Literature review of upland saxicolous lichen and bryophyte communities Report No. F01AC201/1 For further information on this report, please contact: David Horsfield Scottish Natural Heritage 2 Anderson Place Edinburgh EH6 5NP This report should be quoted as: Alan Orange (2002). Literature review of upland saxicolous lichen and bryophyte communities. Scottish Natural Heritage Commissioned Report F01AC201/1 This report or any part of it should not be reproduced without the permission of Scottish Natural Heritage, which will not be unreasonably withheld. The views expressed by the author of this report should not be taken as the views and policies of Scottish Natural Heritage.  Scottish Natural Heritage 2002. COMMISSIONED REPORT F01AC201/1  SCOTTISH NATURAL HERITAGE 2002 COMMISSIONED REPORT Summary LITERATURE REVIEW OF UPLAND SAXICOLOUS LICHEN AND BRYOPHYTE COMMUNITIES Report No: F01AC201/1 Contractor: Alan Orange, Department of Biodiversity and Systematic Biology, National Museum and Gallery, Cardiff CF10 3NP. Tel. 029 20 573264. E-mail: alan.orange@nmgw.ac.uk BACKGROUND Upland rock habitats include scree, boulder, rock face and crevice (chasmophytic) communities. The GB lichen and bryophyte flora is one of the richest in Europe and important internationally. However, little is known about the lichen and bryophyte communities of rock habitats, which are among the most important habitats for these lower plants. Five upland rock habitats are listed in the EC Habitats Directive including scree, chasmophytic habitats and limestone pavement. Special Areas of Conservation have been designated for these habitats based primarily on the vascular plant flora, but also for the areas known to outstanding for lower plant species. Information on the communities of lichens and bryophytes of these habitats will help to identify the more valuable areas, assess their vulnerability to threats and help set management aims and objectives. The published literature covering the British Isles is reviewed, along with available unpublished reports. Important European phytosociological works are also included. There is an overview of the known communities in the British Isles. This provisional literature review will be revised when the initial phase of the field survey part of the project is completed in 2003/04. MAIN FINDINGS • The studies reviewed cover a range of rock types including granite, sandstones, limestone, schists, rhyolite and pumice-tuff from Dartmoor to the Scottish Highlands. Many of the rarer lichens occur on calcareous rocks at high altitude in the Scottish Highlands. Many of the rarer bryophytes occur in base-rich overhangs and crevices. • The major divisions are of 1) mostly lichen communities occurring on the following kinds of rock: limestone and other calcareous rocks (low altitude), montane base-rich rocks, siliceous rocks, nutrient-enriched rocks, mineral-rich rocks, flushed rocks, rocks in snow-beds; 2) aquatic communities with either lichens or bryophytes abundant; and 3) mostly bryophyte-dominated terrestrial communities of overhangs, crevices and boulders (including woodland). • Environmental factors known to influence the species composition of the communities are rock type, altitude, shelter, shade, humidity, and variation in flushing by water and nutrient enrichment. For further information on this project contact: David Horsfield, SNH, Advisory Services, 2 Anderson Place, Edinburgh EH6 5NP: tel. 0131 554 9797. For further information on the SNH Research & Technical Support Programme contact ASCG@SNH.GOV.UK COMMISSIONED REPORT F01AC201/1  SCOTTISH NATURAL HERITAGE 2002 TABLE OF CONTENTS 1 INTRODUCTION ............................................................................................................... 1 2 LITERATURE REVIEW ..................................................................................................... 1 3 OVERVIEW OF UPLAND SAXICOLOUS COMMUNITIES................................................ 3 3.1 Introduction to the communities.................................................................................. 3 1 Limestone and other calcareous rocks .................................................................... 4 2 Montane base-rich rocks ........................................................................................... 6 3 Siliceous rocks with basic influence, not flushed ................................................... 7 4 Siliceous rocks........................................................................................................... 7 4.1 Dry shaded siliceous rocks ....................................................................................... 7 4.2 Exposed siliceous rocks ........................................................................................... 9 5 Nutrient-enriched rocks........................................................................................... 12 6 Mineral-rich rocks .................................................................................................... 14 7 Aquatic communities ............................................................................................... 15 8 Flushed rocks........................................................................................................... 16 9 Snow beds ................................................................................................................ 17 10 Bryophyte dominated terrestrial communities ...................................................... 17 4 REFERENCES ................................................................................................................ 19 COMMISSIONED REPORT F01AC201/1  SCOTTISH NATURAL HERITAGE 2002 1 INTRODUCTION This literature review and overview of saxicolous lichen and bryophyte communities indicates what is known about these communities in the British Isles. This report will be expanded and rewritten at the culmination of the planned fieldwork on this project in 2003 to incorporate the results of fieldwork in the uplands of Scotland, England and Wales. 