Phytosociology of terricolous lichen vegetation in the Cairngorm Mountains, Scotland

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1 Lichenologist 33(4): (2001) doi: /lich , available online at on Phytosociology of terricolous lichen vegetation in the Cairngorm Mountains, Scotland Alan M. FRYDAY Abstract: The results of an investigation into the lichen vegetation associated with vascular plant communities in the Scottish Highlands are presented. Most lichen species rarely occur in homogeneous stands of vascular plant vegetation, either occurring around the edges of recognized National Vegetation Classification (NVC) communities or in small-scale mosaics with them. However, some lichen species have a high fidelity to the more open NVC communities. The problems associated with applying NVC survey techniques to lichen assemblages are described and discussed The British Lichen Society Introduction The history, current status and many of the problems of lichen community studies were excellently reviewed by Nimis (1991). The problems are both theoretical and practical and combine in such a way that the method used is very much dependent on the problem to be solved. The theoretical problems mostly concern the decision as to whether to treat the vegetation of an area as a whole (phytocoenosis) or whether to treat the various elements (including the lichen vegetation) separately (synusiae). In theory the former is to be preferred but a number of practical problems intervene: (a) the difficulty of identifying all the organisms at a site; (b) the different minimum areas required for sampling different synusiae; (c) the different microclimate and soil conditions which pertain for different synusiae; A. M. Fryday: Department of Landscape, University of Sheffield, Sheffield, S10 2TN, UK. Present address: Herbarium, Dept of Botany and Plant Pathology, 166 Plant Biology, Michigan State University, East Lansing, Michigan , USA. (c) (d) the often independent behaviour of the synusiae in that their boundaries do not coincide. If the object of the exercise is the description of the vegetation at a given site then there appears to be little alternative to the phytocoenosal approach. However, if the object is to classify the vegetation then the synusial approach appears to be preferable. Other practical problems are: (a) identification of homogeneous stands in lichen vegetation, where microhabitat is such an important influence; (b) lichens often occur in gaps in the vegetation or reach their best development at the boundaries of vascular-plantdominated areas; identification of crustose microlichens in the field. This last problem was investigated by Roux (1990) who compared the literature results of relevés taken by various investigators from the same lichen communities, but with identifications made at three different levels, (a) in the field, (b) difficult specimens removed for laboratory identification and (c) all specimens removed to the laboratory. In all but one case, he reported an /01/ $35.00/ The British Lichen Society

2 332 THE LICHENOLOGIST Vol. 33 increase of over 100% in the number of taxa recorded in the laboratory (c) over that recorded in the field (a). The largest difference was five taxa in the field, 22 taxa in the laboratory. The lichen vegetation of the Western Highlands is, in general, far more important than that of the Eastern Highlands, both in terms of species diversity and rarity. Unfortunately, the description and characterization of the lichen vegetation of the Western Highlands is beset with problems (see below) and is outside the scope of the present study. This contribution deals only with the lichen vegetation of the Eastern Highlands where lichens play a structural role in the terricolous vegetation and are more readily accommodated within vascular plant communities. There are also many problems concerned with the sampling of saxicolous lichen communities; mostly a consequence of the topography of the substratum and the multitude of microhabitats this produces. In this respect, they are very different from most vascular plant communities. Whereas vascular plant communities in montane areas can, typically, be considered as a 3-dimensional covering of a 2-dimensional surface, saxicolous crustose lichen communities are a 2-dimensional covering of a 3-dimensional surface. The influence of microhabitat on small-scale lichen distribution is so great that the sampling of a homogeneous stand of any size is virtually impossible. Where one does exist it must usually be regarded as atypical. For these reasons, only terricolous communities dominated by macrolichens are considered here. Some work has been done on saxicolous communities and terricolous, microlichen dominated communities, especially those that occur in the vicinity of areas of late snow-lie, and this has been published elsewhere (Fryday 1997a, 2001). The National Vegetation Classification (NVC) (Rodwell ) has provided the definitive work on plant communities in the British Isles for the foreseeable future. The expressed aim of this project was to give priority to the definition of vegetation types rather than to the construction of a hierarchical classification (Rodwell, op. cit.) and, in this, it follows the British tradition of delimiting plant communities in a pragmatic fashion, as a tool for ecological research, rather than following the purely academic approach typical of phytosociology. Unfortunately, the scope of NVC was set out as covering all terrestrial plant communities... except where non-vascular plants were the dominants (Rodwell ), although a number of bryophyte dominated communities (e.g. U10 12, M31 33) and a few with fruticose macrolichens as co-dominants (e.g. U13, H19) are included. However, NVC is poor when dealing with lichens. Much of the lichen data is, at best, unreliable (e.g. Cladonia crispata see below), and appears to have been taken from previously published accounts (e.g. McVean & Ratcliffe 1962) with little or no reference to subsequent lichen phytosociological work (e.g. James et al. 1977). Nomenclature follows Dahl (1968), which, although admirable in its day, even in 1991 had long been superseded by later, more comprehensive and more widely known works (e.g. Duncan 1970; Hawksworth et al. 1980; Dobson 1981; Cannon et al. 1985). Some of the names used have not been current for many years (e.g. Cetraria glauca has been known as Platismatia glauca since 1965) and many species mentioned in the NVC cannot be traced in the current lichenological literature (e.g. Purvis et al. 1992, 1994). This research was undertaken with the aim of adding more reliable lichen data to those montane NVC communities in which lichens are an important component. Methods Data were collected from the Cairngorm Mountains of eastern Scotland, especially Cairn Gorm (GR: 38/ ) and Cairn Lochan (GR: 28/985026), although also visited were Braigh Riabhach (Braeriach) (GR: 28/953800), MacDuibh (Ben Macdui) (GR: 27/991996), a Bhuird (GR: 37/092985), Lochnagar (GR: 37/224861), and Glas Maol (GR: 37/167766) (Fig. 1). In general, a 2 2 m quadrat size was chosen as this was the size used as standard by the NVC for recording most short, herbaceous vegetation

