups and their

Acta Phytogeogr. Suec. 75 16 Elfn Gunnlaugsd6ttir

homogeneity and repetition of the relocation and b) The ORDINA program (Roskam 1971) per fusion procedure with other options. forms a centred, non-standardized principal com The following options were used throughout the ponent analysis (PCA), based on a Euclidian treatments: The minimum cluster size was chosen as distance matrix, following Orloci (1966). The 1 because there are several releves of special floristic percentage of explained variances are calculated, composition involved. The threshold value was and a measure of success relating the new distances chosen as 0 to avoid residual groups, and the fusion to the original one is given. level as 0.5 to get clusters homogeneous enough for The minimum number of clusters chosen varies interpretation as associations (cf. Westhoff & van from one data set to another. In the P-data set the der Maarel 1978). A high fusion level would result minimum number is 15; in the H-data set it is 16 and in too many, though more homogeneous, clusters at in the S-data set 12 or as many as the expected a lower phytosociological level. The frequency limit number of community types in each set. The initial was chosen as 0.6 to obtain fairly constant species cluster array of the P-data set was obtained with the in the blocks of differentiating species. systematic-random device provided by the pro gram. Cluster arrays for the other two data sets were devised on the basis of field knowledge.

Acta Phytogeogr. Suec. 75 3 Statistics on species occurrences

3.1 Introduction entire data set. The present 79 samples were taken of the S-data set with 73 taxa (Fig. 8a) and 201 Altogether there are 203 taxa involved in the various samples of the H-data set with 152 taxa (Fig. 8b). data sets; 152 in the H-data set, 73 in the S-data set In addition there are 43 samples, i.e., the first and 158 in the P-data set. analyses of each of the permanent plots from the P The taxa of vascular plants amount to 105, data set with 130 taxa (Fig. 8c). belonging to 32 different families (see Table 1). The Clearly the number of species increased with the total number of cryptogam taxa (lichens, mosses, total number of samples involved and no plateau is liverworts) is 98 (see Table 2 for details). reached. This suggests that the species-area relation is a logarithmic one, either according to Williams a semilogarithmic (Dahl 1956, Williams 1964), or a double-logarithmic one according to Preston 3.2 Relation between number of (1962). In our case the Preston curve gave best fit. taxa and number of plots For the 43 plots of the P-data set and 130 taxa the

equation is log y = 1.1 + 0.66 log x from which it The number of plots in relation to the number of was calculated that about 35 plots are sufficient to species per plot for each of the two data sets (H and get complete taxa composition. S) is shown in Figs. 7a & 7b. Clearly the deflated The equation for the S-data set of 79 samples and areas are much poorer in species. The mean 73 taxa is log y = 1.12 + 0.39 log x from which it numbers of taxa per plot are 25 and 12 respectively. was calculated that about 80 plots are sufficient to The distribution curve for the uneroded plots is get complete taxa composition. almost normal, that of the deflated plots is skewed For the H-data set of 201 samples and 152 taxa to the right (Fig.7b). The distribution curve for the the equation is log y = 1.62 + 0.24 log x, which P-data set (Fig. 7c) is still more skewed because of reveals that about 215 plots are sufficient for com the more pronounced heterogeneity of the data. plete taxa composition. However, the mean number of taxa per plot is 23, almost as high as in the uneroded plots. The same relation for the first analyses of each of the 43 per 3.4 Phytogeographical observations manent plots shows still more discontinuity (Fig. 7d). The P-data set is mainly from deflated areas The geographical distribution of the species in and also from uneroded areas as well as from volved in these studies, both in Iceland itself and in species-rich revegetated areas, which contributes to the neighbouring countries, will be treated briefly keep the mean number of taxa per plot relatively below. high. Many of the species are mountain species in the neighbouring countries, although they grow in the lowland in Iceland. About half of the species studied 3.3 Relation between cumulative are Arctic species and the other half European ones number of taxa and number of plots (cf. classification by M0lholm Hansen 1930), the European species mainly being found in the north The cumulative number of species was determined ern groups (Table 3). The Arctic species are species in relation to the cumulative number of plots in of common occurrence in the arctic and subarctic order to investigate the species-area relation in the regions, but they are absent or rare in temperate

Acta Phytogeogr. Suec. 75 18 Elln Gunnlaugsd6ttir

Table 1. Number of vascular plant taxa Table 2. Number of taxa belonging to per fam ily. different cryptogam groups.

Data set : H s p All Data set : H s p All Families: Lichens 1 Poaceae 15 11 18 20 folio se 9 3 8 11 2 Caryophyllaceae 4 8 10 10 fructicose 21 10 16 27 3 8 2 3 8 1 Cyperaceae crustaceous I I 4 Asteraceae 5 1 4 5 Bryophyta Polygonaceae 2 1 5 5 liverworths 14 13 17 6 Gentianaceae 4 5 mosses 7 Brassicaceae 2 acrocarpeous 19 23 30 8 Juncaceae 3 pleurocarpeous 8 8 0 9 Salicaceae 3 I cladocarpeous 2 2 2 10 Rosaceae 4 11 Equisetaceae 3 Total number: 73 24 71 98 12 Ericaceae 3 13 Rubiaceae 3 14 Saxifragaceae 2 15 Betulaceae 1 16 Ophioglossaceae 1 17 Empetraceae 1 Table 3. Percentage of Arctic and European taxa 1930} 18 Ranunculaceae 2 (or species sensu Molholm Hansen within 19 Scrophulariaceae 2 the data sets. 20 Lam iaceae Data set : H _A _I__I 21 Orchidaceae s p 22 Plumbaginaceae Arctic taxa ( 45. 7} ( 48. 9) (44. 9) ( 45. 7) 23 Liliaceae A 1 12.7 10.2 10.2 8. 6 24 Plantaginaceae A 2 12.7 16.3 14.9 17.1 25 Lentibulariaceae A 3 20. 3 22.4 19.8 20. 0 26 Crassulaceae European (51. 9) ( 45. 0} (51. 7) ( 49. 5) 27 Selagi nellaceae taxa E 1 6. 3 4. 1 4. 6 5. 7 2 8 Violaceae E 2 11. 4 8. 2 13.8 10. 5 29 Athyriaceae E 3 16. 5 18. 4 20. 7 19.0 30 Fabaceae E 4 17.7 14. 3 12.6 14.3 31 Onagraceae 32 Pyrolaceae Ungrouped taxa 2. 4 6. 1 3.4 4. 8 104 Total number: 79 49 88 100. 0 1 00. 0 100. 0 100.0

Number of plots 15 a

Number ofplots 10 10

5 5

5 10 15 20 25 30 35 40 45 5 10 15 20

Number 20 of plots c

10 Fig. 7. The frequency distribution

5 of taxa number/plot. (a) Data from the H -data set. (b) Data from the S-data set. (c) Data from 5 10 15 25 30 35 40 45 50 55 the P-data set. (d) Data from the first year of analysis of the 43 per d of plots manent plots. Mean number of -r-· LJ � taxa/plot taxa is ea. 25, 12, 23 and 23, J:l r:l 0 I I 00 I I r:l r:l respectively. 5 10 15 20 25 30 35 40 45 50

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 19

Log no.of zones. The European species are common or typical taxa of more southerly regions. Further subdivsion of 2.0 both groups into minor groups (the Arctic species into three minor groups, Al-A3 and the European species into four minor groups El-E4) is according 1.6 0 to the northern limits of the species. The species with the highest values extend farthest north in each of • • the groups (cf. M0lholm Hansen 1930 pp. 20 ff.) . 1.2 •

0.8 Fig. 8. The logarithmic relationship between the cumulative number of taxa and the number of plots for (a) 201 plots in the heathlands near Gunnarsholt farm, data from the H-data set, (b) 79 plots in the Assandur 0.4 Log no. of plots area, data from the S-data set and (c) the 43 permanent plots, a part of the P-data set. 0.4 0.8 1.2 1.6 2.0 2�

Acta Phytogeogr. Suec. 75 4 Phytosociological classification

4.1 Introduction releves ones, are represented by their constancy classes (1-V) and abundance, viz. the rounded-off The TABORD clusters of the data sets (H, P and S) average values of the transformation numbers. form the basis of the phytosociological classifica The combined constancy figures of the synoptic tion, viz. full TABORD tables of the H- and S-data T ABORD tables of the three data sets were sets and the 43 first analyses made of the permanent transformed into the following 1-9 scale suggested plots of the P-data set. by van der Maarel (pers. comm. 1983). The nomenclature of vascular plants follows II Ill IV V Tutin et al. (1964- 1980); that of mosses follows 1 1 Corley et al. (1981); that of hepatics Grolle (1976), 2 1 2 and that of lichens Krog et al. ( 1980), with the excep 3 1 2 3 tion of Cladonia gracilis ssp. macroceras (Florke) 4 1 2 3 4 FlOrke and Cladonia conoidea Ahti. 5 1 2 3 5 6 1 2 3 4 6 The following abbreviations are used for prac 7 1 2 3 5 7 tical reasons in the text and tables: Festuca pruinosa 8 2 3 5 7 8 (for F. rubra ssp. pruinosa), which is the only native 9 3 5 7 8 9 Festuca rubra F. rubra (F. taxon in the data sets. Actually, the values occurring in the material in rubra rubra), Luzu/a multiflora ssp. is sown, (L. cluded only 1-9 in class V, 1-5 in class IV and 2 multiflora ssp. multiflora), L. sp icata (L . sp icata in class Ill. Thus, in fact, mainly the constant ssp. sp icata), Trisetum pilosiglume (T. sp icatum species contributed to the synoptic values. ssp. pilosiglume), Silene maritima (S. vulgaris ssp. The new data set compiled, called the C-data set, maritima), Thymus arcticus (Thymus praecox ssp. with 43 synoptic releves, was again run with the arcticus), Empetrum nigrum (E. nigrum ssp. T ABORD program. Because the three data sets con nigrum), Deschampsia alpina (D. cespitosa ssp. tain partly the same units, the 43 units could be a/pina), D. cespitosa (D. cespitosa ssp. cespitosa), grouped into 28 initial clusters. The number of end Juncus trifidus (J. trifidus ssp. trifidus) , Cladonia clusters was chosen as 23 in order to allow the pro gracilis (C. gracilis gracilis), C. macroceras ssp. and gram to fuse clusters that might be similar. The (C. gracilis macroceras) . ssp. other options used in this T ABORD run were the same as in the former T ABORD run (2. 7). The result of this T ABORD run is shown in Table 4. 4.2 Procedure

Interpretation of results As the three separate data sets partly overlap, it be came necessary to reorganize them in order to com The interpretation of the synoptic table (Table 4) of bine the vegetation types they have in common. The the second T ABORD run is as follows: The clusters clusters of the TABORD results of the three data (C-clusters) of Table 4 are interpreted phyto sets had previously been accepted as vegetation sociologically as associations or as communities, units, altogether 43 units. The full TABORD tables i.e., neutral units without a syntaxonomical status. of the H- and S-data sets and a selected part of the Several clusters are grouped together into one P-data set were converted into synoptic tables. association as they have species in common, which There the taxa of all the clusters, single or multi- are association character species, e.g., C-10, 11, 13,

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 21

Table 4. The T ABORD result for the 43 synoptic releves and 1 1 S taxa with 2 3 end clusters (C-clusters) grouped into 8 associations/communities with the character species underlined. 1 . The Armerio - Silenetum acaulis, Table 4 (cont. 2 . the Racomitrio - Thalictretum alpini, 3. the Efretrum nigrum - Racomi J trium lanuginosum community , 4. the Agrostio - ylocomietum splendentis, Ass . /comm . no .: 1 111 1 1 111111 111 55662222222332 3781 1 111 444444 rthe Festuca v1vipara - Racomitrium canescens community , 6. the Racomitrio - Gentianetum nivalis, 7. the DrySs oc opetala - Betula nana community , 11111 1 111 1 1 11110000000000000001222211100000 � Cluster no .: 12 22 1 and 8. the Kobresia myosuroides- � anata commumty .-- 996666644783333333366 88888893 1 0 0577743 ------2 2-----2------Po lytrichum alpinum 4 1 ------Ass./comm . no . : 1 111111 111 1 1 11155662222222332 37811111 444444 Cladonia arbuscula 2 2 C. furcata ------1---- 2------1 11111 1 111 1111100000000000000012222 11100000 ------Cluster no. : C. uncialis 1 22 2 2 221 1 996666644783333 33 33661 8888889 0 os 77745 Thamnolia vermicularis ------1--1-- 2------1 ------Festuca prui nos a 2 34543 32 2 52 74433 3 5 5343422222 2- 34442 4 2 344633 Rhytidium rugosum 7 1 -1 1------2---- - 2 1 22--2 22------Silene acaulis 1 3 1 32 11 2 2------1 - 32 1------ Thalictrum alpinum 1 ------2- - 1------Ce ratodon purpureus --56633------1 ------2 6 16="=------Pti lidium ciliare 2 1 22 33 ------==-=-2- 2------Agrostis vinealis 444132241 52 53333532 5211 - 2- 22- 33----3545-- Erigeron boreale =------1------Cardaminopsis pe traea 1 - 2 1-111 2 11- 2 1 1-- 2------1 1 1 ------Peltigera leucophlebia 3 -1 ------Cerast1um alpinum 1 2 1 22--2------2---3-----2----2------Arctostaphylos uva-ursi 4 2 3 ------1-2 ---- 2 - 2 ------Thymus arcticus 2- 21 2 332 33- 1 1 22- 42232132 - 12- 223- 45211 - 1 ---- Salix herbacea 3 3 1 ------2-- -- - 1------2-- Arenaria norveqica ---1-3- 2 1 ------Trisetum pilosiglume 2 1 2 1 - 11 12 --21---22 ------2------Vaccinium uliginosum ------42 - 52------M inuartia rubella 1 Poa glauca 1 - 22- 3- 221 1 222--321------1-3- 1 -- 1 ------Betula nana ------7------2------Calluna vulgaris ------1------1 1-- 1 ----42--24------Deschampsia flexuosa ------Empetrum nigrum ------1 ----- 331352- 34- 4632 7 33------Dryas octopetala 6 ------uncus trifidus -----33--1-----1 -- 1 - 2 322- 2- 223------Salix callicarpaea 3 J ------2------Luzula spicata --2-- 332- 3- 2- 3--2- 2------2------1 ------S. phylicifolia 2:------2 1------2------Poa alpina --2----1-3- 2------1 - 2------Bryum spp . 3 ----=------Rumex acetosella ------4--2--- 1 2------Timmia austriaca 1 ------2------Cladonia spp . ------8------Salix Janata 3 76 ------=------Cornicularia aculeata ------3------2-- 1 ------ris - 1 2----2------Peltigera spuria ---221---3------1 ------1 ------�ia��a P�a��ltat ------�------Stereocaulon glareosum ------1 ------Pohlia cruda 2 ------Stereocaulon spp. --- 1 -11 --5------3--2------Stereocaulon rivulorum 1 ---2------2------�------Cladonla imbricaria ------1 ------Agrostis stolonifera s-- 1 643 ------1 ------Achillea millefolium ---2-1--1 1 1 21 1 1 ------Lychnis alpina 21 1 2 1 ------5----- Agrostis capillaris 5 1 3 2--2 3- 2 32 47 45 Leontodon autumnalis ------Botrychium lunaria ------1 2------1 1------1 --1 ----- 2----- Leymus arenarius 3 ------2----- Silene maritima -1------1 - 1 ----2------2------Taraxacum sp, ------Cerastium fontanum ------221------1 -1----- Brachythecium albicans 1 2 2 ------2 ------1------2-- Equisetum arvense ------1 --- 1 ---2 322222 32----2 1 333 411 Peltigera polydactvla ------2 1------Festuca vivipara ------1 ------2 42 334--2---113 1 -----3332 42 3 P. apthosa. ------Galium normanii --1 ------2---22221222221 --2- 3----212----- Cladonia pyxidata 1 ------Luzula multiflora ---1 ------2222 2 221--2- 2------22 1 2 22 C. macroceras 1 ------Drepanocladus uncinatus ------7 3 32 32 s-----1 ------8 7887 C. chlorophaea 1 ------2------Racomitrium canescens ------76 98621 32------1 21 5 22 3 Tritomaria quinquedentata ------Peltigera canina ------322 32- 32--2212------1 3 322 Scapania cf. curta 11 ------Cetraria islandica ------22- 2222--22------Nardia scalaris 1 ------ciadonla gracilis ------1 2-- 1 ----2------1 -- Lophozia ventricosa 11 ------Carex bigelowii ------2 --- 1 22- 3 32--2 3------3--- L. alpestris ------=---- 1 ------1------Galium boreale ------43--32 5322- --2------22 2 34 Lophozia spp . ------1 ------verum ------1-2- 2221 2--2--2------62- - 33 Barbilophozia hatcheri 1 1 C. ------2------Kobresia myosuroides ------462 3332-- 33- 5------2--3 3 B. barbata ------2------Polygonum viviparum ------2---22222- 2--222------12 Anthelia juratzkana ------1 ------Hylocomium splendens ------6 96653- 331 2------11- 2 48 Encalypta procera ------2------Racom itrium lanuginosum ------2 2-- 42 838999996------Dicranum congestum 1 ------1------Rhyt1d1adeiph us squarrosus ------2--- 1 33------=------7 4635 3 D ichodontium pellucidum ------1 ------R. triquetrus ------2222---- 1 ------=-== Bartramia ithyphylla ----- 1 ------2------Stereocaulon alpinum ------2- 1 3212321--2 ------Sagina nodosa 3 ------2------Carex capitata ------2-----3------Pinguicula vulgaris ------Equisetum pratense ------2------Lomatogonium rotatum 1 -----2------H ierochloe odorata ------2-----1------H ieracium sp. ------=------2----- 1 ------2 1 2 2-- Centianella amarella ------2------la s ------1 ------==-== Gentiana nivarrs ------=-2------1 ------1 ----=------�Polytrichump�:t�� juniperinum ------22-- 2------11------Fe stuca rlilJ"i'a ------2------P. piliferum ------1 --�------11-- 1 -----1 ----3------Euphrasia frigida --11 ------1------Selaginel la selaginoides ------2 1 2--2 1-1 ------Draba incana 1 ------2------Armeria maritima --2----2---1 1 -----2---1 ------2------Cystopteris fragilis ------Equisetum variegatum ------2- 2-----2------Betula pubescens 3 Potentilla crantzii ------1------

14, 16-22, or 1, 2, 6 and 8 (pro parte), or 4, 5, 7 character species of a certain community, one or and 15. C-clusters may also be divided when parts two others may take over as dominants. Such of them have their own group of character species, communities are said to be phytosociologically un e.g., C-3, 8 (cf. Table 4). Clusters were considered saturated. Such communities may phytosociologic a community if no character species could be iden ally be interpreted as sociations, sensu Du Rietz. tified or if there are too few analyses available for They can be interpreted as basal communities (BC) a formal association description. Barkman et al. or derivative communities (DC), as suggested by (1976) recommend at least 10 analyses for such a Kopecky & Hejny (1973). The difference between formal description. Here the association descrip the two types is rather unclear as described by the tions are sometimes based on less than 10 analyses authors. A basal community is considered of equal as these have their own groups of character species. rank with an association, and can be assigned to a Under extreme conditions communities can not higher unit in the syntaxonomical system, i.e. an develop completely and in such cases instead of the alliance, order or class. The BC thus contains char-

Acta Phytogeogr. Suec. 75 22 Elfn Gunnlaugsd6ttir acter and differential species of higher syntaxa to Roman figures for the syntaxonomic units (and gether with companion species, one or two of which even form the forms). The percentage values of the are dominant. The BC is named after one or two presence of the taxa in each vegetation unit are ac class character species, which have the highest con cording to the following scale: stancy and dominance in the communities. The name of the higher syntaxon is given in brackets. 80. 1-100 o/o constancy class V A derivative community (DC) is similar to the BC, 60. 1- 80 % IV 40. 1- 60 % Ill but its characterizing species are of narrower 20. 1- 40 % 11 amplitude than those of the BC, and furthermore, 10.1- 20 % I their character species are plants that have been 5.1- 10 % + stimulated-by various human activities-and have 0- 5% r thus become dominant. The name of the DC is com posed in a similar way to that of the BC, but with The tables also show the mean abundance, being the dominating species and the name of higher syn the average of the transformation values of each of taxa in brackets. the taxa in the syntaxon. At the bottom of the tables A sociation sensu Du Rietz (1921) has been de the total number of taxa for each releve and vegeta fined by Mueller-Dombois & Ellenberg (1974 p. tion unit are given together with the number of cryp 172) "as a recurring plant community essentially togam taxa. Taxa of the genuses Bryum, Cladonia homogeneous species composition with at least cer and Lophozia, which are impossible to identify as tain dominant species in each layer''. species, are not included in the number of taxa in As the association concept may be considered to the tables. be very useful for purposes of comparison, it will be The species of the TABORD tables (output) have applied as far as possible. The sociation concept will been re-arranged in the syntaxonomic tables in not be used here and neither the BC or DC concepts, order to elucidate the phytosociological syntax since the dominating species in the non-association onomic units. communities are frequently character species of Many of the vegetation units (clusters) formed in various higher syntaxa of the phytosociological the T ABORD runs are based on high abundance of system according to the Braun-Blanquet approach. one or few taxa and have no differentiating species The BC and DC concepts might become useful later of their own. These units are not qualified for syn on, when a well established classification system for taxonomical description as they have no constants Icelandic vegetation types exists. The non-associa as differential species towards each other. These tion communities described in this paper are units have occasionally been given status as a assigned to alliance or higher syntaxa as well as the "form" of a certain association or subassociation, associations due to floristic affinities. and are not units of the syntaxa system. Lower syntaxa can be distinguished within Another reason for not giving these units status associations. These are characterized by differential in the syntaxa system is that the analyses were made species or rather by preferential species against each in restricted areas. In one such area, the heathland other based on different constancy values of the in the vicinity of Gunnarsholt, the vegetation gra species. For syntaxa represented by > 5 releves, the dient is indicated by the ordination of the H -data set system is as follows: (Fig. 9). The main feature of the ordination of the releves shows the ''horse-shoe'' form, which in V against 11, I, +, r and absence dicates a floristic gradient. In the S-data set the or Ill, IV against I, +, r and absence 11 against absence dination hardly shows any cluster formation at all (Fig. 10). For syntaxa represented by 5 releves: In the tables the abbreviations are as follows: Ch

= character species of association or higher syn 5,4 or 3 against absence taxa; D = differential species of association or

The syntaxonomic tables (Tables 8a-15a) give the higher syntaxa; d = differential species of lower transformation values and the constancy classes in units of syntaxa or forms; Comp. = companions.

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 23

Fig. 9. PCA-ordination diagram dimensions 1 and 2 of the 20 1 plots of the H-data set shown.

The percentage of extracted 2 2 2 2 variance for first four dimensions 2 2 2 2 2 2 2 2 � 7 are 30, 12, 9 and 4. (1-4) Various 27 7 2 � 2 2 2 7 7 7 7 7 units of the Racomitrio - Thalic 2 10 2 10 7 7 7 7 7 7 9 8 10 8 tretum alpini, (5) the Empetrum 7 7 7 77 8 1 1 8 9 1 1 nigrum - Racomitrium lanugino 1 1 1 2 9 1 1 1 1 10 � s 10 9 sum 9 9 community, (6-9) various 1 1 11 1 1 1 1 10 10 units of the Agrostio - Hylo 1 1 1 1 4 3 1 5 1 3 1 1 4 10 comietum splendentis, (10) the 1 1 5 1 1 4 4 4 Festuca vivipara - Racomitrium 4 4 11 4 4 1 4 canescens community and (1 1) the 4 5 5 3 3 4 3 4 6 3 Armerio - Silenetum acaulis. 6 6 6 6 6

1 1 1 Fig. 10. PCA-ordination diagram 1 2 111 1 3 11 1 1 2 2 2 dimensions 1 and 2 of the 79 plots 11 1 1 2 of the S-data set. The percentage 2 2 2 of extracted variance for the first 1 2 2 1 2 four dimensions are 28, 10, 8 and 1 1 2 2 1 2 6. (1) The typical variant and (2) 11 1 the Ceratodon purpureus variant of the Armerio - Silenetum acaulis achilleetosum millefolii, (3) the Kobresia myosuroides - Salix lanata community.

Site and vegetation characters The slopes are divided into categories slightly modified from those used by Birse (1980): Tables 8b-15b show various site and vegetation characters, including, for example reference no., oo level altitude, date ofobse rvation, aspect, slope, and also 0°-2° very gentle 3°-5° gentle the percentages of bare ground (B), litter (L) and 6°-10° moderate percentage cover of each of the vegetation layers; 11o -15 ° moderately steep i.e., the field layer (F), the bottom layer (M) and the 16°-25° steep shrub layer (S). The height of vegetation is also 26°-40° very steep >40° precipitous given when available and in some cases a few soil factors, i.e., pH in H 0, meq K+ /100 g soil dry The different pH ranges are termed sensu Ferreira 2 weight and mg PI 100 g soil dry weight are given in (1959), viz. pH 5.0-6.0 slightly acid; pH 6.0-7.0 Tables 8c, 9c, 12c and 14c. neutral and pH > 7 alkaline.

Acta Phytogeogr. Suec. 75 24 Elfn Gunnlaugsd6ttir

4.3 Other calculations and communities, e.g, the arctic vascular plants and cryptogams, which were not evaluated by Ellenberg In addition to the multivariate methods, statistical (1978, 1979). Most of the European character calculations have been used in describing vegetation species involved are members of two of the class types. The species diversity of each vegetation type groups he defined, i.e., stony places and alpine is expressed as the alpha index according to Dahl grassland, and anthropogenic and zoogenic heaths (1956): and meadows (Ellenberg 1979). sn - s, Multivariate methods have been used for the in a=--- corporation into higher syntaxa, i.e., to combine 1n n the synthetic releves of the C-data set into larger where sn is the total number of species per vegeta groups interpreted as alliances or higher syntaxa. tion type, S, the mean number of species per These are then compared to alliances and higher analysis in the type and n the number of analyses in syntaxa already described in C Europe, Scotland, the type (ln = natural logarithm). Scandinavia, Greenland and Iceland (Tiixen 1937; The vegetation types (associations, communities) Ellenberg 1978, 1979; Birse 1980; Nordhagen have been compared with related plant communities 1927-28, 1936, 1943; Dahl 1956; de Molenaar described earlier by various authors. Comparisons 1976; Daniels 1982; Tiixen & Bottcher 1969). have been based on the similarity ratio, but for In order to establish "alliances" or community presence-absence data. In this form the formula is groups, the C-data set was treated once again with identical with Jaccard's coefficient: the TABORD program in the following way: Own c initial cluster array based on field knowledge, maxi ISJ = 100 X mum 17 clusters, minimum 6 clusters, minimum a + b + c cluster size 1, threshold value 0, fusion level 0.4 in where c is the number of species in common; a is the order to get larger clusters (here A-clusters) suitable number of species unique to the first community for interpretation as "alliances". The frequency and b is the number of species unique to the second limit was chosen as 0.6 in order to obtain constants community (Mueller-Dombois & Ellenberg, 1974 p. which differentiate the clusters. The TABORD out 213). Earlier descriptions of Icelandic vegetation put is shown in Table 5a, with 7 end clusters, which have usually only treated vascular species, and thus are difficult to interpret as 7 different "alliances" in the present context only the vascular plants of the because there are only few analyses involved in some vegetation units described here have been taken into of them. In combination with the ORDINA (PCA) account in the comparisons. Only if both vascular run of the C-data set and the T ABORD A-clusters, plants and cryptogam species are present in both four groups have been distinguished. These four communities being compared, are all the taxa taken groups might be interpreted as four different com into account. munity groups (alliances or higher units). The inter pretation of the ordination diagram is shown in Fig. 11. An attempt has been made to assign these four 4.4 Assignment to higher syntaxa community groups to alliances or higher syntaxa already described in literature (see below) by means The assignment of the heathland associations and of the presence of their character and differential communities to the syntaxonomical system is not an species (see Table 5b ). Table 5b shows that the char easy task. There are relatively few of the Central acter and differential species of these syntaxa do not European character species involved (usually indisputably separate the community groups. The 30-50 o/o , occasionally more), species which repre character and differential species of the Sedo sent various groups, classes, order or alliances in Thymion, the Equiseto-Galion alliances or the class Europe, but comprise an association or community Carici-Kobresietea are found more or less in most in Iceland. Other species than the European charac of the vegetation types described here. On the other ter species are most important in these associations hand, characterizing species are found for the four

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 25

Fig. 11. PCA-ordination diagram Dim 2 dimensions 1 and 2 for the com munity groups (alliances or higher syntaxon) upon 43 synoptic releves and 118 taxa of the C-data set. The percentage of extracted variance for the first four dimen sions are 23, 19, 8 and 6. (7) The Racomitrio - Thalictrion alpini, (6) the Equiseto - Galion borealis, ( 1, 2, 4) the Sedo - Thymion drucei and (12, 13) the communities of Dim1 the class Carici-Kobresietea. The numbers refer to the T ABORD clusters in Table 5a.

community groups (cf. Table 5b), so floristically (1) Armerio - Silenetum acaulis Hadac 1972 em. they are distinguishable as separate groups. Subass. achilleetosum millefolii subass. nov. There is only one species, Achillea millefolium, Typical variant var. nov. characterizing community group a, implying that Ceratodon purpureus variant var. nov. there is no reason to establish a new alliance. Subass. cerastietosum fontani subass. nov. Community group b has more characterizing Subass. galietosum normanii subass. nov. species, which allows the description of a new Alliance Racomitrio - Thalictrion alpini all. nov. alliance, the Racomitrio-Thalictrion. The two com (2) Racomitrio - Thalictretum alpini (Stein munity groups a and b share several character d6rsson 193 6) ass. nov. species of higher syntaxon, namely the order Sedo Subass. galietosum normanii subass. nov. Poietalia glaucae. Typical form Community group c has clearly got characterizing Peltigera leucophlebia form species of its own. As there is already an alliance Cerastium alpinum form formed by closely related plant communities de Subass. inops subass. nov. scribed in literature as the Equiseto-Galion borealis, (3) Empetrum nigrum - Racomitrium langui a new alliance would be premature. nosum community comm. nov. For community group d too few analyses are available to enable the establishment of a higher Class Molinio-Arrhenatheretea Tx. 1937 syntaxon. Order Molinietalia Koch 1926 Alliance Equiseto - Galion borealis Tx. 1969 (4) Agrostio capillaris - Hylocomietum splenden tis (Steind6rsson 1936) ass. nov. 4.5 Plant communities Subass. inops subass. nov. Subass. racomitrietosum canescentis subass. Synopsis of the vegetation types nov. Class Koelerio-Corynophoretea Klika apud Klika et Typical variant var. nov. Novak 1941 Typical form Order Sedo - Poietalia glaucae de Molenaar 1976 Drepanocladus uncinatus form Alliance Sedo - Thymion drucei de Molenaar 1976 Thymus arcticus variant var. nov.