2 LITERATURE REVIEW Remarkably, little has been published on upland lichen and bryophyte communities in the British Isles. Possible reasons for this include the relatively small number of active cryptogamists compared to vascular plant botanists, an emphasis in recent decades on recording and mapping, identification difficulties associated with saxicolous crustose lichens, and perhaps a distrust of phytosociological methods. Floristic works sometimes contain mentions of named lichen associations, but the treatment is often rather perfunctory and contains little original data. Such works may also contain indirect information about the range of lichen communities present in a site or area, but generally these have been omitted from this review. Few accounts have considered both lichens and bryophytes together, or have included only bryophytes and macrolichens. Important phytosociological works on saxicolous lichen communities covering parts of central Europe, France and Scandinavia are Klement (1955), Wirth (1972), Roux (1978) and Creveld (1981). These contain descriptions of some noda which can doubtless be found in Britain. However, these works are not of direct relevance as they do not contain data from Britain. Nimis (1991) provides a review of phytosociological thought in relation to lichen studies. The main references are listed below. Other accounts of communities and relevé data, doubtless occur in unpublished reports or are held by individuals, but these are difficult to trace. Some of the examples below were kindly suggested by Ben Averis. A brief summary of the communities identified in some of them is provided in the overview of communities below (section 3, p. 3) with an update of the nomenclature. Richards (1938) described the bryophyte communities of woodland in Killarney, including two on boulders, and noted that the two were different stages in a cyclical succession. Yarranton (1962) described the bryophyte communities of the dolerite of Breidden Hill, North Wales. Forty homogeneous stands were selected, and the whole stand was studied unless very large. The final relevés varied from 1.5 to 300 square metres, and many almost certainly included what would be regarded as a mosaic of different noda by the present writer. Seven groupings were distinguished, which showed a correlation with pH and degree of shading, amongst other factors. Yarranton (1967) studied bryophytes and macrolichens at 64 sites on the Dartmoor granite. Sites were sampled using a fishing net spread over the rocks, and at each of 250 intersections per site, the species present, and the species touching it nearest to the intersection, were recorded. Positive associations between species were presented as a diagram. A correlation matrix enabled eight groups to be distinguished, which appear to correlate only broadly with clusters in the interspecific association diagram. This ‘plotless’ method of recording in the field was intended to avoid problems related to quadrat size and the identification of homogeneous areas. The groupings identified can be broadly interpreted by the reader as assemblages of species of exposed rock, shaded rock, rock with peaty COMMISSIONED REPORT F01AC201/1  SCOTTISH NATURAL HERITAGE 2002 accumulation, and so on. The results appear to have limited use for the description and classification of the vegetation. James et al. (1977) provided a valuable overview of lichen communities in the British Isles, which remains the standard reference to date. The composition, habitats and relationships of the associations are described, but there are few floristic tables, and these typically contain no more than six relevés each. Pentecost (1980) compared the lichen and bryophyte flora of rhyolite and pumice-tuff outcrops in North Wales, using a randomly placed quadrat of area 0.07 m2. The 50 relevés recorded are tabulated and the properties of the two rock types were compared. Gilbert et al. (1982) described a base-rich high-altitude flora from a small site on Aonach Beag in the Ben Alder range, at 1030 m altitude, associated with limestone and epidiorite. The survey was essentially floristic, and the lists of species according to substrate do not necessarily correspond to communities. Bryophytes were not included, and the emphasis was apparently on the rarer lichens. The site had a complex assemblage of communities, and the limits between communities of rock, soil, moss cushions and organic debris were not always well defined. The authors considered this site to be one of the two richest sites in Britain for montane calcicolous lichens. The richness was attributed to a combination of climatic features (the site is both oceanic and alpine in climate), and to a diversity of rock type, degree of dampness and exposure within the site. The site is small, and it was pointed out that further collection of lichens as vouchers was unnecessary. McCarthy (1983) described the lichen-dominated communities of limestone at a site in the Burren, western Ireland. A randomly placed 10 × 10 cm quadrat was used to sample 113 stands. Five noda were distinguished by inter-specific association. Although most of the relevé data were listed, they were grouped by type of substrate rather than nodum, and floristic tables as such were not presented. Degree of moisture, insolation, and bird manuring were important features influencing the flora; smooth, exposed clint surfaces were an inhospitable environment for lichen growth. Two kamenitzas (water-holding depressions on clint surfaces) were described by transects. Gilbert et al. (1988) described the montane lichen flora of Ben Lawers, with particular reference to calcareous mica-schist and metamorphosed limestone. The