3 2001 Phytosociology of montane lichens in Scotland Fryday 333 Aviemore CAIRN GORM BRAIGH RIABHACH CAIRN LOCHAN BEINN MACDUIBH BEINN A ' BHUIRD 80 Braemar LOCHNAGAR 10 Km Ground over 1000 m GLAS MAOL 30 FIG. 1. Map of the Cairngorm Mountains, north-east Scotland, showing survey sites and ground over 1000 m altitude. and dwarf-shrub heaths (Rodwell ). In smaller scale mosaics a 1 1 m size was used. In each terricolous quadrat all vascular plants and lichens, along with the most prominent bryophytes, were recorded and assigned a score on the Domin scale (see Table 1). Also recorded for each quadrat were percentage total cover of vascular plants, bryophytes, lichens, rocks and bare peat/gravel, as well as the slope of the ground and its aspect. Definition of terms Montane is used in preference to Alpine as the former portrays a much more accurate picture of the British mountains, which although above the tree-line are largely snow-free for much of the year. The terms low- and mid-montane similarly are equivalent to the more usual low-alpine (e.g. above the tree-line but below the upper limit of ericaceous shrubs) and midalpine (e.g. above the level of ericaceous shrubs but below the permanent snow-line). In this paper macrolichens are considered to be those whose thalli have a fruticose or foliose habit, whereas microlichens are those with a crustose habit, even though some can have large and conspicuous thalli (e.g. Ochrolechia spp.). In montane situations, most macrolichens are fruticose (Cetraria spp., Cladonia spp.), foliose lichens being very rare. The phytosociological term Fidelity (from the Zürich-Montpellier school) is used to describe the characteristic species of a community rather than Constant (present in more than 60% of stands) that is used in the NVC. This reflects the occurrence of many lichen species, in that the characteristic species of a community are often sparsely distributed and, consequently, only rarely recorded in relevés. Constant species are usually widely distributed and of very limited value in characterizing a community. It also reflects the objective of this paper, which is to add lichen species to already existing NVC communities, not to describe new ones. The three grades of fidelity used are all for characteristic (faithful) species. Fidelity V exclusive species, completely or almost completely confined to one community; Fidelity IV selective species, found most frequently in a certain community but also, though rarely, in other communities; Fidelity III

4 334 THE LICHENOLOGIST Vol. 33 TABLE 1. Relevés collected from NVC H13 Calluna vulgaris Cladonia arbuscula heath Locality Constancy class* a Bhuird Cairn Gorm Range Grid Ref. 37/ / / / / / / / / / / / / /0006 Alt. (m) Date recorded 18/7/94 15/6/94 15/6/94 16/6/94 16/6/94 18/6/94 18/6/94 18/6/94 18/6/94 19/6/94 19/6/94 22/8/95 22/8/95 16/9/95 Vegetation cover (%) Height of vegetation (cm) Lichen cover (%) Gravel (%) Rocks (%) Slope ( ) Aspect ( ) Vascular plants Calluna vulgaris V Empetrum nigrum V Loiseleuria procumbens V Vaccinium myrtillus III V. vitis-idaea II Arctostaphylos uva-ursi I Pinus sylvestris I Carex bigelowii V Juncus trifidus III Carex pilulifera II Deschampsia flexuosa II Trichophorum cespitosum I Huperzia selago V Diphasiastrum alpinum II Bryophytes Racomitrium lanuginosum III Barbilophozia floerkei II Hypnum cupressiforme II Polytrichum piliferum II Diplophyllum albicans I Gymnomitrion concinnatum I Pohlia nutans I Terricolous lichens Cetraria islandica V Cladonia furcata V C. uncialis subsp. biuncialis V Flavocetraria nivalis V Micarea lignaria V Ochrolechia frigida V

5 2001 Phytosociology of montane lichens in Scotland Fryday 335 TABLE 1. Continued Locality Constancy class* a Bhuird Cairn Gorm Range Alectoria nigricans IV Baeomyces rufus IV Cetraria aculeata IV Cladonia arbuscula IV C. coccifera aggr. IV Dibaeis baeomyces IV Alectoria sarmentosa subsp. vexillifera III Cladonia bellidiflora III C. portentosa III Lecanora symmicta III Ochrolechia tartarea III O. xanthostoma III Thamnolia vermicularis III Alectoria ochroleuca II Cladonia rangiferina II Micarea leprosula II M. turfosa II Pycnothelia papillaria II Trapeliopsis granulosa II Arthrorhaphis grisea I Cetraria ericetorum I Cladonia chlorophaea I C. ciliata I C. fimbriata I C. floerkeana I C. luteoalba I C. zopfii I Hypogymnia physodes I Icmadophila ericetorum I Lecidea limosa I Micarea cinerea f. tenuispora I M. viridiatra I Ochrolechia androgyna I Parmeliopsis ambigua I P. hyperopta I Placynthiella icmalea I P. uliginosa I Platismatia glauca I Trapeliopsis gelatinosa I Saxicolous Lichens Porpidia crustulata III

6 336 THE LICHENOLOGIST Vol. 33 Table 1. Continued Locality Constancy class* a Bhuird Cairn Gorm Range Rhizocarpon geographicum III Umbilicaria cylindrica III Allantoparmelia alpicola II Cornicularia normoerica II Fuscidea intercincta II F. kochiana II Lecanora polytropa II Lecidea lithophila II L. pycnocarpa II L. swartzioidea II Porpidia tuberculosa II Pseudephebe pubescens II Umbilicaria proboscidea II Claurouxia chalybeioides I + Fuscidea cyathoides I + F. gothoburgensis I + Lecidea?lithophiloides I + L. pycnocarpa f. sorediata I + + Lecidella carpathica I + Micarea leprosula I + M. lignaria I + Miriquidica liljenstroemii I + M. lulensis I + M. nigroleprosa I + Ochrolechia tartarea I + Arctoparmelia incurva I + Pertusaria corallina I + + Porpidia striata ad int. I + + Rhizocarpon hochstetteri I + R. aff. eupetraeoides I + R. jemtlandicum I + Rimularia gyrizans I + + Schaereria cinereorufa I + S. fuscocinerea I + + Sphaerophorus globosus I + + Tremolecia atrata I + Umbilicaria torrefacta I + *Constancy classes: I=present in 1 20% of stands; II=21 40%; III=41 60%; IV=61 80%; V=81 100%. Numbers refer to the Domin Scale: 10=91 100% cover; 9=76 90% cover; 8=51 75% cover; 7=34 50% cover; 6=26 33% cover; 5=11 25%; 4=4 10% cover; 3=<4% cover, many individuals; 2=<4% cover, several individuals; 1=<4% cover, few individuals; + =<4% cover, single individual. On Calluna vulgaris stems. Lichenicolous fungus on Baeomyces rufus.