Acta Phytogeogr. Suec. 75 26 Elfn Gunnlaugsd6ttir

Table Sa . The T ABORD result for the 43 synoptic releves and 1 1 8 taxa with Table Sa (cont .) 7 end clusters (A-clusters) with their blocks of differentiating species . Four community groups (CG) (alliances or higher syntaxa) have been distinguished Community group : t--- a �d io'-- b ---->1<-- c �1'- a ->1 (cf. the ORDINA (PCA) result Fig . 1 1 ): (a) the Sedo-Thymion including 1 . 1111111 11 1111 222222 22 111 111 the Armerio-Silenetum ; (b) the Racomitrio - T halictrion aloini including 2 . the Vegetation unit no. : 1 7 333 55444466448 3 . - Racomitrio-Thalictretum and the §_. nigrum �- lanuqinosum community ; A-Cluster no .: 000000000000001 0000000000000000000001 000000 (c) the Equiseto-Galion including 4. the Agrostio- Hylocomietum_, 5. the E· 222222222222242 7777777777766666666663 1 1111 1 vivipa ra - �community and 6. the Racomitrio-Gentianetum; and �- Dichodontium pellucidum ------1------(d) the Carici-Kobresietea including 7. the octopetala �community �· -: �- Brachythecium albicans ------1 22------and 8. the myosuroides - lanata community. The character and differ !5_. �· Bartramia ithyphylla ential species of the alliances and the class are underlined . ------1------Viola palustris ------1 ------Taraxacum sp. ------2------Silene maritima ----- 1 ------2-----21--1 Community group : a �d!'--- b c a r-- � �dr -,l( Selaginella selaginoides ------2- 1-2- 1 -12------Vegetation unit no .: 1 1111 1111111 1172222223332255444466448111111 Sagina nodosa ------3 1 ------2------Potentilla crantzii ------1 ------A-cluster no .: 000000000000001 0000000000000000000001 000000 Poa pratensis ------1 ------2-1--2--22------222222222222242 7777777777766666666663 1 11111 Pinguicula vulgaris ------2------2------2- 2-1--1--- 1 ------1---- 1 22 22 11 2 3 2 - 1 Lychnis alpina = 45 224 2 41 353- 34- 1 2 351 - 2 2- 2 2335--4 35533--1 --- Lomatogonium rotatum ------1 ------x���il�mCardaminopsisVIa��m petraea 2- 1212- 1111--1------2----11111- Leymus arenarius ------3------Festuca pruinosa 4 722 544 3343445 3 2 43322- 22 2 43343345 5 6342 4222 3 Leontodon autumnalis ------2------Poa glauca 222222- 3- 2--113------1 --3----21----111 -- Hierochloe odorata ------2---- 1 ------Si le ne acaulis 3- 21 1 --1 3- 2 2 3 1 1 ------2-----1111 Hieracium sp . ------2------21 2 3 112332254332 331 -122- 22- 41 ---22--- 11- 22- Gentianella amarella ------1 ------2- 1 21- 1 - 11-- 1 ------=--!-'= Gentiana nivalis ------2------I�KI'II�=Botrychium lunaria ��urn ------1 ------1----"-- 11- 21--2--- Festuca rubra ---- 11------Juncus trifidus ------33----1 -22- 3- 2 3- 2221 ------1 ------Euphrasia frigida ------2------Luzula spicata 222----333---3------2---2-----2------1- Erigeron boreale ------22------1------M inuartia rubella 2- 221------1 ------2------Equisetum variegatum ------2------2 2------Rumex acetosella -----2------4------1----2------2------Cladonia spp . ------8------rab�a a 1 11- 1 ------=------ Cornicularia aculeata ------1 3------2 ------�Cystopte;��!�ris fragilis ------2------Peltigera spuria ----2- 2 1----1 3------1 ------Cerastium fontanum ------2----2 1-1-- 1---- Stereocaulon glareosum ------1 ------Carex capitata ------3------2 ------Stereocaulon spp . ---- 1 -- 11----5------3---- 2- Betula pubescens ------3------Cladonia imbricaria ------1 ------Arenaria norvegica --21 1 --3------Agrostis capillaris -----3------52---3------2--2 4542- 7 3--- 1 --- Agrostis stolonifera ----2 ------6 1 ------5------2----3--4- Calluna vulgaris ------12---1 ---42 ------1 1 --4------Empetrum nigrum ------1 3435-- 4 7632233---- 1 3-- 3------Poa alpina 221------32------1 ------Arctostaphylos uva ursi ------3------24------Armeria maritima 212--1------2- 1 ------2------Betula nana ------7------Deschampsia flexuosa ------2 ------= =�======;= = = ;= � � �;�;;;;; ;� ;: ;= = = == Salix�c:c��i��:: callicarpaea ------�;=3------S. herbacea ------2-----31 2 3- 2------1 ------S. lanata ------7------2------3--6------S. phylicifolia ------2------2------Trisetum pilosiglume 22------1 -----2------111- 2------12- 1 ------Vaccinium uliginosum ------2------542------Sryum spp. 2 3- 1------2------·Table Sb. Synoptic table for the four community groups (CG) with the Ceratodon purpureus 5---6- 633--6 1-2------1 --6------constancy of their characterizing species. Character (Ch) and differential Poly tr1chum�um ------1---2--1------22---=::: (D) species of the alliances and class which the vegetation types are Timmia austriaca ------1------prov isionally assigned to are also given. See legend in Table for the Galium no rmanii 12------3221221--- 2 2 22----2 2- 2- 1 2--- Sa CG and vegetation types. ------2 2222- 22-- 2 22--1 2------�:�:R��um ------212--222--21 r-:===: ------Community group (CGJ : b b d d bigelowii ------3-1 2 32 3-- 2 22---- 3------�;h11if�t� Vegetation type no. : Galium verum ------21 22--22--21- 2 33- 2--6------Kobresia myosuroides ------1 3342 32 3--36--2 33-----5------Ch. D. of the Sedo-Thymion Hylocomium 56663- 2 331 9-- 1 48---21------& splendens ------= Cerastium alpinum Racomitrium lanuginosum ------83489969992 22------11 V Ceratodon purpureus Ptilidium ciliare ------2 1-- 2--331 2- 2------Ill IV Luzula s�icata Cetraria islandica ------22 2- 2 22- 22------V V Lychnis alpina Stereocaulon alpinum ------32 31 21---2 2- 2-----1------IV Thymus arcticus Galium boreale ------2 3352----22 432 342--2------IV V Luzula multiflora ----1 ------1222 ---2- 22- 222 212222 ------Species characterizing CG Peltigera canina ------2 33---22212- 3322-22 3 1 ------�: Achillea millefolium Equisetum arvense - 11------2 322-----2223311 3 2 2 43- 1 2---- [@ Drepanocladus uncinatus ------35----1 - 2 73 77- 832 88------Ch. of the Racomitrio-Thalictrion ------2 3 1 ------2 765 2 3- 9821- 21 Racomitrium canescens 6 or species characterizing CG b: ------1 3------32- 3 --3 ------Rhytidiadelphus squarrosus 45 6 7 Cetraria islandica ------1------r 11 Parnassia palustris Cladonia uncialis Tofieldia pusilla ------2------2------Ptilidium ciliare I Rhytidium rugosum ------1 ----7------Racomitrium lanuginosum 11 Thamnolia vermicularis ------1--- 1---2------1------Stereocaulon rivulorum Ch. D. of the Equiseto-Galion ------1------2------& Peltigera polydactyla Carex bigelowii ------V Ill 11 - P. leucophlebia_ 3 1 - Equisetum pratense I I I P. apthosa ------21------Galium boreale V Cladonia uncialis ------1 ---- 2--2------V V G. verum V C. pyxid� ------�------1 ------IV lii Ill Luzula multiflora IV V C. macroceras ------1------V V Polygonum viviparum V III I 11 C. gracilis ------1------22------1 ------Taraxacum sp. 11 C. furcata ------2------1------C. chlorophaea ------1 ------Species characterizing_ CG �: C. arbuscula ------2------2------Agrostis capillaris V Tritomaria quinquedentata ------2------I Ill Poa pratensis IV 11 Scapania cf. curta ------11------I Cerastium fo ntanum I V V Nardia scalaris ------1------Gentiana nivalis I Lophozia ventricosa ------1------V Ranunculus acris I L. alpestris ------1 ------1 ------Lophozia spp . Ch . of the Carici-Kobresietea ------1----1------1------Barbilophozia hatcheri Dryas octopetala r ------2------B. barbata Kobresia myosuroides ------2------V IV 11 Anthelia juratzkana Silene acaulis [] IV !I 11 Rhytidiadelphus triquetrus ------2 2 2----1-2------1 ------1----1 ------11------Polytrichum piliferum 3 Species characterizing CG d: ------2------1-22------P. alpinum 4 Arctostaphylos uva-ursi ------Poh lia cruda 5 Betula nana ------1 ------E ncalypta procera Platanthera hyperborea [J] Dicranum congestum ------2-1------

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 27

% %

I 11 Ill IV V Class

Fig. 12. The frequency distribution of taxa in Raunkirer's classes for each of the vegetation types. (1) The Armerio - Silenetum acaulis; (la) the achilleetosum millefolii and (1 b) the galietosum normanii of the Armerio - Silenetum acaulis; (2) the Racomitrio lanuginosi - Thalictretum alpini; (2a) the galietosum normanii and (2b) the inops subassociation of the Racomitrio - Thalictretum alpini; (3) the Agrostio capillaris - Hylocomietum splendentis; (4) the Festuca vivipara - Racomitrium canescens com munity and (5) the Racomitrio canescentis - Gene I 11 Ill IV V I 11 Ill IV V I 11 Ill IV V tianetum nivalis. Class

(5) Festuca vivipara - Racomitrium canescens larger than 1, and Ill + IV + V /11 is about 2 community comm. nov. (Westhoff & van der Maarel 1978). (6) Racomitrio canescentis - Genitanetum nivalis Results from the community tables are shown in ass. nov. Table 6. Here again only the Agrostio - Hylocomie tum splendentis and the galietosum normanii of the Class Carici rupestris - Kobresietea bellardii Ohba Racomitrio - Thalictretum alpini are homotoneous. 1974 The other vegetation types would be heterotoneous (7) Dryas octopetala - Betula nana community according to these criteria, i.e., which means that comm. nov. they may contain more than one plant community (8) Kobresia myosuroides - Salix lanata com (Hofmann & Passarge in Westhoff & van der munity comm. nov. Maarel 1978). Indeed, they are disturbed com munities, e.g., the Festuca vivipara - Racomitrium canescens community, which is found in erosion damaged sites or they are various stages of second Homotoneity of the vegetation types ary succession, e.g., all the subassociations of the The relation between constancy classes of Armerio - Silenetum acaulis em. described in this homotoneous tables is: I > 11 > Ill � IV < V paper, the Racomitrio - Gentianetum nivalis and the (Raunkirer'slaw of frequency cf. Dahl 1956). Only inops subassociation of the Racomitrio - Thalic the Agrostio - Hylocomietum splendentis and the tretum alpini. These facts might be the reason for galietosum normanii of the Racomitrio - Thalic their heterotoneity. The Agrostio - Hylocomietum tretum alpini show such figures (Fig. 12). The fol splendentis is also a disturbed community by the in lowing relation between constancy classes is found terference of mineral fertilizer, but in spite of that in homotoneous tables: IV + V /11 + Ill is slightly it is a homotoneous community.

Acta Phytogeogr. Suec. 75 28 Elfn Gunnlaugsd6ttir

Table 6. Relation of constancy classes in the Table 7. The alpha diversity of the vegetation types . Total vegetation types. number of taxa ; ! 5nL number of analyses (n), average number of ( 1) the Armerio - 5ilenetum acaulis of species per analysis (5 ) and the index of alpha diversity · 1 (a). (la) the achilleetosum, ( 1 b) the cerastietosum fo ntani and types 5 n 5 Vegetation n 1 (le) the galietosum of the Armerio - 5ilenetum acaulis, ( 2) the Racomitrio - Thalictretum alpini , Armerio-5 ilenetum 77 107 14.9 14.0 ( 2a ) the galietosum normani i and ( 2b) the inops of the Racomitrio - Thai ictrietum alpini. Racomitrio-Thalictretum 117 122 28. 9 18.5 ( 3) the Agrostio - Hylocomietum sp lendentis, (4) the vivipara - canescens community , and � �· E. ni rum - lanuginosum eo mm. 64 30 . 8 23. 9 ( 5) the Racomitrio - Gentianetum nivalis. g �· Agrostio-Hylocomietum 92 72 20. 2 16. 8 Rel;;tion of constancy classes IV+V /11+111 111+\V+V/11 F. vivipara - �. canescens comm . 79 32. 6 22. 3 Vegetation type : 0. 5 1.5 1 a 0. 4 1.1 Racomitrio-Gentianetum 85 44.0 22. 9 1 b 1.2 3.3 5 1 c 3. 2 9. D. octopetala-�. nana comm. 40 33. 5 9. 4 2 1.2 2. 4 2a 1.2 2.5 K. myosuroides - 5. lanata eo mm. 27 20. 0 10. 1 2b D.7 2. 4 3 1. 4 2. 3 4 0. 6 1. 2 2. 4 7. 3

Alpha diversity of the vegetation types

The a diversity of the vegetation types (this paper) - Racomitrium canescens community has high a is shown in Table 7. The Empetrum nigrum - Raco diversity which may be related to the fact that it is mitrium lanuginosum community has the highest found in half-eroded sites and may therefore in value. This community may include more than one clude community fractions. vegetation unit. The secondary succession associa The a diversity indices here vary between 9.4 and tion Racomitrio - Gentianetum nivalis has also high 23.9. Dahl (1956) found a diversity indices varying a diversity due to different age and state of the between 4.3 and 29.8 in his vegetation types of the regrowth of the plots involved. The Festuca vivipara Rondane, S Norway; these ranges are similar.

Acta Phytogeogr. Suec. 75 5 Synopsis of plant communities - description and phytosociological affinities

5.1 Gravel flat vegetation The constant companions of the association are Festuca pruinosa (V4), Agrostis vinealis (IV3), Gravel flat vegetation is an open sward where the Thymus arcticus (IV2) and Poa glauca (IV\ soil surface is only partly covered with vegetation. Most species belong to the hemicryptophyte life Still, many species are found in these vegetation form group (Fig. 17). The Arctic species are more types. The most common species are Agrostis common than the European ones (Table 16) due to vinealis, Armeria maritima, Cardaminopsis strong exposure. petraea, Cerastium alpinum, Festuca rubra s.l., Poa The soil is usually coarse to very coarse sand and glauca, Salix herbacea, Silene acaulis, S. maritima gravel intermingled with silt-loamy soil. The soil is and Thymus arcticus. Arctic species (sensu fairly fresh to well drained with a surface open to M0lholm Hansen 1930) are more common than the drying-out effect of wind. European ones. Cryptogams are rare and usually The nutrient status of the soil of the association have low abundance. is low with, on average, 0.1S mg P (variance 0.19) The soils are gravelly, sandy or silt-loamy of vari and 0.25 meq K+ (variance 0.13). The soil is ous depth. Pebbles and blocks are spread over the neutral with a pH of 6.95 (variance 0.61), the figures soil surface. The nutrient status of the soils is ex being based on 15 analyses. tremely low (see below). They are well drained. The bare soil surface is exposed to the desiccating effect Three subassociations can be discerned: of winds and to strong heat on sunny summer days. (1) Subass. achilleetosum millefolii subass. nov. The uppermost soil layer often becomes dry in the (Table Sa, b & c; ref. no. 1-S9; Plate 1). The dif summer (Gunnlaugsd6ttir 1982a), which facilitates ferential taxa are Achillea millefolium (IV1) and the removal of fine soil grains by the wind. As the Stereocaulon spp. (S. glareosum + S. rivulorum) areas are strongly windswept the snow shelter is (111). The subassociation is found in rather coarse usually blown off in the winter, and the silt-loamy to coarse alluvial gravel intermingled with sandy soil becomes exposed to frost-heaving action. and silt-loamy soil. It is found on level ground to Polygons are common. gentle slopes and sometimes on moderate slopes at Gravel flat vegetation types are very common in altitudes of 20-26 m. The nutrient status of the soil Iceland, both in the lowland and the highland. They of the subassociation is low with, on average, 0.20 have mainly been created by wind erosion and defla mg P (variance 0.43), 0.22 meq K+ (variance tion, especially in the lowland. 0.0005); the soil is alkaline with a pH of 7.05 (variance 1.03), the figures being based on 5 (1) Armerio - Silenetum acaulis Hadac 1972 em. analyses. (Table Sa, b and c; ref. no. 1-107; Fig. 13; Plates Two variants are discerned: 1-6). The association has the following character a. Typical variant var. nov. (Table Sa, b & c; ref. species: Silene acaulis (IV1) and Cardaminopsis no. 1-44). This variant is found in the unfertilized petraea (IV1). parts of the alluvial gravel flats of the Assandur Festuca pruinosa, Agrostis vinealis and Thymus area. arcticus dominate the physiognomy. The field layer b. Ceratodon purpureus variant var. nov. (Table Sa covers 19 0"/o , the bottom layer 16 %, litter 19 % & b; ref. no. 45-S9). Differential taxa are and bare ground ea 6S %. The average height of the Ceratodon purpureus (V6) and Peltigera sp uria vegetation is l.S2 cm. (IV2). This variant is found on the same kind of

Acta Phytogeogr. Suec. 75 30 Elfn Gunnlaugsd6ttir

Table Armerio - Silenetum acaulis Sa. (1-96). 1. (1-44) , 2. (45-89) , A. achilleetosum millefol ii typical variant Ceratodon purpureus variant B. cerastietosum fontani (90-96) . 97- 1 07) . C. galietosum normanii ( C A Subunit: A A c 2 1 Synop 1 1 1 ______8 9 7 11 107 ____ 44 4 5 �� value �N�um�b�e�r�o�f�r�e�le�v�e�s:�------�4�4------4�5------_ ��-- 11111111

11111111112222222222333333333344444 444445555555555666666666677777777778888888888 9999999 99900000000 789 01 23456 78 901 2 3456 7 1234 56 7890123456 7 8901234 56 7890123456 7 8 901 2 34 56 7 8 901 234567 8901 23456 7 8 901 2 3456 7 890123456 Ref. no .:

Ch. Ass. .11..1.131 113111.111.113111...... 143 1111. ..11111 .....1.1. ..13 ... 11.31111.1. ..1 331 14322. .1. ..2222. 43223 1.0 Silene acaulis 1 V 1311.1.11.1111.1111.1... 1.1 2 12212221 11131311 4 ...... 13 11.63 ....3 .. 13113... 13 1111.... 11.2 2 ..2221 2 ..21 112221 2 IV Ill IV 1 1. 0 Cardaminopsis petraea IV . Ill IV IV IV

d. of subass. � var. . . 11111 . 1111. 1. .... 1. 111. . 111122. 1311 . 3. . 1 11111. ...3 ... 11. 1111.111. 11 ..113 . 3. 1.. . 1. 1222 ... 2 ...... + 0. 7 Achillea millefolium 1. IV Ill IV Ill . 11.333 ...41 11. 1 1 .. 1111111. ..11. 3 ...21 . 0. 6 Stereocaulon spp . 113.. 1 ..111 .....1. 1 ...... 1 ...... 1. 43. 4 ...... I! Ill I 11 . 51 . 551 3 ..3533. 1531 . 331 ...115 . 3.1. 11.1. ...31 ...... 1 .... 0. 7 Peltigera spuria . 3 ...3 ...... 1 ...... 3 ...... + Ill !I + I! ...... 2. 1 ...... 1 ...... 7 774 8396486733 56883735 7 7 5887 9 989776331 7 7 477 7 3 1 .....7226 7 2. 7 Ceratodon purpureus ..1 V Ill Ill Ill ...... 1 ...1 ...... 1...... 12212 0. 1 Cerastium fontanum IV ...... 1 .. . 11.11. .1... 2 .. 0. 1 Racomi trium canescens ······· ····································· Ill I r ...1 .....1 ...... 11.11 ...... 1111 ...... 1 ..1 ...... 1 .... 12213. 13222 0. 3 Armeria maritima . 11 I V 1 1 1 ...... 1 ...... 3 ...... 11 ... 42221132234 0. 3 Galium normanii ...... •...... r r 11 V I 1.1 ...... •...... 1 ...... 213...... 5 ...... 1 ...31 1 ...... •...... 1, "2.. " 2. 21 1 . 22222 0. 4 Poa a1pina 1. I I I V 11 111.. 1 ...... 1 ...... 11 22.... 1 ...111 .. 3 ...... 1 ....1 ...... 1. 12 1. . 2222 .2221 1 0. 4 Minuartia rubella I! 11 I V !I .....1 ...... •...... 1 ...... 1 .... 1 ...... 1 ...... 1.11 1. 11" . 2222 0. 2 D raba incana IV I ...... 1...... 3 ...... 1 ..3 ..3 ..1 ...... 1 . 122.3. 22 . 0. 3 Festuca vivipara ·············· . 1 ...... Ill I ...... •...... 1 ...... 1 ...... 2 .. ".1212 2 0. 1 Trisetum pilosiglume ...... ················· ·············· 1 Ill Ch. All. 11.11...... 1...... 1 ...... 111 ... 113. ....1 ...... 1.3 ..1 ..1 ...513. 1. 1 ...1112 2. . . 221 . 23222 2. 1 Lychnis alpina 1 I Ill 11 IV 11 31 131 ... 11 ...1 ....1 ...... 1 .....333. 1311. 3331 . 1 . 3 .... 11. . 3113135 ..41 314. 4 ...33 .. 3 ..21 . ".221 . 22222. 22222 1.1 Luzula spicata 11 Ill Ill Ill V Ill . 1 ... 1 ..31 1.1 ... 1.1 ..1 .....21 22 .... . 4. 1131 1. 3.131. ... 41 .1111. 3 ..31 11111 ... 11.3. 31 222 .1.... 2.221 . 2332 . 0. 8 Cerastium alpinum ... 1. Ill Ill Ill I IV Ill 31 11 311 . 131 331 31 331 31 1 .....322 22. 11333 331 1 31 111 .. 1311533351 . 43. 1 51 . 5531 ....13 3. 135621 1 ..111.1 22221 1 23222 1.7 Thymus arcticus 1.. V IV V Ill V IV Ch. Ord . & Cl . 113331 3. 1.1 ....1113 .1.11.11222225221 .. 3. 1 .. 31... 14 33 .. 71 .3.1.1.. 4 .. 113.. 13.3.1 ..31 113 2.2211. 22222. 22212 1.2 Poa glauca ... 4 IV Ill Ill IV V IV .1 ...1. .. 1 .. 1...... 1 ...... 2331 41 .1... 1. 1..5.1..3. 13. 31 331 .. 13.35 ...... 13 31 . .. 1. ....2 221 . .. . 2 ...... 0. 7 Rumex acetosella . 11 Ill 11 Ill + I! ······•••··••••••••·•··••··•••·••••••·•·•••• •..•.•••..••.1 •••••...... •...•...... • 0. 01 Peltigera po lydactyla

Comp. 1 54533533331 3333331 313331 3222 32 355453141 3331 5555 35346435335535143366633335663653343364438 5 35531 3 7 322 32H62 5 3. 7 Festuca pruinosa V V V V V 2. 7 Agrostis vinealis 365655333333333. 1 ...... ,. 21 2222214...... 663535557755353335531 67735513 758443133 ...53 63 ...... 5. 222. 25633 Ill V IV V I V 5 .111.1.... 111 ...11 ...... 121. ....3 .. 111. 3 ...... 31 ...1 ...1.1 ... . 1 ...... 3 .....1.11 ...... 2221 . 122 .. Arenar ia norveg ica 11 11 1 1 IV 11 o. 1 1 ...... 11 ... 0. 4 Agrostis stolonifera ...... 1 ...... 43535335 ...... 1 .....3 .....3 .. 1 ..3.415 .... 5395222 5232222 .2...... + 1 . . 11 1 1 11 V I I 3 ..1 ...1 ...... 31 .....1.11111 ..1.11 21 ...... 13 ..11 .... 1 ..31 ..33 ....1.11 ...... 11 ..... 1 ...2 22122 .. . 2 ...... Silene maritima 11 11 11 IV + I 1 o...... 33 ...... 3 ...63 .....3.3 ... 1 ...... 31 ...... 2 ...... 36 0. 4 Bryum spp . 1 11 I 11 I ...... 3 ...... 12 .. 12 3525 ...... 4 ....4 ..3 ...... 63 ...... 4 As;rostis capi llaris . 1 I I o. " ... " .."" " ... "1. .... " ..""." .. "." . ". ".". " .. "". " ..""".""" ." ". ." 3322223 121111.2.21 11 0. 3 Equisetum arvense I ...... 3. 112...... •....3 ...... •...... 3 ..5 ... 3 ...... 3 ..13 ...... 0. 3 Festuca rubra (sown) + I ..1 ...... 3 ....1 ...3 ..3 ...... 1 ...... 1 ..4 ...1 ..1 ...... 1 .. 1. 0. 2 Polytrichum piliferum r I 11 ...11 ...... 1 ...... •...... 1.1 .... 11 ...... 1 ...... 11 ...... 1...... 1. 0. 1 Botrychium lunaria ..•..... 11 I 0. 2 Juncus tri fidus ... 1 ...... ••...... 1 ....1 ...... 1. 1 ...1 ...... 33 ..33 ... . Cornicularia aculeata .....•...... 1. 1 ....3 ...... 3 ...... 3 ...... 11 ...... 1 .. . 1 .... . 0. 1 ... 1 ••...... •••...... •....•...... 5 ..4, .. . 6 •...... 1 ""2 .."2 2 0. 2 Equisetum variegatum ...... •...... !I Empetrum nigrum .1... 1 ...... •...... 1 ...... 5 .. 1.11 ..1 ...... 1 .. 1 0. 1 .... 1 22. 2 ...... 4 ...... 1 ..... 31 .. 1 ...... 1 ... 0. 2 Sagina nodosa •...... • ...... • ...... 2 ...4 ...... 3 ...... 1 0. 2 Polytrichum juniperinum ...... • . . 6 .1... ..•...... •...... 5 ...... 11 ...... 11 0. 1 Luzula multiflora 1 Salix lanc;ta ... 1 •...... ••...... •...... 1 ... 111.. 1 ...... 0. 1

....••.•....•••...... •...... 1 .....4 ...... 2 .. ..1 ...1 .•....1 ... . 0. 1 Polytrichum alpinum r I 1 •...... •...... ••.•..•....•...... 3 1 1 ...... 5 ...... • 0. 2 Pohlia cruda .• .•...... Poa pratensis (sown ) ...... •....1 ...... 11...... 3 ...... 1 .. 0. 1 Cladonia coccifer;; ...... 1 ...... 1 ..3 ...... 1 ...... 1 ...... 0. 1

. ....1 1 ...... 8 ...... •...... 1 ...3 ...... 1 .. 0. 1 Cladonia spp ...... •...... 1 11.... 1 ..1 ...... ••...... 0. 1 Lathyrus japonicus ..•......

1111 11 11 1111111121 1111 111111 1111 1112112112111111111 1111 111121 21 1 11111 22121 Total number of taxa : 18448604009789559777497855732622042019 01 5096 51330056000476 2113201732162116248427197135728 781 1187 58776701909

No. of cryptogam ta"a : 11 1 2 1 1 4 1 134223331 133281 282522251122433312133 14131 1432 34 1 1 11 151131

Table 8a. Accessory species with their reference number.The transformation values are given within brackets if higher than 1. In subunit AI: 2 Betula nana; 2, 36 Calluna vulgaris; 23 Carex maritima; 36 Cladonia imbricaria; 4 Juncus arcticus; 7,21, 32 Leymus arenarius; 34 Poa pratensis and 36 Stereocaulon glareosum. In subunit A2 : 64 (4) Anthelia juratzkana; 64, 66, 67 Betula nana; 64, 67 B. pubescens; 61 Calluna vulgaris; 87 Cetraria delisei; 58, 61 (5) Cladonia imbricaria; 61 C. pocillum; 58 C. pyxidata; 58 C. stricta; 75 (3) Drepanocladus uncinatus; 67 Galium verum; 77 Leymus arenarius; 52, 63 Lophozia excisa; 61 (3) Peltigera sp.; 61 (3) Psoroma hypnorum; 67 Salix herbacea; 61, 64, 66, 67 S. phylicifolia; 61, 63 Stereocaulon glareosum and 82 S. rivulorum. In subunit B: 92 (2) Cerastium cerastoides; 92 (2) Deschampsia alpina; 92 (2) Drepanocladus revolvens; 92 (2) Philonotis tomentella; 93 Poa pratensis; 92 Polygonum viviparum and 90 Spergula arvensis. In subunit C: 107 Bartramia ithyphylla; 103 Cetraria islandica; 98 Euphrasia frigida; 98 Galium verum; 107 Poa pratensis; 105 Salix callicarpaea; 104 Saxifraga cespitosa and 98 Spergula arvensis.

substrate as the typical variant, but it has been fer Racomitrium canescens (1111). The subassociation tilized with mineral fertilizer (NPK, NPKS). is found in deflated lava-fields on silt-loamy and sandy soil on level ground to gentle slope at altitudes (2) Subass. cerastietosum fontani subass. nov. of 1 10-120 m in the Eldivioarhraun lava-field. The (Table Sa, b & c; ref. no. 90-96; Plate 2). The dif nutrient status of the subassociation is low with, on ferential taxa are Cerastium fo ntanum (IV1) and average, 0. 17 mg, P (variance 0.058), 0.34 meq K+

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 31

Table 8b . Site and vegetation characters of the Armerio - Table 8b (cont. J Silenetum acaulis. Bare ground (B). litter field layer (L), (F). Average bottom layer The cover percentage for litter, field layer and the (M). Ref. Date of Alt . Slope bottom layer is calculated by grouping together each five adjacent Plot % Cover height of no . obs . As�ect de9. sgm B ves. (cm) read ings of the line transect in the three layers. The percentage of bare L F M 51 14. 7. 1 981 25 0 10 15 30 10 78 1.2 ground is calculated for each five adjacent readings without hits. This f 981 . 52 13. 7. 1981 25 0 10 10 75 18 33 2. 2 refers to the analyses in ! Other cover values are estimated . f 53 17.7.1981 24 5 10 - 98 59 5 4. 5 Fertilized vegetation (f) . f w 54 f 27. 7. 1 981 24 0 10 23 16 41 54 1.9 Avarage 55 18.7.1981 24 0 10 GB 20 16 21 2. 3 Ref. Date of Alt. Slope Plot % Cover height of 56 f 28. 7. 19B1 21 0 10 23 45 19 39 4. 0 obs . As�ect deg. sgm B L F 1\/l ves. (cm) 57 f 1B. 7. 1981 24 0 10 79 9 14 3 1. 2 58 18.7. 1981 24 0 10 51 34 16 6 1 22. 7.1981 24 10 89 5 7 0. 1 f 2. 1 59 25. 7.1981 21 0 10 25 29 64 13 3. 4 2 f 17.7. 1981 24 10 60 28 24 2. 2 f 60 31 .7. 1981 23 0 10 59 21 18 14 3 25. 7.1981 21 10 76 16 14 1.6 f 1.3 61 31 . 7. 1 9B1 21 3 10 3 48 30 90 1.4 4 25. 7.1 981 23 10 51 29 29 1.5 f w 62 1. 8. 1981 24 0 10 8 50 28 5 25. 7. 1981 21 10 70 16 19 2.0 f 69 2. 6 63 28. 7. 19B1 23 0 10 80 9 13 4 0. 9 6 f 1.8.1981 24 10 78 23 9 1.1 64 23. 7, 1981 23 7 5. B. 1981 20 10 79 26 1B 2. 0 0 10 55 15 19 29 1.2 65 1. B. 19B1 24 B 17. 7. 1981 25 10 95 3 4 1.2 f 0 10 68 13 13 15 1.6 66 9 2B. 7. 1981 24 10 B6 5 10 0. 6 f 31 .7. 19B1 21 0 10 - 98 33 25 2. 5 67 27. 7.1981 23 10 25. 7. 1981 21 10 89 9 6 1.3 f 0 10 1 95 46 2, B 68 1. 8. 1981 so 11 23. 7. 1 9B1 21 10 96 3 3 0. 3 f 21 0 10 18 66 51 31 2. 7 69 31 .7.1981 12 17.7 . 19B1 25 10 96 1 f 21 0 10 34 55 25 8 4. 0 o. 70 24 13 28. 7. 1981 25 10 B9 1.0 f 27.7.1981 0 10 28 20 24 53 0. 6 71 3. 8. 1981 14 28. 7. 1981 23 10 96 1.0 f 25 0 10 1 61 30 60 2. 6 72 15 1. B. 1981 24 10 91 1.3 f 4. 8. 1981 25 0 10 63 4 10 29 2. 5 73 16 25.7.1981 21 10 93 1. 5 f 3. 8. 1981 25 0 10 18 29 8 75 1.0 74 3. 8. 1 98 1 17. 23. 7.1981 21 10 93 0. B f 25 0 10 - 25 59 96 2. 1 75 3. 8. 1981 18 22. 7.1981 24 10 96 2. 0 f 25 0 10 5 64 21 60 3. 7 76 8. 19B1 25 0 10 1 51 88 79 7 19 29.7.1981 21 10 96 0. 1 f s . 5. 77 f 8. 1 981 20 3 10 49 21 9 28 3. 0 20 28.7. 19B1 25 10 98 1.0 s . SW 78 4. 8. 19B1 20 3 10 1 80 32 3. 6 21 25. 7. 1981 20 10 99 0.1 f SW s s 22 25.7.1981 21 10 99 0. 8 79 f 4. 8. 1981 20 SW 3 10 29 59 26 19 2. B 80 23 26. 7. 1981 20 10 96 1.8 27. 7. 1981 24 0 10 83 8 14 3 1.0 81 22. 7.1 981 24 0 10 78 9 14 24 27.7.1981 20 10 96 0. 9 f 3 1.7 82 25 25.7.1981 21 10 99 1 0. 1 f 1. B. 1981 26 0 10 80 5 9 17 1.0 83 17. 7. 1 981 26 0 10 23 40 11 43 2. 8 26 5. 8. 1981 20 SW 10 95 4 1.7 f 84 13.7.1981 26 0 10 44 26 10 36 1.6 27 10.7.1974 20 SW 12 97 3 85 28 20. 7. 1980 25 12 99 5 f 13. 7. 1981 26 4 10 - 66 95 5 5. 6 86 3. 8. 1981 29 13.7. 1 974 25 0 12 99 1 f 25 0 10 40 2 40 31 2. 2 87 24. 7. 1980 25 0 12 70 9 2 27 30 f 14. 7, 1974 25 0 12 92 8 f 88 31 18.7.1978 25 0 12 98 1 f 23. 7.1980 25 0 12 41 9 30 29 B9 7. 1974 25 0 12 64 - 32 2 32 f 10.7.1974 20 SW 3 12 96 4 f Ill. 90 16.8.1974 110 0 12 75 - 25 33 f 24.7.19 8 20 SW 3 12 83 17 7 91 16.8. 1974 110 0 12 91 9 34 f 23. 7. 1978 20 SW 3 12 61 20 39 92 22. 8. 1975 210 0 12 89 - 11 35 f 24.7.1978 20 SW 3 12 95 5 f 93 22. 8. 1975 210 0 12 94 6 36 f 29. 7. 1 981 21 3 10 16 35 31 73 2. 3 f w 94 23. 8. 1975 210 0 12 98 2 37 18. 7. 1981 2 4 10 10 B3 6 14 1.9 f s 95 23. 8. 1 975 210 3 12 99 1 38 22. 7.1981 24 0 10 81 8 15 0. 7 f w 96 23. 8. 1975 210 3 12 9B 2 39 f 18. 7. 1981 25 0 10 39 48 20 2. 0 f w 97 19.7. 1974 380 20 12 55 55 40 22. 7.1981 24 0 10 88 6 1. 5 f N - 98 41 28.7.1981 24 0 10 76 20 0. 8 13. 8. 1974 130 SW 5 12 96 4 99 42 18.7.1981 24 0 10 91 4 1.8 17. 7. 1974 380 N 20 12 98 2 43 18.7. 1981 22 0 10 85 9 1.3 100 19.7.1974 380 N 20 12 97 3 44 25. 7. 1 9B1 20 0 10 99 1 0. 1 101 26. 7.1979 370 0 12 94 4 102 16.7. 1982 150 3 6 99 1 45 22. 7. 19B1 24 0 10 29 3 39 42 2. 0 w 103 16. 7. 1980 370 0 12 3B 46 f 14.7. 1981 25 0 10 10 64 45 45 2, 4 f 5 19 28 104 16.7.1974 380 20 12 79 - 20 1 47 12.7.1981 24 10 10 6 66 14 59 2. 4 f N f N 1 18.7. 1984 380 20 12 62 3B 48 f 31 .7.1981 23 3 10 51 39 21 5 2. os f N - w 5 106 28.7. 1979 370 4 12 15 6 24 49 f 27.7. 1981 24 0 10 10 34 6 74 1.3 f N ss 107 29.7.1979 370 3 12 27 50 f 18. 7, 1981 24 0 10 23 59 24 29 1.5 f E 10 21 42

(variance 0.043); the soil is neutral with a pH of 6.84 (variance 0.17), the figures being based on 5 analyses.

(3) Subass. galietosum normann subass. nov. {Table 8a, b & c; ref. no. 97-107; Plates 3-6). Dif- ferential taxa are Armeria maritima (V2), Galium Table Be. Soil factors of the 1 Armerio - Silenetum acaulis. normanii {V2), Poa alpina (V ), Minuartia rubella Available phosphorus {mg) and 1 exchangeable potassium {meq) (VI), Draba incana (IV'), Festuca vivipara (III ) in 100 g soil {dry weight) ; pH in water. and Trisetum pilosiglume (III1). The subassocia- Ref. Soil factors tion is found on silt-loamy soil in deflated lava- no. �H meg K+ mg p 27 fields, mainly in areas poor in precipitation. It is an 7. 6 • 24 . 07 29 7. 3 • 22 • 17 inland community found on level ground to gentle 30 6. 9 . 21 • 27 32 7. 1 • 22 . 17 slopes, but also on steep slopes at altitudes of (130) 89 6. 3 • 23 . 34 26 92 6. 9 • . 34 370-380 m in the area Hei3arspor3ur and the 93 7. 0 • 35 . 17 94 7. 0 . 22 • 17 Palssteinshraun lava-field. 95 6. 8 . 45 96 6. 5 • 44 • 17 The nutrient status of the subassociation is low 97 7. 0 .11 . 07 07 99 7. 5 . 14 • with 0.18 mg p (variance 0.087), 0. 17 meq K+ 100 7. 3 .14 .07

104 6. 5 • 25 .34 (variance 0.14); the soil is neutral with a pH of 7.0 105 6. 5 • 22 . 34 (variance 0.83), figures being based on 5 analyses.