authors concluded that the lichen flora had international importance. The paper is floristic in content, but includes numerous ecological notes, which give an indication of the range of communities to be found, which include numerous montane calcicolous rarities. Graham (1988) listed a small number of relevés as examples of lichen and bryophyte dominated communities in Durham, and grouped them by habitat (the present writer would disagree with some of the associations identified). Giavarini (1990) published a floristic study of the lichens of the Dartmoor rocks, with ecological notes that name some phytosociological associations, and give an indication of the range of noda that are present. Granite and dolerite bore a rather differing flora. In very exposed situations, typically maritime species sometimes occurred. Grazing, trampling, burning and nutrient enrichment were mentioned as threats to lichen diversity. Rodwell (1991-2000) provides a modern phytosociological description of British higher plant vegetation, which includes those (usually terricolous) bryophytes and macrolichens that occur in higher plant stands. Only bryophyte-rich stands in rock crevices containing small ferns (communities OV39 and OV40) are directly relevant to this study (Rodwell 2000). COMMISSIONED REPORT F01AC201/1  SCOTTISH NATURAL HERITAGE 2002 Purvis (1996) discussed the occurrence of lichens on metal-rich rocks, and described a new lichen association represented in Britain by a species-poor facies from Coniston, Lake District. Averis (1998a) presented a classification of bryophyte dominated communities in Scottish Highland woods. Averis (1998b) classified bryophyte-dominated stands in woodland in Mid Wales into a number of associations, including nine on rock. Averis & Averis (1998c) listed presence and absence data for 23 relevés on well-drained acid rocks and on wet rocks. Orange & Fryday (1998) studied lichens and bryophytes by means of 136 relevés on upland rocks in Eryri (Snowdonia), and provisionally identified 17 noda. Some of these could be broadly correlated with assemblages previously noted in the literature, while others appeared not to be formally recognised. In the field relevés were placed in subjectively selected stands, which were judged to be homogeneous. A quadrat of 25 × 25 cm was used for most relevés, and a quadrat of 50 × 50 cm (or equivalent area) was used for some bryophyte-dominated stands. Orange (1998) described the lichen-dominated communities of Carn Ingli SSSI in Pembrokeshire, on exposed outcrops of rhyolite, tonalite and dolerite, and on the ground. Eighty-three relevés were grouped provisionally into 12 saxicolous and 2 terricolous noda. Averis & Averis (1999) listed relevé data for three lichen and bryophyte assemblages on acid and basic rocks on Ben Lui. Orange (1999) recorded 40 relevés from beside a wooded stream in North Wales, identified 5 noda and made a preliminary attempt to relate them to duration of inundation throughout the year. Averis (2000) described several bryophyte-dominated assemblages and provided relevé data. Averis & Averis (2000) provided relevé data for several quadrats on rocks and scree on Cadair Idris. Fryday (2001) carried out a detailed survey of lichens in snow beds, at four localities in the Scottish Highlands. Species on small rocks and pebbles were recorded in 2 × 2 m quadrats together with vascular plants and the more abundant bryophytes. Species on the surfaces of more or less horizontal boulders were recorded in 1 × 1 m relevés. The author discussed earlier work on snow bed lichens, and concluded that the Scottish communities were important in their own right, and were not simply attenuated facies of Scandinavian snow bed communities. 3 OVERVIEW OF UPLAND SAXICOLOUS COMMUNITIES 3.1 Introduction to the communities A brief overview of the range of communities recognised up to now in Britain is presented below. This is to highlight the communities to include in any comprehensive review of saxicolous lichen and bryophyte vegetation. It would not be useful at this stage to attempt to COMMISSIONED REPORT F01AC201/1  SCOTTISH NATURAL HERITAGE 2002 reconcile the various sources into a single classification. The overview is based on James et al. (1977), with other sources included where appropriate. All communities and habitats have been covered except for maritime communities. Freshwater communities are relevant to upland work, as in high rainfall areas flushed surfaces are frequent, and it is not always easy to make a sharp distinction between freshwater and terrestrial stands. Rocks within woodlands are not to be sampled in the present survey, but some woodland communities may occur on upland rocks (for instance below overhangs). In any case, references to such vegetation are so few they have been included for completeness. The main noda have been numbered below, and what appear to be facies of the main nodum have been listed afterwards. Single records or species lists not collected by phytosociological methods have been included as unnumbered ‘examples’. 1 Limestone and other calcareous rocks 1.1 This community is found on well-lit dry limestone. Aspicilia calcarea, crustose Verrucariaceae including Verrucaria baldensis, V. muralis, V. hochstetteri, more rarely Polyblastia albida, P. cupularis, P. dermatodes, Thelidium decipiens and T. incavatum are present. This is a widespread and variable community (Caloplacetum heppianae, James et al. 1977). McCarthy (1983) identified the community above from upper surfaces of rocks in the Burren, as two different noda, the first with Aspicilia calcarea, Caloplaca citrina, Verrucaria nigrescens and others, and the second with Verrucaria baldensis, V. dufourii and Protoblastenia incrustans. The first probably represents a slightly more nutrient enriched nodum than the second. Facies: 1.1.1 Caloplaca aurantia and C. flavescens are dominant (mostly southern, rare in Scotland; James et al. 1977). 