7 2001 Phytosociology of montane lichens in Scotland Fryday 337 preferential species, present in several communities more or less abundantly but predominantly, or with better vitality, in one certain community. Lichen nomenclature follows Purvis et al. (1993). Where later names have been used their name is given as a synonym. Bryophyte nomenclature follows Blockeel & Long (1998) and vascular plants Stace (1991). Results Terricolous communities In the British Isles, terricolous lichens are important as a structural element of montane vegetation only in the Eastern Highlands. Further west, ground conditions are, in general, too wet to support the type of lichen vegetation described here and it is replaced by internationally important lichendominated communities rich in endemic and rare species (Fryday 2001 & unpublished data). In the east, the vegetation described here ranges from Ben Kilbreck in the north to the Breadalbane Mountains in the south, although it reaches its optimum development in the Cairngorm Mountains. Only three NVC communities were found to support significant lichen vegetation. H13 Calluna vulgaris-cladonia arbuscula heath H19 Vaccinium myrtillus-cladonia arbuscula heath U9 Juncus trifidus-racomitrium lanuginosum rush heath All three communities occur in exposed situations in the Eastern Highlands, arranged with increasing altitude. H13 is the lowest, occurring in the low-montane zone, and grades into H19 with increasing altitude. U9 occurs on exposed summits and ridges in the mid-montane zone and is usually separated from H19 by an intermediate zone, often including U7 Nardus stricta- Carex bigelowii grass-heath and U10 Carex bigelowii-racomitrium lanuginosum moss heath. The species recorded from these three NVC communities in the present study are listed in Tables 1 3, with the constancy classes for each community summarized in Table 4. The characteristic lichen species for each community are given in Table 5. H13 Calluna vulgaris-cladonia arbuscula heath (Table 1) The facies of this community with the most diverse lichen vegetation is H13c Cladonia crispata-loiseleuria procumbens subcommunity (one of a group of communities also referred to as prostrate Calluna vulgaris heath). This is almost completely confined to the Cairngorm Mountains of north-east Scotland, where it covers large areas of lowmontane ground, typically of wind-swept, exposed ridges (c m) but occasionally also in less-exposed sites (Fig. 2). It is characterized by a dwarfed mat of Calluna vulgaris, often with fruticose macrolichens as co-dominants. The Calluna mat is commonly less than 5 cm high and can form a continuous cover, but is usually discontinuous, often fragmentary, due to severe exposure. Lichen diversity is greatest in those stands from the northern Cairngorms, decreasing further east or west due to increased vascular plant or bryophyte cover respectively. H13 is characterized by macrolichens with a fruticose habit (Cetraria spp. and Cladonia subgen. Cladina spp.) that are mostly confined to less-prostrate areas of vegetation in the lee of banks, although there is also a high percentage cover of the crustose microlichen Ochrolechia frigida overgrowing the prostrate Calluna vulgaris. A number of species qualify as constants, being present in more than 60% of stands. These are the macrolichens Alectoria nigricans, Cetraria aculeata, C. islandica, Cladonia arbuscula, C. coccifera aggr. (probably C. diversa), C. furcata, C. uncialis subsp. biuncialis and Flavocetraria nivalis (syn. Cetraria nivalis), and the microlichens Baeomyces rufus, Dibaeis baeomyces, Micarea lignaria and Ochrolechia frigida. Of these, Alectoria nigricans and Flavocetraria nivalis are more frequent here than in any of the other communities studied but the rest are mostly equally constant in other communities and are of little value in characterizing the community. Cladonia portentosa, although not achieving 60% constancy, is more frequent in H13 than in the other communities studied as it is a lowland

8 338 THE LICHENOLOGIST Vol. 33 TABLE 2. Relevés collected from NVC H19 Vaccinium myrtillus Cladonia arbuscula heath Locality Constancy class* Lochnagar Glas Maol a Bhuird Cairn Gorm Cairn Lochan Range Grid Ref. 37/ / / / / / / / / / / /9704 Alt. (m) Date recorded 8/7/95 8/7/95 7/7/95 18/7/94 18/7/94 16/6/94 16/6/94 16/6/94 18/6/94 18/6/94 16/9/95 24/8/95 Vegetation cover (%) Height of vegetation (cm) 5 5 1(5) Lichen cover (%) Gravel (%) Rock (%) Peat (%) Slope ( ) Aspect ( ) Vascular plants Empetrum nigrum V Vaccinium myrtillus V V. uliginosum III V. vitis-idaea III Melampyrum pratense II Calluna vulgaris I Loiseleuria procumbens I Carex bigelowii V Deschampsia flexuosa IV Juncus trifidus III Carex pilulifera I Festuca vivipara I Minuartia sedoides I Nardus stricta I Trichophorum cespitosum I Huperzia selago III Diphasiastrum alpinum I Bryophytes Racomitrium lanuginosum V Dicranum scoparium IV Pleurozium schreberi III Barbilophozia floerkei II Hylocomium splendens II Polytrichum piliferum II Rhytidiadelphus loreus II Anastrepta orcadensis I Calypogeia sp. I Diplophyllum albicans I Hypnum cupressiforme I Plagiothecium undulatum I 1 0 1