Acta Phytogeogr. Suec. 75 32 Elfn Gunnlaugsd6ttir

Remarks Gravel flat vegetation has been described in Iceland by e.g., J6nsson (1895 pp. 80, 81); M0lholm Hansen (1930 pp. 43 ff. , 80 ff.); Steind6rsson (1945, p. 466; 1967 pp . 67 , 75); Hadac (1972 pp. 350 ff.) and Ventze (1982). However the distribution of the Armerio - Silene tum acaulis em. in Iceland is still insufficiently known. It is probably found here and there on gravel flats in the lowland and in the wind-eroded areas both in the lowland and the highland. Further investigations are needed. The distribution of the association as far as known is shown in Fig. 13. The subassociations de Fig. 13. The known distribution of the Armerio - Silene scribed here are (1) cerastietosum fontani, (2) achil tum acaulis in Iceland. See text for explanation of the numbers 1-7. leetosum and (3) galietosum normanii, and the com munities which might be members of the association being described in literature are: (4) the Melar retea Klika apud Klika et Novak 1941, through e.g., vegetation M0lholm Hansen ( 1930) Table 10: 1-7: Ceratodon purpureus Polytrichum piliferum the Melar vegetation M0lholm Hansen (1930) (5) Cladonia pyxidata s. str. Racomitrium canescens Table 19: 1-3; (6) the Silene acaulis - Festuca rubra Peltigera polydactyla Rumex acetosella soc. Steind6rsson (1967) Table XXXVII: 1-3, and (7) the Armerio - Silenetum acaulis Hadac ( 1972) The association is assigned provisionally to that Table 1. The numbers 1-7 refer to Fig. 13. class. It also has relatively strong affinities to the 1976 The Armerio - Silenetum acaulis Hadac 1972 is order Sedo - Poietalia glaucae de Molenaar assumed to be part of the association Armerio - through the presence of Silenetum acaulis Hadac 1972 em. due to the pres Cerastium alpinum Poa glauca ence of the two character species of the association �estuca vivipara Thymus arcticus (syn. T. druce1) described in this paper. The Armerio - Silenetum acaulis Hadac 1972 has received here a new status and to the alliance Sedo - Thymion drucei de as the subassociation racomitrietosum lanuginosi of Molenaar 1976 through the Armerio - Silenetum acaulis Hadac 1972 em. Cerastium alpinum Lychnis alpina (syn. The subassociation racomitrietosum lanuginosi is Ceratodon purpureus Viscaria alpina) differentiated toward the other subassociations of Thymus arcticus the Armerio - Silenetum acaulis Hadac 1972 em. by Racomitrium lanuginosum, Rumex acetosa s.l., and is therefore assigned to this syntaxon. Oxyria digyna and Sa fix herbacea. The class Koelerio - Corynephoretea Klika apud In the neighbouring countries open sward com Klika et Novak 1941 has the following faithful taxa munities have been described by several authors, (cf. de Molenaar 1976 p. 241), viz.: e.g., for Greenland by de Molenaar (1976 pp. 242 Ceratodon purpureus Racomitrium canescens ff.), for Norway by Nordhagen (1955 p. 21 1), for Cladonia fo liacea Rumex acetosella C. furcata (in casu R. tenuifolius) Finland by Kalela (1939 pp. 360 ff.) and for C. pyxidata var. ch/oro- Scleranthus perennis Scotland by Birse (1980 pp. 113, 114, 116-118). phaea S. polycarpos None of the communities described outside Iceland �estuca ovina s. str. Trifolium arvense correspond to the association Armerio - Silenetum Peltigera polydactyla Veronica verna acaulis em. Po/ytrichum piliferum V. dilleni Potentilla argentea The Armerio - Silenetum acaulis em. has a relatively great floristic affinity, especially regard The class includes open pioneer communities to ing cryptogams, to the class Koelerio - Corynepho- closed communities. Hemicryptophytes dominate

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 33 the communities and they are also fairly rich in be the single dominant of the bottom layer or it may therophytes. The substrate is somewhat unstable be intermingled with other mosses, e.g., sand or weathering rocks, which is influenced by ex Hy locomium sp lendens, R. canescens and treme temperature fluctuations and strong dessica Rhytidium rugosum or with a few lichens, e.g., tion. The soil is oligotrophic to eutrophic Cladonia uncia/is, Stereocaulon alpinum or others. (moderately eutrophic in Iceland); sometimes In the field layer the graminaceous species calcareous medium acid to neutral-basic (sensu de (Poaceae, Juncaceae, Cyperaceae) are commonly Molenaar). This class includes both lowland and found, e.g., Agrostis vinealis, Carex bigelowii, alpine communities of Europe and Greenland (de Festuca rubra s.l., Kobresia myosuroides, Poa Molenaar 1976). glauca or small herbs, e.g., Armeria maritima, The order Sedo - Poietalia glaucae de Molenaar Polygonum viviparum and few dwarf shrubs, e.g., 1976 has the faithful species: Calluna vulgaris, Empetrum nigrum s.l., Salix her Festuca ovina Sedum annuum bacea, Thymus arcticus and Vaccinium uliginosum. F. vivipara Thymus arcticus Arctic species are more common than European Poa glauca Veronica jr uticans ones, which indicates the hardness of the en vironmental conditions. and the differential species towards the other orders The R. lanuginosum heaths are found in rainy of the class Koelerio-Corynephoretea are (cf. de areas in exposed sites such as the gravelly flat vegeta Molenaar 1976): tion (see above). It is found in lava-fields with Bryum elegans Luzula sp icata almost no soil at all as a stage of primary succession Campanula gieseckiana Sedum rosea and as a degeneration stage in areas with shallow The alliance Sedo - Thymion drucei (B0cher 1954) soils. The nutrient status is extremely low (see de Molenaar 1976 has the following faithful and dif below). The soil is well drained but the R. ferential taxa, viz.: lanuginosum carpet itself is able to keep its own water reservoir (see J6nsd6ttir Svane 1964). Cerastium alpinum ssp. Saxifraga aizoon var. R. lanuginosum lanatum neogaea The heath types are best Ceratodon purpureus Sedum annuum developed in the SE, S, SW, W and NE parts of Ice Draba norvegica Thymus arcticus land and are found both in the lowland and the high Luzula sp icata Ve ronica jr uticans land. Lychnis alpina Woodsia ilvensis

The association Armerio - Silenetum acaulis em. (2) Racomitrio lanuginosi - Thalictretum alpini is provisionally assigned to the alliance Sedo - Thy mien drucei (B0cher 1954) de Molenaar 1976, be (Table9a, b&c; ref. no. 1-222; Fig. 14; Plates 7,8). cause of floristic affinities. The environmental The character species of the association are factors are in some degree similar too (cf. those of Racomitrium lanuginosum (V7), Th alictrum the class). The description of the alliance is partly alpinum (IV2), Cladonia uncia/is (Il2), Ptilidium ciliare 2 Cetraria islandica 2 Barbilophozia based on the Veronica jruticans - Sedum annuum (IV ), (V ), type described by B0cher (1954), and found in areas hatcheri (I), and Rhytidium rugosum (II\ of diabase (a basic bedrock) in W Greenland. In the physiognomy Racomitrium lanuginosum dominates whereas Kobresia myosuroides, Hy locomium sp lendens, Festuca pruinosa, Racomitrium canescens and Empetrum nigrum are 5.2 Racomitrium lanuginosum subdominating. The field layer covers 16 %, the heaths bottom layer 82 %, litter 7 OJo and bare ground 2 %. Racomitrium lanuginosum predominates physio The constants of the association are Kobresia gnomically in these vegetation types, and gives them myosuroides (V3), Hy locomium sp lendens (V3), their special greyish colour. The R. lanuginosum Festuca pruinosa (V3), Galium boreale (V2), heaths are therefore easily distinguished from other Polygonum viviparum (V2), Stereocaulon alpinum types of heathland vegetation. R.lanuginosum may (V2), Galium normanii (V2), Carex bigelowii (V2),

Acta Phytogeogr. Suec. 75 34 Elfn Gunnlaugsd6ttir

95'1 16) 1-48) . 2. 49-94). 3. Cerastlum alplnum form ( alpini . A. ga lietosum normanii 1-116). 1. typical form Peltige ra leucophlebia form ( · Table 9a. Racomitrio lanuginosi - Thalictretum ( ( B. Inops. A A ;ubunit: A A 3 1 2 1 2 Synop. 48 46 22 116 6 122 value �umber of releves: 48 ------�46�------"'22:..__..,.1'""11..,.11'"'"1�11'"'"1'""11..,.1'""11..,.110"71 111111 111111111122222222223333333333344444444 4555555555566666666667777777777888888888899999 9999900000000001111111 111222 �ef. no . : 123456789012345678901234567890123456789012345678 9012345678901234567890123456789012345678901 234 56789012345678901 23456 789012

:h. Ass. 798999789999999896695889989998877999989897999999 57. 521 56535523.267535335331 26665. 4232432332283 9999999999999999999999 989999 6. 7 Racomitrium \anuqinosum ... 32.22 ..21.2 ... 2 ...11. ..2. 1..1.. 12 .. 22 ..1. .11.2 2222222222222.222.222. 22321 . V V V V V V 1.5 2 212122 22223 2 2 2222 232123. 2222121 IV 11 V IV V IV Thalictrum alpinuni 3i212222 l22 2 ·2·.2: ....21 . 222211. ...1...... 12 2 223.1..1..1 ...... 1...... 1.2 .... 1 32222322 .... 232 ...... 2. 0. 7 Cladonia uncialis 33323. 323333221 323331 . 32. 32 ..326. 2 .....22 335332 ....13. 2 .. 12. 1 3323132221 121222 .. 232. 1 ..22 . Ill 11 Ill Ill I 11 1. 8 33323233i 23i2ii 1 i12. 32325223223. V V IV Ill IV Ptilidium ciliare 212222322222232. 222222333222222332221222222122. 2 223222. 32122222. 3 ..2 .. 2 .. 22222. 2. 3. 222. 12. 22. 2 332322222222223221 2 ..2 32223. IV 1.8 Cetraria islandica 2 2 2 2 V IV V V V V 0.3 Barbilophozia hatcheri ��::3i::�::ii:i::�::;::i::�: :�:i.. .. , : ii : ::: · · · -· ... 13 .. .. 1 .:�:i::;::;�:::�.:i::i · ···· 11 I I I I I 0. 5 Rhytidium rugosum . · · :::: :: �i3:: 3 : ; :::::\;::: I! 11 11 11 11 d subass. 23222222222222. 321 22. 222222222 ..222222. 222222222 222.222.2. 22222222221 .212122.22.22.2.222.22222 222222222222222222.222 2 ..1 .. 1.7 Galium normanii 22.1. 1.. 1222 2222222233222323. 23322.2222. 22.2. 212 2.22. 12222 1. 22 .. 2. 22222...... 1. .... 2. V V V V 11 V 1.4 221211222 12 22332 232212222.2.222. IV V Ill IV I IV Luzula multiflora 22222 22 2. 2 ..22 l222 ..2. 2 .. 22. 222222221 .2. 2 .. 222. 22. 23 ..22. 22. 232222233223222 232. 2221 222221 2 .. 22221. 22. 22. 2 ...2. 2 ...... 1.4 Galium verum 2 2.: 22222: ...... 22 ....2222 ..22 ..... 221 2 2.22222 ....2 .. 2.2 ..2 .....21 .1.11222 ..22 .2.22. 2 .. 22. 22 ..21 122.1 ...2 .. IV V IV l V 0.9 Equisetum variegatum 11.23:22 .... Ill Ill Ill Ill Ill d form ... ..2 ...22 4 ...1 ...... 2.. 2 . 0. 4 . . . 1...... 2 3 .. 22 ..13. 22. 3 .. 32 .. 2. 32 . r Peltigera leucophlebia ...... ••..•...... 2..... 23. 22 ... 3 ...3 .....2 ...2 ...1 22 ...... 223 ...... Ill I 11 0. 3 Agrostis capillaris 3 323. 22. 12 2 .. . 22 .. 12.. 1. 11 I 0. 6 :::::::i:i::i:i:::::::::i::: ..... • .1.12 ...... 1. ....2 ...... + Cerastium alpinum . I I I I I ... 1...... 2 ... 1...... 1 ... 2.. · ··· .2... 1 ...... 23 ....1..1 12.. 2 ..... 1 ..... 1...... 2222 .. 2.22122 ... 121. ..21 .. . 0. 4 Poa glauca I Ill 11 11 I! 0. All . 53333333233333. 3533333333333222333324333333. 2333 4435235.5553532533. 534333353323435333563335723 222323232322333333232. 221 332 3. 0 Kobresia myosuroides 3323323332222323232333322332321 23222233333322322 32533223233222. 23. 2333523322333223223232232212 2222332 222222222232322 2. 223. V V V V V 2.4 Stereocaulon alpinum .12.212.2.2. . ... 1. ...112 .12. 2221. 12222. 2 ..1211 .12222222.122.1 ...... 2 ...1.2 2 ...... 11.112 212 ...... 1 ...... 12 .. ...1.. V V V IV V 0. 7 Selaginella selaginoides . 1 Ill Ill Ill I Ill Ch. Order 2.13223232231. 333232353222.2222.222.2323. 2222321 3333532353.344355352.33333334333333323232352 .. . 1. 1 ...332. 2 ...222. 2 .. 12.. 2. 2.1 Festuca vivipara 3. 33323222222323321332122222222232 ..2223. 2222322 3253. 22 ..33323. 2.333333332321 122322.4233332113 .. 22. 3. .... 2.22 .2 Ill V 11l IV 1.7 Thymus arcticus I IV IV I V Ch. Class 324322625.223. 253. 32 ..4322 ..2. 37532 ..3141 431 .3.. 67658777667 2565356 778688876656658768763266 221 3 322. 22. 3. 32 ..22 .. 2. 5 .. .5.. 2. 3.3 Racomitrium canescens .33 ...... 11. 2 .. 33. 2313 .. 222 ..... 322 .. 3 .... 2 ...... 3 .. 2.113..... 2 .. 3. 23. 2 ....13 3 .....2. 1 .. 1.. 2 1 ..2. 3.2 .. 12.22 .. ..1. IV V Ill V 11 IV 0.8 Cladonia furcata 21.1 .. 1 ....1. 3 ..11.2 2.1. ..1. . 2...... 1.. 2 .. 1 .... 11. 1 ...3 .. 22. 22. 21... 1. 3122.2 ..2 .. 2 ..1 ... .. 1 .. .. 2 ...... 2 . Ill 11 11 I! I !I 0. 5 Peltigera polydactyla .1.1. .. 11 ...... 1.1.1..1. .. 11.1.2 .. . . ?- 1 ...... 1. 1...... 1. 2. 22. 2.1 ...2 ... 2. 21. .. 1 ...... 11 Ill 11 I 11 Cladonia pyxidata ...... 1 ...... 1 ...... 11 ...... 2 ....1 ..11 .. . 1 ..... 11 11 r 11 11 0.o. 1s C. chlorophaea I Camp. 7 465 45 56432 5526 7 58832 3 762 744442 456 55 4 7 364 74 536 51 752658667822 77965533571 63488756968672 797869966 2233232524325324333331 .2.. 22 2. 6 Hylocomium splendens 3333332323232 .333333.33232.2222222222323. 3222222 5343323333333333323.3324333332332333.333335234 2233333323222322222322 222. 22 V V V V Ill V 2. 6 Festuca pruinosa 22.. 222332 .3.233.33. 3332222223222223322333. 22 .. 2 533333233323343. 23333433333432233332. 332. 32253 . 2. 2222322 ..33 223. 323. .2122 . V V V V V V 2.2 Galium boreale 32223323. 333323.3222. 333323324143333323232233322 . 31. 32. 3 ..2 ...3. 2. 2. 2. 2 2212122222. 2122. 3 ..222. 3333322333332 333333232 2. 242. V V IV V IV V 2. 0 Carex bigelowii 222222222.22222. 2.22222233222222222222 .. 2.2. 22. 2 222222222�2222322222223232232232322122. 2222222 . 122 ...... 2222. 222 .. 222222 V IV V V I V V 1.7 Polygonum viviparum 2. 331 1222.33232 ...... 222232222222222221 1 .222222 212. 2 ...... 2. 211 ...2222. 2332 ... 12. 2 ..2.12 32 1231.22.32. 32 ..2 ..22 .. 222212 V V Ill V V V 1.3 Juncus trifidus 5. 556273333. 55333.. 386233553565 573.3.35365335532 53781 533 ..366335666. 316666526 76. 4'56.6. 365521 . 3 .. 2 ...... 1. 13. 3. 535363 V Ill Ill IV V IV 3.2 Empetrum nigrum 333..... 2222 ..3. 213. 3. 32. 32222222222. 3. 3. 232. 322 32232 ..3. 3. 33. 53333333. 33323333333332332331352 22.2222 ..2222. .•22... 22222 22 ...2 V V 11 IV V IV 1.9 Agrostis vinealis 332232322312232. 23323. 31 .222222. 222.2222322 ..221 2333. 32233433335354323.23232334334333. 232222.3 2.2112. 2 . 2.222 ...11 ... .1... 1 IV V IV IV Ill IV 1.9 Peltigera canina 22222222. 122231 32322322222 ..2. 22212222. 2. 2. 222. 2 22222122242. 232223322222222312212222. 1222. 2223 1.1212..... 222 ...221 ...... 2. V V Ill V 11 IV 1.6 Equisetum arvense 23222222222222. 32122. 222222222 ..222222. 222222222 2 32 ...... 32. 3122. 3. 323 ..2 ..31 233233. 2. 322. 22 .. 332. 1.2. 11. 2. 2 ..2. 2 ...... 2 .. V V Ill V l IV 1.4 Cladonia gracilis 3. 2 ...1. 2. 1 . 21221 . 3. 2.3 . . 22 ..2. 22 332 .. 532 .... 12. 3 ..2. 12322323. 33. 3. 12232332. 22 ..3. 1. 6332222 ...... 12.2 .. 32.2.. 1 ... .. 1. .. V IV Ill IV I IV 1.2 Rhytidiadelphus triquetrus 11111 ....3.1 ....1 ..12 .. 1 ..1 12. . 1..22 .. 1.... 1. 1 .. 2. ....3322 5. 525533423221. 13326. 62222 .. 2225. .2 . ...1. .. 1 ...... 2 .. 1 ..... lll IV !I Ill I Ill 1.1 [)repanocladus uncinatus 2212.2... 23. 2.2 ..... 32 ..22222 ..23. 2.33 ....22. 2 ...... ss22 ...... 31 ..5232 .....32 .. 323. 3. 1. 2 ..2. 221 .. .11112...... 334252 Ill IV !I Ill I Ill 1.0 Salix herbacea 12121122 ....1 ..11. 1, ...1 .....1 ..122 ..... 1111. 1.. 21... 32. 13326326232 .... 3132 .. 122... 1.13 2.3333. .2 ...... 21 .2...... Ill Ill !I Ill V Ill 0.9 Rhytidiadelphus squarrosus . . . . 122.. 211 ...1 .....1.1 .... 1. 22 ...2 ...... 1. 1. 21222 ..121 . 1.. 12112.2.. 21. ... 1 ..121. 2222 .. 12.. 1 ..11 1 ...... 11 ..1. Ill IV I! Ill !I! 0. 8 Trisetum pilosiglume 11 Ill I !I Ill !I ....1 ••....•...•...3. 3 ...... 226. 3 ..2. 3. 1. 5 ...... 26. 3 ..333. ..333 ...33 ...... 36. 3 ..1...... 1.2.. 0. 7 Call una vulgaris 2 ....4. 2.2112 .. 13 . 32 ...... 2. 12 2 ...... 2 2. 622223...... ·...... 1 ...... 2 ... 123. 1 ...... !I 11 11 I! I! 0. 5 Cladonia arbuscula 222122.21.2222.12.. 2 .... 2.2. 11...... 12 .. 111 .... 1 ...... 1 ..1 .....2 ..2 ..2 .....22 ...... 2 ...... 1 12. 2. 2 ... .2...... 212. 2. I! l i ll I 11 0.6 Thamnolia vermicularis . 2 ...1 ....2222 . 211 ....2 ...2.2 .... 1.1.2 ... 2 ... 1.. 2 .. 2 .. 2 ...22 .... 2 ...... 1 ...... 1 ..2 ..2 ..1. 22 ...... 12 .. Ill 11 11 !I Ill 11 0. 4 Cornicularia aculeata 11 I 11 11 11 11 ....2 ....1211 ...... 1. 2 .....21 .. 1 ...... 2 ..221 ..2 ...2 ....1 .....212 ... 11 .. ...2 .....1. 2...... 1 ..2 ...... 2.1.1 + 0. 4 Polytrichum juniperinum . 2.12 ...... 2 ..22 ..... 2 ....12 ... 2. 1. ....2 ..2 1 .... 21.2...... 31 ...22.2 ...... 2 .. 1 .....2 ...... 1. 21 ..2 ...... 2 ..... 11 11 11 Ill ll 0. 3 P. alpinum ...... 111 ... 1 ...... 2 ....2 ...... 2 ...•. 2 ...... 2 ...... 1 ...3 .. 22.. 1. 11 !I I 11 11 0.2 Silene acaulis . 3 ..1 3 ...... 31 .22 1 ...... ······ 2 .....····· 32 · ···· ...12 2 ...31 ...... 1 ..... 1 ..2 ...... 2 .. I r + Ill l 0. 3 Cladonia macroceras ...2 ..•.1.2 .2...... •...... 12...... •...11...... 2 ...... 222. 33 ....•...... 1...... 3 . ....2 ..2 ...... 2 .. ... I I l l 0. 3 Car ex capitata · · l I I 1.2...... 2 .•...... 2 .... 21 ...... 2 .....2 ..•...····. 122.· ··221···. ....· ··1. ·· ...... 1 .. ... 1 ...... 1.1 ... 1 .... .2.... 0. 3 Luzula spicata ...•...... 1 .....2 ...... 23 ..1 ...1 ...... 2. 1 ..2 ...... 1 ..1 ...2 ..3 ...... 2 3 ..2 ...... 2 ...... 22 ...... 2 .. I I! I 0. 3 Equisetum pratense . 2.22 ..... 1 ...... 2 ..2 ...... 1...... 1 ...... 2 .•.•.....2 ...... 11 .. ... 1 ...... l I I 0. 2 Dicranum congestum I I r l ...... 1 ...... 2 2 ...... 1.1...... 1 ...2 .... 1...... 12..... 11...... 2 ...... 1 ...... 2 ...... + 0. 2 Botrychium lunaria 2 ...... •.....2 ...... 2 ..1. ....21 .21 ...... 2 ...... 2 ...... 1. .... 1 ..1 ..2 .. 1 ...... 2 . I I I 0. 2 Poa pratensis •....•...•.•.....111...... •...... 2 ..1. ..•..•.•...... 1.12... 2 ...... 1 .2.22.2.. 11 ...... 1.1 I 11 I 0.2 Potentilla crantzii · · · · ·· · · ·· · ·· · ·· ·· I 11 l · · · ··· · · · · · · · Total no. of taxa : 33333333324332 2232232233232332333322232212222323 3333332332342223323322323232333222224223223323 2233322212222212112211 231221 &8298033250� 079586606603827076423289531699485961 61244693063076602844736939162628529639861 48683 7604262896385691583552 638463 __:____:__.:..__.::___.:::c_.:____ _ No. of cryptogam taxa : 121211111 1111 121111 11 11111111111 1 1111 111 11111111111111 11 12 11 11111111 12111 11 1 111111 1 11111 1 11 645192453976449001272925932082223410718803207290 9314143352672183393090683130364397804127886294 414341 8381931386459644 097114 _4:._ _..:.._--=.___::..__..:._--=._ . ___

Table 9a. Accessory species with their reference number. The transformation values are given within brackets if higher than 1. Insub unit AI: 11 (2), 24 Anthelia juratzkana; 13, 25 (2), 28 (2), 32, 38Armeria maritima; 1, 2 Barbilophozia barbata; 48 Bartramia . ithyphylla; 24 Bryum sp.; 18 (2) Carex nigra; 4, 28, 32, 33 Cladonia coccifera; 5 (2), 45 C. mitis; 22 (2) C. pocillum; 15,31 C. verticillata; 27 Cladonia spp.; 8, 9, 19 (2), 41 Climacium dendroides; 24, 25 (2), 46 Ditrichum flexicaule; 26 Encalypta procera; 4 Erigeron boreale; 21, 23 (2) Euphrasia frigida; 25 Gentianella amarella; 17 Hierochloe odorata; 31, 32 Lophozia alpestris; 22 Nardia geoscyphus; 31 N. scalaris; 5 Peltigera apthosa; 7, 8 (2) 9, 12, 47 P. neckeri; 2, 6 P. rufescens; 2 Plagiochila porelloides; 48 Poa alpina; 12, 29 Polytrichum piliferum; 26 (2) Polytrichum sp.; 4 Timmia austriaca; 31 (2), 33 Tofieldia pusilla and 28 (2) 41 Vaccinium uliginosum. Subunit A2: 60 (2) Alchemilla alpina; 55 (3), 60 (2), 62 (3), 75 (2) Anthoxanthum odoratum; 85 (2), 94 Armeria maritima; 49, 60, 67, 85, Barbilophozia barbata; 55 B. kunzeana; 71 (2) Bartramia ithyphylla; 68, 85 (2) Brachythecium albicans; 85 B. reflexum; 51 Bryum pallescens; 63 Cardamine nymanii; 51, 56 Carex capillaris; 83 (2) C. nigra; 54 (3), 67C. panicea; 85 (2) Ceratodon purpureus; 79, 85 Cladonia coccifera; 85 C. mitis; 67 C. pocillum; 62 C. verticillata; 59 (2) 68 Cladonia spp.; 50, 52, 53, 54 (3), 56 (2), 80, 84 Climacium dendroides; 86 (2) Deschampsia flexuosa; 60 Distichium capillaceum; 52, 57 Ditrichum flexicaule; 60 (3) Dryas octopetala; 71, 85 (2) Euphrasia frigida; 51 (2), 52 (3), 53 (2), 54 (2), 65 (2), 83 (2), 93 (2) Hierochloe odorata; 67, 85 Lophozia alpestris; 60, 68 L. ventricosa; 79, 87, 88 Peltigera apthosa; 58 (2), 68, 85, 87 (2) P. neckeri; 68 Plagiochila porelloides; 66 (2) Plantago maritima; 60 (2) Platanthera hyperborea; 60 Pohlia filum; 85 (2), 93 Polytrichum piliferum; 60 Rhinanthus minor; 59, 69, 71, 72 , 83 , 85 (4), 90 (3) Salix lanata; 60, 68, 71 Scapania curta; 94 (3) Stereocaulon vesuvianum; 52 (2) Tofieldia pusilla; 84, 88, 90 (2) Vaccinium uliginosum and 54 (2), 56 (2), 92 Viola palustris.

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 35

Table 9b . Site and vegetation caracters of the Racomitrio Table 9b (cont.) lanuginosi - Thalictretum alpini . Bare ground (B), litter ( LJ , field layer (F) and bottom layer (M) . Estimated Ref. Date of Alt. Slope Plot % Cover cover va lues. no . obs . m As�ect deg. sgm B L F M Ref. Date of Alt . Slope Plot Cover 61 4. 8. 1982 150 0 6 14 84 66 no . obs . Asf:!ect deg. sgm B L F M 62 5. 8. 1 982 160 SE 25 6 31 28 68 63 5.8.1982 155 NW 45 6 7 11 89 15. 7. 1982 140 10 25 82 64 5.8. 1982 155 w 35 6 29 31 53 65 5. 8.1982 140 0 - 15. 7. 1 982 140 s 15 3 5 100 6 13 34 53 15. 7. 1 982 150 NW 15 27 20 87 66 5. 8. 1982 140 SE 25 6 23 41 46 17. 7. 1982 140 7 12 100 67 5. 8.1982 140 0 6 - 21 37 56 17.7.1982 130 0 5 27 87 68 5.8.1982 140 SSE 15 6 3 27 14 56 17. 7. 1 982 140 SW 30 14 7 67 69 5. 8. 1 982 145 SE 25 6 13 17 14 79 7 19. 7. 1 982 150 s 50 29 87 70 6. 8 .1982 145 NW 10 6 5 15 17 63 8 19. 7. 1982 160 0 13 7 97 71 6. 8. 1982 140 SE 10 6 5 - 23 80 9 1 9. 7. 1982 160 0 5 5 92 72 6. 8. 1982 140 SE 10 6 12 39 76 10 1 9. 7. 1 982 160 NE 40 3 5 97 73 6. 8. 1982 140 0 6 11 35 63 11 19.7.1982 160 0 5 9 96 74 6. 8. 1982 135 0 6 27 26 54 12 20. 7. 1982 150 0 9 9 100 75 9. 8. 1 982 130 0 6 20 17 80 13 20.7. 1982 160 NW 20 13 85 76 9.8. 1982 145 w 40 6 7 18 93 14 27.7. 1982 150 10 8 97 77 9. 8. 1 982 135 0 6 32 74 78 11. 8. 1982 135 15 27.7. 1982 150 w 55 8 99 0 6 41 62 - 16 27. 7. 1982 160 SW 40 18 83 79 11. 8. 1982 135 0 6 11 28 61 17 27. 7. 1 982 160 NW 10 9 18 92 80 1 1. B. 1982 135 0 6 17 15 98 18 29.7.1982 150 SE 20 6 13 89 81 18.8.1982 130 0 3 16 97 19 29. 7. 1982 150 N 10 15 11 93 82 18. 8.1982 130 0 25 93 83 1 8. 1982 130 20 29. 7. 1 982 150 s 50 48 3 9 40 B. 0 25 75 21 5. 8.1982 140 SE 55 38 53 9 84 1 B. 8. 1982 130 0 7 9 96 22 6. 8. 1982 140 0 37 27 56 85 18.8. 1982 130 SE 5 11 4 25 49 23 11. 8. 1 982 130 0 6 12 94 86 19. 8. 1982 135 SE 10 8 12 14 66 87 24. 8. 1 982 145 24 1 B. 8. 1 982 140 0 4 7 100 0 6 10 20 90 25 1 B. 8. 1 982 140 0 14 99 88 24. 8. 1 982 150 SE 15 6 10 44 46 26 19.8. 1982 140 0 15 93 89 24. 8. 1 982 160 SE 10 6 18 93 90 28. 1 982 150 27 1 9. B. 1982 140 0 6 14 93 B. SE 10 6 38 29 55 28 19.8.1982 140 0 6 8 96 91 12. 8. 1 974 125 0 12 29 97 92 19. 7. 1 975 125 29 1 9. B. 1 982 140 0 6 8 99 0 12 16 90 30 19. 8. 1982 150 SE 25 6 26 77 93 29. 7. 1 982 150 0 6 - 21 17 95 31 19. 8. 1 982 150 E 5 6 22 74 94 17. 7. 1982 130 NW 30 6 - 27 15 70 32 19. 8. 1982 150 NW 50 6 11 85 95 15. 7. 1982 150 0 6 1 2 100 96 15.7. 1982 150 NW 5 33 20. B. 1982 150 SE 10 6 44 64 6 1 100 34 20. 8. 1982 150 0 6 4 5 99 97 16. 7. 1982 155 0 6 3 100 35 20. 8. 1982 150 0 6 2 4 100 98 16. 7. 1982 150 NW 5 6 3 100 36 20. 8. 1982 150 0 3 6 98 99 17.7.1982 140 0 6 2 100 37 20. 8. 1982 150 0 4 7 99 100 17.7.1982 130 0 6 3 99 38 24. 8. 1 982 150 0 6 14 88 101 19.7.1982 170 0 6 1 99 39 24. 8. 1 982 150 0 2 13 92 102 19.7.1982 175 0 6 8 95 40 24. 8. 1982 160 0 10 10 91 103 1 9. 7. 1 982 175 0 6 2 98 41 24. 8. 1982 160 0 3 22 83 104 1 9. 7. 1 982 175 0 6 4 99 42 24. 8. 1982 150 0 3 3 100 105 19. 7. 1982 180 0 6 2 99 43 26. 8. 1 982 150 0 3 3 100 106 19. 7. 1982 175 0 6 4 99 44 26. B. 1982 150 0 3 5 100 107 19.7.1982 165 WNW 5 6 3 99 45 26. 8. 1 982 150 0 2 10 91 108 2 7. 7. 1982 165 0 6 4 99 46 26. B. 1 982 160 SW 30 6 3 11 94 109 11. 8. 1 982 140 0 6 5 100 47 26. 8. 1 982 160 0 6 3 3 98 110 20. 8. 1 982 145 0 6 3 99 111 24. 8. 1 982 155 48 18.7. 1975 140 s 5 12 3 95 0 6 6 97 49 15.7.1982 130 0 6 27 84 112 24. 8. 1 982 160 0 6 5 100 50 17. 7. 1982 130 SW 40 6 17 82 113 26. 8. 1 982 155 0 6 6 100 114 26. 8. 1982 155 6 51 20. 7. 1 982 150 s 55 45 51 w 5 1 95 115 26. 8. 1982 155 52 20.7. 1982 125 s 30 65 53 0 6 6 98 53 20.7.1982 130 0 26 13 80 116 23. 8. 1 982 160 0 6 1 99 54 20. 7. 1982 140 N 20 - 23 11 95 117 1 9. 7. 1 982 160 E 10 6 18 11 83 55 20.7.1982 150 SW 35 22 21 57 118 20. 7. 1 982 160 w 10 6 21 7 70 56 27.7.1982 140 SE 20 15 85 119 27. 7. 1982 1 65 NE 5 6 3 8 95 57 27. 7. 1982 140 0 - 31 25 69 120 20. B. 1982 145 NE 5 6 5 95 58 29. 7. 1 982 150 0 17 26 69 121 24. B. 1 982 150 0 6 23 89 59 4. 8 .1982 150 SE 15 21 12 58 122 23. B. 1982 160 0 6 3 96 60 4. 8. 1982 150 s 10 46 47

Table 9c . Soil factors of the Racomitrio lanuginosi - Ref. Soil factors Thalictretum alpini. Available no. + pH meq K phosphorus (mg) and exchange- mg p

able potassium (meq) in 100 g 54 6. 1 . 50 • 50

so il (dry weight); pH in water. 55 6. 0 • 47 . 47 In subunit A3: 95 Barbilophozia barbata; 95 , 99 B. floerkei; 99 59 6. 1 • 60 • 10 Ref. Soi l factors 63 6. 2 • 60 • 10 (2), 105 (2), 106 Calamagrostis stricta; 109 (2) Carex nigra; 113, no. + 67 6. 1 . 58 . 10 �H meq K mg p 114 (2) Cetraria delisei; 97 Cladonia coccifera; 106 Cladonia 72 6.0 • 50 . 40 1 5. 9 • 47 . 50 75 6. 0 . 50 . 40 spp.; 102 Climacium dendroides; 106 Ditrichum flexicaule; 107 4 6. 2 . 45 . 40 78 5. 3 • 53 . 60 7 5. 9 . 50 . 50 Lophozia ventricosa; 97 Nephroma expallidum; 99 Peltigera ap- 82 6. 0 • 74 .10 10 6. 1 . 37 • 20 thosa; 95 P. neckeri and 106 P. rufescens. 87 6. 0 . 53 . 40 14 6. 0 . 37 • 70 BB 5. 8 . 66 . 40 16 6. 0 . 55 • 40 In subunit B: 117 (2), 118 (2) Anthelia juratzkana; 118 Armeria 89 6. 1 • 53 . 20 19 6. 2 • 58 . 40 maritima; 117 Bryoxiphium norvegicum; 118 (2) Dryas oc- 91 6. 1 . 43 . 07 20 6. 1 . 63 • 10 92 5. 9 . 39 . 40 24 6. 0 . 45 1.00 topetala; 117, 120, 122 Encalypta procera; 117 Erigeron boreale; 96 6. 0 • 32 . 50 118 Lophozia ventricosa; 120 Nardia geoscyphus; 120 N. 26 6. 1 • 45 . 10 104 5. 9 . 42 . 50 30 6. 2 .68 . 10 113 6. 3 . 39 . 50 scalaris; 118 (2) Pinguigula vulgaris; 119 (2) 121 Polytrichum 35 6. 3 . 55 . 20 114 6. 4 . 42 • 40 piliferum: 118 Saxifraga oppositifolia; 118 Sedum villosum; 117 40 6. 0 • 55 . 70 118 6. 1 . 37 . 20 51 6. 0 . 58 . 50 120 6. 3 • 37 • 10 (3) Stereocaulon vesuvianum and 118 Timmia austriaca. 52 6. 2 . 37 • 40