1.1.2 Caloplaca teicholyta is abundant (eastern; James et al. 1977). 1.1.3 Solenopsora candicans is abundant (western; James et al. 1977). 1.1.4 Caloplaca aurantia and C. flavescens is rare; Rhizocarpon umbilicatum, Caloplaca variabilis, Polyblastia deminuta, Protoblastenia incrustans and foveolate Verrucariaceae are present. Communities with reduced representation of species occur in dry sites (perhaps not a distinct facies; James et al. 1977). 1.1.5 This facies is bryophyte-rich, poor in Caloplaca species, but with Caloplaca cerina var. stillicidiorum, Collema multipartitum, Lecidea ‘templetonii’ (L. hypnorum agg.), Protoblastenia incrustans, Solorina saccata and Squamarina cartilaginea. Found in high rainfall areas with low sunshine (James et al. 1977). 1.1.6 Lecanora dispersa is dominant, sometimes with Candelariella aurella; Caloplaca aurantia and C. flavescens absent. Found in polluted urban areas (James et al. 1977). 1.1.7 Caloplaca decipiens and Xanthoria elegans are frequent. Found on mortar in eastern Scotland (James et al. 1977). COMMISSIONED REPORT F01AC201/1  SCOTTISH NATURAL HERITAGE 2002 1.2 This community is found on damp limestone in shade. Gyalecta jenensis or sometimes Petractis clausa are dominant. Other characteristic species include Acrocordia conoidea, Caloplaca cirrochroa, Diploschistes gypsaceus, Farnoldia jurana, Opegrapha saxatilis, O. saxicola, Porina linearis and Clauzadea metzleri. Belonia nidarosiensis is locally abundant (Gyalectetum jenensis, James et al. 1977). Facies: Some stands of nodum SX15, Orange & Fryday (1998) may be related, with Gyalecta jenensis, Lepraria eburnea and calcicolous mosses. 1.3 This community is found on sheltered limestone on slightly shaded near vertical, often north-facing surfaces. This community is dominated by Dirina massiliensis f. sorediata and shares many species with 1.1 but Caloplaca aurantia and C. flavescens are rare. Other species include Caloplaca ochracea, Lecanactis grumulosa, Opegrapha calcarea, O. mougeotii and O. subelevata.(Dirinetum stenhammariae, James et al. 1977). 1.4 This community is found on sheltered limestone in humid sites. Abundance of one or more of Lepraria nivalis, Lepraria ‘incana’ (not this species), Lepraria lesdainii, Leproplaca chrysodeta and L. xantholyta. The community is species poor and widespread (Leproplacetum chrysodetae; six relevés listed, James et al. 1977). McCarthy (1983) identified this nodum in the Burren, with Lepraria nivalis and Caloplaca xantholyta. 1.5 A distinctive stand with Belonia russula, Ionaspis epulotica and Opegrapha saxicola was noted by Gilbert et al. (1988) as occurring on sheltered montane mica schist. Despite this, the authors stated that there did not appear to be a specialised montane mica-schist assemblage in shaded overhangs on Ben Lawers. 1.6 This community is found on well-lit damp limestone. There are abundant cyanolichens and shade-loving pyrenocarps, including Placynthium nigrum, Collema spp. including C. auriforme, C. crispum, C. cristatum, C. multipartitum, C. polycarpon, C. fuscovirens; Leptogium lichenoides, L. teretiusculum, Psorotichia schaereri, Thelidium decipiens, T. papulare, Verrucaria caerulea and V. dufourii (Placynthietum nigri, James et al. 1977). Facies: Species present include Collema auriforme, C. crispum, Cladonia pocillum, Agonimia tristicula, Squamarina cartilaginea and mosses. This community is found on rocks in woodland (James et al. 1977). McCarthy (1983) identified this nodum in the Burren, with Collema multipartitum, C. cf. callopismum, Catillaria lenticularis and Acrocordia conoidea. 1.7 This community is found in water-holding depressions in limestone and is dominated by Lempholemma botryosum (Lempholemma botryosum nodum, James et al. 1977). This nodum was identified in the Burren by McCarthy (1983), in the central parts of kamenitzas (water-holding depressions on clints), but was closely associated with species from 1.6. above. 1.8 This community is found on calcareous pebbles. Main species present are Lecidea lichenicola, Clauzadea immersa, C. metzleri, C. monticola, Sarcogyne regularis, COMMISSIONED REPORT F01AC201/1  SCOTTISH NATURAL HERITAGE 2002 Staurothele hymenogonia, Thelidium decipiens, T. incavatum, Verrucaria hochstetteri, V. muralis, V. dolosa and V. viridula (Lecideetum watsoniae, 5 relevés listed; James et al. 1977). Found on chalk nodules in S.E. England. Facies: Found on flints: Aspicilia calcarea, A. contorta, Caloplaca citrina, C. holocarpa, Lecanora dispersa, Lecidella stigmataea, Protoblastenia rupestris, Verrucaria nigrescens and V. viridula (James et al. 1977). Found on shaded stones in woodland: Pyrenocollema monense, Thelidium zwackhii and Verrucaria muralis; also V. dolosa and V. viridula on flints; the moss Seligeria ‘paucifolia’ is often present (James et al. 1977). 2 Montane base-rich rocks These communities are characterised by the occurrence of rare montane calcicolous lichens (James et al. 1977). Stands occur on epidiorite and mica schist, spreading onto rock debris, bryophytes and soil. The communities apparently comprise vegetation that has been the subject of several recent floristic studies, which is poorly understood from a phytosociological point of view but is united by the occurrence of rare montane calcicolous lichens. Examples: Species occurring on soft limestone faces: Ionaspis epulotica, I. heteromorpha, Polyblastia cupularis, P. theleodes, Sagiolechia protuberans, Toninia aromatica, Verrucaria hochstetteri, Belonia russula, Collema callopismum var. rhyparodes, C. glebulentum, Lempholemma radiatum and Rhizocarpon chioneum. Harder limestone had in addition the common lowland species Aspicilia calcarea, Clauzadea immersa, Placynthium nigrum, Protoblastenia incrustans, P. rupestris and Thelidium decipiens (Gilbert et al. 1982). Species occurring