9 2001 Phytosociology of montane lichens in Scotland Fryday 339 TABLE 2. Continued Locality Constancy class* Lochnagar Glas Maol a Bhuird Cairn Gorm Cairn Lochan Range Pohlia nutans I Polytrichum commune I P. formosum I P. juniperinum I Ptilidium ciliare I Rhytidiadelphus squarrosus I Sphagnum quinquefarium I Terricolous lichens Cetraria islandica V Cladonia arbuscula V C. furcata V C. uncialis subsp. biuncialis V Ochrolechia frigida V Cladonia rangiferina IV Alectoria nigricans III Cetraria aculeata III Cladonia bellidiflora III C. coccifera aggr. III Flavocetraria nivalis III Micarea lignaria III Ochrolechia tartarea III Baeomyces rufus II Cladonia chlorophaea II Lecidoma demissum II Micarea leprosula II Pycnothelia papillaria II Thamnolia vermicularis II Cetraria ericetorum I C. muricata I Cetrariella delisei I Chromatochlamys geislerioides ad int. I Cladonia floerkeana I C. gracilis I C. macilenta I C. portentosa I C. squamosa I C. zopfii I Cladonia sp. (squamules) I Dibaeis baeomyces I Lecidea limosa I 1 0 1

10 340 THE LICHENOLOGIST Vol. 33 TABLE 2. Continued Locality Constancy class* Lochnagar Glas Maol a Bhuird Cairn Gorm Cairn Lochan Range Micarea cinerea f. tenuispora I M. peliocarpa I M. turfosa I Omphalina sp. (sterile) I Placynthiella uliginosa I Pseudephebe pubescens I Trapeliopsis gelatinosa I T. granulosa I Saxicolous Lichens Porpidia tuberculosa III Rhizocarpon geographicum III Fuscidea kochiana II Porpidia crustulata II Pseudephebe pubescens II Stereocaulon vesuvianum II Umbilicaria cylindrica II Allantoparmelia alpicola I + Cornicularia normoerica I + Fuscidea gothoburgensis I + + F. intercincta I + Lecanora polytropa I + + Lecidea lithophila I + L. pycnocarpa I + L. pycnocarpa f. sorediata I + Melanelia hepatizon I + Ochrolechia tartarea I + + Pertusaria corallina I + P. oculata I + Porpidia cinereoatra I + + P. contraponenda I + + Protoparmelia badia I + + Rhizocarpon copelandii s. lat. I + R. lecanorinum I + + Schaereria fuscocinerea I + Stereocaulon dactylopyllum I + Tremolecia atrata I + Umbilicaria proboscidea I + U. torrefacta I + *See footnote Table 1. Numbers refer to Domin Scale (see footnote Table 1).

11 2001 Phytosociology of montane lichens in Scotland Fryday 341 TABLE 3. Relevés collected from NVC U9 Juncus trifidus Racomitrium lanuginosum rush heath Locality Constancy class* Lochnagara a Bhuird Cairn Lochan MacDuibh Braigh Riabhaich Range Grid Ref. 37/ / / / / / / / / / / / / /9498 Alt. (m.) Date 8/7/95 18/7/94 18/7/94 17/6/94 17/6/94 19/6/94 19/6/94 19/6/94 19/6/94 17/6/94 17/6/94 17/6/94 17/6/94 20/7/94 Vegetation cover (%) Height of vegetation (cm) Lichen cover (%) Gravel (%) 0 nd nd Rocks (%) 0 nd nd Peat (%) 2 nd nd Slope ( ) Aspect ( ) Vascular plants Salix herbacea IV Empetrum nigrum subsp. hermaphroditum I Vaccinium myrtillus I Deschampsia flexuosa V Juncus trifidus V Carex bigelowii IV C. pilulifera I Festuca ovina I Luzula spicata I Nardus stricta I Huperzia selago I Bryophytes Racomitrium lanuginosum V Polytrichum piliferum IV Gymnomitrion sp. III Barbilophozia floerkei II Dicranum scoparium II Kiaeria starkei II Racomitrium heterostichum II Bryum?alpinum I Campylopus sp. I Dicranum fuscescens I Marsupella spp. I Polytrichum alpinum I P. commune I Polytrichum sp. I Ptilidium ciliare I Racomitrium fasciculare I

12 342 THE LICHENOLOGIST Vol. 33 TABLE 3. Continued Locality Constancy class* Lochnagara a Bhuird Cairn Lochan MacDuibh Braigh Riabhaich Range Terricolous lichens Cladonia coccifera aggr. V C. uncialis subsp. biuncialis V Ochrolechia tartarea V Cetraria islandica IV Cladonia bellidiflora IV C. furcata IV Dibaeis baeomyces IV Lecidoma demissum IV Micarea turfosa IV Ochrolechia frigida IV Baeomyces rufus III Cetraria aculeata III C. ericetorum III Cetrariella delisei III Cladonia arbuscula III Micarea cinerea f. tenuispora III M. lignaria III Stereocaulon condensatum III Arthrorhaphis grisea II Cladonia sp. (squamules) II Frutidella caesioatra II Lecidea hypnorum II Lepraria neglecta II Alectoria nigricans I Baeomyces placophyllus I Catillaria contristans I Cladonia chlorophaea I C. ciliata var. tenuis I C. gracilis I C. pyxidata I C. rangiferina I Epilichen scabrosus I Flavocetraria nivalis I Lecidea limosa I Pertusaria oculata I Pycnothelia papillaria I Stereocaulon saxatile I S. vesuvianum I Stereocaulon sp. I Thamnolia vermicularis I Toninia squalescens I 1 0 1

13 2001 Phytosociology of montane lichens in Scotland Fryday 343 TABLE 3. Continued Locality Constancy class* Lochnagara a Bhuird Cairn Lochan MacDuibh Braigh Riabhaich Saxicolous Lichens Lecidea lithophila III L. pycnocarpa III Porpidia crustulata III Rhizocarpon geographicum III Porpidia tuberculosa II Stereocaulon vesuvianum II Tephromela atra II Lecanora leptacina I + L. polytropa I + Lecidea limosa I + L. pycnocarpa f. sorediata I + L. swartzioidea I + Lepraria neglecta I + Miriquidica lulensis I + Ochrolechia tartarea I + Protoparmelia badia I + Rhizocarpon copelandii I + + R. hochstetteri I + Rimularia gyrizans I + Stereocaulon evolutum I + Umbilicaria cylindrica I + *See footnote Table 1. Numbers refer to the Domin Scale (see footnote Table 1). Lichenicolous fungus on Baeomyces rufus. Range