Acta Phytogeogr. Suec. 75 36 Elfn Gunnlaugsd6ttir

Racomitrium canescens (IV3}, Empetrum nigrum Steinkrossbrun, Dagver3arnesm6ar heathlands on (IV3}, Festuca vivipara (IV2}, Agrostis vinealis wind-eroded revegetated hill-tops and in the young (IV2), Peltigera canina (IV2}, Thymus arcticus lava-field Su3urhraun on level ground to moderate (IV2}, Equisetum arvense (IV2}, Luzu/a multiflora slopes at altitudes of 145-160 m. (IV1), Galium verum (IV1), Juncus trifidus (IV1) The galietosum normanii subassociation is a and Cladonia gracilis (IV1}. degeneration community of the "original" vegeta Most species belong to the bryophyte and the tion and the inops is a stage of secondary succession, hemicryptophyte life-form groups (Fig. 17) due to both probably derived from Betula pubescens humid and relatively mild climate. The Arctic woodland. species are more common than the European ones (Table 16) due to strong exposure. Remarks The soil is silt-loamy, intermingled with pumic sand and gravel. It is usually shallow, ea. 5 cm in R. lanuginosum heaths have been treated in Iceland depth, but may be deeper. It is fresh to well-drained by, e.g., Ostenfeld (1905 p. 116); J6nsson (1895 pp. as it lies on very porous lava bedrock. 70-73; 1906 pp. 40-43) and by Steind6rsson (1930 The nutrient status is low with, on average, 0.37 p. 10) and described by M0lholm Hansen (1930 pp. mg P (variance 1.4), and 0.50 meq K+ (variance 40 ff.); Steind6rsson {1936 pp. 464 ff.; 1945 pp. 453 1 .03); the soil is neutral with pH 6.0 (variance 1.17), ff. ; 1957 pp. 139 ff. & 1966 pp. 86 ff.); by J6nsd6ttir the figures being based on 35 analyses. Svane (1964 pp. 233 ff.) and by Hadac (1972 pp . 352 ff.). The distribution of the Racomitrio lanuginosi - Two subassociations are discerned: Thalictretum alpini association in Iceland is not (1) Subass. galietosum normanii sub ass nov. (Table known, but probably it is to be found in the lowland 9a, b & c; ref. no. 1-116). The differential taxa are of S, SW and W Iceland and along the coast of NE Galium normanii (V2), Luzu/a multifl ora (IV2), Iceland. The known distribution of this association Galium verum (IV2}, Equisetum variegatum (III1} is shown in Fig. 14: (1) Racomitrio - Thalictretum and Rhytidiade/phus squarrosus (III1). alpini (this paper), and the plant communities de The subassociation galietosum normanii is found scribed earlier and which might be assigned to it, in the heathlands in the vicinity of Gunnarsholt viz.: (2) the Mosathemba Steind6rsson (1936) Table farm, viz. near Kot farm, in Steinkrossbrun, in VIII; (3) the Salix herbacea - Empetrum her Steinkrossm6ar and in Dagver3arnesm6ar. It is mafroditum - Polygonum viviparum soc. Stein found on level ground and on moderate to d6rsson (1966) Table XXIX, 2-4; ( 4) various socia precipitous slopes at altitudes of (125) 130-175 m. tions described by J6nsd6ttir Svane (1964) Tables Three subunits can be distinguished in the IV & V and (5) the Racomitrio - Caricetum bigelowii galietosum normanii subassociation: from SW Iceland described by Hadac 1972 Tables a. Typical form (Table 9a, b & c; ref. no. 1-48). 2 & 3. b. Peltigera leucophlebia form (Table 9a, b & c; ref. In the neighbouring countries various no. 49-94) is differentiated by Peltigera leuco Racomitrium lanuginosum-rich communities have phlebia (III1) and Agrostis capillaris (Il1}, and with been treated and described by many authors, e.g.: relatively high cover of Racomitrium canescens and Treated for Greenland by Hartz (1895 pp. 182, 183 Hy locomium sp lendens. & 204 ff.), Kolderup Rosevinge (1896 pp. 193 & 212 c. Cerastium alpinum form (Table 9a, b & c; ref. ff.), Porsild (1902 pp. 175 ff.), Holttum (1922 pp. no. 95-116) is differentiated from the other form 96, 97) and by Trapnell (1933 pp. 329-333}, and de by Cerastium alpinum (III1} and Poa glauca (lll1}. scribed by e.g., Knapp (1964 pp. 188 ff.) and DanH!ls (1982 pp. 48 ff.). For the Bear Island they were treated by e.g., (2) The inops (species poor subassociation) (Table Summerhayes & Elton (1923 p. 224), for Spits 9a, b & c; ref. no. 117-122) is found in the bergen they were described by Hadac (1946) and for

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 37

Icelandic one having, e.g., Galium boreale, G. verum, Stereocaulon alpinum, Cladonia uncia/is. The Scottish differentiating species mentioned above are acidophytic but the Icelandic ones are basiphytic (sensu Ellenberg 1979). None of the R. lanuginosum-rich communities described outside Iceland are similar to the Icelandic ones and are also assigned to other high syntaxa as they deviate widely floristically from the Icelandic ones. Some species dominating in the field layer of R. lanuginosum communities outside Iceland do not grow in the S Icelandic ones described here (e.g., Nardus stricta) or do not grow in Iceland at all, viz.: Carex binervis Fig. 14. The known distribution of the Racomitrio and Erica cinerea. Na rdus stricta might be excluded lanuginosi - Thalictretum alpini in Iceland. See text for ex planation of numbers. by high pH or lack of sheltering snow cover in the winter. The Racomitrio lanuginosi - Thalictretum alpini has relatively clear floristic affinity to the class Jan Mayen by, e.g., Steind6rsson (1958 p. 85) and Koelerio-Corynephoretea Klika apud Klika et by Lid (1964 p. 83, Table 25). Novak 1941, especially through the presence of R. lanuginosum heaths have been treated in the cryptogam taxa:

Faroes by, e.g., Ostenfeld (1901 pp. 32, 43, 48-50, Cladonia chlorophaea Peltigera po/ydactyla 53, 54; 1906 pp. 997 ff.) and described by B0cher C. jurcata Polytrichum pilijerum (1937 pp. 169 ff. , 185 ff.). C. pyxidata s. str. Racomitrium canescens Racomitrium lanuginosum-rich vegetation has and it also has affinities to the order Sedo - Poietalia been treated in Norway by, e.g., Resvoll-Holmsen glaucae de Molenaar 1976 by the presence of (1920 p. 152) and by B0cher (1937 p. 166) and de scribed by Nordhagen (1943 pp. 205-207), Dahl Cerastium alpinum Poa g/auca (1956 pp. 101 ff.), Skogen (1965 pp. 25 ff.; 1970 pp. Festuca vivipara Thymus arcticus 6, 7). But it has few of the characterizing taxa of the In the British Isles and Ireland R. lanuginosum alliance Sedo - Thymion drucei de Molenaar 1976 rich vegetation was treated by Armstrong et al. and therefore a new alliance is here established: (1930 pp. 442, 443), Evans (1932 p. 33), Watt & Racomitrio - Thalictrion alpini all. nov. Jones (1948 p. 300), Burges (1951 pp. 278 ff.) and The alliance comprises chinophobe communities by Tallis (1958 pp. 27 1 ff.). R. lanuginosum com on windswept places in humic to perhumic , oceanic munities have been described by Braun-Blanquet & boreal climate. Bryophytes dominate the Tiixen (1932 pp. 352 ff.), lngram (1958), McVean physiognomy of the communities and cryptogams & Ratcliffe (1962 pp. 46 ff., 77 ff.}, McVean (1964 play the major role. Of the vascular plants, pp. 524-535) and by Birse (1980 pp. 139 ff. , 143 hemicryptophytes are the most numerous. The soil ff. , 159 ff., 175 ff. , 182-1 87). The Scottish Carex is a neutral, oligotrophic, shallow, sandy and silt bigelowii - Festuca vivipara ass. assigned to the loamy on basaltic lava bedrock; it is well drained. alliance Nardion Br.-Bl. 1926 (Birse 1980 pp. 139 ff. The character species for the alliance are: & Table) and the Racomitrio lanuginosi - Thalic Cetraria islandica Racomitrium lanuginosum tretum alpini (ass. nov.) have floristic affinities Ptilidium ciliare Thalictrum alpinum (IS1 = 20 o/o) and these associations have a number of differentiating species (of high constancy) and differential species to the other alliance of the towards each other; the Scottish one having, e.g., order Sedo-Poietalia de Molenaar 1976 are Galium saxatile, Nardus stricta, Carex pilulife ra, Kobresia myosuroides Stereocaulon alpinum Hypnum cupressiforme spp. ericetorum, and the Selaginella selaginoides

Acta Phytogeogr. Suec. 75 38 Elfn Gunnlaugsd6ttir

(3) Empetrum nigrum - Racomitrium lanuginosum alliance Racomitrio - Thalictrion alpini through the community presence of, e.g., Cetraria islandica, Kobresia myosuroides, Ptilidium ciliare, Racomitrium (Table lOa & b; ref. no. 1-4). The Empetrum nig lanuginosum, Selaginella selaginoides and Th alic rum - Racomitrium lanuginosum community has no trum alpinum. The sociations which are described character species of its own, but several species dif in Tables IV and V might be seen as a subassociation ferentiate from the Racomitrio lanuginosi - Thalic of the Racomitrio - Thalictretum alpini, namely the tretum alpini association, e.g., Hieracium sp., Be vaccinietosum uliginosi differentiated towards the tula pubescens, Tritomaria quinquedentata, Arcto other subassociations through the presence (and staphylos uva-ursi. high frequency) of Anthoxanthum odoratum, The physiognomy is dominated by Racomitrium Cladonia ecmocyna, Deschampsia jlexuosa and lanuginosum. Subdominants are Empetrum Vaccinium uliginosum. nigrum, Vaccinium uliginosum and Arctostaphylos Hadac (1972) described R. lanuginosum-rich uva-ursi. The field layer covers ea. 28 the bot OJo , vegetation types from SW Iceland and interpreted tom layer 66 OJo,litter 1 and bare ground 5 OJo. OJo them as the association Racomitrio - Caricetum The constant companions of the community are bigelowii (Du Rietz 1925) Dahl 1956 with two Racomitrium lanuginosum (48), Empetrum nigrum subassociations of it. A great floristic difference (46), Vaccinium uliginosum (44), Hy locomium is found between the Racomitrio - Caricetum sp lendens (43), Ptilidium ciliare (43), Peltigera bigelowii described by Dahl (1956) and these SW canina (42) and Salix herbacea (42). Icelandic R. lanuginosum vegetation types (as well Most species belong to the hemicryptophyte and as the Racomitrio - Thalitretum alpini described in the bryophyte life-form groups (Fig. 17) due to this paper) and they deviate too much floristically humid and relatively mild climate. Species of the E to be assigned to the same association. I think that 4 group are the most common ones of the species Hadac's R. lanuginosum vegetation types (Tables 2 groups (Table 16). The community found in the & 3) are better interpreted as one subassociation of Suourhraun and Brejarhraunlava-fields on gentle, the Racomitrio - Thalictretum alpini, namely the moderate or precipitous slopes at altitudes of armerietosum maritimae differentiated towards its 155-160 m is probably a community of primary other subassociations by the presence and high con succession. stancy of A rmeria maritima, Rumex acetosa s .1. and The substrate is a shallow silt-loam and sand in Stereocaulon vesuvianum. lava crevices. The nutrient status is low judged by The armerietosum of the Racomitrio - Thalic the species composition. No chemical analyses are tretum alpini is therefore assigned to the alliance available. Racomitrio-Thalictrion through the presence of Cetraria islandica, Racomitrium lanuginosum, Th alictrum alpinum and also Ptilidium ciliare, Remarks Selaginella selaginoides and Stereocaulon a!pinum. TheEmpetrum nigrum - Racomitrium lanuginosum community has floristic affinity to the class Koelerio-Cornynephoretea through the presence of 5.3 Grassy heathlands Peltigera polydactyla and Polytrichum piliferum, and to the order Sedo - Poietalia glaucae through Grass species are physiognomically predominating Thymus arcticus and Festuca vivipara. It has af in the grassy heathlands, e.g., Agrostis capillaris, A. finity to the alliance Racomitrio - Thalictrion alpini vinealis, Festuca rubra s.l. and F. vivipara. Com all. nov. through Th alictrum alpinum, Raco mon small herbs are, e.g., Equisetum pratense, mitrium lanuginosum, Cladonia uncia/is, Ptilidium Galium boreale, G. normanii, Polygonum vivi ciliare, Centraria islandica, Selaginella se!aginoides parum, Th alictrum alpinum. In some sites dwarf and Kobresia myosuroides. shrubs are found, e.g., Empetrum nigrum s.l., Salix The sociations described by 1 6nsd6ttir Svane lanata, S. herbacea and others. The bottom layer in (1964) in Tables IV and V can be assigned to the cludes mosses, e.g., Drepanocladus uncinatus,

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 39

Table lOa. Empetrum nigrum - Racomitrium lanuginosum Table 1 Ob . Site and vegetation characters of the Empetrum community. igrum - Racomitrium lanuginosum community. Bare ground l8). litter ( L) . field layer (F) . bottom layer (M). Number of releves : Synop . Estimated cover values . Ref. no .: 1234 value Ref. Date of Alt. Slope Plot % Cover no. obs . m Aspect deg. sgm B L F M Ch. & D. All. B996 B. 0 Racomitrium lanuginosum 23. 8. 19B2 160 10 29 62 3223 2. 5 w Ptilidium ciliare 23. 8. 19B2 160 10 33 59 2 2 1.0 s Thalictrum alpinum •• 23. B. 1 9B2 75 5 98 7 1.8 155 w Rhytidium rugosum ••• 23. B. 1 9B2 155 5 52 2 0. 5 Cladonia uncialis ••• s 45 Barbilopho zia hatcheri 11.. 0. 5 2 0. Cetraria islandica •.. 5 Selaginella selaginoides 2. 12 1.3 Kobresia myosuroides 2 .. 3 1.3 Hy locomium sp lendens and Rhytidiadelphus squar Ch. Cl. & Order Peltigera po lydactyla 2. 1. 0.B rosus. Polytrichum piliferum .. 1. 0. 3 23 1.3 Festuca vivipara •• The grassy heathland vegetation types can be seen Thymus arcticus 22. 2 1.5 Comp . as intermediate stages between nutrient richer Empetrum nigrum 6637 5. 5 Vaccini um uliginosum 4325 3. 5 grassland (valllendi) in Iceland (not described in this 3232 2. Hylocomium splendens 5 Peltigera canina 2222 4 2. 0 paper) and the vegetation types of R. lanuginosum 2231 2. 0 Salix herbacea 4 Arctostaphylos uva-ursi 55.2 3. 0 heaths, gravel flat vegetation or dwarf shrub heaths. Calluna vulgaris 32.5 2. 5 Festuca pruinosa 222. 1.5 Physiognomically they are closest related to the Erigeron boreale 22.2 1.5 Agrostis vinealis 22. 2 1.5 grassland vegetation type, partly floristically too Juncus trifidus 2. 22 1.5 through the presence of, e.g., A. capillaris, Peltigera apthosa 221 . 1. 3 Galium verum 21 .2 1. 3 Cerastium fo ntanum, Galium boreale and Poa Trisetum pilosiglume 1.11 0. B 22 1.0 Pinguicula vulgaris •• pratensis. 22 1.0 Luzula multiflora .• 22 1.0 Hieracium sp. •• The grassy heathlands are somewhat less exposed Betula pubescens . 22. 1.0 2 2 1.0 Polygonum viviparum •• than the gravel flat vegetation and the R. Salix lanata 12.. 0. 8 2 1 0. B Polytrichum juniperinum •. lanuginosum heaths (cf. above). The grassy Luzula spicata 1.2. 0. B Tritomaria quinquedentata 1.1. 0. 5 heathlands are found on deep silt-loamy soils of Encalypta procera 11.. 0. 5 11. 0. 5 D repanocladus uncinatus • rather low to intermediate eutrophic nutrient status. Cladonia macroceras 2 ••• 0. 5 Silene acaulis 2 ••• 0. 5 The soils are fresh to well drained and receive their 1 0. 3 Parnassia palustris •.• 0. 3 Gentiana nivalis 1 ..• moisture only from precipitation, as also do the 1 ... 0. Pohlia cruda 3 Cladonia luteoalba 1. .. 0. 3 other heathland types. 1 0. 3 Lophozia ventricosa •.. 1 0. 3 Anthelia juratzkana •.• Grassy heathland vegetation types are common in 0. 3 Nardia geoscyphos 1 •.• 1 0. 3 Bartramia ithyphylla •.• Iceland, especially in the lowland, and are also 1 0. 3 Ditrichum flexicaule •.• 3 .. 0. 8 found here and there in the highland. Salix phylicifolia • 2 0. 5 Galium normanii • .• . 2 0. 5 Deschampsia flexuosa .• 0. 3 Alchemi lla alpina .1 .. Lophozia alpestris .1.. 0. 3 (4) Agrostio capillaris - Hylocomietum splendentis Botrychi urn lunaria .1 .. 0. 3 Cystopteris fragilis ..3. 0. 8 2. 0. 5 Cardaminopsis petraea •. 2. 0. 5 (Table lla, b & c; ref. no. 1-72; Fig. 15; Plates Dicranum congestum •• . 0. 3 Rhytidiadelphus triquetr us . 1. 0. 3 9-1 1). The character species of this association are Nardia scalaris . . 1. Hierochloe odorata . . 1. 0. 3 Agrostis capillaris (V4), Rhytidiadelphus squar 2 0. 5 Peltigera leucophlebia •.. 2 0. 5 Tofieldia pusilla .•. rosus (V4) and Poa pratensis (IV1). 2 0. 5 Cornicularia aculeata ••• Physiognomically dominating are Drepano 4222 Total number of taxa: 2957 cladus uncinatus, Hy locomium sp lendens, Agrostis 1 11 No. of cryptogam taxa : B920 capillaris, Rhytidiadelphus squarrosus, whereas Festuca pruinosa and Racomitrium canescens are subdominating. The field layer covers 24 OJo , the bottom layer 81 OJo , litter 8 OJo and bare ground is 2 OJo. There are several constant companions in this association, viz. Drepanocladus uncinatus (V5), Festuca pruinosa (V3), Galium boreale (V2),

Peltigera canina (V2), Luzula multiflora (V2) ,

Acta Phytogeogr. Suec. 75 40 Elfn Gunnlaugsd6ttir

Table l l a. Agrostio capillaris - Hylocomietum splendentis 1 cinatus �� 9) . la. typical orm (12�32), lb. Drepanocladus un i ri� �m canescentis (12-72) . 1. typical variant (12-4 f �:form ( 33-49) .��! 2. Thym us arcticus va riant ( 50-72).

Subunit: A B B B A B l a lb 2 l a 1b 1 2 Synop . N u mber o re lev es ll 2 1 7 2 3 l l 2 1 7l 38 2 3 61 72 val ue f ______�==""=""'""="""'""',---:...:___::...:__..:...:__:::.::_:::.::_:::..:._...:_.:..__:: ::_:.:::.:..-- ______...:: . _ .;,;:.�� s ---,--,.1 1 1 1\ 111112 2 2 2 2 2 2 2 223 3 3 3 3 3 3 3 334 4444 444 44 s s s s 5 �s =s�s 5666 666 6666 777 ' --'l 2. :.3 4 5 7::..: 8Y:..:..:.O 1 2 34 56 7 8901 2 34 56 7 8901 2 3456 7 890 1 2 3456 7 8 9 �O .!el �2 3c:!4�56�7�8�90�1�2.::_34.:..:5:.::6.:..:7 ::.:89:.:0...:_1 ::..2 ______Ref ·....:..::.no�· - - '-= ..:..::..::6..:... _ !.::.:::.:..:. ...:. - ---- : Ch. Ass . 4. 2 Agrostis cap illaris 62724535. 63 5. 4566557655353625353 36655433334555356 333. 3. 3. 2. 3 .....3352 .76 V V VIII V V 4. 3 Rhytidiadelphus squarrosus 53756576377 3. 232343653. 113337357 865533555631 89775 7363375356536. 3. 5553523 V V V V V V 1.3 Poa pratensis 2 •.22232222 .21 .....21 .2112.22. 22 2 .•1.11 ...•. 22122 213.• 23223. 2232 . 222 ..22 Ill Ill Ill IV IV IV

d subass. ..•..... 4. 2 Hylocomium splendens 3 .. 879998896887999897897 757773333. 5742622 1 ..675. 3. 5253. 232222422 V V V IV V IV 3. 0 Racomitrium canescens ...... 2 33523335625652. 335323 56 ..3333. 333. 32 .2 17665355545633275376322 + V IV V V V IV 1. 9 Kobresia myosuroides ...... 4 .. 3433333. 54333332425 33 ..33 2123531 .32 ..24. 43 ... 25322 .. 33 .. 3 .. V IV IV Ill IV IV 0. 9 Polygonum viviparum . 2122222221 222. 222221 23 ..21 1.1.2221.2.. 32 ..2 ....2.2 .... 2 .•... V IV IV 11 Ill Ill Galium normanii 2.221 2 ...... 1. ....212 222... 2 ...222 ..2. 22 ...2. 2 ..22 2.122 11.2.1 Ill Ill Ill I V Ill Ill 0. 8 . 4 0. 6 Racomitrium lanuginosum ····•······ •.22 ..2. 1.3. 2 ...2. 3 .. 3 ....2 ..•.22 . . . .2.2.. 2.2 ...... 22 .. 2 ... 11 li 11 11 11 11 Climacium dendroides •······•··· ...... 11. .. 121 .221.23 12.. 1 ...... 2 ... ..3. 1.2...... 1 ...... Ill 11 11 I 11 11 0. 3 .. 1 ... 0. 5 Stereocaulon alpinum ...... 22.2.2... 3 2. 1.. 2 ...... 2 ....2 .•.2 ....2 ...... 22232. 1 11 I 11 !I 11 !I Peltigera leucophlebia .. 1 .. 22 ...2 ...... 1 ....2 .... 22 ...2 .... 1.1...... 3 •.....22 .1 I !I !I !I I! I! 0. 3 Cladonia furcata ...... 2 ..32 .....2 ....11.2 .. 2 ...... 2 ...... 33 ...... 2.2 I! I I! I 11 I 0. 4 C. gracilis ...... 2 .....22 .... 1 .....2 ...... 3 ....3 ... 3 ....2 .. 2 ...... 221 1 11 I I 11 11 I 0. 4 Cladonia pyxidata .....111 ...1 ...... 1 .....2 ...... 11 ...... 12221 1. I 11 11 I 0. 3

d var . Thymus arcticus ...... 3222 ...... 2 ...... 3 .. 1.121 .3. 223... 12 252.2 Ill 11 0. 6 Botrychium lunaria ..1 ...... 1.2 ...... 11 2 ..2.2 12.1.2221.2.12.. 2 + Ill 11 0. 4 Salix lanata • ...... • ...... • . . . . . • • ...... 3 ....12 6 ... 51 .... . 11 0. 3 Poa glauca .•...... ••..•.•.•...• •..•.••....•..... ••...1 .....2 .••1 ... 1 .. 1 11 0. 1

Ch. & D. All. Galium boreale . 2232.22232 233343533543355333355 23235333533333332 • 52 ..223 3233331 23223. 22 V V V V V V V 2. 7 2. 4 G. verum 2. 2. 3. 3. 22. 232333232232233322233 22333332233322333 6223. 325322232322222261 Ill V V V V V V 1.8 Luzula multiflora 1. 2. 212. 122 222322322 .21222222222 2222221 1 .. 222222. 22222222222232222222222 IV V V V V V V Carex bigelowii . 3. 245. 53. s .. 3. 3. 13.221. 12.22222 32 ...12. 2. 33. 1232 . 23. 11 .. 22 .. 3 ...... 423 IV IV IV IV Ill Ill Ill 1. 4 . Taraxacum sp . 3 ...21 ....3 • ...... •...... 12 2 2 ..2 ...1 ...113 1.1. 1.... I! I + !I I !I 0. 4 .. . . Equisetum pratense ...... 2 ....21 ... 1...... 33 .....3232 ..3 . . 3 . 3 .. I 11 11 I 0. 4

Ch. Class & Ord. Cerastium fon tanum 1.1..... 1 ...... 1 ....2 ...... 12 ... 2 I! 11 0. 2 Deschampsia cespitosa 3 .....•••....•...... 2 0. 1 Ranunculus acris 2 ...... 0. 03 Festuca rubra ..•.3 ...... 0. 04

Comp . Drepanocladus uncinatus 99798978777 . 33 .....•....3. 531 . 3. 67777999998753677 87575788887879877765797 V !I V IV V IV V 5. 4 Festuca pruinosa 32535533355 33. 3323. 3323322233353 333332-3453. 333333 33335355333333553543365 V V V V V V V 3. 2 Peltigera canina 2. 11 ..... 2. 322323322. 12323331223 2222322. 223323243 113333. 2336323333222223 I! V V V V V V 2. 1 Festuca vivipara ...333. 2253 . 233223 ..33523333. 323 42 ..322 3. 3333333. 33333. 3333532 ..232333. 1 IV V IV IV V V IV 2. 2 Equisetum arvense 51 522.2353. 3. 222233. 13. 1. 12.. 22. 2222121 ..2221 .. 22 3. 23225332333. 22. 322352 V IV IV IV V IV IV 1.9 Agrostis vinealis . 2536365363 . 33 ...3 ..... 2. 33333. 4 ...3 ... 4 .... 5. 43. 43455645563566565655564 V Ill !I !I V IV IV 0.7 ... . Eq uisetum variegatum ...... 11 ..2222. 2 ...... 1.1... 2 ... 1. . . 111.22 ...... 2222 12.. 12 22 . I 11 Ill 11 Ill I! !I 0. 6 .... 1 Peltigera polydactyla ..1 . . 1...... 12 ...... 12. 1 ....2 ....22 ...2 ...... 3 ...... 31 11.3231 2 I 11 11 I! Ill 11 11 0. 5 Cetraria i siand ica 2 ...... 2.22 ..12. 322 ....21. .. 12 ...2 .....2 ...... 223 ...... 2. 1 + 11 11 !I !I 11 !I 0. 5 Hierochloe odorata ...... 2 ..3 ...22 2.2.... 23 ..2 .. . 2 ...... 23 .....3 ...... 2. + I! 11 !I r 11 I o. 4 .. 1 ...... Trisetum pi losigl ume ...... 1 ...... 1 . . . 22 .1.2.2.... 2. 11.. 2 .... 21 + r I I !I 11 I 0. 3 ...... 0. 4 Rhytidiadelphus triquetrus 11.3.. 32 ....2 ....13 .. . 2 .. 3 ...... 3 ...... 3. . 11 I 11 I I Brachythecium albicans ...... 3 2 ...... 2333. 21 r 11 I I 0. 3 .. 1 ...... Cladonia chlorophaea ...... 1 ...... 2 ...... 11 .... 11.. 2 ...1. + !I I I 0. 2 . Polytrichum juniperinum 1 ...... 1 ...... 1 ...... 1. 2 ... 2 ...... 2222. + !I I I 0. 2 Pt ilidium ciliare . 21 ...1 .... 3 ...... 22 •...•..•11 ...... 2. 1 !I 11 I I 0. 2 Salix phylicifolia ...... 3 ...... 7...... 34 ...3...... + 0. 3 Cerastium alpinum 2 ...... • ...... • . . . • • • • . . . . 2 ...... 2.3.. 1 ...... 2 + 0. 2 Luzula spicata •. 1 •..•...••.•..•..•. . •...... 2 ..22 .. 2 0. 1 Barbi lop ho zia hatcheri ...... 22 ..11 0. 1 Viola palustris ...... 2 ..12 ...... 2 ...... •.••...•.•.2 ...1 .... . 0. 1 Cladonia spp ...... 1 ...... 1 .. 1. ...1 0. 1

. Polytrichum alpinum ...... 1...... 2 ...... 2 ..2 •..•..••..•..• 0. 1 . ..••. Empetrum nigrum ...... ! ...... 2 ...... •.1. 1 0. 1 Rhytidium rugosum ...... 12...... 2 ...... 21 .... 0. 1 Thalictrum alpinum . 1...... 22. 1...... 1 ...... • . . . . 2 ....1..... + t1.1 Selaginella selaginoides ...... 1 ...... 12...... 2 .•..•...... •.•...•.•• 0.1

1 111111111 22221 122 1121211222211 3211111111221 1123 22221212212221212333224 3 Total number of taxa : 49424011456 5351 997235081 65022388 431 37972220576860 2201 7971 481 7980771 50851 0

1 11 1 1 11 11 1 1 1 1111111 No. of cryptogam taxa : 42532222343 1 9895 733559896371 9066 51447954440346665 667189581 66 786860173536 7

Table 11a. Accessory species with their reference number. The transformation values are given within brackets if higher than 1. In subunit A: 3 Peltigera neckeri; 3 (3), 6 (2) Potentilla anserina. In subunit B la: 13 (2) Calamagrostis stricta; 13 (2) Carex capitata; 16 C. flacca; 13 (2) Cladonia arbuscula; 19 (2) C. macroceras; 28 Dicranum congestum; 12 Erigeron boreale; 12 (6) Juncus trifidus and 12 Salix herbacea. In subunit B 1 b: 49 (2) Achillea millefolium; 47 Barbilophozia floerkei; 33 Carex capitata; 49 Cladonia conoidea; 49 (3) C. macroceras; 49 (2) Leymus arenarius; 49 Peltigera apthosa and 34, 49 (2) Polytrichum piliferum. In subunit B 2: 72 Achillea millefolium; 68 (3) Agrostis stolonifera; 71 (2) Anthoxanthum odoratum; 68 Barbilophozia floerkei; 62 (3) Calluna vulgaris; 51 (2) Carex capitata; 57 (2) C. maritima; 51 (2) C. panicea; 57, 68, 72 Ceratodon purpureus; 51, 68 Cladonia arbuscula; 68 C. coccifera; 62, 63 C. conoidea; 61 (2) C. macroceras; 58 C. phyllophora; 72 (2) Dicranella subulata; 50 Erigeron boreale; 61 (2) 65 , 69 Gentiana nivalis; 64 (2), 67 (2) Gentianella amarella; 69 G. aurea; 70 G. campestris; 50 (2), 67 Leontodon autumnalis; 50 (3) Leymus arenarius; 71 Lophozia ventricosa; 72 Parnassia palustris; 60, 68 Peltigera neckeri; 62 P. spuria; 68 (2), 72 (2) Rumex acetosella; 72 (2) Sagina nodosa and 72 Scapania curta.