on loosened, weathered material, on moss cushions and around the bases of higher plants on ledges on limestone: Fulgensia bracteata dominant, with Bacidia sabuletorum, Catapyrenium cinereum, Lecidea hypnorum, Polyblastia sendtneri, P. terrestris, Solorina bispora, Toninia lobulata and Micarea turfosa (Gilbert et al. 1982). Species occurring on sharply drained ledges over limestone: including Cladonia pocillum, C. symphycarpa, Polyblastia helvetica, Toninia sedifolia and T. squalida (Gilbert et al. 1982). Species occurring on wetter ledges over limestone: including Pyrenocollema bryospila, Collema ceraniscum, Solorina spongiosa and Thelopsis melathelia (Gilbert et al. 1982). Species occurring on large grassy ledges over limestone: Pannaria pezizoides, Peltigera leucophlebia, P. membranacea, P. praetextata, P. rufescens, P. venosa, Psoroma hypnorum and Solorina saccata (Gilbert et al. 1982). COMMISSIONED REPORT F01AC201/1  SCOTTISH NATURAL HERITAGE 2002 Species occurring on exposed limestone with slight bird manuring: Lecania alpivaga, Acarospora cervina, Cladonia pocillum, Ionaspis heteromorpha, Polyblastia albida and P. cupularis (Gilbert et al. 1982). Species occurring on epidiorite faces: Koerberiella wimmeriana, Lecanora polytropa, Porpidia speirea, Protothelenella corrosa, Polyblastia terrestris, Rhizocarpon umbilicatum, Trapelia involuta, Pannaria hookeri, Stereocaulon evolutum and S. vesuvianum (Gilbert et al. 1982). Species occurring on soil on small ledges over epidiorite, pH 5.2-6.2: Agonimia tristicula, Catapyrenium lachneum, Psora decipiens, Polyblastia melaspora and Solorina crocea (Gilbert et al. 1982). A similar group of species occurs on schist ledges and there is also Cladonia pocillum, Pannaria pezizoides and Peltigera leucophlebia (Gilbert et al. 1988). Species occurring on mildly acid soil over epidiorite, pH 4.4-5.0: Arthrorhaphis alpina, Baeomyces placophyllus, B. roseus and Catolechia wahlenbergii (Gilbert et al. 1982). Species occurring on the edges of turf-covered ledges over epidiorite: Catillaria contristans, Lecidea hypnorum, L. limosa, Ochrolechia frigida, O. geminipara, Peltigera membranacea and occasionally Pertusaria oculata and P. dactylina (Gilbert et al. 1982). Species occurring on weakly calcareous, relatively fast-drying schist: the dominants are the widespread species Catillaria chalybeia, Pertusaria lactea, Polyblastia cupularis, P. melaspora, P. theleodes, Porpidia speirea, Rhizocarpon petraeum, R. umbilicatum, with the rare montane species Lecanora frustulosa and Pannaria hookeri (Gilbert et al. 1988). 3 Siliceous rocks with basic influence, not flushed Species present include Bacidia sabuletorum, Scoliciosprum umbrinum, Caloplaca flavovirescens, Diplotomma alboatra, Candelariella vitellina, Lecanora muralis, Rimularia badioatra, Porpidia speirea, Lecidella stigmataea, Lithographa tesserata, Polyblastia theleodes, Clauzadea monticola, Protoblastenia rupestris, Rhizocarpon petraeum and Thelidium pyrenophorum. These are slightly calcareous rocks, or rocks influenced by calcareous rocks nearby (Rhizocarpon petraeum nodum, six relevés listed; James et al. 1977). This nodum is placed here for convenience, but is closely related to other noda. 4 Siliceous rocks 4.1 Dry shaded siliceous rocks 4.1.1 These communities occur on dry acid overhangs where Lepraria incana is dominant. They are often species poor (Leprarietum incanae of James et al. 1977 in part) (Nodum C12 of Orange 1998). 4.1.2 These communities occur on very sheltered acid rocks in humid areas and are dominated by Lecanora coriensis ined.1 This species often grows adjacent to Lepraria incana, but always grows further into overhangs, so it appears to merit a 1 ined. = ineditus (unpublished) COMMISSIONED REPORT F01AC201/1  SCOTTISH NATURAL HERITAGE 2002 nodum of its own. This is locally abundant in overhangs in the north and west of Britain and is conspicuous on drystone walls in North Wales. Examples: Nodum SX13, Orange & Fryday 1998. Pure stands of Lecanora coriensis ined. growing near to Lepraria incana (Orange 1998). 4.1.3 Communities with Psilolechia lucida dominant, sometimes the only species; sometimes with Lepraria incana (Lecideetum lucidae, James et al. 1977). 4.1.4 Communities of Haematomma ochroleucum, Lecanora gangaleoides, L. subcarnea, Lecanactis dilleniana and Lecanora orosthea; also with Catillaria chalybeia, Porpidia cinereoatra, Tephromela atra, T. grumosa, Lecanora rupicola, Opegrapha saxatilis, O. saxicola, Parmelia glabratula ssp. fuliginosa and Rhizocarpon geographicum. They occur on well-lit sites (Lecideetum orostheae, James et al. 1977). 4.1.5 Communities where Chrysothrix chlorina is dominant and often is the only species. Occurs mainly in the Central Highlands of Scotland (Leprarietum chlorinae, James et al. 1977). 4.1.6 Communities consisting of Psilolechia lucida, P. clavulifera, Micarea lutulata, M. bauschiana, M. sylvicola and Lepraria incana which are developed in humid and often shaded recesses (Micareetum sylvicolae, six releves listed; James et al. 1977). 4.1.7 Communities consisting of Opegrapha gyrocarpa and Enterographa zonata are characteristic, sometimes with Opegrapha lithyrga, O. saxigena, Porina chlorotica, P. lectissima, Enterographa hutchinsiae and Rinodina oxydata. They occur in shaded humid overhangs (Opegraphetum horistico-gyrocarpae, James et al. 1977). Examples: A community occurring on overhangs below granite, Dartmoor: with Opegrapha saxigena, O. gyrocarpa, Porina chlorortica and P. lectissima (Giavarini 1990). A community occurring on acid overhangs (many relevés of nodum SX12, Orange & Fryday 1998). Other species include Fuscidea recensa. 4.1.8 Communities occurring on shaded, overhanging acidic rocks and shaded stones below tree roots on river banks, protected from rain but within reach of flood levels. Species typically include Bacidia carneoglauca, often also with B. trachona, Opegrapha lithyrga, Porina chlorotica, P. lectissima and Enterographa hutchinsiae (pers. obs.). 