14 344 THE LICHENOLOGIST Vol. 33 TABLE 4. Terricolous lichens having a constancy of over 20% (Class II) in at least one of the three NVC communities studied Taxon H13 H19 U9 Alectoria sarmentosa subsp. vexillifera III (0 3) A. ochroleuca II (0 3) A. nigricans IV (0 2) III (0 3) I (0 1) Arthrorhaphis grisea* I (0 1) I (0 1) II (0 1) Baeomyces rufus IV (0 1) II (0 2) III (0 2) Cetraria aculeata IV (0 3) III (0 3) III (0 3) C. ericetorum I(0 1) I (0 3) III (0 3) C. islandica V(0 4) V (0 5) IV (0 4) Cetrariella delisei I(0 1) III (0 2) Cladonia arbuscula IV (0 5) V(0 6) III (0 2) C. bellidiflora III (0 2) III (0 2) IV (0 3) C. chlorophaea I(0 1) II (0 1) I (0 1) C. coccifera aggr. IV (0 3) III (0 3) V(0 4) C. furcata V(0 4) V (0 3) IV (0 4) C. portentosa III (0 2) I (0 1) C. rangiferina II (0 2) IV (0 4) I (0 2) C. uncialis subsp. biuncialis V(0 5) V (0 5) V (0 5) Cladonia sp. (squamules) I(0 2) II (0 3) Dibaeis baeomyces IV (0 2) I (0 1) IV (0 3) Flavocetraria nivalis V(0 3) III (0 2) I (0 1) Frutidella caesioatra II (0 3) Lecanora symmicta III (0 2) Lecidea hypnorum II (0 1) Lecidoma demissum II (0 I) IV (0 3) Lepraria neglecta II (0 1) Micarea cinerea f. tenuispora I(0 2) III (0 2) M. leprosula II (0 1) II (0 1) M. lignaria V(0 3) III (0 2) III (0 1) M. turfosa II (0 I) I (0 1) IV (0 3) Ochrolechia frigida V(0 5) V (0 4) IV (0 3) O. tartarea III (0 3) III (0 1) V(0 3) O. xanthostoma III (0 1) Pycnothelia papillaria II (0 1) II (0 1) I (0 1) Stereocaulon condensatum III (0 2) Thamnolia vermicularis III (0 2) II (0 3) I (0 1) Trapeliopsis granulosa II (0 1) I (0 1) *Lichenicolous fungus on Baeomyces rufus. On Calluna vulgaris stems. species that becomes rare at higher altitudes. The NVC reported Cladonia crispata as a constant in H13c but this species was not recorded during the present study and it is probable that most records of its occurrence here are misidentifications of other Cladonia spp., most probably C. furcata, which according to the NVC has a very low occurrence in the community. Three characteristic lichen species can be recognized at Fidelity V: Alectoria ochroleuca, A. sarmentosa subsp. vexillifera, and Ochrolechia xanthostoma (on Calluna vulgaris stems), and three at Fidelity III: Alectoria nigricans, Flavocetraria nivalis and Ochrolechia frigida (Table 5). Purvis et al. (1992) give the habitat of A. ochroleuca as In Rhacomitrium (sic)-empetrum communities above c. 800 m. but in this study it was found to be restricted to the lower facies of the prostrate Calluna vulgaris heath, often on the upper edge of the cline between this

15 2001 Phytosociology of montane lichens in Scotland Fryday 345 TABLE 5. Characteristic lichen species of the main NVC communities in the Cairngorm Mountains of north-east Scotland H13 Calluna vulgaris Cladonia arbuscula heath Fidelity V Alectoria ochroleuca Fidelity III Alectoria nigricans A. sarmentosa subsp. vexillifera Flavocetraria nivalis Ochrolechia xanthostoma Ochrolechia frigida H19 Vaccinium myrtillus Cladonia arbuscula heath Fidelity III Flavocetraria nivalis Ochrolechia frigida U9 Juncus trifidus Racomitrium lanuginosum rush heath Fidelity IV Catillaria contristans Fidelity III Micarea cinerea f. tenuispora Lecidoma demissum M. turfosa U7 Nardus stricta Carex bigelowii grass heath Fidelity V Cladonia maxima FIG. 2. H13 Calluna vulgaris-cladonia arbuscula heath. Creagan Dubh, northern Cairngorms. community and that in which Arctostaphylos uva-ursi becomes frequent (H16 Calluna vulgaris-arctostaphylos uva-ursi heath). Flavocetraria nivalis was also found to be most frequent in H13, in spite of the somewhat wider ecological amplitude given to it by Purvis et al. (1992). H19 Vaccinium myrtillus-cladonia arbuscula heath (Table 2) This community has a similar geographical distribution to H13, replacing it at higher altitudes. The Calluna vulgaris of H13 is replaced by Vaccinium myrtillus, which does not generally become as prostrate as C. vulgaris and, consequently, those crustose lichens that are able to overgrow the prostrate Calluna are not as numerous (Fig. 3). Conversely, as the sward tends to be taller the abundance of macrolichens is often greater. The variation in this community follows the same geographical trend as H13, with lichen diversity being greatest in those stands from the northern Cairngorms and decreasing further east and west. The lichen vegetation of this community is similar to that of H13, although constants are fewer, only Cetraria islandica, Cladonia arbuscula, C. furcata, C. rangiferina, C. uncialis subsp. biuncialis and Ochrolechia frigida being recorded from more than 60% of the