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 41

Table 11b. Site and vegetation characters of the Agrostio Table 11c. Soil factors of the capillaris - Hylocomietum splendentis . Bare ground (Bj , l itter Agrostio capillaris - Hylocomietum ( L) , field layer (F), bottom layer (M ). Fertilized vegetation (f) splendentis. Available phosphorus and wind deposit affected vegetation (d). Estimated cover values. (mg) and exchangeable potassium (meq ) in 100 g soil (dry weight) ; Ref. Date of Alt. Slope Plot % Cover pH in water . no . obs . m Aspect deg. sqm 8 L F M Soil factors 1 d 9. 8 .1982 135 45 - 12 31 91 s Ref. 2 f 11. 8. 1982 125 0 - 2 100 pH meq K+ mg P no. 3 f 10.8.1982 100 56 59 10 97 lj f 10.8.1982 100 1 6. 2 . 71 . 70 5 f 10.8. 1982 100 37 83 3 5. 7 . 81 . 50 24 95 6 f 10.8.1982 100 s 16 6. 1 . 55 • 40 7 f 10.8.1982 100 SE 21 73 21 6. 0 . 50 . 40 27 81 8 f 10.8. 1982 110 SE 5 27 5. 8 • 63 . 60 - 12 92 9 f 10.8. 1982 110 0 37 5. 9 • 55 . 60 10 f 10.8 . 1982 110 SW 5 - 17 58 85 40 5. 9 . 63 . 60 11 d 16.8. 1982 115 E 5 9 26 77 44 6. 0 . 50 . 70 12 20.7. 1982 130 s 10 6 - 39 24 72 57 5. 7 . 66 . 20 13 29. 7. 1 982 150 0 6 7 11 99 60 5. 8 . 74 . 20 11! 29.7. 1982 140 0 6 - 15 21 93 64 5. 8 . 68 . 40 15 4. 8. 1982 140 SW 10 6 9 21 82 66 6. 0 . 63 . 40 16 6. 8. 1982 140 NW 5 6 9 24 94 69 5. 9 . 71 . 00 17 6. 8. 1982 140 NE 10 6 - 10 21 79 18 9. 8. 1982 130 0 6 - 15 26 80 19 9. 8 1981 140 s 10 6 7 17 89 20 9. 8. 1982 135 0 6 - 41 41 47 21 9. 8. 1982 130 0 6 - 11 22 84 Galium verum (V2), Hy locomium sp lendens (IV4), 22 11.8.1982 130 s 6 - 19 20 78 23 12.8. 1982 135 E 6 - 13 22 87 Racomitrium canescens (IV3), Festuca vivipara 21! 12.8 .1982 125 NE 5 6 - 14 12 91 25 12.8 .1982 125 0 6 - 20 1 9 97 (IV2), Kobresia myosuroides (IV2), Equisetum 26 12.8.1982 120 0 6 9 18 94 - 27 12. 8. 1982 120 s 10 6 25 30 76 arvense (IV2) and Agrostis vinealis (IV1). 28 12.8 .1982 120 0 6 5 14 93 - 29 12. 8. 1 982 120 w 5 6 15 19 89 Most species belong to the hemicryptophyte life 30 12.8. 1982 120 N 5 6 - 1 3 17 84 17). 31 13.8. 1982 120 s 5 6 6 20 92 form group (Fig. The European species are 32 13.8.1982 120 0 6 - 11 23 77 33 d 6.8. 1982 135 0 6 - 13 82 much more numerous than the Arctic ones (Table 31! 9. 8. 1982 140 0 6 - 25 69 16) 35 d 9. 8. 1982 130 0 6 9 18 86 due to relatively mild climate and mineral fer 36 d 9. 8. 1982 130 0 6 7 16 80 37 d 9. 8. 1982 130 0 6 - 17 20 65 tilization. 38 11. 8. 1982 130 0 6 - 11 13 91 39 11. 8. 1982 130 E 5 6 8 11 92 The Agrostio capillaris - Hylocomietum splen 40 d 11. 8. 1 982 125 SE 6 9 14 96 dentis is found in the heathlands near Gunnarsholt. 41 d 11. 8. 1 982 125 w 6 - 13 98 125 6 - 12 92 42 f 11. 8. 1982 w The heathland has been partly affected by mineral 43 f 11.8. 1 982 125 s 6 - 23 81 44 f 11.8.1982 125 6 - 24 76 fertilizers (NPK) and/ or by wind-borne deposits 45 d 1 2. 8. 1 982 125 6 - 15 23 75 46 d 12.8. 1982 125 6 - 10 16 97 from the deflated, fertilized surroundings. 47 d 13.8 . 1982 125 6 - 16 17 76 48 d 16.8.1982 115 E 6 - 11 54 76 The soil is a thick to very thick (5-10 dm or 49 d 17. 8. 1982 120 SE 6 6 12 57 50 f 17. 8. 1982 100 12 - 56 93 more), loessial, silt-loam, rich in organic matter and 51 1. 8. 1982 150 6 - 32 17 86 52 9.8. 1982 135 6 - 48 22 50 with tephra layers. It is somewhat fresh to well 53 d 9. 8. 1982 125 6 - 18 74 54 12.8 .1982 125 6 - 22 71 drained, with fresher parts in the depressions, where 55 d 12.8. 1982 120 SE 10 6 - 26 81 56 f 10. 8. 1982 100 s 15 6 - 28 86 the soil has lower drainage capacity. 57 f 10.8 . 1982 110 N 5 6 - 28 80 58 f 10.8. 1982 110 SE 10 6 - 21 86 The nutrient status is rather low, with 0.43 mg P 59 f 13.8. 1982 115 E 10 6 - 29 85 0.53) 0.64 0.1 1). 60 f 13. 8. 1982 115 s 15 - 23 82 (variance and meq K+ (variance 61 f 13.8. 1982 115 N 5 - 20 84 10 - 41 77 The soil is slightly acid with pH 5.9 on average 62 f 13.8. 1982 115 s 63 f 13. 8. 1 982 115 SE 15 - 29 79 64 f 13. 8. 1982 115 0 - 14 88 (variance 0.28), figures being based on 13 analyses. 65 f 16. 8. 1982 115 NW 10 - 33 85 66 f 16.8. 1982 115 s 10 - 31 66 67 f 17.8. 1982 120 SE 10 27 - 33 40 68 f 17.8.1982 120 SE 15 6 - 25 70 Two subassociations are distinguished: 69 d 17.8. 1982 120 0 6 46 - 19 35 (1) 70 d 20. 8. 1982 135 0 6 19 - 19 62 Subass. inops subass. nov. (Table lla, b & c; 71 f 8. 8. 1974 125 0 12 - 40 98 ref. no. 1-11). The subass. inops of Agrostio 72 f 12.8. 1974 120 0 12 - 10 90 capillaris - Hylocomietum splendentis is mainly found in the Brekknahei3i heathland and excep tionally in the Steinkrossmoar, Steinkrossbrun and Dagver3arnesm6ar heathlands. It is found on level ground to gentle slopes, exceptionally on precipitous slopes at altitudes of 100-130 (150) m. The inops is most often found in sites where the vegetation has been damaged by frost ("kal"). In

Acta Phytogeogr. Suec. 75 42 Elfn Gunnlaugsd6ttir this case the damage occurred in the spring of 1981. southern part of Iceland and found in small patches This kind of frost damage or frost killing here and there elsewhere. The distribution of the ("svellakal") occurs when semi-melted snow and Agrostio capillaris - Hylocomietum splendentis and water freezes into ice and smothers the plants. The the earlier described plant communities which have frost-heaving action tears the roots. Frost damage been assigned provisionally to it is shown in Fig. 15: ("kal") may occur in this kind of vegetation from (1) the Agrostio - Hylocomietum splendentis (this time to time (cf. Steind6rsson 1964b, p. 121), even paper); (2) the Grresmark Steind6rsson 1936 Table if it is not fertilized. All the Drepanocladus XI: 1-7; (3) the Elyna bellardi - Carex rigida Ass. uncinatus-rich vegetation units of the association Steind6rsson 1945 Table IX: 1-3; (4) the Festuca are affected by mineral fertilizer (NPK). rubra - Kobresia myosuroides soc. Steind6rsson 1964a Table VII: 1-2 and (5) the Kobresia (2) Subass. racomitrietosum canescentis subass. myosuroides - Carex bigelowii - F. rubra soc. Stein nov. (Table 11a, b & c; ref. no. 12-72). Species dif d6rsson 1964a Table X: 1-6. ferentiating this subassociation from the inops In Norway grassy heathland or meadow vegeta (species-poor subassociation) are Hy locomium tion has been described by, e.g., Resvoll-Holmsen sp lendens (V5), Racomitrium canescens (V4), (1912 pp. 25 ff. ; 1913 pp . 27 ff.; 1914 pp. 49 ff. , 54 Kobresia myosuroides (IV2), Polygonum vivi ff.), by Nordhagen (1921 pp. 80 ff. ; 1943 pp. 199 parum (III1), Galium normanii (III1), Racomitrium ff., 250, 388 ff.) and by Gr0nlie (1948 pp. 144 ff.); lanuginosum (le), Cetraria islandica (le) and in Finland by, e.g., Kalela (1939 pp. 88 ff. , 330 ff.), Climacium dendroides (II1) and others. and in the British Isles related vegetation has been The following subunits can be distinguished, but treated by, e.g., Asprey (1947 p. 187) and by Fer some of them are not qualified for syntaxonomical reira & Wormell (1971); furthermore it has been de descriptions: scribed by Ratcliffe (1959 pp. 379 ff.), by McVean a. The typical variant (Table 11a & b; ref. no. & Ratcliffe (1962 pp. 52 ff.); lvimey Cook& Proctor 12-49). It has two forms. ( 1966 pp. 246 ff.) and by Birse ( 1980 pp. 89 ff. , 96 aa. The typical form (Table lla, b & c; ref. no. ff., 105 ff.). 12-32). Most closely related are the Norwegian com ab. The form dominated by Drepanoc/adus un munities described by Resvoll-Holmsen in 1912

cinatus (Table 11a, b & c; ref. no. 33-49). Table 3: 1-4, p. 25 (IS1 = 21 OJo) and in 1913

b. The Thymus arcticus variant (Table 11a, b & c; Table 5: 1-2, (IS1 = 20 %), which have many ref. no. 50-72; Plate 3), is differentiated from the vascular plant species in common with the Agrostio typical variant by higher constancy of Thymus arc capillaris - Hylocomietum splendentis. These com ticus (IV1), Botrychium lunaria (IV1), Salix lanata munities are distinguished from the Icelandic (II1) and Poa glauca (II1) and is rich in both D. un vegetation types of the Equiseto - Galion borealis by cinatus and Racomitrium canescens. It is found at high constancy of, e.g., Alchemilla vulgaris, Cam the edges of the uneroded areas which are influenced panula rotundifo lia, Festuca ovina, Rumex acetosa by soil deposits from the surroundings. and Trifolium repens. The Norwegian communities are probably growing on somewhat nutrient-richer soil. The Festuca ovina - Potentilla crantzii soc. in Remarks Nordhagen 1943 Table 27, pp. 199 ff. (IS1 = Grassy heathlands or hillside vegetation or meadow 22 %) is also closely related and is distinguished vegetation in Iceland have been described or treated from the Icelandic ones by Festuca ovina, Potentilla by several authors (e.g., M0lholm Hansen 1930, crantzii, Carex vagina fa, Vaccinium vitis- idaea and 6skarsson 1932, Steind6rsson 1936, 1945, 1964a other species. The Icelandic vegetation unit is dif and 1964b, Tiixen & Bottcher 1969 and Knauer ferentiated from the Norwegian ones through 1966), and by many authors in the neighbouring Kobresia myosuroides, Galium normanii, G. verum countries. and Luzula multij/ora. The Agrostio capillaris - Hylocomietum splen Also one British community shows relatively dentis association is probably common in the close floristic affinity to the Icelandic association,

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 43

here provisionally assigned to the class Molinio Arrhenatheretea Tx. 1937 rather than to the Koelerio-Corynephoretea. The Agrostio - Hylocomietum splendentis, the F. vivipara - R. canescens community and the Racomitrio - Gentianetum nivalis have the follow ing species in common with the Molinietum coeruleae Koch 1926 Table X (Koch 1926): Galium verum and Anthoxanthum odoratum and in com mon with its subassociation caricetosum tomen tosae Koch 1926: Galium boreale, Cladonia pyxi data and Rhytidium rugosum. These floristic af finities support the provisional assignment of the Fig. 15. The known distribution of the Agrostio capillaris above-mentioned vegetation types of the - Hylocomietum splendentis in Iceland. See text for ex Molinietalia Koch 1926 even if they are weak. planation of numbers. The Agrostio - Hylocomietum splendentis, the F. vivipara - R. canescens community and the Racomitrio - Gentianetum nivalis have weak viz. the species-poor Agrostio-Festucetum in floristicaffinities to the class Molinio - Arrhenetere McVean & Ratcliffe 1962 Table 24: 1-14 & p. 25 tea Tx. 1937 through the presence of ff. (IS1 = 21 OJo ), in which, e.g., Galium saxatile, Cerastium fo ntanum Ranunculus acris Potentilla erecta, Viola riviniana distinguished it F. rubra s. str. Rhinanthus minor from the Icelandic vegetation types. The Icelandic Poa pratensis associations and the community (see above) are dis They have floristic affinities to the order tinguished from the British community by Kobresia Molinietalia Koch 1926 only through Luzula myosuroides, Galium normanii, Agrostis vinealis multiflora and Deschampsia cespitosa and strong and Festuca vivipara. floristic affinities to its alliance Equiseto - Galion None of the above-mentioned communities de borealis Tx. 1969 through the presence of scribed outside Iceland are so floristically related to the Icelandic associations and communities that Carex bigelowii G. verum Equisetum pratense Luzula multiflora they are considered to belong to the Icelandic Festuca vivipara Polygonum viviparum vegetation types. Galium boreale Taraxacum sp. The floristic affinities of the Agrostio - Hyloco mietum splendentis, the Festuca vivipara - Racomi The character species of the Molinio-Arrhenathere trium canescens community and the Racomitrio - tea Tx. 1937 are (cf. Ellenberg 1979) Gentianetum nivalis to the alliance Equiseto - Agrostis gigantea Holcus lanatus Galion borealis Tx. 1969 are strong, but they are not Alopecurus pratensis Lathyrus pratensis strong to its order Molinietalia Koch 1926. In fact, Cerastium fo ntanum Plantago lanceolata these vegetation types also have relatively strong Colchicum autumnalis Prune/la vulgaris Dactylis glomerata Ranunculus acris floristic affinities to the class Koelerio-Corynepho Dactylorhiza incarnata Rhinanthus minor retea and to its order Sedo - Poietalia glauca de Euphrasia rostkoviana agg. Trifo lium pratense Molenaar 1976 owing to the same species ensemble Festuca pratensis Vicia cracca as the vegetation types assigned to its alliances the F. rubra ssp. rubra Sedo - Thymion drucei and the Racomitrio - Thalic trion alpini in this paper (see above). The environmental conditions of the associations As some meadow species, e.g., Cerastium jo n and communities described by Tiixen ( 1937) might tanum, Luzula multiflora, Poa pratensis and be assigned to the present class. These vegetation Rhytidiadelphus squarrosus, have high constancy in types of pastures and meadows are found on these grassy heathland vegetation types they are nutrient-poor to nutrient-rich soil, sometimes fer-

Acta Phytogeogr. Suec. 75 44 Elfn Gunnlaugsd6ttir

Table 12a. Festuca vivipara - Racomitrium canescens Table ------12b. Site and vegetation characters of the Festuca commumt-y-. -- vivipara - Racomitrium ca nescens community. Bare ground (B). litter (L), field layer (F). bottom layer (M). Number of relevees : Synop . Estimated cover values. Ref. no . : 12345678 va lue Ref. Date of Alt. Slope Plot % Cover Ch. & D. All. no . obs . m Aspect deg. sqm . B L F M Galium boreale 4. 333323 V 2. 6 Festuca vivipara 23553333 V 3. 4 20. 7. 1 982 1 50 0 36 1 2 63 .3322222 2.0 4. 8 .1982 150 40 6 88 Luzula multiflora V SE 17 2 13.32. .. 1.1 4. 8 .1982 50 25 14 3 8 Galium verum Ill 1 s 1 2 4 2 2 . . 3. .. o. 6 4. 8. 1982 150 30 42 40 9 Carex bigelowi i . I I s 2 Polygonum viviparum 2...... I o. 3 4. 8 .1982 1 50 NW 30 17 20 64 Eq uisetum pratense . 2...... I 0. 3 6. 8. 1982 135 0 11 44 52 17.8 .1982 130 19 5 1 8 0 1 1 2 Ch . Class 17. 8. 1982 130 57 8 20 15 Cerastium fontanum .12221 22 V 1.5 0 Poa pratensis 2.2. .... I I o. 5 Rhinanthus minor ..2. .... I o. 3 Comp. Racomitrium canescens 75668765 V 6. 3 Drepanocladus uncinatus 7261 2333 V 3.4 tilized. The soil may be calcareous or not; wet, very . 5543532 4 Thymus arcticus V 3. Festuca prui nosa 33353333 V 3. 3 fresh to moderately dry. 23532324 3. Equisetum arvense V o Empetrum nigrum 3. 1 63721 V 2. 9 The character species of the order Molinietalia Agrostis vinealis 323. 3353 V 2.8 Pe ltigera canina . 2333322 V 2. 3 Koch 1926 are (cf. Tuxen 1937) e.g., Galium normanii 23. 22222 V 1.8 Racomitrium lanuginosum 22. 22321 V 1.8 Achillea ptarmica agg. Filipendula ulmaria Polytrichum alpinum 2.221 222 V 1.6 1.5 Angelica sylvestris Luzu/a multiflora Luzula spicata .2211222 V Poa glauca .3333. 23 IV 2.1 · Caltha palustris Lychnis flos-cuculi Stereocaulon a lpinum . 22333. . IV 1.3 Rumex acetosella . 231 .. 12 IV 1.1 Deschampsia cespitosa Parnassia palustris ... 22122 Barbi lophozia hatcheri IV 1.1 Equisetum palustre Succisa pratensis Cladonia macroceras 112. 2 2. . IV 1.0 Brachythecium albicans ..21 .. 35 Ill 1 .4 Peltigera polydactyla .1.3.23. Ill 1.1 Equisetum variegatum ...221 2. III 0. 9 Trisetum pilosiglume .2221 ... Ill 0. 9 0.8 Ceratodon purpureus . . 1.1.22 III J uncus trifidus 12. . 21 .. Ill 0. 8 (5) Festuca vivipara - Racomitrium canescens com .2... 1.2 Cardaminopsis petraea Ill 0. 6 Cladonia pyxidata .111..2. Ill 0. 6 munity Agrostis stolonifera 5 ...2.3 . II 1.3 Hylocomium splendens 6 . . . 22. . II 1.3 Kobresia myosuroides ...33 .3. II 1.1 (Table 12a & B; ref. no. 1-8; Fig. 16) This plant ..2 . Botrychium lunaria . 21 . II 0. 6 Polytrichum juniperinum ..212. .. I! 0. 6 community has no character species of its own . Peltigera leucophlebia ....2. 3. I! 0.6 Polytrichum pi liferum .2... 12. II 0. 6 The physiognomy is dominated by Racomitrium Peltigera spuria ...2 ..12 II 0. 6 Dichodontium pellucidum ..112 ... II 0. 5 canescens whereas subdominating species are . 3. o. Silene acaulis 1.... I I 5 Cladonia gracilis . 2 ..2. .. !I 0. 5 Festuca vivipara, Drepanocladus uncinatus and F. 0. 5 Bartramia ithyphylla ...... 22 11 ....2 .. pruinosa. %, Peltigera venosa 1 11 0. 4 The field layer covers 24 the bottom ... Rhytidiadelphus squarrosus 2 . 1.. !I 0. 4 2 ....1.. OJo, %. Thalictrum alpinum II 0. 4 layer 38 litter 7 OJo and bare ground is 11 .1 ...2. . Arenaria norvegica I! 0. 4 There are many constant companions in this com Carex capitata 21 ...... 11 0. 4 Euphrasia frigida ..1.1... II 0.3 Cerastium alpinum ..1.1... I! 0.3 munity, namely Racomitrium canescens (V6), Nardia scalaris ...1 . . 1. I! 0.3 Festuca vivipara Drepanocladus uncinatus Cornicularia aculeata ....11.. I! 0.3 (V3), .. 0.3 Barbi lophozia barbata . . 1..1 II (V3), Thymus arcticus (V3), F. pruinosa (V3), Lophozia alpestris .... 1.1. 11 0. 3 Cladonia verticil lata ...11... II 0.3 Equisetum arvense (V3), Empetrum nigrum (V3), Agrostis capillaris .. 3. . ... I 0. 4 Gentiana nivalis .. 2. .... I 0.3 Agrostis vinealis (V3), Galium boreale (V3), Salix herbacea ... 2. ... I 0. 3 Timmia austriaca .... 2. .. I 0. 3 Peltigera canina (V2), Luzula multiflora (V2), Peltigera neckeri .... 2. .. I 0. 3 Silene maritima ...... 2. I 0. 3 Galium normanii (V2), Racomitrium lanuginosum 22334332 Cerastium fo ntanum Luzula sp icata Total number of taxa : 395841 47 (V2), (V2),

Number of 1122111 (V2), Poa glauca (IV2) and other species. cryptogam taxa : 80403363 Most species belong to the hemicryptophyte life form group (Fig. 17). Arctic species are more com mon than the European ones (Table 16) due to

Table 12a. Accessory species with their reference number. 3 An strong exposure and erosion damage of the vegeta thelia juratzkana; 8 Barbilophozia floerkei; 3 Bryum sp.; 3 tion. Cephaloziella cf. rubella; 1 Cladonia chlorophaea; 4 C. pocillum; The Festuca vivipara - R. canescens communitx 4 Ditrichum flexicaule; 4 Encalypta rhabdocarpa; 5 Lophozia ventricosa; 5 Pohlia filum; 4 Pohlia sp.; 6 Rhytidiadelphus tri is found on land damaged by wind erosion and quetrus; 1 Ptilidium ciliare and 3 Selaginella selaginoides. might be interpreted as a late stage of the degenera-

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 45

Table 13a. Racomitrio canescentis - Gentianetum Table 13b. Site and vegetation characters of the Racomitrio nivalis. canescentis - Gentianetum nival is. Bare ground ( B), field layer (F) , bottom layer (M ) and fertilized vegetation (f) . Estimated cover va lues. Number of releves: Synop . Ref. no . : 123456 value Ref. Date of Alt. Slope Plot % Cover no. obs . m Ast�ect de9. sgm B L F M Ch. Ass. - Gentiana nivali s .12221 V 1.3 1 1 4. 7. 1974 110 12 10 22 85 Salix lanata .13355 V 2.8 2 f 24.7.1975 60 12 10 - 15 75 S. phylicifolia .321 51 V 2.0 3 19.8.1975 110 WNW 12 19 - 26 68 - Lophozia ventricosa .. 2221 IV 1.2 4 f 16. 8. 1 975 110 12 6 69 88 Gentianella amarella .2122. IV 1.2 5 20. 8. 1975 110 WNW 12 7 - 63 74 Lomatogonium rotatum .2221 . IV 1.2 6 f 15.8.1975 110 12 96 25 Dicranella subulata 11.1.1 IV 0. 7 Pa rnassia palustris . 2. 2.1 I I I 0. 8 Bryum inclinatum . 111.. o. 5 I I I Table 13c. Soil factors of the Ch. All. Racomitrio canescentis - Festuca vivipara 252525 V 3. 5 Gentianetum nivalis. Available Luzula multiflora 222221 V 1.8 phosphorus (mg) and exchang Galium verum 2.2.1. Ill 0.8 able potassium (meq ) in 100 g Po lygonum viviparum .21... Il 0. 5 soil (dry weight) ; pH in water.

Ch. Class Ref. Soi l factors Cerastium fontanum 21 1111 1.2 no. t�H meg K + m9 p Poa pratensi s . 2 •••• 0.3 Comp . 6. 6 . 29 6. 4 . 26 . 17 Racomitr ium canescens 978987 8. 0 V 6.3 . 33 Agrostis vinealis 5. 5779 V 5. 5 6. 0 . 40 . 17 Festuca pruinosa 555565 V 5. 2 Empetrum nigrum 113353 V 2. 7 2. 2 Peltigera canina 251131 V Gali urn normanii 222222 2. 0 V Table 13a. Accessory species with their reference number. The Luzula spicata . 2 2 222 V 1.7 Eq ui set urn arvense 2. 2222 V 1.7 transformation values are given within brackets if higher than 1. Armeria maritima . 22222 1.7 V 1 (2) Arenaria norvegica; 6 (3) Betula pubescens; 3 Bryum Thymus arcticus 12222. V 1. 5 Calluna vulgaris 121121 V 1.3 caespiticium; 3 Bryum spp.; 2 (2) Carex nigra; 1 (2) Car Botrychium lunaria 211112 V 1.3 daminopsis petraea; 1 Cladonia furcata; 1 C. pyxidata; 2 Si lene acauli s . 231 11 V 1.3 Cerastium alpinum . 22211 V 1.3 Climacium dendroides; 1 Dichodontium pellucidum; 5 Salix herbacea . 12211 V 1.2 Dicranum congestum; 5 Ditrichum flexicaule; 2 (2) Epilobium T risetum p i losiglume . 21121 V 1.2 Polytrichum pili fer urn palustris; 5 Heterocladium dimorphum; 2 Hylocomium 1. 1111 V o. 8 Scapania cf. curta 11111. V 0. 8 splendens; 4 (2) Kobresia myosuroides; 6 (2) Leymus arenarius; Drepanocladus uncinatus 371 . 1. 2. 0 IV 3 Peltigera polydactyla; 2 Pinguicula vulgaris; 6 Plantago Polytrichum juniperi num 252. 2. IV 1. 8 Poa glauca . 222.2 IV 1. 3 maritima; 5 Pohlia cruda; 2 Psoroma hypnorum; 4 (2) Ranun .21.23 1. 3 Brachythecium albicans IV . 5. 11. 2 culus acris; 2 (2) Sedum villosum; 1 (2) Silene maritima and 5 Polytrichum alpinum IV 1. Sagina nodosa 2.12. 1 IV 1.0 Solorina sp. Euphrasia frigida 2. 121. I V 1.o Lychnis alpina 212. 1. I V 1.0 Minuartia rubella 211.1. IV o. 8 Stereocaulon alpinum . 1211. IV o. 8 J uncus trificius ..11 21 I V o. 8 The nutrient status of the soil is low, with 0.4 mg Pe ltigera leucophlebia ..21 11 IV 0. 8 Ceratodon purpureus . 1111. I V o. 7 P (variance = 0) and 0.63 meq K+ (0.66 and 0.60 Peltigera spuria ..1111 IV o. 7 Anthelia juratzkana .. 325. I I I 1.7 cf. ref. no. 2 and 6 resp.; variance 0.002). The soil Rumex acetosella 21 . 2 .. I I I o. 8 Bartramia ithyphylla ..21 . 1 Ill 0. 7 is neutral with pH 6.0 (6. 1 and 5.9 resp.; variance Cladonia spp. .1.11. !I I o. 5 Agrostis stolonifera . 5. 2. 2 Ill 1.5 0.02); only 2 analyses were involved . A. capillaris 2. 2. 2. I I I 1.0 Selaginella selaginoides . 1.2 .. I I 0. 5 Nardia scalaris ..11.. I I 0. 3 Vaccinium uliginosum . 1... 1 I I 0. 3 Lop hozia spp. . ..1. 1 I I 0. 3 (6) Racomitrio canescentis - Gentianetum nivalis Peltigera venosa •..11. I I o. 3 Cephaloziella cf. rubella .•• 11. 0. 3 ]] (Table 13a, b & c; ref. no. 1-6; Fig. 16; Plate 12). 344443 Total number of taxa : 189998 Character species: Gentiana nivalis (V1}, Salix 111121 No . of cryptogam taxa : lanata S. phylicifolia Lophozia ven 04871 0 (V3), (V2), tricosa (IV'), Gentianella amarella (IV'), Lomatogonium rotatum (IV1), Parnassia palustris tion of the "original" vegetation. It is found on (III1), Bryum inclinatum (III1} and Dicranella level ground or on steep to very steep slopes of vari subulata (IV} ous aspects at altitudes of 130-150 m in the The physiognomy is dominated by Racomitrium Steinkrossbrun and Dagveroarnesmoar heathlands. canescens. Subdominating are Agrostis vinealis, The soil is silt-loamy of various depths lying on Festuca pruinosa and F. vivipara. The field layer porous lava bedrock. It is fresh to rather well covers 49 OJo,the moss layer 69 OJo and bare ground drained. is ea. 10 OJo.

Acta Phytogeogr. Suec. 75 46 Elfn Gunnlaugsd6ttir

There are many constant companions in the been described by B0cher (1937 pp. 176 ff.). Ranun association (Table 11a). The most important ones culus acris, Rhytidiadelphus loreus, Sibbaldia pro being Racomitrium canescens (V8), Agrostis cumbens and other species distinguish it from the vinealis (V6), Festuca pruinosa (V5), F. vivipara Racomitrio-Gentianetum and the F. vivipara - R. (V4), Empetrum nigrum (V3), Peltigera canina (V2), canescens community. Birse (1980 p. 114 ff.) de Galium normanii (V2), Luzula sp icata (V2), scribed a related association in Scotland, but An Equisetum arvense (V2), Armeria maritima (V2), thy/lis vulneraria, Galium sterneri, Linum cathar Thymus arcticus (V2), Silene acaulis (V1), ticum and other species distinguish it from the Cerastium alpinum (V1), Salix herbacea (V1), above-mentioned Icelandic vegetation types. Cerastium fo ntanum (V1), Trisetum pilosiglume (V\ Drepanocladus uncinatus (IV2) and Polytrichum piliferum (IV2). Most species belong to the bryophyte and the 5.4 Dry as octopetala - heaths and hemicryptophyte life-form groups (Fig. 17) due to related dwarf shrub heaths humid and relatively mild climate. European species are more common than the Arctic ones (Table 16) Dryas octopetala predominates physiognomically due to relatively mild climate. in the D. octopetala-heaths. Other common dwarf The Racomitrio canescentis - Gentianetum nivalis shrubs in these heaths are, e.g., Calluna vulgaris, association is found in the deflated lava-fields of Betula nana, Empetrum nigrum s.l. and Salix Vesturhraun (near Gunnlaugssk6gur) and Reyoar lanata. The bottom layer is usually scarce but vatnshraun; also in the alluvial sand area at lichens may be dominating (see Egilsson 1983). Ketlusandur on level ground to gentle slopes at The D. octopetala - B. nana community (this altitudes of 60-110 m. The soil is silt-loamy inter paper) and other Dryas octopetala communities mingled with sand and pebbles. It is fresh to rather assigned to it (see below and Fig. 16) has strong well drained. floristic affinities to the Dryas integrifolia com The nutrient status is low, with 0.09 mg P munities in Greenland (B121cher 1954, 1963; Daniels (variance 0.03) and 0.32 meq K+ (variance 0.01). 1982) through, e.g., Cerastium alpinum, Ceratodon The soil is neutral with pH 6.3 (variance 0.19), purpureus, Drepanocladus uncinatus, Kobresia figures being based on 4 analyses. myosuroides, Luzula sp icata, Poa glauca, The distribution of the Racomitrio canescentis - Polygonum viviparum, Polytrichum juniperinum, Gentianetum nivalis is not known. The association Salix callicarpaea, S. herbacea, Silene acaulis, probably occurs in the lowland of southern Iceland Th alictrum alpinum and Thymus arcticus. It also in revegetated, formerly deflated areas. has strong affinities to Dryas octopetala com munities in Fennoscandia and in Svalbard (Nord hagen 1936, Mork & Heiberg 1937, Kalliola 1939, Remarks R121nning 1965, Bringer 1961a, b and Hedberg et al. In Iceland Racomitrium canescens-rich sociations 1952) through, e.g., Dryas octopet ala, Empetrum have been described by J 6nsd6ttir Svane (1964) nigrum s.l., Juncus trifidus, Kobresia myosuroides, Tables VI & VII. None of these sociations are the Polygonum viviparum, Salix herbacea, S. lanata, same community as the F. vivipara - R. canescens Silene acaulis, Th alictrum alpinum and Vaccinium community or the Racomitrio canescentis - Gen uliginosum. tianetum nivalis as they deviate too much The Icelandic D. octopetala communities are floristically. The sociations in Table VI might be found on thin silt-loamy soil, which may be thick characterized by, e.g., Anthoxanthum odoratum, near eroding areas (Steind6rsson 1980). The surface Cetraria islandica, Deschampsiaflexuosa and Viola is often hummocky. The soil is well drained and palustris and those in Table VII by, e.g., Cassiope receives its moisture only from the precipitation. hypnoides, Dicranum starkei and Sibbaldia pro The D. octopet ala communities are always exposed cumbens. to wind and therefore the sheltering snow cover is In the Faroes R. canescens-rich vegetation has usually blown away in winter.

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 47

Table 14a. Dryas octopetala - Betula nana 2 Salix callicarpaea 2 Th alictrum alpinum community . (2 ), (2 ), (22), Vaccinium uliginosum (22) and Bryum in Number of rei eves : 2 Synop . Ref. no . : 12 value clinatum (22). Ch. Class In the field layer, which covers 84 OJo on the aver D ryas octopetala 75 2 6. 0 Kobresia myosuroides 2. 1. 0 age, Dryas octopetala, Betula nana and Salix lanata Silene acaulis 11 1. 0 Botrychium lunaria 1. 0. 5 are physiognomically dominating and S. phylici Comp. Salix lanata 67 6. 5 fo lia is subdominating. The bottom layer covers Betula nana 67 6. 5 Ceratodon purpureus Salix phylici folia 25 3. 5 only 4 OJo where is the most s. ca llicarpaea 23 2. 5 common species. Litter is negligible and bare Call una vulgaris 32 2. 5 Empetrum r. igrum s.l. 32 2. 5 ground is ea 11 OJo.The height of the vegetation is Festuca pruinosa 23 2. 5 Thymus arcticus 23 2. 5 20-40 cm (Salix spp. and B. nana). Arctostaphylos uva-ursi 32 2. 5 Poa glauca 23 2. 5 There are equal numbers of species of the Po lygonum viviparum 22 2. 0 Ceratodon purpureus 22 2. 0 chamaephyte and the hemicryptophyte life-form Trisetum pi losiglume 22 2. 0 Vaccinium uliginosum 22 2. 0 groups (Fig. 17). Arctic species are somewhat more Galium normanii 22 2. 0 Agrostis capillaris 22 2. 0 common than the European ones (Table 16) due to Deschampsia flexuosa 22 2. 0 Bryum spp. 22 2. 0 cool climate and strong exposure. Festuca vivipara 12 1. 5 Armeria maritima 12 1.5 The community is a secondary one, derived from Salix herbacea 21 1.5 Thalictrum alpinum 21 1.5 Betula pubescens and Salix spp. shrub vegetation Poa alpina 12 1.5 Polytrichum juniperinum 11 1.0 after centuries of grazing and wood cutting. Bryum inclinatum 11 1.0 Timmia austriaca 11 1.0 The soil is a very deep, sandy silt-loam. Wind Platanthera hyperborea 11 1.0 J uncus trifidus 2. 1.0 borne deposits from the enormous sand dunes in the Luzula spicata 2. 1. 0 Equisetum arvense 1. 0.5 H6lssandur area are still accumulating in the dwarf E. pratense 1. 0.5 Galium verum . 2 1.0 shrubs. The nutrient status is presumably low Cerastium fontanum .1 0. 5 judged by the species composition. No chemical Drepanocladus uncinatus .1 0. 5 Pyrola minor . 1 0. 5 analyses are available . Peltigera sp. .1 0,5 The Dryas octopetala - B. nana community is 33 Total number of taxa : li 3 found on steep slopes with large knolls, moderately No . of cryptogam taxa : 46 6 high. It is found in the dwarf shrub heath in the H6lssandur area at altitudes of ea. 215 m. One of Table 1l!b. Site and vegetation characters of the D.ryas octopetala - Betula nana community. Bare ground (B), the analyses is from a grazed area (Table 14, ref. no. fi eld layer ( F) , bottom layer (M ). Estimated cover value. 1) and one from an area kept ungrazed for about 30 Ref. Date of Alt. Slope Plot % Cover no . obs . m Aspect deg. sqm B F M years (Table 14, ref. no.2). In the grazed area Dryas

11.7. 1974 21 5 ·W 20 12 14 85 octopetala and Arctostaphylos uva-ursi are more 12.7.1974 21 5 20 12 6 86 w· prominent whereas Salix lanata and S. phylicifolia are dominant in the ungrazed one.