4.1.9 Communities with abundant Cystocoleus ebeneus or Racodium rupestre, sometimes with some Lepraria incana or Leproloma membranaceum; many other species may enter including Diplophyllum albicans, Dicranela heteromalla, Sphenolobus minutus and Trentepohlia aurea. They occur on shaded humid rocks. (Racodietum rupestris, eight relevés listed; James et al. 1977). Examples: COMMISSIONED REPORT F01AC201/1  SCOTTISH NATURAL HERITAGE 2002 Communities occurring on overhangs on granite on Dartmoor: with Cystocoleus ebeneus, Racodium rupestre, Lepraria incana, Leproloma membranaceum, Micarea botryoides, Dicranoweissia cirrata and Diplophyllum albicans (Giavarini 1990). 4.1.10 Communities of Arthonia arthonioides, Cystocoleus niger, Diploschistes scruposus and Haematomma ochroleucum occurring on rocks in old coniferous woodland in central Scotland (James et al. 1977). 4.2 Exposed siliceous rocks 4.2.1 Communities consisting of characteristic species including Fuscidea cyathoides, Porpidia crustulata, P. tuberculosa, Lecidea lithophila and Rhizocarpon geographicum. They occur on siliceous rocks and pebbles (Lecideion tumidae, James et al. 1977). 4.2.2 Communities consisting of characteristic species which are Baeomyces rufus, Porpidia macrocarpa, P. crustulata, P. tuberculosa, Lecanora polytropa, Micarea erratica, Lecidea plana and Rhizocarpon reductum. They often occur on small pebbles and stones (Huilietum crustulatae, James et al. 1977). Facies: This is dominated by Baeomyces rufus and Trapelia coarctata. It occurs on shaded stones in humid sites (James et al. 1977). Also probably related are recently exposed areas of acid boulders in upland areas, which become colonised by species including Trapelia coarctata and T. involuta (pers. obs.). 4.2.3 Communities consisting of Buellia aethalea, Porpidia cinereoatra, P. macrocarpa, P. tuberculosa, Lecanora intricata, L. soralifera, Lecidea fuscoatra, L. lithophila, L. lactea and Rhizocarpon geographicum. It occurs on sunny rocks and screes (Lecideetum lithophilae, James et al. 1977). Facies: Communities consisting of Miriquidica leucophaea, Amygdalaria pelobotryon, Placopsis lambii, Pilophorus strumaticus, Trapelia coarctata, T. mooreana and Stereocaulon pileatum. It occurs on wetter sites (James et al. 1977). In this community Acarospora fuscata and Candelariella vitellina are often also present. The places where the community occurs are nutrient enriched (James et al. 1977). 4.2.4 Communities consisting of Cladonia diversa, C. squamosa, Diploschistes scruposus, Fuscidea cyathoides, Protoparmelia badia, Lecanora polytropa, Miriquidica leucophaea, Porpidia tuberculosa, Parmelia glabratula ssp. fuliginosa, P. saxatilis, Pertusaria corallina, P. aspergilla, P. lactea, P. pseudocorallina, Rhizocarpon geographicum, R. lecanorinum, Schaereria cinereorufa and Umbilicaria polyphylla. This occurs on well lit rocks, often on vertical faces (Pertusarietum corallinae, James et al. 1977). 4.2.5 This is a crustose lichen community usually occurring on steeply sloping rocks which are not strongly acidic, with constant Pertusaria pseudocorallina, P. lactea and Porpidia tuberculosa (nodum SX7, Orange & Fryday 1998). Nodum C4 of Orange (1998) is similar, with constant Pertusaria corallina and P. pseudocorallina. Probably this has been included in 4.2.4., but the latter is more narrowly defined here. COMMISSIONED REPORT F01AC201/1  SCOTTISH NATURAL HERITAGE 2002 4.2.6 In this community the characteristic species include Bryoria fuscescens, Cetraria chlorophylla, Hypogymnia physodes, H. tubulosa, Ochrolechia androgyna, Parmelia saxatilis, P. sulcata, Parmeliopsis ambigua, Platismatia glauca and Pseudevernia furfuracea. Occurs on acid rocks (also bark). (Pseudevernietum furfuraceae, 4 relevés are listed for rock; James et al. 1977). Facies: These develop in polluted areas where the community may be much simplified. 4.2.7 A community consisting mainly of crustose lichens on very hard rocks. Fuscidea kochiana is dominant, with Tephromela atra, Lecanora intricata, L. soralifera, L. polytropa, Miriquidica leucophaea, Lecidea lithophila, L. lactea, Schaereria tenebrosa, Parmelia incurva, Pertusaria corallina, P. pseudocorallin and Rhizocarpon geographicum (Fuscideetum kochianae, James et al. 1977). Examples: These occur on vertical or sloping granite on Dartmoor. In this habitat, the species represented include Fuscidea cyathoides, F. kochiana and F. lygaea, all dominant. In less stressed habitats the community also occurs with Lecanora gangaleoides, L. polytropa, Lecidella scabra, Miriquidica leucophaea, Ophioparma ventosum, Pertusaria corallina, Tremolechia atrata and Rhizocarpon geographicum (Giavarini 1990). 4.2.8 A community consisting of crustose lichens of hard nutrient poor rocks. Fuscidea kochiana is constant, often with F. cyathoides, F. lygaea, F. intercincta or F. gothoburgensis, but with only infrequent Rhizocarpon geographicum (nodum SX6 of Orange & Fryday 1998). Probably equivalent to parts of the noda above, but more narrowly defined. 4.2.9 This is a montane community, with the following species abundant: Rhizocarpon alpicola, R. geographicum, Lecanora intricata and L. polytropa. Also present are Andreaea alpina, A. nivalis (very rare), Grimmia donniana, Racomitrium sudeticum (?), R. lanuginosum, Tremolechia atrata, Lecidea confluens, L. lapicida, L. lactea, Porpidia tuberculosa and Pseudephebe pubescens. Rarely Orphniospora atrata and Lecanora leptacina are present (Rhizocarpon alpicolae, James et al. 1977). Facies: A facies occurs with Cornicularia normoerica, Ophioparma ventosum, Protoparmelia badia, Schaereria tenebrosa, Allantoparmelia alpicola, Parmelia incurva, P. omphalodes, Umbilicaria cylindrica, U. hyperborea, U. polyphylla and U. torrefacta represented (James et al. 1977). In wetter sites in areas of late snow-lie, a facies with Rhizocarpon badioatrum occurs (James et al. 1977). 