16 346 THE LICHENOLOGIST Vol. 33 FIG. 3. H19 Vaccinium myrtillus-cladonia arbuscula heath. Maidan Creag an Leth-choin, northern Cairngorms. stands. The macrolichen vegetation differs from H13 mainly in the absence of the characteristic species Alectoria ochroleuca and A. sarmentosa subsp. vexillifera, and the higher incidence of Cladonia rangiferina. The two Fidelity III species, Flavocetraria nivalis and Ochrolechia frigida (Table 5) do occur but are less frequent than in H13. Another difference is an increase in terricolous crustose species that occur in gaps in the vegetation, rather than overgrowing prostrate vegetation. This is consistent with the generally higher altitude of this community as these species, which include Chromatochlamys geislerioides ad int., Lecidoma demissum and Micarea cinerea f. tenuispora, have more affinity with midmontane communities (e.g. U9 Juncus trifidus-racomitrium lanuginosum rush heath) than the low-montane conditions of H13. This is an indication that macrolichens and microlichens need to be considered as separate groups, as the greatest change in the macrolichen vegetation occurs between H19 and U9 whereas for microlichens it is between H13 and H19. However, some microlichens occur in both H13 and H19 and more work is required to clarify this proposition. U9 Juncus trifidus-racomitrium lanuginosum rush heath (Table 3) This is the dominant community on exposed summits in the Cairngorm area, occurring more locally elsewhere in the Scottish Highlands. It is a community of exposed summit ridges and plateaux, typically occurring as clumps of Juncus trifidus dispersed on gravelly ground (Fig. 4). As with H13 and H19, lichen diversity is greatest in the stands of U9 in the northern Cairngorms (Cairn Lochan). To the east, on Lochnagar, the increasingly continental climate allows vascular plants to attain a higher altitude with the result that stands of U9 are not only smaller but vascular plants fill those gaps in the community that are occupied by lichens on Cairn Lochan. Further west, on Braigh Riabhaich, Racomitrium lanuginosum forms a much greater component of the vegetation and lichens are largely absent. Further west still (e.g. Mam Sodhail/Carn Eige in the Central Highlands), R. lanuginosum is often replaced by damp peat covered with a bryophyte/microlichen mat, and lichen species diversity can be very high (Fryday 2001 & unpublished data).

17 2001 Phytosociology of montane lichens in Scotland Fryday 347 FIG. 4. U9 Juncus trifidus-racomitrium lanuginosum rush heath. Cairn Lochan. In U9, the shift away from the macrolichens characteristic of H13, that was apparent in H19, is much more pronounced, with the former being confined to clumps of vascular plant vegetation and the latter mainly occupying the bare soil between them. Constant species are the macrolichens Cetraria islandica, Cladonia bellidiflora, C. furcata and C. uncialis subsp. biuncialis, and the microlichens Dibaeis baeomyces, Lecidoma demissum, Micarea turfosa, Ochrolechia frigida and O. tartarea. Compared with H13 and H19, the decline in cover and occurrence of the fruticose macrolichens Cetraria islandica (to some extent replaced by C. ericetorum and Cetrariella delisei) and Cladonia subgenus Cladina is particularly apparent. However, three macrolichens, Cladonia bellidiflora, Stereocaulon saxatile and S. condensatum, are more frequent in this community than in either H13 or H19. The first two species were considered by Gilbert & Fox (1985) to be constant species of late snow-lie vegetation and they are now known to be much more widespread (Fryday 1997b, 2001 & unpublished). Microlichens are a much more important component of this community than either H13 or H19, largely due to the lower cover of vascular plants. Lecidoma demissum is particularly characteristic of this community, often occurring as large thalli, along with Catillaria contristans, Frutidella caesioatra, Lecidea hypnorum, L. limosa, Lepraria neglecta, Micarea cinerea f. tenuispora and Ochrolechia tartarea. Although some of these species (i.e. Lecidea hypnorum, Lepraria neglecta) also occur in other mid- to highmontane communities (e.g. U8 and late snow-lie vegetation), most reach their best development in U9, at least in the Cairngorms, and can be considered as characteristic species in this area. Lecidoma demissum and Ochrolechia tartarea are best assigned to Fidelity IV, and Micarea cinerea f. tenuispora to Fidelity III (Table 5). It is probable that this lichen-dominated vegetation should be recognized as a separate community as it occurs throughout the Scottish Highlands associated with a wide range of NVC communities (e.g. U8, U12, CG11) (Fryday 1997b, 2001, unpublished data). Other NVC communities Two other important NVC montane communities, U7 Nardus stricta-carex bigelowii grass-heath and U10 Carex bigelowii- Racomitrium lanuginosum moss-heath were also sampled, but were of only minor lichenological interest. In both these

18 348 THE LICHENOLOGIST Vol. 33 communities lichens occurred mostly in gaps in the vegetation and so were not strictly part of the community. Two very rare Cladonia species, C. phyllophora and C. trassii (syn. C. stricta auct. p.p.) were among the species recorded, but these are both more strongly associated with areas of late snow-lie. U7 does, however, have one characteristic species at Fidelity V, Cladonia maxima that occurs within the Nardus sward (Table 5). Rodwell (1991) also includes Cetrariella delisei (as Cetraria delisei) as a rare species occurring in this community (as well as in U8 and U9) but the actual ecology of this species is somewhat more complex. This lichen occurs on the boundary between U7 and the other communities (see below). Also of interest were U8 Carex bigelowii- Polytrichum alpinum sedge heath, U11 Polytrichum sexangulare-kiaeria starkei snow-bed and U12 Salix herbacea-racomitrium heterostichum snow-bed. U8 was difficult to sample adequately as it was usually seen only as very small stands in mosaics with other communities and the microclimatic effects associated with the boundaries of the community rendered it almost impossible to recognize an homogeneous stand. Only on a Bhuird were stands of any size encountered and there the lichen vegetation differed little from that of U9. U11 and U12, which are strongly characterized by their lichen component, are confined to areas of late snow-lie and are dealt with elsewhere (Fryday 1997b, 2001). Saxicolous communities Tables 1 3 include a large number of saxicolous lichen species but, as outlined above, the problems associated with phytosociological studies of saxicolous lichen communities are numerous and they need to be considered separately from the surrounding terricolous vegetation. Some distribution patterns are discernable, but these are probably related to changes in altitude, rather than the species having an affinity with a specific community. None of the species can be regarded as constants as none have a constancy of greater than III (60%) for any of the three TABLE 6. Saxicolous lichens having a constancy of over 20% (Class II) in at least one of the three NVC communities studied Taxon H13 H19 U9 Allantoparmelia alpicola II I Cornicularia normoerica II I Fuscidea intercincta II I F. kochiana II II Lecanora polytropa II I I Lecidea lithophila II I III L. pycnocarpa II I III L. swartzioidea II I Porpidia crustulata III II III P. tuberculosa II III II Pseudephebe pubescens II II Rhizocarpon geographicum III III III Stereocaulon vesuvianum II II Tephromela atra II Umbilicaria cylindrica III II I U. proboscidea II communities involved. Furthermore, those that achieve this level of constancy are mostly widespread, common species (e.g. Porpidia crustulata, P. tuberculosa, Rhizocarpon geographicum). However, a number of species reach their highest constancy in H13 and decrease in frequency with increasing elevation (i.e. Allantoparmelia alpicola, Cornicularia normoerica, Fuscidea intercincta, Umbilicaria cylindrica), whereas two, Fuscidea kochiana and Pseudephebe pubescens, are of equal frequency in H13 and H19, but absent from U9. Conversely, two species, Lecidea lithophila and L. pycnocarpa, are most frequent in U9, and Tephromela atra was recorded only from this community. The constancy classes for saxicolous lichens in each community are summarized in Table 6. Discussion Initially it was planned to analyze the data collected from the relevés using TWIN- SPAN. However, while collecting data it became clear that this would be a poor utilization of time and resources as the macrolichen data appeared to fit very well