The Dryas octopetala - heaths are found both in Remarks the lowland and in the highland in Iceland. They have been described mainly from the northern and Dryas octopetala heaths have been described from eastern part of the country. Iceland by e.g., Steind6rsson (1936, 1945 and 1966), M0lholm Hansen (1930), McVean (1955) and Egilsson (1983). (7) Dryas octopetala - Betula nana community The Dryas octopetala - Betula nana community (Table 14a&b; ref. no. 1-2; Fig. 16; Plate 13) The (this paper) together with the Dryas octopet ala com most important constants of this community are the munities described by Steind6rsson (1936, 1945 and following: Betula nana (27), Salix lanata (27), Dryas 1966) and by M0lholm Hansen (1930) which are octopetala (26), Arctostaphylos uva-ursi (23), Tim assigned to it, (Fig. 16) have floristic affinity to mia austriaca (22), Deschampsia flexuosa (22), Pla three different classes, 1) the Loiseleurio-V accinie tanthera hyperborea (22), Polygonum viviparum tea Eggler 1952 em. Schubert 1960 (syn. Vaccinio-

Acta Phytogeogr. Suec. 75 48 Elin Gunnlaugsd6ttir

Empetrum nigrum - Dryas octopetala - Elyna bellardi Ass. Steind6rsson 1945 Table XVI: 8; (8) the Empetrum hermafroditum - Dryas octopetala soc. Steind6rsson 1966 Table XXII: 6-10; (9) the Cal/una vulgaris - Empetrum hermafroditum - Dryas octopetala soc. Steind6rsson 1966 Table XXII: 11; and (1 0) the Salix lanata - Dryas oc topetala - Kobresia myosuroides soc. Steind6rsson 1966 Table XXVII: I 0-11. The open Dryas heath described by Me Vean (1955) from E Iceland has many species which are not found in my Dryas octopetala - Betula nana community mentioned above, e.g., Racomitrium Fig. 16. The known distribution of (1) the Racomitrio lanuginosum, Alchemilla alpina, Erigeron boreale canescentis - Gentianetum nivalis, (2) the Festuca vivipara and Veronica fr uticans whereas B. nana, Poa - Racomitrium canescens community in Iceland. Also the glauca, Tofieldia pusilla and other species are not known distribution of (3-10) the Dryas octopetala - Betula nana community (3-10, see text for explanation) found by McVean (op. cit.). and that of (11) the Kobresia myosuroides - Salix lanata In the neighbouring countries Dryas heaths have community. been described by many authors. From Greenland they have been treated by Hartz (1895 pp. 116, 182) Pieceetea Br.-Bl. apud Br.-Bl., Siss. et Vlg. 1939) Hartz & Kruuse (1911 pp. 347, 351, 370, 376, 393, through Arctostaphylos uva-ursi, Betula nana, 401, 402, 411, 416, 418 & 422) and by Seidenfaden Pyrola minor and Vaccinium uliginosum; 2) the & S0rensen (1937 p. 121); described by Seidenfaden Nardo-Callunetea Prsg. 1949 through Botrychium (1931 Tables XXV & XXVI, pp. 15, 16 & 18-21), lunaria, Calluna vulgaris and Empetrum nigrum by B0cher (1954 pp. 139 ff. & 1963 pp. 193 ff.) and s.str. and 3) the Carici - Kobresietea bellardii Ohba by Daniels (1982 Tables 16 and 17 pp. 57 ff.). From 1974 through Dryas octopetala, Kobresia Spitsbergen (Svalbard) Dryas octopetala com myosuroides and Silene acaulis (and to the alliance munities have been treated among others by Sum Thymo arctici - Kobresion bellardii Ohba 1974 merhayes & Elton ( 1923 pp. 250, 261) and described through Thymus arcticus) . The Dryas octopetala by R0nning (1965). From Norway Dryas octopetala Betula nana community has provisionally been heaths are described by e.g., Nordhagen (1936, pp. assigned to the latter class as it has strong floristic 36 ff.) and by Mork & Heiberg (1937 Table col. 21, affinities to Dryas-communities in Greenland and pp. 650, 651). From Sweden they have been treated Fennoscandia (see above) which are assigned to this by, e.g., Fries (1913 p. 89) and byTengvall (1920pp. class by, e.g., Ohba (1974) & Daniels (1982), which 379 ff.) and described by Hedberg et al. (1952) and supports this assignment. Bringer (1961a and b). From Finland by, e.g., The Dryas octopetala communities are scattered Kalliola (l932pp. 22-24 and 1939Table 16pp. 119 in the heathlands of Iceland forming small patches. ff.), from Scotland by, e.g., McVean & Ratcliffe Several of the earlier-described Dryas octopetala (1962 Table 23 pp. 47 ff.). communities are here assigned to the Dryas oc All the Dryas heath vegetation types described in topetala - Betula nana community. Their distribu other countries have ISi levels of less than 20 OJ'o tion, as shown in Fig. 16, lies in the northern part when compared to the Dryas octopetala - Betula of the country. The figures in the map refer to the nana community (this paper), and they have many following units: (3) the D. octopetala - B. nana com species that differentiate from the D. octopetala - B. munity (this paper), (4) the Mo vegetation M0lholm nana community and other Icelandic Dryas oc Hansen 1930 Table 19: 4-7; (5) the Dryas - Empe topetala communities (Steind6rsson 1936, 1945, trum - Salix lanata Ass. Steind6rsson 1936 Table 1966, M0lholm Hansen 1930, McVean 1955 and VII: 9; (6) the S. lanata - Dryas octopetala Ass. Egilsson 1983). Steind6rsson 1945 Table XI: 6-7, (7) the The Fennoscandian communities and those of

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 49

Svalbard (see above) have Astragalus alpinus, Ce Table 15a. Kobresia myosuroides - Salix lanata community . traria nivalis, Salix reticu/ata, Saussurea alpina and Number of releves : 2 Synop . Vaccinium vitis-idaea and many other species, Ref. no .: 12 value which distinguish them from the Icelandic ones. The Ch. Class Kobresia myosuroides 73 2 5.0 D. integrifolia communities in Greenland have, Botrychi urn lunaria 11 2 1.0 e.g., Carex nardina, Cetraria nivalis, C. ericetosum, Comp. Ceratodon purpureus 75 6. 0 Cornicularia muricata and D. integrifolia, which Salix lanata 65 5. 5 Festuca pruinosa 54 4. 5 distinguish them from the Icelandic Dryas oc Thymus arcticus 53 4. 0 Calluna vulgaris 17 4. 0 topetala communities. Empetrum nigrum 16 2 3. 5 Agrostis vinealis 33 3. 0 The phytosociological status of the Dryas oc Stereocaulon spp. 33 3. 0 Eq uisetum variegatum 51 3. 0 topeta/a - Betula nana community is uncertain, but Tofieldia pusilla 13 2.0 Parnassia palustris 11 1.0 it has been assigned to the class Carici-Kobresietea Trisetum pilosiglume 11 1.0 Ohba for floristic reasons. Achi Ilea mi llefolium 11 1.0 1974 Cornicularia aculeata 3. 1. 5 Faithful species of the class Carici - Kobresietea Lychnis alpina 1. 0. 5 Draba incana 1. 0. 5 bellardii Ohba are for example: Vaccinium uliginosum 1. 0. 5 1974 Arctostaphylos uva-ursi 1. 0.5 Minuartia rubella 1. 0. 5 Astragalus alpinus Gentiana nivalis Anthelia · juratz kana . 5 2. 5 Carex glacialis Gentianella tenella Cetraria deli sei . 3 1.5 Juncus trifidus . 1 0. 5 5 C. rupestris Kobresia myosuroides Platanthera hyperborea . 1 0. Betula pubescens . 1 0. 5 Dryas octopetala s.l. Potentilla crantzii B. nana . 1 0. 5 Erigeron unifl orus Silene acaulis 22 2 Total number of taxa : 00 7 The class is found on poor, dry mineral soil with No . of cryptogam taxa : 24 4 high pH in arctic and alpine areas (Daniels 1982). None of the character species of the order Table 15b. Site and vegetation characters of the Kobresia myosuroides - Salix lanata community . Bare Kobresio-Dryadetalia Ohba 1974 are found in the ground (B), litter (L), field layer (F), bottom layer (M). See also legend in Table 8b for cover. Icelandic communities named above. The order Ref. Date of Alt. Slope Plot % Cover Thymo - Kobresietalia Ohba 1974, which has its no . obs. m Aspect deg. sqm B L F M main distribution in Iceland and Scotland (op. cit.) 23.7.1981 24 10 8 51 69 30 27.7. 1981 24 10 23 15 69 14 (not found in Greenland, cf. Daniels 1982) has only two species that differentiate it from the other orders of the Carici-Kobresietea, viz. Thymus arc ticus and Gentianella amarella. T. arcticus is physiognomically dominating and Kobresia myosu represented in Icelandic Dryas octopetala heath roides is a subdominating species. Litter covers vegetation, but G. amarella is not. G. amarella 33 % and bare ground is ea. 14 OJo . The moss layer grows on slightly moister and somewhat nutrient covers 23 % and the dominating species is Cerato richer, more fine-grainy soils in Iceland than T. arc don purpureus. ticus. The most important constants of the community In contrast, the following constants of Icelandic are: Ceratodon purpureus (26), Salix lanata (26), Dryas octopetala heath vegetation types might be Kobresia myosuroides (25), Festuca pruinosa (25), character or differential species towards the other Thymus arcticus (24), Calluna vulgaris (24), orders or alliances of the class Carici - Kobresietea Empetrum nigrum (24), Agrostis vinealis (23), bellardii Ohba 1974, viz. Armeria maritima, Stereocaulon spp. (23) and Tojieldia pusilla (22). Galium normanii, Poa glauca and T. arcticus (cf. Most species belong to the hemicryptophyte and Steind6rsson 1936, 1945, 1966, M0lholm Hansen the chamaephyte life-form groups (Fig. 17). Euro 1930, McVean 1955 and Egilsson 1983). pean species are more common than Arctic ones (Table 16) probably due to snow shelter in winter. The community is found on level ground on the (8) Kobresia myosuroides - Salix lanata community banks of the glacial river J okulsa i Axarfir3i in the (Table 15a & b; ref. no. 1-2; Fig. 16; Plate 14). In Assandur area, at altitudes of 24 m. The community the field layer, which covers 77 OJo , Salix lanata is is a stage of secondary succession, which is found

Acta Phytogeogr. Suec. 75 50 Ef{n Gunnlaugsd6ttir in places where fine grainy fluvio-glacial deposits 5.5 Comparison with other vegeta have accumulated in the surroundings of river bran tion types ches. The soil is composed of several dm thick sandy, The eight vegetation types described in this paper fluvio-glacial deposits on a shingle bank. The have been compared with related communities de nutrient status is low judged by the species composi scribed with tables in literature. For each of the eight tion. No chemical analyses are available. types one or more qualitative similarity values (IS1) were calculated using synoptic tables of com munities in literature with similar composition ac cording to a visual inspection. If the IS1 value ob Remarks tained was lower than 20 OJo the two communities The syntaxonomic status of the Kobresia were not considered as belonging to the same myosuroides - Salix lanata community is uncertain. association. Because of low floristic affinities It has floristic affinities to (1) the Loiseleurio-Vacci these communities have many differentiating nietea Eggler 1952 em. Schubert 1960 through the species. Community pairs with IS1 higher than presence of Arctostaphylos uva-ursi, Betula nana 20 OJo were examined for mutual differential and Vaccinium uliginosum, (2) to the Nardo-Callu species, i.e., having a high constancy in either of the netea Prsg. 1949 through the presence of communities. When such species groups were found Botrychium lunaria, Cal/una vulgaris and the communities were considered to belong to dif Empetrum nigrum s.str. and (3) to the Carici ferent associations. The foreign communities rupestris - Kobresietea bellardii Ohba 1974 through usually deviate widely floristically from the Icelan Kobresia myosuroides (and to the alliance Thymo dic ones and IS1 values are generally below 20 % arctici - Kobresion bellardii Ohba 1974 through the and only in very few cases slightly above. These presence of Thymus arcticus). communities are easily distinguished from the The Kobresia myosuroides - Salix lanata com Icelandic ones by character and differential species. munity has therefore weak affinity to all of those The comparison by use of IS1 values between the classes. Due to strong floristic affinities to the vegetation types described in this paper and the Dryas octopetal a- Betula nana community it is pro Icelandic communities described in literature with visionally assigned to the same class as that com Raunkirer's circling method (sociations based on munity, namely the Carici - Kobresietea. frequency analyses often without considering the

Table 16. The percentage distribution of the taxa of vegetation types described in this paper upon different speCies groups (sensu M�lholm Hansen 1930) .

S�ecies grou�s Vegetation types n A3 A2 Al E4 E3 E2 El A E

Armerio-Silenetllm 49 24. 5 22.4 10.2 18.4 16. 3 6. 1 2. 0 57. 1 42. 9

Racomitrio-Thalictretum 55 23.6 20.0 9. 1 20.0 14.5 10.9 1.8 52.7 47. 2

�. nigrum - �. lanuginosum comm,34 14. 7 17.6 17.6 23. 5 11.8 11.8 2.9 50. 0 50. 0

Agrostio-Hylocomietum 54 16.7 9.3 9.3 22.2 18.5 18. 5 5.6 35.2 64. 8 Heath/and communities in Iceland 51 cryptogams) is difficult to carry out and even when 1972. This suballiance is characterized by Car the IS1 values are high (40-55 OJo ) the interpreta daminopsis petraea and the dominance of tion if they belong to the same association or not re Racomitrium lanuginosum. In my opinion, the mains uncertain. This is particularly the case as they choice is not appropriate as the real dominance of lack cryptogams and especially as the vegetation R. lanuginosum would exclude Cardaminopsis types are rich in cryptogam species. It cannot be petraea. reliably settled whether the sociations are part of the Indeed, the open sward vegetation and the associations judging only by the presence of Racomitrium lanuginosum heaths have several vascular plants. In cases of relatively low IS1 values species in common, which may allow us to put them (20-40 %) and if the cryptogams are also treated, together into one higher syntaxon (order), e.g., the vegetation types being compared usually have Armeria maritima, Cerastium alpinum, Silene groups of differentiating species and are then if acaulis, and also Salix herbacea, Trisetum possible assigned to the association involved in the sp icatum s.l., Luzula sp icata, Poa alpini, Polygo comparison but as its subassociation. Several socia num viviparum. tions being described in literature have been The Armerio - Silenetum acaulis Hadac 1972 has assigned provisionally to certain associations, (cf. some floristic affinity to the acid grass heath alliance remarks above). Juncion trifidi (Krajina 1933) em. Nordhagen 1943 (cf. Braun-Blanquet 1949 p. 26), e.g., through the presence of Lychnis alpina, Juncus trijidus, Cor Syntaxonomical comparison nicularia aculeata and Luzula sp icata. It has weak In many cases species which together characterize floristic affinities to the suballiance Armerio - Jun an Icelandic plant community type are known as cion trifidi Hadac 1972 through the presence of Car characterizing species of different syntaxa (alliances daminopsis petraea and Armeria maritima. It also and higher units) in the neighbouring countries. has relatively strong floristic affinities to the Therefore it is difficult to classify the Icelandic alliance Sedo - Thymion drucei de Molenaar 1976 vegetation into a non-Icelandic system. through the presence of Cerastium alpinum, This might be explained by the special environ Ceratodon purpureus, Luzula sp icata and Thymus mental conditions in Iceland. The bedrock is differ arcticus (syn. T. drucel) and it has floristic affinities ent (mostly basalt, a basic rock) and the climate is to the order Sedo - Poietalia glaucae de Molenaar more oceanic with lower effective temperatures for 1976 and to the class Koelerio-Corynephoretea (see growth (cf. 1.4). (Corresponding values are not the description of the association) due to relatively available for Greenland, but they are probably still strong floristic affinities. Therefore, it is assigned to lower than the Icelandic ones.) Alternating freezing the latter syntaxa (cf. 5.1). Besides, it will hardly be and thawing are common. Frost-weathering pro assigned to an alliance with acid soils as the Icelan ducts and wind-erosion products are continuously dic soils usually are just slightly acid to neutral. being deposited in the vegetation, a procedure The associations and communities namely the which prevents the pH from droppning, as also does Racomitrio - Thalictretum alpini, the Empetrum the basic tephra from time to time in various places. nigrum - R. lanuginosum community, the Agrostio Another reason is that the soils are oligotrophic, the - Hylocomietum splendentis, the F. vivipara - R. oligotrophy depending basically on low canescens community and the Racomitrio temperatures which cause slow chemical weathering canescentis - Gentianetum nivalis can all be assigned of the rocks. The overgrazing for many years is not to the class Koelerio-Corynephoretea and its order a negligible factor in the oligotrophy of the soils. Sedo-Poietalia by means of the same species groups Hadac (1972) assigned the Armerio - Silenetum (cf. the remarks on the Racomitrio - Thalictretum acaulis Hadac 1972 from SW Iceland, (now with alpini above). But they can also be assigned to the status as racomitrietosum lanuginosi of the Armerio alliance Equiseto - Galion borealis Tx. 1969, an - Silenetum acaulis em.), to the alliance J unci on alliance which the author assigned to the trifidi Krajina 1933 and established at the same time Molinietalia by means of the character and differen a new suballiance Armerio - Juncion trifidi Hadac tial species group of this special alliance. The

Acta Phytogeogr. Suec. 75 52 El(n Gunnlaugsd6ttir

associations and communities, which are provision oJo1 2 ally assigned to the Equiseto - Galion borealis, viz. the Agrostio - Hylocomietum splendentis, the F. vivipara - R. canescens community and the Racomitrio canescentis - Gentianetum nivalis have very weak floristic affinities to the higher syntaxa of the alliance, probably because of more nutrient 4 poor soil of the above-mentioned associations and community. The communities described by Tiixen ( 1969) have greater floristic affinities to the Molinio-Arrhenatheretea and the Molinietalia than the associations and communities described in this paper do. 6 The Agrostio - Hylocomietum splendentis, the

F. vivipara - R. canescens community and the Racomitrio - Gentianetum nivalis have been as signed to the same alliance, as they formed one group in the multivariate methods (T ABORD cf. Table 5a and ORDINA(PCA) diagram, Fig. as 11) 8 well as due to their physiognomic characters. The species group characterizing the Equiseto - Galion borealis might be more appropriate when characterizing higher Icelandic syntaxa, e.g., order or class, but this will not be settled until much more G H extensive researches of Icelandic vegetation have Th G H Ch B L Th Ch B L been completed using the Braun-Blanquet ap Fig. 17. Life-form spectra of vegetation types. proach. Both the description of the Equiseto - Therophytes (Th), geophytes (G), hemicryptophytes (H), chamaephytes (Ch), bryophytes (B) and lichens (L). (1) Galion borealis Tx. 1969 and the Racomitrio - The Armerio - Silenetum acaulis, (2) the Racomitrio - Thalictrion alpini (this paper) might be inap Thalictretum alpini, (3) the Empetrum nigrum - Ra propriate and not hold after continued phyto comitrium lanuginosum community, (4) the Racomitrio sociological studies in Iceland, as they are based canescentis - Gentianetum nivalis, (5) the Festuca vivipara upon a restricted number of analyses from small - Racomitrium canescens community, (6) the Agrostio capillaris - Hylocomietum splendentis, (7) the Dryas oc areas. There might still be undescribed vegetation topetala - Betula nana community and (8) the Kobresia types which may change the picture. myosuroides - Sa fix lanata community.

Life-form spectra and species groups but in the dwarf shrub heath they and the chamae The life-form spectra (Fig. 17) show that thero phytes are of equal importance. Chamaephytes are phytes are of little importance in the associations relatively numerous in the open sward association and communities, but are of somewhat greater im the Armerio - Silenetum acaulis em. and in the portance in the erosion-damaged (the F. vivipara Kobresia myosuroides - Salix lanata community. R. canescens community) or the secondary succes Cryptogams and especially byrophytes are promi sion communities (the Racomitrio - Gentianetum nent in the heathland communities of S Iceland (the nivalis) in S Iceland than in the other communities. Racomitrio - Thalictretum alpini, the Empetrum Geophytes are somewhat more numerous than nigrum - R. lanuginosum community, the Raco therophytes and are proportionally most abundant mitrio - Gentianetum nivalis and the F. vivipara - R. in the dwarf shrub heath (the Dryas octopetala - B. canescens community), but the lichens are relatively nana community). Of the vascular plants, the more numerous in the open sward association, the hemicryptophytes play the major role in most cases, Armerio - Silenetum acaulis em. The somewhat

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 53 drier climate in the northern part of Iceland, as well numerous of the life-forms in the Racomitrio as the drying-out effect of winds and greater fluc lanuginosi - Thalictretum alpini, probably due to tuations in temperatures in the vegetation-poor moister and milder climate. communities, favourize the lichens, whereas the The Agrostio capillaris - Hylocomietum splen precipitation-rich climate in the south favourizes dentis has a larger number of European species than the bryophytes there. Arctic ones, in contrast to the most related com Arctic species are more numerous in the wind ex munities described by Steind6rsson 1936 Table XI: posed communities (the Armerio - Silenetum acaulis 1-7, 1945 Table IX: 1-3, 1964a Table VII: 1, 2 em., the Racomitrio lanuginosi - Thalictretum alpi and Table X: 1-6 (see 5.3). The latter three are ni, the Festuca vivipara - Racomitrium canescens highland communities and the former is a lowland community) and European species in the fertilized community from NE Iceland, all from more severe communities in S Iceland (the Agrostio - Hyloco climatic conditions than the Agrostio capillaris - mietum splendentis, the Racomitrio canescentis - Hylocomietum splendentis from S Iceland. Most Gentianetum nivalis) and in the Kobresia myo species are hemicryptophytes due to the moist suroides - Salix lanata community from N Iceland climate. The same applies to the Racomitrio (Table 16). canescentis - Gentianetum nivalis, which also has The Armerio - Silenetum acaulis em. described in more European than Arctic species. this paper has a larger number of Arctic species than The strongly wind-exposed Festuca vivipara - European ones like the most related vegetation de Racomitrium canescens community has more Arc scribed in literature (Steind6rsson 1967 Table tic than European species and the hemicryptophyte XXXVII: 1-3, M0lholm Hansen 1930 Table 10: life-form is the most important one due to the moist 1-7 and Table 19: 1-3 (see 5.1)). The most com climate. mon life-forms are sometimes chamaephytes and The Dryas octopetala - Betula nana community sometimes hemicryptophytes. The life-form spec has more Arctic species than European ones and the trum of the Armerio - Silenetum acaulis em. is simi chamaephytes and the hemicryptophytes are of lar to that of the gravel flat vegetation given in Table equal importance, due to cool and relatively dry 38 by M0lholm Hansen (1930). climate. The life-form spectrum is similar to that of The Racomitrio lanuginosi - Thalictretum alpini gravel flats according to M0lholm Hansen (1930 has a larger number of Arctic than European Table 38), probably due to strong exposure to wind. species, as well as in its most related communities The Kobresia myosuroides - Salix lanata com described by Steind6rsson 1936 Table VIII and 1966 munity has more European species than Arctic ones Table XXIX: 2-4 (see 5.2). In contrast to these and the hemicryptophytes form the largest life-form Racomitrium heaths (where the chamaephytes are group, probably due to moist conditions on the river most numerous) the hemicryptophytes are the most bank.

Acta Phytogeogr. Suec. 75 6 Soil factors and vegetation

these analyses, but it is a component of the mineral 6.1 Introduction fertilizer used in most of the areas and undoubtedly The values for pH, contents of available affects the grass growth temporarily, e.g., in the phosphorus and exchangeable potassium in the soil Agrostio capillaris - Hylocomietum splendentis and obtained in the present investigation correspond to in other communities. other analyses from similar kinds of Icelandic soils. Various solvents have been used in the analyses M0lholm Hansen (1930) reported pH values of of potassium contents of the soils, e.g., neutral am 6.1-6. 8 in soils of heaths and gravelly flats and monium acetate (J6hannesson 1960); 1 m sodium J6nsd6ttir Svane (1964) got pH of 5.3-6.6 in acetate (Helgason & Guobergsson 1977, Gunn Racomitrium heaths near I>ingvellir, S Iceland. The laugsd6ttir 1982a) and acetic acid in the soils of the pH of silt-loamy soils and soils of the Betula uneroded heathland near Gunnarsholt farm. As the pubescens woodland at Hallormsstaoaskogur, NE values lie within the same range in every type of soil Iceland, are 5.4-6.6 (J6hannesson 1960, Helgason whatever the used solvent has been, the results have & Guobergsson 1977). The top-soil of eroded land been regarded as comparable. had pH of 6. 1-7.0 (J6hannesson 1960). In soils of the uneroded heathland communities near Gunn arsholt farm pH values were 5.3-6.4 and in soils 6.2 Statistical comparison of vari of the deflated heathland vegetation 6.3-7.6 (this ous phytosociological units paper). The phosphorus contents in the silt-loamy soils of the Hallormsstaoaskogur woodland were A comparison of the contents of potassium and 0.83-2.76 mg P/100 g dry soil (Helgason 1965 , phosphorus and the soil pH values of different Helgason & Guobergsson 1977) which is not high vegetation units is made by two sample t-tests. The enough to support good grass growth (Helgason results are given below. Several significant dif 1965). The soils of the uneroded heathland com ferences have been found, which in some cases could munities described in this paper had 0-1.0 mg explain the presence and dominance of certain P/100 g dry soil and the deflated ones 0-0.34 mg. species. As regards exchangeable potassium, the contents in silt-loamy soils was 0.47-2.7 meq K+ /100 g dry Comparison between the lower units of Racomitrio soil (Johannesson 1960) and in the soils of the lanuginosi - Thalictretum alpini Hallormsstaoaskogur woodland 0.3-1.4 meq (Helgason & Guobergsson 1977). The highest values No significant differences were found between the (1.4 meq) are obtained in rather good grass fields in pH values of the lower units (Table 17). Iceland (op. cit.). The contents of potassium in the Significantly more P was found in the subassocia uneroded heathland soils near Gunnarsholt farm tion galietosum normanii ( 1) than in the inops were 0.37-0.81 meq K+ /100 g dry soil or some subassociation (2) (Table 17) as well as it being what lower. In eroded soils the contents of higher in the Cerastium alpinum form (le) of the potassium were 0. 11-0.45 meq (J6hannesson subassociation galietosum normanii (2). The low 1960). The same range was recorded in the deflated phosphon:�s contents can be related to the occur soils of the investigated areas described in this paper rences of the inops on deflated hill-tops. (0. 11-0.45 meq K+/10 0 g dry soil). Significantly more K + was found in the typical The nitrogen content has not been considered in form (la) of the galietosum normanii subassocia-

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 55

Table 17. Significant differences between soil tion than in its Cerastium alpinum form (le). More factors of the lower units of the Racomitrio lanuginosi - Thalictretum alpini. ( 1) the typical K was found in the Peltigera leucophlebia form subass. ; (la) the typical fo rm of the typical sub + subass. ; (lb) the Peltigera leucoph lebia form ; (le) (1 b) than in the inops subassociation (2). This can the Cerastium �form; and ( 2) the inops . be related to the occurrence of the Cerastium No . of sub- alpinum form on uneroded hill tops with shallow unit. Mean Var . la lb le pH 6. 03 1.128 soils and the occurrence of the inops on deflated hill 1 K + .50 0. 31 5 tops. ___ !'.'- ----"'��-! "'��z------_ !'.'�.?.J; _ pH 6. 06 0. 168 la K+ . 51 0. 105 P<2% ___!'_' _____ !.�!_Q!.!i��------Comparison between the lower units of the Agrostio pH 5. 99 0. 718 1 b K+ . 53 0. 1 37 P<5% capillaris - Hylocomietum splendentis ---!'.'_---- "'�LQ"'� �------pH 6. 13 0. 168 + There are no significant differences between the le K . 39 0. 0006 ___ !'.'_ ___-"'�.!I_Q "'Q QZ� ______!'.'�l !>_ mean values of pH in the soils of the lower units of p H 6.20 0.019 2 K + . 37 0 the Agrostio capillaris - Hylocomietum splendentis . 15 0. 0049 p (Table 18). Significantly more P is found in the inops

Table 18. Signi ficant differences between soil factors subassociation (1) than in the Thymus arcticus of the lower units of the Agrostio capillaris - Hylo comietum splendentis. ( 1) the inopsis subassociation ; variant (2b) of the racomitrietosum canescentis ( 2) the racomitrietosum canescentis; ( 2a) the typical variant of the racomi tdetosum canescentis; ( laa) the subassociation and more P is found in the typical form imd (lab) the Drepanoc iadus uncinatus Drepanocladus uncinatus form (2ab) of the typical fo rm; (lb) the Thymus arcticus variant of� racomitrietosum canescentis. variant of the racomitrietosum subassociation than No . of in the Thymus arcticus variant (2b). subunit. Mean Var. 2a 2aa 2ab 2b Significantly more K + is found in the inops pH 5. 90 1. 124 K+ . 76 0. 005 P<5% subassociation (1) than in the Drepanocladus un p . 55 0. 134 P<5% cinatus form (2ab) and more in the Thymus arcticus pH 5.89 0. 154 variant (2b) than in the Drepanocladus uncinatus K + • 62 0. 060 p . 41 0. 448 form. The higher amount of phosphorus and pH 5.94 0.062 potassium are clearly caused by fertilization in the 2a K+ .56 0.017 p .55 0.075 area. pH. 5. 97 0.047 2aa K + .56 0.009 p .47 0.027 Comparison between associations and communities pH 5.9 2 0.012 2ab K+ . 56 0. 009 P<2% of the Equiseto - Galion borealis p .63 0.007 P

Table 19. Significant differences between the Racomitrio - Gentianetum nivalis. soil factors of the associations and community of the Equiseto - Galion borealis. ( 1) the Significantly more P and K + is found in the Agrostio - Hylocomietum splendentis; ( 2) the Racomitrio canescentis - Gentianetum nivalis; Agrostio - Hylocomietum splendentis than in the (3] the Festuca vivipa ra - Racomitrium Festuca vivipara - Racomitrium canescens com canescens community . munity and in the Racomitrio - Gentianetum No . of unit. Mean Var. nivalis. pH 5. 90 0. 278 P

Acta Phytogeogr. Suec. 75 56 Elfn Gunnlaugsd6ttir

20. F. vivipara - R. canescens community in eroded sites Table Significant differences between the alliances ( 1) the Sedo - Thymion and the occurrence of the Racomitrio canescentis - drucei; (2) the Racomitrio-Thalictrion; (3) the Equiseto - Galion borealis. Gentianetum nivalis in deflated areas. No . of unit Mean Var. 6. 95 0.61 P<0. 1% P<0. 1% pH K + .25 0. 13 P<0. 1% P<0. 1% Comparison between alliances . 18 0.19 P

Racomitrio - Thalictrion alpini in areas with Armerio-Silenetum 7.67 2.42 3. 75 4. 89 4. 5 0 3. 04 ______� ____ }o ____!� ____ �Q ____ �z___ -� � __ --�z ____�Q __ _ organogenous soil and the occurrence of the Racomitrio-Tha lictretum 7. 75 2.33 4. 00 5.40 5.03 2.47 Equiseto - Galion borealis in areas with fertilized ------�----}!i____ !�--- -��----�Q ____�!----� �----�7__ _ 7. 57 2. 00 3. 41 79 4.40 2.14 E. nigrum - R. lanuginosum comm. 4. organogenous soil. =---==---=------�----?�____ !!_ ___!? ____ !�----�Q----��----�L- Agrostio-Hylocomietum 7. 29 2.67 3. 65 5. 41 4. 93 3. 00 ------�----�?----! �----?�---- � �----� §----��----�§--- F. vivipara - R. canescens comm. 7.41 2.25 4.00 4. 60 5.30 2.52

=----=-=-=-----=----�-----�----?? ____ !§____ !� ----?�--- - �Q____ ?L __�? ___ Ecological evaluation Racc;mitrio-Gentianetum 7.65 3. 36 3. 61 5.21 4. 81 2.61 6.3 ------�----�" ----! "- - --?� ---- ��---- �§_ ---� !_ -- -�! --- 7.27 2.36 4. 26 4. 73 4.30 2.42 �· octopetala - �· � comm. ------�----?§____ }!j ____ !�----��----?Q____ ?!j____ �" --- �· myosuroides - �· lanata comm. 7.67 2.14 4.55 4. 83 3.82 1.93 The ecological indicator values given by Ellenberg 15 7 11 12 11 15 23 (1979) have been used to calculate ecological values for the vegetation units regarding light, pacity of soils is high and the drying-out effect of temperature, continentality, moisture, reaction the wind is great. The values for reaction (R) are be (pH) and nitrogen. Although many of the taxa in tween 3.82-5.30, i.e., the soils are acid to weakly volved are not or incompletely covered by acid. Taxa from various pH categories are found Ellenberg's system, reasonable calculations could growing together in the vegetation units. There is no be performed for all vegetation types treated (Table significant correlation between the R-values of the 21). vegetation units and the corresponding average pH The results based on taxa presence are the com of the soil. The values for nitrogen (N) are between munity values for light (L), which vary between 1.93-3 .04, showing that the soils are very poor to 7.27-7.67, indicating half light to full light condi poor as regards nitrogen supply. As the nitrogen tions, as can be expected in heathland vegetation. content of the soil has not been measured in this in The values for temperature (T) are 2.0-2.36, thus vestigation the Ellenberg values could not be indicating cool to cold climate. These values ought checked. However, the contents of potassium and perhaps to be still lower as many of the arctic taxa phosphorus measured are low, as discussed above; found here are not included in Ellenberg's list. The suggesting that also the nitrogen contents will be values for continentality (K) are 3.41-4.55 showing low. the suboceanic character of the species composi The variation in the Ellenberg values within this tion. The moisture values (F) are 4.60-5.41 in material is only small; no correlation between posi dicating fresh soil. The highest values are found in tion in the ordination diagram (Fig. 11) and the the mossy heathland communities of S Iceland Ellenberg values could be shown. In summary, the where the climate is more humid than in the north Ellenberg indicator values show a very generalized ern part of the country (cf. 1 .4). The lower moisture geographical and edaphic pattern agreeing with the values are found in the Dryas heath in N Iceland and overall European pattern but do not reveal any local in the open sward vegetation where the drainage ea- ecological differentiation.

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 57

a b TOTAL TAXA DENSITY CRYPTOGAM TAXA DENSITY

• • 50 • 30 • •

• . . 40 20 • • • • •• • • • • • • • • •• • • • •• • • • • • • ••• • •• •• • • • 30 10 • • •• . • •• ·" ••• : . • • • • • • • • - . .·- . • • • • • . .• • . •• 20 • • • • 5 6 7 8pH • • • - • • • • • • • • • 10 • • • •

Fig. 18. The relationship between (a) total taxa density 5 6 7 8 pH and soil pH and (b) cryptogam taxa density and soil pH.

6.4 The relation between taxa den fewer taxa are found at higher pH values. Within a sity and soil pH wider range of pH it is expected that the species den sity will increase as the soil pH increases (Rorison The relation between total taxa density (total 1970, Grime 1981). (This relationship cannot be number of taxa/analysis) and soil pH is shown in established on the basis of this investigation. The scatter diagrams in Fig. 18a and scatter diagrams of minerogeneous Icelandic soils have relatively high cryptogam taxa density and soil pH in Fig. 18b. pH and low taxa density whereas the well-vegetated The distributions of the points are not linear in soils have intermediate pH. The highest taxa densi neither of the cases and indeed the figures are simi ties may possibly be found at intermediate pH lar. The taxa are most numerous around pH 6 and levels.)

Acta Phytogeogr. Suec. 75 7 Vegetation dynamics

7.1 Introduction 1939) in his studies of the reinvasion by plants in areas of glacier retreat in Alaska. E. Einarsson The observations of the vegetation in the permanent (1970) studied plant succession on nunataks in the plots began in 1974 and 1975 respectively; the last Vatnajokull glacier, SE Iceland. Some authors have ones were carried out in 1980. The analyses were used miscellaneous multivariate methods to illus concentrated to approximately the same time of the trate the overall changes in vegetation, e.g., Austin growing season, to exclude seasonal variation. The (1977) and van der Maarel (1980). The results of the purpose of the observations was to follow the permanent plot studies in the Icelandic heathland changes in the vegetation, and especially whether communities will be elucidated here using the PCA the use of mineral fertilizer would speed up succes ordination. sion, i.e., induce a directional change towards a more complex unit. The plots were placed in fer tilized and unfertilized areas and in grazed as well 7.2 Data analysis as ungrazed areas (cf. Table 22 for managements and years of analyses). The P-data set concerning the permanent plots (180 The plots have been characterized by letters, in analyses of 43 different plots) includes altogether dicating the area to which they are located viz., 153 taxa. In 36 of these plots repeated analyses have (Figs. 1 and 2), A (Assandur), H (Hei3arspor3ur), been carried out, 2 to 6 times in each. The vegetation M (near Melakot), P (Palsteinshraun), Ho (H6ls dynamics of these 36 plots has been analysed and in sandur), Sm (Steinkrossm6ar), Sb Steinkrossbrun), terpreted below. Cover-abundance data of the taxa Bh (Brekknahei3i), Ak (near Akurh611), Ga (Gari), have been converted into a 1-9 ordinal scale (van G (near Gunnlaugssk6gur) and R v ( Rey3arvatns der Maarel 1979) for the data treatment with the hraun). TABORD and (PCA) ORDINA programs. The data consist of observations (analyses) made in a number of plots (q) at various times (t) as regards a variety of taxa (s), i.e., their performance values. The data from the vegetation analyses have 7.3 Results been treated with multivariate methods, viz., Classification TABORD and (PCA) ORDINA. The data were given in tables published earlier (cf. mainly Gunn The first analyses of the permanent plots have been laugsd6ttir 1982a; also 1979 for vascular plants, used within another larger material for 1982b for cryptogams). phytosociological classification of syntaxa as The vegetation of the sites has been classified and associations, subassociations and variants (or provisionally assigned to various higher forms) of syntaxa (see chapters 4 and 5). phytosociological syntaxa (cf. chapter 4), viz. the The plots from the open sward vegetation, given Sedo - Thymion drucei, the Carici-Kobresietea, the the letters A, H, M and P (referring to certain local Racomitrio lanuginosi - Thalictrion alpini and the ities cf. 6.1) are from the association Armerio - Equiseto - Galion borealis. Silenetum acaulis em. of the alliance Sedo - Thy Several authors have described vegetation mion drucei; Ho-plots are from the dwarf shrub changes by using repeated analyses of the same site heath, namely the Dryas octopetala - Betula nana through time, for example Cooper (1923, 1931, community, class Carici-Kobresietea; Sb- and Sm-

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 59

Table 22. The permanent plots (characters cf. the text) and the year of observation. Managements: (G) grazed , [UG) ungrazed , [5) Danish grass seed sown, [F) fertilized, [UF) unfertilized .