4.2.10 A community that is characterised by abundant Parmelia omphalodes along with Cladonia species. Other species include Bryoria bicolor, B. fuscescens, Cetraria chlorophylla, Ophioparma ventosum, Hypogymnia physodes, H. tubulosa, Lecanora polytropa, Schaereria tenebrosa, Lepraria caesioalba, Ochrolechia androgyna, O. tartarea, Parmelia glabratula ssp. fuliginosa, P. saxatilis, Pertusaria corallina, P. COMMISSIONED REPORT F01AC201/1  SCOTTISH NATURAL HERITAGE 2002 lactea, P. pseudocorallina, Platismatia glauca, Sphaerophorus globosus and Usnea flammea. The community is often rich in bryophytes, including Andreaea rothii, A. rupestris, Cynodontium bruntonii, Hypnum cupressiforme agg. (probably often H. andoi), Isothecium myosuroides, Orthotrichum anomalum, Racomitrium fasciculare and R. heterostichum agg. This community is widespread (Parmelietum omphalodis, James et al. 1977). At high altitudes the community grades into 4.4.2.9. Facies: A facies with Parmelia omphalodes constant and often abundant, with other macrolichens including Cornicularia normoerica, Parmelia saxatilis, Umbilicaria cylindrica, U. polyphylla and U. torrefacta (nodum SX9, Orange & Fryday 1998). This is found on crests of boulders that are slightly enriched from bird droppings. The community is also related to facies of the next nodum. Also similar is nodum C9 of Orange (1998), with its abundant Parmelia omphalodes, sometimes with P. saxatilis, P. sulcata and P. glabratula. Another facies, of relatively species rich stands, with species including Parmelia omphalodes, P. saxatilis, Sphaerophorus globosus, Platismatia glauca, Usnea flammea and Racomitrium heterostichum (nodum C10 of Orange 1998). 4.2.11 This is a very variable community of well-lit upland rocks. It may contain strictly montane macrolichens including: Cetraria commixta, C. hepatizon, Cornicularia normoerica, Hypogymnia intestiniformis, Allantoparmelia alpicola, Parmelia stygia, Platismatia norvegica, Pseudephebe pubescens, Umbilicaria cylindrica, U, hyperborea, U. polyphylla, U. polyrrhiza, U. proboscidea and U. torrefacta, but these species may be absent. Crustose species include Fuscidea cyathoides, F. lygaea, Ophioparma ventosum, Lecanora intricata, L. polytropa, Lecidea lactea, L. sulphurea, Rhizocarpon geographicum, R. reductum and R. polycarpon (Umbilicarietum cylindricae, James et al. 1977). This is a poorly defined nodum, which includes a range of stands from those dominated by crustose lichens to those dominated by macrolichens, and is likely to be divided after further work. Noda SX5 of Orange & Fryday (1998) and C3 of Orange (1998) are equivalent to some of the stands dominated by crustose lichens, and represent one of the most abundant communities of acid upland rocks. Facies: Fuscidea lygaea is dominant, with F. cyathoides and Rhizocarpon geographicum. It occurs on exposed sunny rocks (James et al. 1977). The nutrient poor, species-poor stands of nodum SX5 of Orange & Fryday (1998) are similar, also nodum C3 of Orange (1998). Fuscidea austera is dominant. It occurs on shady and rather dry rock in Scotland (James et al. 1977). One relevé placed in nodum SX6 by Orange & Fryday (1998) may be similar. Fuscidea cyathoides is dominant, with Miriquidica leucophaea, Lecidea lithophila, L. lactea, Pertusaria corallina and Rhizocarpon geographicum; sometimes also Umbilicaria species. It is often relatively lowland, e.g. in Pennines and Peak District (James et al. 1977). Lecidea lithophila is dominant, also with L. lapicida and Miriquidica leucophaea; frequently also with Alectoria nigricans and Coelocaulon aculeatum on mosses. It occurs on mineral-rich rocks in moist situations (James et al. 1977). COMMISSIONED REPORT F01AC201/1  SCOTTISH NATURAL HERITAGE 2002 This facies is dominated by Clauzadeana macula and Rhizocarpon geographicum; often also with Lecidea lactea and Schaereria tenebrosa. Distribution is western, on sunny rocks; and it is well developed in the Rhinogs (James et al. 1977). Umbilicaria deusta is dominant. It occurs by mountain streams (James et al. 1977). Umbilicaria hyperborea nodum, occurring at high altitude (James et al. 1977). Umbilicaria crustulosa is dominant. It occurs on near-vertical, hard rocks on Langdale Pikes (James et al. 1977). This facies is characterised by high frequencies of Umbilicaria cylindrica, U. polyphylla, U. polyrrhiza and U. proboscidea, or U. torrefacta; also Cornicularia normoerica, Pseudephebe pubescens, and the bryophytes Andreaea rupestris, Grimmia donniana, G. trichophylla, Gymnomitrion spp., Hedwigia ciliata agg., Ptychomitrium polyphyllum, Racomitrium fasciculare and R. heterostichum agg. It occurs on well-lit coarse-grained montane rocks (James et al. 1977). A facies that is probably related occurs on exposed ‘acid’ dolerite rocks. Species present include the mosses Schistidium apocarpum, Grimmia trichophylla, Polytrichum piliferum, Racomitrium heterostichum agg. and Hedwigia ciliata agg. Lichens were not recorded (Group V of Yarranton 1962). 4.2.12 A community occurring on siliceous pebbles on coastal shingle. Species present are Rinodina aspera, Buellia aethalea, Micarea erratica and Porpidia tuberculosa; occasionally with Catillaria chalybeia, Buellia ocellata, Lecanora dispersa, L. polytropa, Rhizocarpon constrictum, R. reductum and Verrucaria nigrescens (Lecideetum erraticae, James et al. 1977). 4.2.13 A community occurring on slightly basic or moisture retentive exposed upland rocks, with constant Racomitrium sudeticum, Andreaea rupestris and Cladonia cervicornis, with one or more of Gymnomitrion crenulatum, G. obtusum, Stereocaulon evolutum or S. vesuvianum (Nodum SX4, Orange & Fryday 1998). Probably overlaps with some noda mentioned above, but not previously recognised as distinct. 