19 2001 Phytosociology of montane lichens in Scotland Fryday 349 with NVC communities whereas the microlichen data showed little correlation with it. The relevé size used to sample NVC communities (2 2 m) was also far too large to provide the required homogeneous stand of microlichen-dominated vegetation. Although not completely without value, TWINSPAN added little to what was apparent from hand-sorting and visual inspection of the data. Two main factors have emerged from the present study which need to be taken into account when recording lichen data for phytosociological studies. These are mostly due to the sensitivity of lichens to small environmental changes (a) Some NVC types are actually small-scale mosaics. These cannot be treated as homogeneous stands when investigating the lichen vegetation as each microenvironment has its own characteristic lichen vegetation. The NVC treated mosaics as a single vegetation type where they were repeatedly encountered in the same form or where the scale made it quite impossible to sample the elements separately (Rodwell ). This approach will obscure the basic pattern of lichen synecology, which is characterized by small-scale mosaics determined by slight changes in the microecology of the substratum. Rocks, low boulders and banks or even variations in the luxuriance of the dominant vascular plants can create microhabitats with their own distinctive lichen vegetation. In such cases, inclusion of comprehensive lichen data only serves to complicate the delimitation of NVC communities as microlichens operate on a very different environmental scale to vascular plants. An example of this is U9 Juncus trifidus- Racomitrium lanuginosum rush-heath in the Cairngorms where R. lanuginosum is often scattered and Juncus trifidus occurs as isolated clumps separated by areas of gravel (Fig. 4). In these situations the relative shelter afforded by the J. trifidus clumps allows the development of macrolichens (e.g. Cladonia subgen. Cladina spp., Cetraria spp., Stereocaulon spp.), whereas the decaying bases are colonized by Cladonia subgen. Cladonia spp. and the larger crustose lichens (e.g. Lecidoma demissum, Ochrolechia spp.). The gravel between the clumps is, when stabilized, the habitat of smaller microlichens, (e.g. Catillaria contristans, Dibaeis baeomyces, Lecidea limosa and Micarea spp., especially M. turfosa). There is considerable overlap between the lichen vegetation of these last two habitats and there is a case for recognizing this as a distinct community. It is possible that if the vegetation of an area were to be studied using smaller relevés then characteristic microlichens would emerge as this may reveal that they are associated with small vascular-plant stands that can be assigned to a relevant NVC community. It is more probable, however, that it will be necessary to investigate the microlichen vegetation separately from the vascular plants if a more detailed picture of the synecology of the lichen vegetation is to be attained. (b) Lichens, especially microlichens, are sparse in the homogeneous stands of vascular plant vegetation studied. Lichen-rich areas often occur where vascular plants are sparsely distributed. Where the vascular plant vegetation forms a continuous stand only macrolichens are able to compete well enough to play a structural role in the vegetation (e.g. Cetraria islandica, Cladonia subgen. Cladina spp.). Hence, they are reasonably well covered in the NVC. However, even macrolichens often reach their optimum development where vascular-plant growth is sparse. The habitat of Cetrariella delisei in the Cairngorms illustrates this problem. The NVC includes this, as a rare species, in U7 Nardus stricta-carex bigelowii grass-heath, U8 Carex bigelowii-polytrichum alpinum sedge-heath, and U9 Juncus trifidus-carex bigelowii rush-heath but closer examination reveals that Cetrariella delisei does not form part of any of these communities. It rarely occurs within the N. stricta sward, as do some other macrolichens (e.g. Cladonia