Plot Year of observation Managements Sm '74, '76- '80 G UF Sm 2 '75- '80 G F '75 (NP) Sb '75, '77- '80 G UF Ho '74, '77, '78 G UF Ho '74, '77, '78 UG UF A '74, '76-'80 UG UF A '74, '76- '80 UG S & F 'GO (NPK), F '77 (NPKS) A ' 74, ' 76-' 80 UG F '77 {NPKS), '78 (NPKS), F '79 (NPKS) A '74, '7G-'80 UG S & F '73 (NPK) A '74, '76- ' 80 UG S & F '71 (NPK), F '73 (NP K), F '78 (NPKS) A la '78- '80 UG F '77 (NPKS) A 2a '78- '80 UG S & F '60 (NPK), F '76 (NPKS)

A 2b '78- '80 UG S & F 'GO (NPK) A 3a '78- '80 UG UF G H '74, '7 -'80 G UF H '74, '7G-'80 G UF H 1 74, '76-'80 UG F '73 (NPK), F '78 (NPKS) H '74, '76- '80 UG F '71 (NPK), F '78 (NPKS ) H '74, '7G- '80 UG S & F '71 (NP K), F '78 (NPKS) H '79, '80 G UF H '79, '80 UG F '73 (NPK) H '79, '80 UG F '73 (NPK), F ' 78 (NPKS)

p '74, '78 G F '78 (NPK) M '75-'80 UG F '74 ( NP) , '78 (NPK)

M '75-'80 UG F '75 (NP) , F '77 (NPK l M '75- '80 UG F '74 (NP) M '75- '80 G F '77 (NPK) M '75-'80 G F '74 (NP) Ak '74, '78- ' 80 UG F now and then (since 19G3 ?), { NP, NPK l Ga '74, '77, '79, '80 G F now and then since 1959, fNP, NPK) Bh '74, '77- '80 G F now and then (since 1959?), ( NP, N PK ) Rv '74, '77 , '79,'80 G F now and then since 1963 , F 1986 ( NPK) G '75- '80 G F June 1980 (NPK) G '75-'80 G F '73 & '74 (NP) G '75- '80 UG F June 1980 (NPK) G 175- '80 G F '73 & '74 (NP)

Fig. 19. PCA-ordination diagram dimensions 1 and 2 of the P-data set. The percentage of extracted variance for the first four dimen sions are 26, 16, 9 and 8. See text for explanation of the encircled groups of points (I-VI).

Acta Phytogeogr. Suec. 75 60 Elln Gunnlaugsd6ttir plots belong to the Racomitrio - Thalictretum VlVlpara, and A. capillaris and frequent species are alpini (galietosum normanii), alliance Racomitrio Galium boreale, G. verum and Equisetum arvense, at least in some sites. This vegetation belongs to the Equiseto Thalictrion alpini. Bh-, Ga- and Ak-plots belong to - Galion borealis. the Agrostio - Hylocomietum splendentis, alliance Equiseto - Galion borealis. Group VI. (Rv, G) The moss layer is dominated by Racomitrium canescens and frequent species in the field layer are Festuca pruinosa, Agrostis vinealis and some Ordination times A. capillaris. Group VIa is species-poor and poor in dwarf shrubs, but group VIb is species-rich and in Fig. 19 presents the ordination diagram dimensions cludes the dwarf shrubs S. lanata, Empetrum nigrum 1 and 2 (program ORDINA) for the P-data set. Sev s.str. and in some sites also S. phylicijolia. The grass eral groups of points are discerned on the basis of species Festuca vivipara is one of the dominants in group results obtained with the TABORD program. These VIb. This vegetation belongs to the Equiseto - Galion borealis. groups are interpreted by their dominant species as well as their syntaxonomical position (alliance or class).The vegetation in groups I and 11 has been assigned to the Racomitrio - Thalictrion alpini. 7.4 Interpretation of the ordination diagrams Group I. (Sm). Hy locomium splendens dominates in the moss layer and Rhytidiadelphus squarrosus is sub Two approaches can be used in studying succession, dominating. Kobresia myosuroides, Agrostis vinealis, A. as mentioned by Austin (1977), the dynamic ap capillaris, Festuca vivipara, F. pruinosa, Galium verum proach and the static approach, both of which are and G. boreale are frequent in the field layer. utilized here. The dynamic approach is used for Group Il. (Sb) The moss layer is physiognomically vegetation in the permanent plots subject to dominating and the single dominating moss is repeated analysis with time intervals, whereas the Racomitrium lanuginosum. The most frequent species of static approach is used for approximately the field layer are Kobresia myosuroides, Carex bigelowii simultaneous analyses of different successional and Empetrum nigrum s.str. stages, such as around lakes, or for vegetation sub Group Ill. (Ho) The dwarf shrub heath is ject to different time periods of certain treatments physiognomically dominated by Dryas octopetala, Salix for revegetation. lanata and Betula nana. In the grazed area (Ho 1), also Arcotstaphylos uva-ursi, Calluna vulgaris and Empet rum nigrum s.l. are frequent and in the ungrazed one (Ho 2) Dynamic approach Safix callicarpaea and S. phylicifolia. The most common grasses are Festuca pruinosa and Deschampsia flexuosa. The ordination diagrams are useful to summarize The vegetation belongs to the Carici-Kobresietea. large amounts of data and to illustrate the temporal vegetation changes. The time-site analyses of sev Group IV. (A, H, M, P) This is an open sward vegetation eral plots are shown in Figs. 20-23 in conjunction with very low vegetation cover. Frequent species are Festuca pruinosa, Agrostis vinealis, and/or A. with trajectories showing their shifts from year to stolonife ra. Various small herbs and graminaceous year in the first two dimensions. The interpretation species have temporarily become frequent, viz., Rumex of the shifts of the permanent plots is based on acetosella, Silene acaulis, Galium normanii, Cerastium changes in cover I abundance of the taxa and the alpinum, C. jo ntanum, Lychnis alpina, Armeria species composition. The species with the highest maritima, Equisetum arvense, E. variegatum, Poa alpina, P. glauca, Luzula sp icata and the half-shrub Thymus arc performance values also have the greatest effects on ticus, but also the acrocarpous mosses Ceratodon pur the shifts but as many species are participating, it is pureus and Bryum ssp. and the lichen Peltigera sp uria. not possible to refer the shifts to changes in only a This vegetation belongs to the Sedo - Thymion drucei. few species. Such a reference is easier to carry out when the species are relatively few and there are few Group V. (Bh, Ga, Ak) The moss layer is dominated by Drepanocladus uncinatus, sometimes with Rhytidiadel dominants in the process of changing. The species phus squarrosus as codominant species. The field layer is with the greatest effect on the shifts in the plots dominated by Agrostis vinealis, Festuca pruinosa, F. (Figs. 20-23) are mentioned below.

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 61

11 11 Sm1 8 9• �4 •0 7

Sb 1('go8 5

Fig . 20. A part of the ordination diagram (in Fig. 19) Fig. 21. A part of the ordination diagram (in Fig. 19) showing the time trajectories of two of the plots with showing the time trajectories of the plots with Carici Racomitrio - Thalictretum alpini vegetation. The Kobresietea vegetation. The numbers 4 to 8 refer to the numbers 4 to 0 refer to the years 1974-1980. year 1974-1978.

Table 23. Values fo r total number (T) of species found in a plot , and A. capillaris, which were temporarily favoured mean number (m) of species per plot and "temporal" (a) diversity ca lculated per plot over the period of analyses . by mineral fertilizer, and in the cover of Kobresia No.of Vascular pl ants Cryptoga ms All taxa Plot anal. T T m T myosuroides and Hy locomium sp lendens, which Sm 24 21 .17 1.58 36 19. 50 9. 21 60 40. 67 10. 79 were disfavoured by the fertilizer. The cold weather Sm 26 28.75 2. 70 25 14. 17 6. 0 5 51 42. 92 8. 75 Sb 24 20.60 2.11 18 14.60 2. 11 42 35.20 4. 22 13 in 1979 was unfavourable for the grasses and for K. Ho 33 29. 00 3.64 4. 0 6. 9 8 46 33. 00 10. 6 2 34 29. 00 4.55 10 3. 2 4. 25 44 32. 20 80 Ho B. 11 myosuroides and Carex bigelowii. A 1 1 7 0 67 1 0 86 7.67 1.86 A 18 14.00 2.23 0. 67 1.86 22 14.67 4. 09 A 20 14.17 5.83 3.07 1.50 27 15.67 8. 90 According to the ''temporal'' alpha diversity in 17 15.17 1.02 70 4. 17 1 6 1 9 34 3. 72 A 2. 0 5 18 12.00 3.35 4.67 2. 42 27 16.67 77 dices (Table 23) the changes in species composition A s. A la 16 10. 33 5. 16 0.67 1.21 18 11.00 6. 37 A 2a 15 13.00 1.82 1. 00 1.82 18 14.00 3.6 4 are great, especially among cryptogams, which are 2 12 11.33 0. 61 0. 10 1.82 1 5 1 1 0 43 2 34 A b 0 A 3 a 15 12.33 2.43 0. 83 1.06 17 13. 16 3. 49 disfavoured by the mineral fertilization. These 1 17 14. 50 1.40 17 14.50 1.40 H 2 1 8 1 50 1 7 1 58 18 15.17 1.58 H 0 changes to some extent affect the fluctuations 3 21 19.17 1,02 3. 8 3 2. 33 29 23. 00 3. 35 H 4 18 17.17 0.47 3.67 2.42 26 20. 84 2. 89 H within the plots. H 5 17 14.00 1.67 2. 50 0. 8 4 21 16. 50 2. 5 1 17 16.5 0 0.72 17 16.50 0. 72 H 6 4. 00 1.44 24 22. 00 2. 88 H 1 9 1 8. 00 1 44 H 21 18.50 3.60 5.00 4. 33 29 23. 50 7. 93 21 19.00 2.89 1 . 50 1.44 24 20. 50 4. 33 p 24 18.33 3. 16 4.83 2.33 33 23. 16 5.49 Th e Carici - Kobresietei vegetation M 6 13 11.33 0. 93 12 3.33 4. 84 25 14.66 5.77 M 6. 1 3 1 1 50 0 84 3 1 30 1. 12 1 6 1 2 0 80 1 96 M 0 0 0 0 The dominants of the Ho-plots (Group Ill) have 6 12 8.33 2. 05 0.83 0.09 13 9. 16 2. 14 M 6 12 10.67 0.74 2.67 1.30 17 13.34 2.04 M undergone the following changes in cover/abund Ak 17 15.00 1. 44 5.5 0 1.08 24 20 .50 2. 5 2 28 22.50 3. 97 27 17.25 7.03 55 39. 75 50 Ga s. ance during the years (cf. Gunnlaugsd6ttir 1979 Bh 23 19.00 2. 89 14 9.00 3. 61 37 28. 00 6. 50 Rv 25 21 .75 2.34 28 13.75 10.28 53 35.50 12.62 Table Ilia, 1982b Table Xla) . 36 33. 00 1.67 36 23. 83 7. 35 72 56. 83 9. 02 G 36 21 . 7 3. 1 35 2 4 0 83 50 1 2 71 46.00 8. 93 G 1 B 33 27. 67 2. 98 45 25. 10. 8 8 7 8 53. 1 7 1 3 86 The fluctuations in the plots of the class Carici G so 0 35 23. 50 6. 42 21 10.17 5. 67 56 33. 67 12.09 G Kobresietea (Fig. 21) are mainly due to flucutations in the cover of dwarf shrubs B. nana, D. octopetala, Salix lanata, S. callicarpaea, Thymus arcticus and Th e Racomitrio - Th alictrion alpini vegetation the grass species Deschampsia flexuosa. The dominants in the Sm- and Sb-plots (Groups I According to the "temporal" alpha diversity in and 11) have undergone the following changes in dices (Table 23), the changes in species composition cover/abundance over the years (cf. Gunnlaugsd6t are rather far-reaching, which also affects the fluc tir 1 982a Table Xla and Table XII a, 1982b Table V a tuations within the plots. and Table Xa). The fluctuations in the plots of the Racomitrio - Thalictrion alpini alliance (Fig. 20) are mainly Th e Sedo - Thymion drucei vegetation caused by changes in the cover I abundance of the The dominants of the A-, H-, M- and P-plots grasses, namely A. vinealis, F. pruinosa, F. vivipara (Group IV) have undergone the following changes

Acta Phytogeogr. Suec. 75 62 Elfn Gunnlaugsd6ttir in cover/abundance during the years of observa time, the total changes are relatively small and we tions (cf. Gunnlaugsd6ttir 1979 Table VII a: 3; 1982a must thus interpret them as fluctuations. Evidence Tables Ila, Ilia, Va; 1982b with cryptogams in for multidirectional succession was also given by Tables la, Ila, IVa, XIVa). van der Maarel et al. (1984). Such fluctuations are The fluctuations in the plots of the Sedo - Thy often induced by fertilizations with mineral fer mion drucei (Fig. 22) are mainly caused by fluctua tilizer or by unfavourable weather conditions (in tions in cover of F. pruinosa, Agrostis spp. (A . 1979). However, the multidirectional character of vinealis, A. stolonijera and A. capillaris) , also of the changes does not preclude succession, as was Poa a/pina, P. g/auca, F. rubra, Rumex acetosel/a, shown by van der Maarel et al. (1984) . Thymus arcticus or more rarely of Lychnis alpina, Cerastium alpinum, C. fo ntanum, Galium nor Static approach manii and E. arvense, all these species being tem porarily favoured by mineral fertilizer. The fluctua To obtain an idea about possible long-term succes tions are also caused by the establishment and high sions in the heathland communities, the static ap degree of cover of Ceratodon purpureus, Peltigera proach was used: Plots of the same year or of a sp uria and Bryum spp., all favoured by the mineral limited number of years but in different areas of fertilizer. The plots rich in C. purpureus are marked development have been compared. with stars in Fig. 22. Erosion of the vegetation, e.g., the Racomitrio - According to the ''temporal'' alpha diversity in Thalictretum alpini (1 and 2 in Fig. 24) may lead to dices (Table 23) the changes in species composition an open sward vegetation of the Sedo - Thymion are minor and do not greatly affect the fluctuations drucei ( 4 in Fig. 24). in the plots. The fertilizations of, e.g., the Racomitrio - Tha lictretum alpini (1) may lead to a Drepanoc/adus Th e Equiseto - Galion borealis vegetation uncinatus-rich form of the Agrostio capillaris - Hy The dominants of the Ak-, Ga- and Bh-plots (Group locomietum splendentis (5) (Fig. 25). V) have undergone the following changes. in Successions may lead from the open sward cover/abundance during the years of observation vegetation of the Sedo - Thymion drucei (4) to the (cf. Gunnlaugsd6ttir 1982a Tables VIa, IXa, and Agrostio - Hylocomietum splendentis (5) of the Xa; 1982b Tables VIa, IXa and VIlla). alliance Equiseto - Galion borealis by mineral fer The fluctuations in the plots of the Equiseto - tilizations now and then over a period of ea. 20 years Galion borealis (Fig. 23), are chiefly caused by (Fig. 25) or to the Racomitrio canescentis - Gen changes in cover of F. pruinosa, A. vinealis, F. tianetum nivalis (5) by fertilizations now and then vivipara and also of E. arvense, Galium verum and in grazed areas for 20 years (6a) or by keeping these G. boreale (all of which may be favoured tem areas ungrazed for 50 years (6b) (Fig. 25). The latter porarily by the mineral fertilizer), and in the cover areas have been kept partly ungrazed for all these of Racomitrium canescens, Drepanoc/adus un years, partly grazed for the last 20 years and partly cinatus, Rhytidiade/phus squarrosus and fertilized in the two last years before the analyses Brachythecium albicans. The grasses and herbs be were made. Despite this, the vegetation of the plots came disfavoured by the cold weather in 1979. is relatively similar and forms cluster together. According to the "temporal" alpha diversity in dices (Table 23) the changes in species composition are large among cryptogams in several of the plots, 7.5 Species behaviour which will also influence the· fluctuations of the plots. The grasses, especially Agrostis vinealis, F. pruinosa and F. vivipara, show a big response to the Discussion fertilizations and increase in growth. The same reac As the dynamic approach shows, the shifts of the tion is seen in A. capillaris and A. stolonijera. permanent plots over the years are in various direc Miscellaneous investigations and experiments show tions, i.e., they are not unidirectional. At the same that various grass species are favoured by the NPK

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 63

11 11 11 H1 9 11 H6 0 MS A2a 1 ---+------�- 5 6,7,8,0 5 9�0 --.� 4 H 9 A3 7 8�7 � 8 7 4 4 0 9 6� I 8 9 0 9

11 A2 11 11 M2 8 9 11 A1a 5 4,7>1o 9 I I �� 1 � 6 6-0-.4 H2 s.:?!;,o + 8 AS A ..-::!o4 :_Jt � 4 7 8 9 6,7 8 9 H3 9

Fig. 22. A part of the ordination diagram (in Fig. 19) showing the time trajectories of several of the plots with Sedo - Thymion drucei vegetation. The numbers 4 to 0 refer to the years 1974-1980.

G2 � �& :�& G1 !�5'l_ 7 9 5 08

11 . 1--+ ------Ak 8 9 9�� 4 ·�, 7 0

9�8 G4 5 �� 16,0 '!( G3 5,7

Fig. 23. A part of the ordination diagram (in Fig . 19) showing the time trajectories of the plots with Equiseto - Galion borealis vegetation. The numbers 4 to 0 refer to the years 1974-1980.

Acta Phytogeogr. Suec. 75 64 Elfn Gunnlaugsd6ttir

Fig. 24. A part of the ordination diagram (in Fig . 19) indicating that the wind erosion and soil deflation of the communities of (1, 2) the Racomitrio - Thalictrion alpini leads to communities of (4) the Sedo - Thymion drucei.

� / .s , ...,� �--?..... , • 5 Fig. 25. A part of the ordination diagram (in Fig. 19) showing the suggested succession of (4) the open sward communities of the Sedo - Thymion drucei to (5, 6) • 6 various communities of the Equiseto - Galion borealis and the development of (1) community of ...... the Racomitrio - Thalictrion --...... __ 6 alpini to (5) community belonging to the Equiseto - Galion borealis through fertilization.

fertilization (see e.g., Liidi 1936, Bradshaw et al . Cerastiumfontanum are also temporarily favoured. 1960, Willis 1963, Jones 1967 in Harper 1970, Jef The alien grasses sown here, Poa pratensis and F. frey 1970, Jeffrey &Pigott 1973, Rosen 1980, 1982). rubra s.str, also declined as time elapsed. Some The creeping half-shrub Thymus arcticus declined small herbs at Braunton Burrows, not the same as after fertilization in sites, where the grass growth here, were also temporarily favoured by mineral had become dense. The same reaction of T. arcticus nutrients (Willis 1963), but they were eliminated or (syn. T. drucel) at Braunton Burrows was observed reduced in importance by the dense growth of by Willis (1963). But in more open vegetation the T. grasses. arcticus increased after fertilization and declined The grasses Poa alpina and Trisetum pilosiglume later on in the same way as the grasses. together with Luzula sp icata and the small herb The arctic-alpine species Poa glauca, Cerastium Galium normanii increased first in cover after the alpinum, Lychnis alpina, Armeria maritima, decrease of intense grass growth. Among the species Arenaria norvegica, Cardaminopsis petraea and which characterize an eutrophic status (Dahl 1959) Draba incana increased one year after fertilization are Trisetum sp icatum, Luzula sp icata, Poa alpina (NPK) but decreased later on. Rumex acetosella and and Cerastium alpinum; all of them reacted

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 65 positively to the fertilizations of the Icelandic plots of the deflated areas, i.e., Assandur, deflated heathland. Hei3arspon)ur near Melakot and in the Palsteins There are some herbs that decreased almost im hraun lava-field near Steinkrossm6ar (Table 21). mediately after fertilization, for example Silene The value is somewhat higher in the fertilized plots acaulis, but which recovered again to some extent. of these areas, depending both on higher diversity The same tendency was found in Galium verum and or dynamics of the vascular plant species and the Polygonum viviparum. The biennials Gentiana establishment of the cryptogams in the fertilized nivalis, Gentianella amarella and Euphrasia fr igida sites. diminished after fertilization because of the dense In areas where the restoration of the vegetation grass growth (Gunnlaugsd6ttir 1982a). These small has developed more, i.e., in the Vesturhraun lava herbs are weak competitors. field near Gunnlaugssk6gur, in the Rey3arvatns Kobresia myosuroides became nearly eliminated hraun, in the Gari area and in the area near because of fertilizations (NP). The same reaction to Akurh6ll, the a values are high, with the exception mineral nutrients was shown by the related species of the plot near Akurh6ll, which is ungrazed. These K. simpliciuscula in Upper Teesdale (Jeffrey 1970, high values depend mainly on changes in the cryp Jeffrey & Pigott 1973). togam flora. High values are also found in the plots The acrocarpous mosses Ceratodon purpureus of the uneroded heathlands at Steinkrossm6ar and and Bryum spp., and the lichen Peltigera sp uria be H6lssandur, which is due to the larger number of came established shortly after the fertilization, but cryptogams. In the ungrazed plot at H6lssandur the declined later. Racomitrium canescens decreased ''temporal'' alpha value based on vascular plants is temporarily because of dense grass growth. The higher than in the ·grazed plot. The values are dominant Hy locomium sp lendens was probably relatively low in the fertilized heathland vegetation replaced by Drepanocladus uncinatus and at Brekknahei3i and in the Racomitrium lanu Rhytiadelphus squarrosus in the more or less con ginosum heath at Steinkrossbrun. These plots are tinuously fertilized areas. The two latter species relatively stable in floristic composition. have intermediate requirements as regards nutrients In general, the cryptogam flora has got the higher (Lye 1968) and Hy locomium sp lendens is a species importance in the dynamic changes and these of nutrient-poor substrate. The lichens Peltigera changes are more pronounced in the semi-revegetat canina, P. leucophlebia and P. polydactyla were ed areas than in the deflated areas where the restora disfavoured by the mineral fertilizer. tion is just started as there are more species to par Lichens and mosses at Braunton Burrows became ticipate in the changes. reduced in importance following the addition of mineral nutrients (Willis 1963) but of the cryptogam species found at Braunton Burrows only one, Peltigera canina is in common. 7.7 Discussion

As seen above, the year-to-year vegetational 7.6 The alpha diversity index (a) as changes are not unidirectional, and the shifts of the an indication of floristic dynamics plots go in various directions (Figs. 20-23). The changes here are nondirectional (fluctuation), ac In some cases the year-to-year floristic changes were cording to the dynamic approach. The fluctuations small, e.g, in the deflated areas, in other ones they are often caused by fertilizations or by un were more pronounced, e.g., in fertilized plots. The favourable weather (low temperatures), but some indices of diversity a calculated for a series of plots times by the dynamics of the vegetation itself, e.g., in time can be used as a measure of floristic in the unfertilized plots. dynamics. Table 21 presents such "temporal diver The dynamic approach may also reveal succes sity'' values for all experiment plots subject to sional trends in vegetation. Van der Maarel (1978, repeated analyses. 1982) found both fluctuations and succession in There are low values ofthe index in the permanent coastal dune vegetation in the Netherlands and in-

Acta Phytogeogr. Suec. 75 66 Elfn Gunnlaugsd6ttir terpreted them in view of environmental dynamics tion at the very beginning of the vegetational concerning moisture conditions and rabbit grazing. restoration. The static approach reveals (Fig. 25) a succes The successional changes are slow in the cool sional trend if plots from the open sward vegetation climate and nutrient-poor soil and annual analyses of the earliest stage of the secondary succession are do not seem to reveal them, whereas analyses of per linked with later stages of the secondary succession. manent plots at longer time intervals might succeed The revegetated areas have all had similar vegeta- better.

Acta Phytogeogr. Suec. 75 8 Discussion and conclusion

8.1 General temperatures, the short vegetation period and the generally oligotrophic environment. Most Icelandic plant communities have not yet been The year-to-year analyses described in this paper described in full according to the Braun-Blanquet suggest that most of the vegetation changes approach. Many, though, have been assigned provi observed are fluctuations. These fluctuations are sionally to higher syntaxonomical units in caused by both mineral fertilizations and their neighbouring countries. Comparisons at the diminishing effects afterwards, and extremely cold association level are difficult because Icelandic weather conditions in 1979. Otherwise the fluctua communities deviate widely floristically from the tions in the vegetation are not directly related to the vegetation in surrounding countries because of dif dynamics in the year-to-year weather conditions ferent environmental conditions. (see Fig. 3 a-c). The most important differences are found in the Successional trends may be revealed over a longer climate, different bedrock and volcanism, all period of time by comparing restored unaffected creating differences in soil types. Also the utiliza (e.g. by mineral fertilizer) vegetation and vegetation tion of the vegetation is of importance. with different restoration ages. The extreme subarctic or oceanic-boreal climate Progressive secondary succession (cf. Sjors 1980) of Iceland, with both low summer temperatures and may be discerned leading from the gravel flat frequent freezing and thawing has excluded many vegetation, the Armerio - Silenetum acaulis em., to species from growing there, species which are able the Racomitrio canescentis - Gentianetum nivalis or to survive under more stable environmental condi to the Agrostio capillaris - Hylocomietum splen tions in other northern countries. dentis. Retrogressive succession (op. cit.) leads The bedrock of Iceland, basalt, is also found in from the Agrostio capillaris - Hylocomietum splen W and E Greenland, Jan Mayen, the Faroes, N dentis or from the Racomitrio lanuginosi - Thalic Ireland and the Inner Hebrides, but there the recent tretum alpini to the Festuca vivipara - R. canescens volcanism is missing. community through wind erosion and/ or to the Ar Detailed comparisons of the major nutrients of merio - Silenetum acaulis em. as a consequence of Icelandic soils and arctic-alpine soils in neighbour soil deflation. ing countries have so far been impossible because of different methods used from country to country (see Effects of mineral fertilizer e.g., Hinneri et al. 1975). Due to continuously new aeolian deposits the Icelandic soils have a relatively The most prominent effect of fertilization with min high pH in many places, which allows calciphytic eral nutrients (N, P, K) is the strongly increased species to occur often in the neighbourhood of indif growth, especially of grasses, lasting for 2-3 years. ferent and acidiphytic species. The nutrient status of The increase in flowering of grasses and herbs also these soils is low and therefore most species are occurs after fertilization and numerous seedlings known to be oligotrophic. were found temporarily afterwards (Gunnlaugs d6ttir 1982a). But soon the vegetation changes back to a state similar to the one it had before the fertiliza 8.2 Vegetation dynamics tion inputs. The fertilization of the open sward community As elsewhere in arctic-alpine areas, natural succes causes a small increase in vegetation for the next sion proceeds slowly, because of the low decades. In better vegetated land, where the grass

Acta Phytogeogr. Suec. 75 68 Elfn Gunnlaugsd6ttir cover becomes dense, several weak competitors vegetation has been accessible to grazing livestock, were temporarily excluded. but it has hardly any value as pasture. Moreover, the Changes in dominants may have taken place as a trampling of the livestock hampers natural consequence of mineral fertilization in the Agrostio revegetation. Areas with this kind of vegetation, as - Hylocomietum splendentis, where Hy locomium well as with the Kobresia myosuroides - Salix lanata sp lendens was replaced by Drepanocladus un community, are recommended to be kept ungrazed. cinatus, probably because of the mineral fertilizer; The Racomitrio lanuginosi - Thalictretum alpini statistical comparisons of the potassium and and the Empetrum nigrum - R. lanuginosum com phosphorus contents of the soil in the lower units of munity have also very low grazing value. The the Agrostio - Hylocomietum splendentis gave no Agrostio - Hylocomietum splendentis has the significant results. If the Agrostio - Hylocomietum greatest value for agricultural use as pasture and its splendentis is subject to ceased fertilization it will grazing value has been increased by spreading min probably return to the original state, namely the eral fertilizer. The Racomitrio canescentis - Gen typical variant of the racomitrietosum canescentis tianetum nivalis is the second best grazing com of the Agrostio - Hylocomietum splendentis. munity due to fertilization, but it has to be con trolled and protected from too intense grazing pressure. The Dryas octopetala - Betula nana com 8. 3 Aspects of nature conservation munity has some value for light browsing of sheep. and vegetation development

The associations and communities described in this 8. 5 Restoration treatments and paper are supposed to be common in Iceland and recommendations for the future therefore there is no direct reason for their conserva tion. Furthermore, they will remain fairly un Restoration treatments as carried out at present are changed if managed and utilized in the same way as (1) to fence out deflated areas and protect them now. from grazing and trampling (exceptionally con The association Racomitrio canescentis - Gen trolled grazing is allowed), (2) to spread mineral fer tianetum nivalis is probably a rare vegetation type tilizer from time to time and (3) to sow seed of vari and as it is a community of secondary succession it ous grasses usually imported (Danish) seed of e.g., may be unstable and still developing. If kept Festuca rubra and Poa pratensis (but seed of the ungrazed, the dwarf shrubs will become dominating native Leymus arenarius in the easily blowing sand). but under continued fertilization and controlled Fencing of areas, protecting them from grazing grazing some kind of grassland may develop. animals, is the most important treatment for the The semi-permanent Armerio - Silenetum acaulis vegetation restoration. The fertilization somewhat Hadac 1972 em. will develop in different directions increased the potassium and the phosphorus con depending on restoration treatments and the en tents of the soil. The sowing of imported grass seed vironmental conditions in each of the sites. has often failed but the native vegetation has oc The Racomitrio lanuginosi - Thalictretum alpini, cupied the fertilized strips of land and survived in if kept ungrazed for decades or centuries, will prob somewhat better condition than earlier. Betula ably develop to some kind of shrub land with Fertilization once or twice does not maintain the pubescens Salix (S. phylicifolia, S. lanata). and spp. growth of, e.g., grasses. Fertilization almost every The shallow soil will hardly be able to support year is necessary for that purpose. Yearly fertiliza Betula pubescens, woodland of but the deep soil of tion is not necessary in ungrazed areas and perhaps the Agrostio - Hylocomietum splendentis will be. the nitrogen might be excluded there. For a short period of time fertilization gives a very 8.4 Evaluation for agricultural use good effect (see also Frioriksson 1969a & b) but to evaluate the long-term result of fertilizations it is The vegetation described in this study has been used necessary to have an unfertilized area for com as pasture for centuries. Even the open sward parisons. It is important to evaluate those aspects

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 69 from both ecological and vegetational points of species might be chosen with respect to the species view. composition in the most related vegetation types in The progressive succession of vegetation of the Iceland or in neighbouring countries. Such plants or deflated areas takes a long time and that fact must seed should be collected from other parts of Iceland be respected when restoration treatments are or from areas where environmental factors are most chosen. It might be a wise strategy to ensure that similar to those in Iceland. The grazing value of, areas not planned for grazing after restoration are e.g., the Racomitrio canescentis - Gentianetum kept unfertilized during restoration to allow sponta nivalis and the Agrostio capillaris - Hylocomietum neous native vegetation, whereas areas planned for splendentis, might be increased by introducing cer grazing could be fertilized and where more valuable tain new species. Experiments and measurements species for grazing could be introduced during dif are recommended to be carried out before each ferent stages of the secondary succession. These large-scale practical management input takes place.

ACKNOWLEDGEMENT

I wish to thank most warmly Professor Eddy van der Maarel, Head of the Institute of Ecological Botany, Uppsala, for valuable advice and encouragement during the comple tion of this work. Warm thanks are also due to Hugo Sjors, Professor Emeritus, for his advice and support during earlier stages of this work. I am also greatly indebted to Dr.F.J .A. Daniels, Utrecht, for critical reading of the phytosociological part of the manuscript and for offering valuable suggestions for im provements. I thank Professor Dr. Horour Kristinsson, Reykjavik for identification of certain li chens (Cladonia spp. mainly), cand. real. Bergpor Johannsson, Reykjavik for checking certain bryophytes; Docent 0. Martensson, Uppsala, for advice in the identification of hepatics, and the staff of the Agricultural Research Institute, Keldnaholt, Iceland, for chemical analyses of soil samples. I also thank Agneta Ekstrom for typing parts of the manuscript, Marta Ekdahl for typing the tables, Agneta Nordgren for drawing the figures, Folke Hellstrom for photo graphic work, Nigel Rollison for the linguistic revision, and the editors Gunnel Sj ors and Erik Sjogren for editorial scrutiny of the manuscript, tables and figures. I wish to express my sincere thanks to all my friends at the Institute of Ecological Botany, Uppsala, and at the Museum of Natural History, Reykjavik and the staff at the Icelandic State Soil Conservation for all help during field work.

Acta Phytogeogr. Suec. 75 References

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1-144. Naturv. Rcekke 1920-21 (1): 1-149. Kopeck)!, K. & Hejny, S. 1973. Neue syntaxonomische - 1927-28. Die Vegetation und Flora des Sylene Auffassung der Gesellschaft ein- bis zweijahriger Gebietes. - Skr. norske Vidensk.-Akad. mat.-na Pflanzen der Galio-Urticetea in Bohmen. - Folia turv. Kl. 1927(1): 1-612. geobot. phytotax. 8: 49-66. - 1936. Versuch einer neuen Einteilung der subalpinen Kolderup Rosevinge, L. 1896. Det sydligaste Gmnlands alpinen Vegetation Norwegens.- Bergens Mus. Arb. vegetation. - Meddr Gmnland 15: 1-463. 1936 (7): 1-88. Krajina, V. 1933. Die Pflanzengesellschaften des - 1943. Sikilsdalen og Norges fj ellbeiter. En Mlynica-Tales in den Vysoke Tatry (Hohe Tatra). - plantesociologisk monografi. - Bergens Mus. Skr. Beih. Bot. Zbl. 51: 1-224. 22: 1-607. Krog, Hildur et al. 1980. Lavflora. Norske busk- og - 1955. Studies on some plant communities on sandy bladlav. - Oslo. 312 pp. river banks and seashores in eastern Finnmark. - Lid, J. 1964. The Flora of Jan Mayen. - Skr. norsk Archvm Soc. zool.-bot. fenn. Vanamo, Suppl. 9: Polarinst. 130: 1-107. 207-225. Liidi, W. 1936. Experimentelle Untersuchungen an Ohba, T. 1974. Vergleichende Studien iiber die alpine alpinen Vegetation. - Ber. schweiz. bot. Ges . 46: Vegetation Japans. 1. Carici rupestris - Kobresietea 632-681. bellardii. - Phytocoenologia I: 339-401. Lye, K.A. 1968. Moseflora. - Oslo. 140 pp. Olsen, S.R. et al. 1954. Estimation of available Maarel, E. van der 1978. Experimental succession phosphorus in soils by extraction with sodium bicar research in a coastal dune grassland, a preliminary bonate. - U.S. Dep. Agri. Circular 939: 1-19. report. - Vegetatio 38: 21-28. Or loci, L. 1966. Geometric models in ecology. 1. The - 1979. Multivariate methods in phytosociology, with theory and application of some ordination methods. reference to the Netherlands. - The study of vegeta - J. Ecol. 54: 193-215. tion. The Hague. pp. 161-225. 6skarsson, I. 1932. Some observations of the vegetation - 1980. Vegetation development in a former orchard of Eyjafjo�ur and Akureyri. - Soc. Se. Isl. 13: under different treatments. A preliminary report. - 1-46. Vegetatio 43 : 95-102. Ostenfeld, Ch. 1901. En botanisk rejse til Fcemerne i - 1981. Fluctuations in a coastal dune grassland due to 1897. - Bot. Tidsskr. 24: 23-78. fluctuations in rainfall. Experimental evidence. - - 1905. Skildring af vegetationen i Island. 3. - Bot . Vegetatio 47: 259-265. Tidsskr. 27: 111-121. Maarel, E. van der, Bost, R., Dorp, D. van & Ryntjes, - 1906. The land-vegetation of the Fceroes with special J. 1984. Vegetation succession on the dunes near reference to the higher plants.- Botany of the Fceroes Oostvoore, The Netherlands; a comparison between 3: 867-1023. 1959 and 1980. - Vegetatio (in press). Porsild, N .P. 1902. Bidrag til en skildring af vegetationen Maarel, E. van der, Janssen, J .G.M. & Louppen, J .M. W. paa 0en Disko tilligemed spredte topografiske og 1978. TABORD, a program for structuring zoologiske iagttagelser . - Meddr Gmnland 25: phytosociological tables. - Vegetatio 38: 143-156. 1-308. Magnusson, A. & Vidalin, P. 1710-1 712. J ar�ab6k vol. Preston, F.W. 1962. The canonical distribution of com 2and 11. -Kaupmannahofn 1913-17 and 1943 . 409 moness and rarity. - Ecology 43: 185-215, pp. and 496 pp. 410-432. McVean, D.N. 1955. Notes on the vegetation in Iceland. Ratcliffe, D.A. 1959. Vegetation of the Carneddau, - Trans. bot. Soc. Edinb. 36: 320-338. North Wales. 1. Grasslands, heaths and bogs. - J. - 1964. The montane zone. - The vegetation of Ecol. 47: 371-413. Scotland. Edinburgh. pp. 48 1-558. Resvoll-Holmsen, Hanna 1912. Om vegetationen ved McVean, D.N. & Ratcliffe, D.A. 1962. Plant com Tessevand i Lom. - Skr. Vidensk.-selsk. Christiania munities of the Scottish Highlands.- Monogr. Nat. I Mat.-Naturv. Kl. 1912 (16): 1-50. Conserv. 1: 1-445. - 1913. Statistiske vegetation unders0kelser fra Molenaar, J.G. de 1976. Vegetation of the Angmagsalik Maalselvdalen i Troms0 Amt. - Ibid. 1913 (13): district, Southeast Greenland. 2. Herb and snow-bed 1-42. vegetation. - Meddr Gmnland 198(2): 1-265. - 1914. Statistiske vegetation unders0kelser fra Mork, E. & Heiberg, H.H. 1937. Om vegetation i Hir Foldalsfjeldene. - Ibid. 1914 (7): 1-74. kj0len fors0ksomnide. - Medd. norske Skogfor - 1920. Om fjeldvegetationen i det Ostfjeldske Norge. S0ksvesen 5: 621-684. -Arch. Math. Naturv. 37: 1-266. Mueller Dombois, D. & Ellenberg, H. 1974. Aims and Rorison, I.H. 1970. The use of nutrients in the control of methods of vegetation ecology. - New York. 547 pp. the floristic composition of grassland. - Symp. Br. M0lholm Hansen, H. 1930. Studies on the vegetation of ecol. Soc. 11: 65-77. Iceland. -The Botany of Iceland. 3(1): 1-186. Rosen, E. 1980. Application of permanent sample plots Nordhagen, R. 1921. Vegetationsstudien aufder Insel Ut for conservation of vegetation on the alvar of Oland. sire im westlichen Norwegen. - Bergens Mus. Aarb. - Phytocoenosis 7: 317-332.