20 350 THE LICHENOLOGIST Vol. 33 Conclusions FIG. 5. Cetrariella delisei forming dense sward on edge of Nardus stricta-carex bigelowii grass heath (U7) where it gives way to Carex bigelowii-polytrichum alpinum sedge heath (U8). a Bhuird. maxima, Cetraria islandica and C. ericetorum), but reaches its optimal development on the edge of the grassland where U7 gives way to other communities, most frequently U8 Carex bigelowii-polytrichum alpinum or U9 Juncus trifidus-carex bigelowii (Fig. 5). In this situation it is often associated with Stereocaulon saxatile and it is possible that a separate community will be required to accommodate this assemblage. Microlichens are more confined to places where the vascular plant vegetation is so sparse as to allow semi-permanent gaps to appear (e.g. U9 Juncus trifidus-racomitrium lanuginosum rush-heath) or where they can overgrow it (e.g. H13 Calluna vulgaris- Cladonia arbuscula heath) and, consequently, do not fit well into the NVC classification. Most phytosociological studies of montane plant communities exclude crustose lichen species that grow on soil and all saxicolous lichen species, concentrating instead on the fruticose macrolichens that form a structural element of the terricolous vegetation. This has resulted in the widely held belief among ecologists and conservationists that, in montane areas at least, lichens are important in the continental east, and bryophytes in the oceanic west, a view largely perpetuated by the NVC (Rodwell ) which treats only those cryptogamic communities dominated by macrolichens or bryophytes. However, the lichen vegetation of the Eastern Highlands is best considered as a speciespoor outlier of that of the Scandinavian heaths, for example, the Loisleurieto- Arctostaphylion (Nordhagen 1928) or the Arctostaphyleto-Cetrarion (Dahl 1965), and is, on an international scale, of only minor importance. In the Western Highlands, terricolous macrolichen diversity is much reduced, largely due to the damper soil conditions. However, important microlichen-dominated communities occur on rocks and damp soil that are of great intrinsic importance as they include many undescribed, and apparently endemic, species and are also major contributors to the botanical biodiversity of the montane ecosystem (Fryday 1997a & b, 2001 & unpublished). Unfortunately, their synecology is poorly understood, not least because species concepts in many critical genera are unclear and until these are resolved, phytosociological work is likely to be of limited value. The present work has been most successful when sampling large areas of homogeneous, lichen-rich vascular plant vegetation that occupy an ecologically uniform habitat, especially where the lichen vegetation is dominated by macrolichens. Elsewhere, the lichen component of what appears to be homogeneous vascular-plant vegetation is very rarely homogeneous. Because of the sensitivity of microlichens to fluctuations in the microenvironment, minor

21 2001 Phytosociology of montane lichens in Scotland Fryday 351 changes in the relief of the ground or small differences in the vascular plant vegetation often result in variations in the lichen vegetation. Conversely, the same assemblage of microlichens will occur in a specific habitat regardless of the associated vascular plant community. Consequently, characteristic microlichens with a high degree of fidelity to a vascular plant community are rarely encountered. Although lichen and vascular plant communities are only poorly correlated in montane habitats in the Scottish Highlands, this is not always the case elsewhere in the world. Glew (1997) found a better correlation in some heaths and snow-beds in the NW USA, although the vegetation she describes appears very different from that of the Scottish Highlands. I am particularly grateful to Dr A. M & A. B. G. Averis who made many useful comments on the first draft of this manuscript, and to Dr O. L. Gilbert for comments on an earlier version and for assistance with the fieldwork on Cairn Gorm and Cairn Lochan. I acknowledge the award of a research scholarship from the University of Sheffield and several short-term contracts from Scottish Natural Heritage and The Natural Trust for Scotland that facilitated the gathering of data upon which this paper is based. Note added in proof: Mr J. Laundon (pers. comm.) has pointed out that the new combination Micarea cinerea f. tenuispora (Fryday 2001) is invalid as the date of publication of the basionym was omitted. The necessary corrected new combination is made here: Micarea cinerea (Schaer.) Hedlund f. tenuispora (D. Hawksw. & Poelt) Fryday comb. nov. Basionym: Hastiferea tenuispora D. Hawksw. & Poelt, Plant Sys. Evol. 154: 198 (1986). REFERENCES Blockeel, T. L. & Long, D. G. (1998) A Checklist and Census Catalogue of British and Irish Bryophytes. Cardiff: British Bryological Society. Cannon, P. F., Hawksworth, D. L. & Sherwood-Pike, M. A. (1985) The British Ascomycotina: An annotated checklist. Kew: Commonwealth Mycological Institute. Dahl, E. (1956) Rondane: mountain vegetation in south Norway and its relation to the environment. Skrifter utgitt av det Norske videnskap-akademi i Oslo. Matematisk-naturvidenskapelig klasse 3: Dobson, F. (1981) Lichens: An Illustrated Guide. 2nd edn. Richmond: Richmond Publishing Company. Duncan, U. (1970) Introduction to British Lichens. Arbroath: Buncle & Co. Fryday, A. M. (1997a) Montane lichens in Scotland. Botanical Journal of Scotland 49(2): Fryday, A. M. (1997b) Ecology and Taxonomy of Montane Lichen Vegetation in the British Isles. Ph.D. Thesis, University of Sheffield. Fryday, A. M. (2001) The lichen vegetation associated with areas of late snow-lie in the Scottish Highlands. Lichenologist 33: Gilbert, O. L. & Fox, B. W. (1985) Lichens of high ground in the Cairngorm mountains, Scotland. Lichenologist 17: Glew, K. A. (1997) Do vascular plant communities influence the structure of alpine lichen communities? Bibliotheca Lichenologica 68: Hawksworth, D. L., James, P. W. & Coppins, B. J. (1980) Checklist of British lichen-forming, lichenicolous and allied fungi. Lichenologist 12: James, P. W., Hawksworth, D. L. & Rose, F. (1977) Lichen communities in the British Isles: a preliminary conspectus. In Lichen Ecology (M. R. D. Seaward, ed.): London: Academic Press. McVean, D. N. & Ratcliffe, D. A. (1962) Plant Communities of the Scottish Highlands. (Monographs of the Nature Conservancy No 1). London: H.M.S.O. Nimis, P. L. (1991) Developments in lichen community studies. Lichenologist 23: Nordhagen, R. (1928) Die vegetation und flora des Sylengebietes. Skrifter utgitt av det Norske videnskaps-akademi. Matematisk naturvidenskapelig klasse 1928: Purvis, O. W., Coppins, B. J., Hawksworth, D. L., James, P. W. & Moore, D. M. (1992) The Lichen Flora of Great Britain and Ireland. London: Natural History Museum Publications. Purvis, O. W., Coppins, B. J. & James, P. W. (1993) Checklist of Lichens of Great Britain and Ireland. London: British Lichen Society. Rodwell, J. S. (ed.) ( ) British Plant Communities. Vols 1 5. Cambridge: Cambridge University Press. Rodwell, J. S. (ed.) (1991) British Plant Communities. 2: Mires and Heaths. Cambridge: Cambridge University Press. Roux, C. (1990) Echantillonage de la végétation lichénique et approche critique des méthodes de relevé. Cryptogamie, Bryologie et Lichénologie 11: Stace, C. A. (1991) New Flora of the British Isles. Cambridge: Cambridge University Press. Accepted for publication 22 January 2001