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 73

- 1982. Vegetation development and sheep grazing in the ecology of Spitsbergen and Bear Island .- J. Ecol. limestone grasslands of South bland, Sweden.- Acta 11: 214-286. phytogeogr. Suec. 72: 1-104. Sremundsson, K. 1977. Geological map of Iceland. Sheet Roskam, S. 1971: Program: ORDINA. Multidimensional 7. NE iceland. - Reykjavik. ordination of observation vectors. - Progr. Bull. Tallis, J.H. 1958. Studies in the biology and ecology of Psych. Lab. Nijmegen 16: 1-18. Rhacomitrium lanuginosum Bird. 1. Distribution and R0nning, 0.1. 1965. Studies in Dryadion of Svalbard. ecology .- J. Ecol. 46: 27 1-288. Skr. norsk Polarinst. 134: 1-52. Tengvall, T.A. 1920. Die Vegetation des Sarekgebietes. Seidenfaden, G. 1931. Moving soil and vegetation in East - Naturw. Unters. Sarekgebirg., 3: 263-436. Greenland. A preliminary report. - Meddr Gmnland Trapnell, C.G. 1933. Vegetation types in Godthaabfjord 87(2): 1-21 . in relation to those in other parts of West Greenland, Seidenfaden, G. & S0rensen, Th. 1937. The vascular and with special reference to Isersiutilik. - J. Ecol. plants of Northeast Greenland from 74°30' to 79°00' 21: 294-334. N.Lat., and a summary of all species found in East Tuhkanen, S. 1980. Climatic parameters and indices in Greenland. - Meddr Gmnland 101(4): 1-215. plant geography. - Acta phytogeogr. suec. 67 : Sigurj6nsson et al. 1958. Sandgrreoslan 50 ara. - 1 - 110. Reykj avik. 359 pp. Tutin, T.C. et al. 1964- 1980. Flora Europea 1-5. - Sjors, H. 1980. An arrangement of changes along gra Cambridge. dients, with examples from successions in boreal Ti.ixen , R. 1937. Die Pflanzengesellschaften Nord peatland . - Vegetatio 43: 1-4. westdeutschlands. - Mitt . flor .-soz. Arbeitsgemein. Skogen, A. 1965. Flora og vegetation in 0rland herred 3: 1-170. S0r-Tmndelag. - K. nor. Vidensk. Selsk. Mus. Arb. Ti.ixen, R. & Bottcher, H. 1969. Weide- und Wiesen 1965: 13-124. Gesellschaften (Molinio-Arrhenatheretea) in Si.idwest - 1970. Studies in Norwegian maritime-heath vegeta Island. - Ber. forschungst. Neori As 1: 1-31. tion. 1. The eco-sociological range of Carex binervis Veorattan 1974 - Sept. 1980, rnanaoar- og arsyfirlit at its northern distribution limit. - Arb. Univ. (monthly and yearly abstract). - Ve0urstofa islands Bergen, Mat. -naturv. Ser. 5: 1-17. (Icelandic Meteorological Office). Reykjavik. Specht, R.L. 1977. Heathlands and related shrublands of Ventze, J.-F. 1982. Zur Biotop- und Vegetationsent the world.- Ecosystems of the world. 9A: 1-17. wicklung auf isHindischen Lavafeldern. - Essener Steind6rsson, S. 1930. Vegetation researches in :bj 6rsar Geogr. Arb. 1: 29-61. dalur, South Iceland during the summer 1930. - Soc. Waiter, H. 1979. Vegetation of the earth, and ecological Se. Isl. 7: 1-15. systems of the geobiosphere. 2nd Ed. - New York. - 1936. Om vegetationen paa Melrakkasljetta i det 274 pp. nord0stlige Island. - Bot. Tidsskr. 43: 436-483. Watt, A.S. &Jones, E.W. 1948. The ecology ofthe Cairn - 1945 . Studies on the vegetation of the Central gorms. 1. The environment and the altitudinal zona Highland of Iceland. - Botany of Iceland. 3(4): tion of the vegetation. - J. Ecol. 36: 283-304. 351-547. Westhoff, V. & Maarel, E. van der 1978. The Braun 1957. Urn gr6our i Reykjaneshraunurn. Er unnt ao Blanquet approach. 2nd ed. - Classification of plant grreoa pau sk6gi ao nyju? - Arsrit rrektunarfelags communities. The Hague. pp . 287-399. Norourlands 3/54. pp. 137-150. W illiams, C. B. 1964. Pattern in the balance of nature and 1958. Jan Mayen. - Natturufrreoingurinn 28: 57- related problems in quantitative ecology.- London. 89. 324 pp. 1964a. Urn halendisgr6our islands. Fyrsti hluti. (On Willis, A.J. 1963. Braunton Burrows: The effects on the the vegetation of the Central Highland of Iceland. 1.) vegetation of the addition of mineral nutrients to dune - Flora 2: 5-49. soil. - J. Ecol. 51: 353-374. 1964b. Gr6our a islandi. - Akureyri. 186 pp. :b6rarinsson, S. 1960. The Postglacial history of Myvatn 1964c. Urn Gr6our i Papey. - Natturufrreoingurinn area and the area between Myvatn and J okulsa a 33: 214-264. Fjollum. -On the geology and geophysics of Iceland. 1966. Urn halendisgr6our islands. :brioju hluti. (On the - The International Geological Congress. Guide to vegetation of the Central Highland of Iceland. 3.) excursion no. A2: 60-69. Flora 4: 49-94. - 1961. Uppblastur a Islandi i ljosi oskulagarannsokna. 1967. Urn halendisgr6our islands. Fj6roi hluti. (On - Arsrit Skogrrektarfelags Islands 1960-1961 : the vegetation of the Central Highland of Iceland. 4.) 17-54. - Flora 5: 53-92. 1974. Sambuo lyos og lands i ellefu aldir. - Saga 1980. Flokkun gr6ours i gr6ourfel6g. - J. Agr. Res. Islands 1. Reykjavik. pp. 29-97. Ice!. 12: 11-52. :borsteinsson, I. 1973. Gr6our og landn)rting. - Land Summerhayes, V.S. & Elton, C.S. 1923 . Contribution to nyiing. Rit Landverndar 3: 26-37.

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SVENSKA V AXTGEOGRAFISKA SALLSKAPET SOCIETAS PHYTOGEOGRAPHICA SUECANA Adress: Vaxtbiologiska institutionen, Box 559, S-75 1 22 Uppsala, Sweden

Sallskapet har till andamal att vacka och underhalla intresse The object of the Society is to promote investigation in flora for vaxtgeografien i vidstracktaste mening, att framja utfors and vegetation, their history and their ecological background. kande av flora och vegetation i Sverige och andra lander och Through publication of monographs, and other activities, the att havda geobotanikens praktiska och vetenskapliga betydel Society tries to stimulate geobotanical research and its appli se. cation to practical and scientific problems. Membership is Sallskapet anordnar sammankomster och exkursioner samt open to all who have a personal interest in the ad vancement of utger tva publikationsserier. Medlemskap kan erhallas efter phytogeography. anmalan hos sekreteraren. Foreningar, bibliotek, laroanstalter Individual members and subscribers (societies, institutes, och andra institutioner kan inga som abonnenter. Arsavgift 50 libraries, etc.) receive the Acta Phytogeographica Suecica for kr (35 fo r studerande). annual dues of 50 Skr plus postage. There are additional fees Sallskapet utger arligen Acta Ph_vtogeographica Suecica . in years when more than one volume are issued. For member Medlemmar och abonnenter erhaller arets Acta mot postfor ship please apply to the Secretary. skott pa arsavgiftenjamte porto och expeditionskostnader. The Society also issues Viixrekologiska studier, which ap Vissa ar utges extraband av Acta, som erhalls mot en till pear irregularly and are available upon request or standing laggsavgift. order. Sallskapet utger ocksa den ickeperiodiska serien Vaxteko Both series can be received by exchange for other scientific logiska studier. Den kan fo rvarvas efter bestallning eller ge publications. Please apply to the Institute Library (address as nom staende abonnemang hos Sallskapet. above). Bada serierna kan ocksa erhallas i byte mot andra publika tioner efter hanvandelse till Vaxtbiologiska institutionens bib liotek.

ACTA PHYTOGEOGRAPHICA SUECICA

I. E. Almquist, Upplands vegetation och flora. (Vegetation 10. B. Lindquist, Dalby Soderskog. En skansk lovskog i and flora of Uppland .) 1929. ISBN 91-72 10-001-X. forntid och nutid. (Zusammenf. : Ein Laubwald in Scho 2. S. Thunmark , Der See Fiolen und seine Vegetation. 1931. nen in der Vergangenheit und Gegenwart.) 1938. 56:-. 46:-. ISBN 91-7210-002-8. ISBN 91-72 10-010-9. 3. G. E. Du Rietz, Life-forms of terrestrial flowering plants. 11. N. Stalberg, Lake Vattern. Outlines of its natural history, I. 1931. 28:- ISBN 91-7210-003-6. especially its vegetation. 1939. 20:-. ISBN 91-72 10-01 1-7. 4. B. Lindquist, Om den vildvaxande skogsalmens raser och 12. G. E. Du Rietz, A. G. Hannerz, G. Lohammar, R. San deras utbredning i Nord vasteuropa. (Summary: The races tesson & M. W ll'rn, Zur Kenntnis der Vegetation des Sees of spontaneous Ulmus glabra Huds. and their distribution Takern. 1939. 20:-. ISBN 91-7210-012-5. in NW. Europe.) 1932. 23:-. ISBN 91-72 10-004-4. 13. Viixtgeografi ska studier tilliignade Car/ Skottsberg pa 5. H. Osvald, Vegetation of the Pacific coast bogs of North sextioarsdagen 1/12 1940. (Geobotanical studies dedica America. 1933. 18:-. ISBN 91-72 10-005-2. ted to C. Skottsberg.) 1940. 62:-. ISBN 91-72 10-0 13-3. 6. G. Samuelsson, Die Verbreitung der hoheren Wasser 14. N. Hylander, De svenska formerna av Mentha gentilis L. pflanzen in Nordeuropa. 1934. 49:-. ISBN 91-7210-006-0. coli. (Zusammenf. : Die schwedischen Formen der Men 7. G. Degelius. Das ozeanische Element der Strauch- und tha gentilis L. sensu coli.) 194L 20:-. ISBN 91-72 10- Laubflechtenflora von Skandinavien. 1935. 62:-. ISBN 014-1. 91-72 10-007-9. 15. T. E. Hasselrot, Till kannedomen om nagra nordiska um 8. R. Sernander, Granskar och Fiby urskog. En studie over bilicariaceers utbredning. (Zusammenf. : Zur Kenntnis der stormluckornas och marbuskarnas betydelse i den sven Verbreitung einiger Umbilicariaceen in Fennoscandia.) ska granskogens regeneration. (Summary : The primitive 1941. 26:-. ISBN 91-7210-015-X. forests of Granskar and Fiby. A study of the part played 16. G. Samue/sson, Die Verbreitung der Alchemilla-Arten by storm-gaps and dwarf trees in the regeneration of the aus der Vulgaris-Gruppe in Nordeuropa. 1943. 35:-. Swedish spruce fo rest.) 1936. 52:-. ISBN 91-7210-008-7. ISBN 91-7210-0 16-8. 9. R. Sierner, Flora der Insel bland. Die Areale der Ge 17. Th . Arwidsson, Studien iiber die Gefasspflanzen in den fa sspflanzen Olands nebst Bemerkungen zu ihrer Hochgebirgen der Pite Lappmark. 1943. 60:-. ISBN Oekologie und Soziologie. 1938. ISBN 91-72 10-009-5. 91-7210-017-6.

Acta Phytogeogr. Suec. 75 75

18. N. Dahlbeck, Strandwiesen am si.idostlichen bresund. Norge . (Summary: Upper limits of vascular plants on (Summary : Salt marshes on the S. E. coast of bresund.) mountains in Southwestern JamtlanJ and adjacent parts 1945. 30:-. ISBN 91-72 10-01 8-4. of Harjedalen (Sweden) and Norway.) 1955. 40:-. ISBN 19. E. von Krusenstjerna, Bladmossvegetation och blad 91-72 10-035-4. mossflora i Uppsalatrakten. (Summary: Moss flora and 36. N. Quennerstedt , Diatomeerna i Uingans sj ovegetation. moss vegetation in the neighbourhood of U ppsala.) 1945. (Summary : Diatoms in the lake vegetation of the Um gan 65 :-. ISBN 91-72 10-0 19-2. drainage area, Jamtland, Sweden.) 1955. 40:-. ISBN 20. N. Albertson, bsterplana hed. Ett alvaromdtde pa Kin 91-72 10-036-2. nekulle. (Zusammenf. : bsterplana hed . Ein Alvargebiet 37. M.-B. Florin, Plankton of fresh and brackish waters in the aufdem Kinnekulle.) 1946. ISBN 91-72 10-020-6. Sodertalje area. 1957. 30:-. ISBN 91-72 10-037-0. 21. H. Sjo rs . Myrvegetation i Bergslagen. (Summary: Mire 38. M.-B . Florin , lnsjostudier i Mellansverige. Mikrovegeta vegetation in Bergslagen, Sweden.) 1948. 62:-. ISBN tion och pollenregn i vikar av bstersjobackenet och insjoar 91-72 10-02 1-4. fran preboreal tid till nutid. (Summary: Lake studies in 22. S. Ahlner, Utbredningstyper bland nordiska barrtradsla Central Sweden. Microvegetation and pollen rain in inlets var. (Zusammenf. : Verbreitungstypen unter fe nnoskandi of the Baltic basin and in lakes from Preboreal time to the schen Nadelbaumflechten.) 1948. 56:-. ISBN 91-7210- present day.) 1957. 16:-. ISBN 91-72 10-038-9. 022-2. 39. M. Fries, Vegetationsutveckling och odlingshistoria i 23. E. Julin, Vessers udde, Mark och vegetation i en igen Varnhemstrakten. En pollenanalytisk undersokning i vaxande lovang vid Bj arka-Saby . ( Zusammenf. : Vessers Vastergotland. (Zusammenf. : Vegetationsentwic klung udde. Boden und Vegetation in einer verwachsenden und Siedlungsgeschichte im Gebiet von Varnhem. Eine Laubwiese bei Bjarka-Saby in bstergotland, Siidschwe pollenanalytische Untersuchung aus Vastergotland den.) 1948. 44:-. ISBN 91-72 10-023-0. (Si.idschweden).) 1958. 26:-. ISBN 91-72 10-039-7. 24. M. Fries, De n nordiska utbredningen av Lactuca alpina, 40. Benl{t PeHersson. Dynamik och konstans i Gotlands flora Aconitum septentrionale, Ranunculus platanifolius och och vegetation. (Resume: Dynamik und Konstanz in der Polygonatum verticillatum. (Zusammenf. : Die nordische Flora und Vegetation von Gotland, Schweden.) 1958. Verbreitung von Lactuca alpina ...) 1949. 20:-. ISBN 75:-. ISBN 91-721 0-040-0. 91-72 10-24-9. 41. E. Ugl{la , Skogsbrandfalt i Muddus nationalpark. (Sum 25. 0. Gj (nevo/1, Sn�leievegetasjonen i Oviksfjellene. (Sum mary: Forest fireareas in Muddus National Park, North mary: The snow-bed vegetation of Mts Oviksfjallen. Jamt ern Sweden.) 1958. 33:-. ISBN 91-721 ()..04 1-9. land, Sweden.) 1949. 30:-. ISBN 91-72 10-025-7. 42 K. Thomasson , Nahuel Huapi . Plankton of some lakes in 26. H. Osvald, Notes on the vegetation of British and Irish an Argentine National Park, with notes on terrestrial mosses. 1949. 20:-. ISBN 91-7210-026-5. vegetation. 1959. 30:-. ISBN 91-7210-042-7. 27. 5. Selander, Floristic phytogeography of South-Western 43 . V. Gillner. Vegetations- und Standortsuntersuchungen in Lule Lappmark (Swedish Lapland). I. 1950. 46:-. ISBN den Strandwiesen der schwedischen Westki.iste. 1960. 91-7210-027-3. 48 :-. ISBN 91-7210-043-5. 28. S. Selander , Floristic phytogeography of South-Western 44 . E. Sjijgren, Epiphytische Moosvegetation in Laubwal Lule Lappmark (Swedish Lapland). Il. Karl vaxtfloran i dern der lnsel bland, Schweden. (Summary : Epiphytic sydvastra Lule Lappmark. (Summary: Vascular flora.) moss communities in deciduous woods on the island of 1950. 38:-. ISBN 91-72 10-028- 1. bland, Sweden.) 1961. 38:-. ISBN 91-72 10-044-3 (ISBN 29. M. Fries, Pollenanal ytiska vittnesbord om senkvartar ve 91-721 0-444-9) . getationsutveckling, sarskilt skogshistoria, i nordvastra 45. G. Wisrrand, Studier i Pite Lappmarks karlvaxtflora, med Gotaland. (Zusammenf.: Pollenanalytische Zeugnisse der sarskild hansyn till skogslandet och de isolerade fj allen. spatquartaren Vegetationsentwicklung, hauptsachlich der (Zusammenf. : Studien i.iber die Gefasspflanzenflora der Waldgeschichte, im nordwestlichen Gotaland, Siid Pite Lappmark mit besonderer Beri.icksichtigung des schweden.) 1951. 49:-. ISBN 91-7210-029-X. Waldlandes und der isolierten niederen Fj elde.) 1962. 30. M. Wa>rn , Rocky-shore algae in the bregrund Archipe 49:-. ISBN 91-72 10-045- 1 (ISBN 91-721 0-445-7) . lago. 1952. 62:-. ISBN 91-72 10-030-3. 46. R. lvarsson , Lovvegetation i Mollosunds socken. (Zu 31. 0. Rune, Plant life on serpentines and related rocks in the sammenf. : Die Laubvegetation im Kirchspiel Mollosund . North of Sweden. 1953. 30:-. ISBN 91-7210-03 1-1. Bohustan, Schweden.) 1962. 40:-. ISBN 91-721 0-046-X 32. P. Kaaret, Wasservegetation der Seen Orlangen und Tre (ISBN 91-72 10-446-5) . horningen. 1953. 20:-. ISBN 91-7210-032-X. 47 . K. Thomasson, Araucanian Lakes. Plankton studies in 33. T. E. Hasselror, Nordliga lavar i Syd- och Mellansverige. North Patagonia, with notes on terrestrial vegetation. ( N ordliche Flechten in Siid- und Mittelschweden.) 1953. 1963. 45:-. ISBN 91-72 1 0-047-8. 46:-. ISBN 91-72 10-033-8. 48 . E. Sj ogren, Epilitische und epigaische Moosvegetation in 34. H. Sjo rs, Slatterangar i Grangarde finnmark. (Summary: Laubwaldern der lnsel bland . Schweden. (Summary: Meadows in Grangarde Finnmark, SW. Dalarna, Swe Epilithic and epigeic moss vegetation in deciduous woods den.) 1954. 36:-. ISBN 91-72 10-034-6. on the island of bla:r1d, Sweden.) 1964. 60:-. ISBN 35. 5. Kilander, Karlvaxtemas ovre granser pa fjall i sydvast 91-721 0-048-6 (ISBN 91-7210-448- 1 ) . ra Jamtland samt angransande delar av Harjedalen och 49. 0. Hedberg , Features of afroalpine plant ecology. (Re-

Acta Phytogeogr. Suec. 75 76

sume fran�ais.) 1964. 60:-. ISBN 91-7210-049-4 (ISBN 64 . M. Ammar. Vegetation and local environment on shore 9 1 -7210-449-X). ridges at Vickleby, bland, Sweden. An analysis. 1 978 . 50. The Plan! Cm·er of Sweden . A study dedicated to G. 65 :-. ISBN 91-72 1 0-064-8 (ISBN 91-72 10-464-3). Einar Du Rietz on his 70t h birthday by his pupils. 1965 . 65 . L. Ku/lman, Change and stability in the altitude of the 110:-. ISBN 91-7210-050-8. birch tree-limit in the southern Swedish Scandes 1915- 51. T. Flensburg, Desmid s and other benthic algae of Lake 1975. 1979. 65 :-. ISBN 91-72 1 0-065-6 (ISBN 91-72 10- Kavsji:in and Store Mosse, SW Sweden. 1967 . 50:-. ISBN 465- 1 ). 91-72 10-05 1-6 (ISBN 91-72 10-45 1-1). 66 . £. W aldemarson Jen sen , Successions in relationship to 52. £. Sk l'e , Lichens and air pollution. A study of cryptoga lagoon development in the Laitaure delta, North Sweden. mic epiphytes and environment in the Stockholm region. 1979. 65:-. ISBN 91-721 0-066-4 (ISBN 91-72 10-466-X). 1 968 . 70:-. ISBN 91-7210-052-4 (ISBN 91-72 10-452-X). 67 . S. Tu hkanen , Climatic parameters and indices in plant 53. Jim Lundqvist, Plant cover and environment of steep geography. 1980. 65 :-. ISBN 91-72 10-067-2 (ISBN 91- hillsides in Pite Lappmark. (Resume : La couverture vege 72 1 0-467-8). tale et !'habitat des tlancs escarpes des collines de Pite 68 . Studies in pian! ecoloRY dedicated to Hugo Sj ors. Ed. Lappmark.) 1968 . 60:-. ISBN 91-72 10-053-2 (ISBN 91- Erik Sjogren. 1980. 95:-. ISBN 91-7210-068-0 (ISBN 91- 7210-453-8). 72 1 0-468-6). 54. Conservation of Ve[;?elalion in Africa Smah of !he Saha 69 . C. Nilsson, Dynamics of the shore vegetation of a North ra . Proc. of symp. at 6th plen. meeting of AETFAT. Ed. Swedish hydro-electric reservoir during a 5-year period. by Inga and Olov Hedberg. 1968 . 80:-. ISBN 91- 1981. 65:-. ISBN 91-72 1 0-069-9 (ISBN 91-72 10-469-4). 72 10-054-0 (ISBN 91-72 10-454-6). 70. K. W arenberg, Reindeer forage plants in the early grazing 55. L.-K. KijniRsson, The Holocene history of the Great Al season. Growth and nutritional content in relation to cli var of bland. 1968. 75:-. ISBN 91-72 10-055-9 (ISBN matic conditions . 1982 . 75:-. ISBN 91-72 1 0-070-2 (ISBN 91-7210-455-4) . 91-72 10-470-8). 56. H. P. Hallherf;? , Vegetation auf den Schalenablageru ngen 71. C. Johansson, Attached algal vegetation in running wa in Bohuslan, Schweden. (Summary: Vegetation on shell ters of Jamtland, Sweden. 1982. 75:- ISBN 91-72Je-07 1-0 deposits in Bohuslan. Sweden.) 1971. 60:-. ISBN 91- (ISBN 91-72 10-47 1-6) . 72 10-056-7 (ISBN 91-72 10-456-2). 72. E. Rosen , Vegetation development and sheep grazing in 57. S. Fra nsson. Myrvegetation i sydvastra Varmland. limestone grasslands of south Oland, Sweden. 1982. 95 :-. (Summary : Mire vegetation in south-western Varmland. ISBN 91-7210-072-9 (ISBN 91-7210-472-4). Sweden .) 1972. 55:-. ISBN 91-721 0-057-5 (ISBN 91- 73. L. Zhang, Vegetation ecology and population biology of 7210 -457-0). Fritillaria meleagris L. at the Kungsangen Nature Reserve, 58. G. Wallin , Li:ivskogsvegetation i Sjuharadsbygden. Eastern Sweden. 1983 . 90: -. ISBN 91-7210-073-7 (Summary: Deciduous woodlands in Sjuharadsbygden, (ISBN 91-7210-473-2). Vastergotland, south-western Sweden.) 1973. 55 :-. ISBN 74. I. Backeus, Aboveground production and growth dynamics 91-72 10-058-3 (ISBN 91-72 1 0-458-9). of vascular bog plants in central Sweden. 1985. 90:-. ISBN 59. D. Johan.1son, Ecology of vascular epiphytes in West 91-7210-074-5 (ISBN 91-7210-474-0). African rain forest. (Resume: Ecologie des epiphytes 75. E. Gunnlaugsd6ttir, Composition and dynamical status of vasculaires dans la fo n�t dense humide d'Afrique occiden heathland communities in Iceland in relation to recovery tale.) 1974. ISBN 91-72 10-059- 1 (ISBN 91-72 10-459-7). measures. 1985 . 90:-. ISBN 91-7210-075-3 (ISBN 91-7210- 60. H. Olsson, Studies on South Swedish sand vegetation. 475-9). 1974 . 80:-. ISBN 91-721 0-060-5 (ISBN 91-72 10-460-0) . 61 . H. H\'ltehorn, Deciduous woodland at Andersby, Eastern Sweden. Above-ground tree and shrub production. 1975. 55:-. ISBN 91-7210-06 1-3 (ISBN 91-72 10-461-9). 62. H. Persson, Deciduous woodland at Andersby, Eastern Sweden: Field-layer and below-ground production. 1975. Limited number of cloth-bound copies of Acta 44, 45, 46, 48 50:-. ISBN 91-72 1 0-062- 1 (ISBN 91-72 10-462-7). 49 , 51, 52, 53, 56 , 57, 61, 63 , 66, 67, 68, 69 , 70, 71, 72, 73 are 63 . S. Brtlkenhielm, Vegetation dynamics of affo rested farm available through the Society at an additional cost of 15:- per land in a district of South-eastern Sweden. 1 977 . 65:-. copy. ISBN nos. in brackets refer to cloth-bound copies. Nos. 1, ISBN 91-721 0-063-X (ISBN 91-72 10-463-5). 9, 20, 59 are out of print.

Acta Phytogeogr. Suec. 75 77

V AXTEKOLOGISKA STUDIER

I. S. Brakenhielm & T. lngelog , Vegetationen i Kungs U mealven. ( Summary: Bioeffects of hydroelectric de hamn-Morga naturreservat med fo rslag till skotse lplan . velopment. A case study based mainly on observations (Summary: Vegetation and proposed management in the along the Ume River, northern Sweden.) 1976. 35:-. Kungshamn-Morga Nature Reserve south of Uppsala.) ISBN 91-721 0-808-8. 1972. 25:-. ISBN 91-7210-801-0. 9. J. Lundqvist & G. Wistrand, Strandtlora inom ovre och 2. T. lngelog & M. Risling, Kronparken vid Uppsala, histo mellersta Skelleftealvens vattensystem. Med en samman rik och bestandsanalys av en 300-arig tallskog. (Summary: fa ttning betraffande botaniska skyddsvarden. (Summary: Kronparken, history and analysis of a 300-year-old pine Riverside vascular flora in the upper and middle catch wood near Uppsala Sweden.) 1973. 25:-. ISBN , ment area of the River Skelleftealven, northern Sweden.) 91-7210-802-9. 1976. 30:-. ISBN 91-7210-809-6. 3. H. Sj ors och medarb ., Skyddsvarda myrar i Kopparbergs 10. A Miiller-Haeckel, Migrationsperiodik einzelliger Algen Jan. (Summary : Mires considered for protection in Kop in Fliessgewassern. 1976. 15:-. ISBN 91-7210-8 10-X. parberg County (Prov. Dalarna, Central Sweden).) 1973. 11. A. Sjodin , Index to distribution maps of bryophytes 25:-. ISBN 91-72 10-803-7. 1887-1975. I. Musci. 1980. 60 (hard-bound). ISBN :- 4. L. Karlsson, Autecology of cliffand scree plants in Sarek 91-72 I 0-R 1 1-8. National Park, northern Sweden 1973. 30:-. ISBN 12. A. $jijdin , Index to distribution maps of bryophytes 91-72 10-804-5. 1887-1975. 11. Hepaticae . 1980. 40:- (hard-bound). ISBN 5. B. Klasvik, Computerized analysis of stream algae . 1974. 91-72 10-8 1 2-6. 25:-. ISBN 91-7210-805-3. 13. 0. Eriksson, T. Palo & L. S<>derstrom, Renbetning 6. Y. Dahlstrom-Ekbohm, Svensk miljovards- och omgiv vintertid. Undersokningar rorande svensk tamrens na ringsekologi under snoperioden. 1981. 25 ISBN ningshygienlitteratur 1952-1 972. Bibliografi och analys. :- 1975. 25:-. ISBN 91-7210-806- 1. 91-72 10-8 1 3-4. 14. G. Wistrand, Bidrag till Pite lappmarks vaxtgeografi 7. L. Rodenborg, Bodennutzung, Pflanzenwelt und ihre . Veranderungen in einem alten Veidegebiet auf Mittel 1981. 25:-. ISBN 91-7210-8 14-2. Oiand, Schweden. 1976. 25:-. ISBN 91-7210-807-X. 15. T. Karlsson, Euphrasia rostkoviana i Sverige . 1982. 35:-. ISBN 91-72 10-81 5-0. 8. H. Sjors & Ch . Nilsson, Vattenutbyggnadens effekter pa levande natur. En fa ktaredovisning overvagande fran

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Acta Phytogeogr. Suec. 75 78 Elfn Gunnlaugsd6ttir

Plate 1. A view of fertilized vegetation in the Assandur area, N Iceland. The subassociation achilleetosum millefolii of the Armerio - Silenetum acaulis. Photo 1979.

Plate 2. The cerastietosum fontani of the Armerio - Silenetum acaulis in the deflated Eldivi�arhraun lava-field near Melakot, S Iceland. Festuca pruinosa and Agrostis stolonifera are dominating in the fertilized vegetation. Photo 1979.

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 79

Plate 3. Fertilized vegetation of the Armerio - Silenetum acaulis galietosum normanii in the Hei3arspor3ur area, N Iceland. Flowering herbs are Cerastium alpinum, Arenaria norvegica, Draba incana and the half-shrub Thymus arc ticus. The grasses are Festuca pruinosa, Agrostis vinea/is and Poa glauca. Fertilized in 1973 and 1978. Photo 1979.

Plate 4. A view from the Hei3arspor3ur area, N Iceland, showing unfertilized area with the Armerio - Silenetum acaulis galietosum normanii. Photo 1979.

Acta Phytogeogr. Suec. 75 80 Elfn Gunnlaugsd6ttir

Plate 5. A view of the Armerio - Silenetum acaulis galietosum normanii in the HeiCiarsporCiur area, N Iceland. Ungrazed, fertilized to right, unfertilized and grazed to left. Photo 1979.

Plate 6. A close view of fertilized Armerio - Silenetum acaulis galietosum normanii in the HeiCiarsporCiur area, N Iceland, fertilized in 1973 and 1978. Grasses (Agrostis vinealis, Festuca pruinosa) and small herbs ( Galium normanii, Armeria maritima, Lychnis alpina and Cerastium alpinum) in flower. Ceratodon purpureus in the bottom layer . Photo 1979.

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 81

Plate 7. A view of the Racomitrio lanuginosi - Thalictretum alpini in the heathland near Kot farm. Photo 1984.

Plate 8. A close view of the Racomitrio - Thalictretum alpini showing Racomitrium lanuginosum (dominating), Kobresia myosuroides and Armeria maritima. Photo 1984.

Acta Phytogeogr. Suec. 75 82 EHn Gunnlaugsd6ttir

Plate 9. A view from the fertilized part of the grassy heathland Brekknahei()i with the Agrostio - Hylocomietum splendentis. Photo 1984.

Plate 10. A close view of the unfertilized Agrostio capillaris - Hylocomietum splendentis showing Galium borea/e and grasses. Photo 1984.

Acta Phytogeogr. Suec. 75 Heath/and communities in Iceland 83

Plate 11. A close view of the fertilized inops subassociation of the Agrostio capillaris - Hylocomietum splendentis showing the grasses Agrostis cap illaris (dominating) and Festuca pruinosa. Photo 1984.

Plate 12. A view of the Racomitrio canescentis - Gentianetum nivalis in the revegetated Vesturhraun lava-field near Gunnlaugsskogur, Gunnarsholt farm, S Iceland. Unfertilized. Empetrum nigrum, Salix lanata and grasses are physiognomically dominating. Photo 1979.

Acta Phytogeogr. Suec. 75 84 EHn Gunnlaugsd6ttir

Plate 13. A view of the Dryas octopetala - Betula nana community in the area H6lssandur. Salix lanata dominating in the ungrazed area (which has been protected from grazing for about 20 years). Photo 1978.

Plate 14. A view of the Kobresia myosuroides - Salix lanata community in the Assandur area. Salix lanata, Betula pubescens - coppices and Empetrum nigrum dominating. Photo 1977.

Acta Phytogeogr. Suec. 75

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