4.2.14 A community occurring on damp rocks at high altitudes (990-1015 m in Eryri). Constants of the community are the crustose Stereocaulon cf. tornense, Rhizocarpon anaperum, Porpidia contraponenda and the moss Racomitrium sudeticum (nodum SX11, Orange & Fryday 1998). 5 Nutrient-enriched rocks 5.1 A community consisting of Acarospora fuscata, Anaptychia runcinata, Aspicilia caesiocinerea, Diploicia canescens, Buellia punctata, Candelariella coralliza, C. vitellina, Lecanora muralis, Physcia caesia, P. dubia, P. tribacia, Ramalina polymorpha, R. subfarinacea, Rinodina gennarii, Xanthoria candelaria and X. parietina. It occurs on nutrient enriched siliceous rocks such as bird-perching rocks (Candelarielletum corallizae, James et al. 1977). Facies: On the seashore additional species are represented such as Aspicilia leprosescens, Caloplaca verruculifera, Lecanora poliophaea and Parmelia britannica; possibly also COMMISSIONED REPORT F01AC201/1  SCOTTISH NATURAL HERITAGE 2002 Lecanora fugiens and L. andrewii; sometimes also Physcia tenella var. marina (Verrucaria fusconigrescens, James et al. 1977). Examples: These occur with either Candelariella coralliza or Xanthoria candelaria, while the macrolichen Ramalina polymorpha is often abundant, and indicative of maritime influence (Nodum C5, Orange 1998). 5.2 Some stands with Ramalina siliquosa or R. subfarinacea are probably related to the species-rich maritime community Ramalinetum scopularis, which can occur inland as species-poor variants (James et al. 1977). Examples: These are noda C6 and C7 of Orange (1998), on rocks influenced in part by bird perching or by maritime influence. 5.3 A community occurring on the crests of acidic upland boulders used as bird perches. The constant species are Candelariella coralliza, Lecanora intricata and Parmelia omphalodes; also with Aspicilia caesiocinerea, A. cinerea, and with locally abundant Lasallia pustulata (nodum SX8, Orange & Fryday 1998). This is perhaps a facies of 5.1. on more acidic rocks. 5.4 A community consisting of numerous crustose species and occurring on siliceous rocks. The characteristic lichens include Acarospora fuscata, Buellia stellulata, Candelariella vitellina, Diploschistes scruposus, Porpidia cinereoatra, Lasallia pustulata, Tephromela atra, T. grumosa, Protoparmelia badia, Lecanora polytropa, L. rupicola, L. sulphurea, Schaereia tenebrosa, Ochrolechia parella, Parmelia conspersa, P. glabratula ssp. fuliginosa, P. verruculifera, Pertusaria flavicans, P. pseudocorallina, Rhizocarpon geographicum, R. viridiatrum and Rinodina atrocinerea (Lecanoretum sordidae, 5 relevés; James et al. 1977). 5.5 A community dominated by foliose species. Characteristic lichens include Acarospora fuscata, Candelariella vitellina, Cladonia diversa, C. ramulosa, C. squamosa, Lasallia pustulata, Lecanora polytropa, Parmelia britannica, P. conspersa, P. disjuncta, P. loxodes, P. mougeotii, P. saxatilis, P. sulcata, P. verruculifera, Trapelia ‘ornata’, Umbilicaria deusta and U. polyrrhiza (Parmelietum glomelliferae, 5 relevés are listed, James et al. 1977). It occurs on siliceous rocks. Facies: One facies occurring on slightly flushed acidic upland rocks with abundant Parmelia conspersa (nodum SX 10, Orange & Fryday 1998). Another facies occurring on slightly flushed and slightly nutrient enriched rocks, with Aspicilia caesiocinerea, Parmelia conspersa, P. loxodes and Rinodina atrocinerea (nodum C2, Orange 1998; but probably not really equivalent to nodum SX10 above). Examples: This one occurs on granite with run-off from soil, on Dartmoor where Lasallia pustulata forms ‘monocultures’ (Giavarini 1990). COMMISSIONED REPORT F01AC201/1  SCOTTISH NATURAL HERITAGE 2002 Another example, probably related to the above, occurs on flushed granite, especially at ground level. Also on Dartmoor and including Aspicilia caesiocinerea, A. grisea, Cladonia subcervicornis, Lecidea fuscoatra, Massalongia carnosa, Pertusaria excludens, P. pseudocorallina, Stereocaulon vesuvianum and Trapelia involuta (Giavarini 1990). 5.6 A community with high frequencies of members of the Physciaceae (Physcia adscendens, P. caesia, Phaeophyscia orbicularis and Physconia grisea) and Xanthoria calcicola or X. parietina; frequently also Caloplaca citrina agg., Candelariella medians and Lecanora muralis. It occurs on nutrient-enriched limestone, less frequently also on siliceous rocks (also on bark) (Physcietum caesiae, James et al. 1977). 5.7 Another community, apparently with many species of 5.4., but differs in that Diploicia canescens, Physcia tribacia and Ramalina lacera are particularly characteristic. It occurs on nutrient enriched calcareous rocks, particularly in farmyards (James et al. 1977). 6 Mineral-rich rocks 6.1 This community is developed on more or less exposed siliceous rocks. Species present are Acarospora sinopica, A. smaragdula, Scoliciosporum umbrinum, Candelariella vitellina, Diploschistes scruposus, Porpidia macrocarpa, Lecanora soralifera, L. polytropa, L. subaurea, Tremolechia atrata, L. lapicida, L. lactea, L. silacea (upland), Rhizocarpon reductum, R. oederi, Stereocaulon nanodes, S. pileatum, S. leucophaeopsis; sometimes also S. dactylophyllum, S. delisei, S. evolutum, S. vesuvianum (Acarosporetum sinopicae, James et al. 1977). Other species include Rhizocarpon furfurosum, Scoliciosporum umbrinum, Miriquidica atrofulva and Stereocaulon nanodes (Purvis 1996). Examples: In one example the species include Acarospora sinopica, Lecanora epanora, Lecidea silacea, Rhizocarpon furfurosum, R. oederi, R. polycarpon, Stereocaulon leucophaeopsis and Tremolechia atrata occurring at an altitude of c. 600 m (Gilbert et al. 1988). One relevé is recorded with a high cover of Porpidia cinereoatra and Rhizocarpon oederi, but also with Amygdalaria pelobotryon, Stereocaulon dactylophyllum and S. pileatum (nodum C11 of Orange 1998). 6.2 A community occurring on dry siliceous rocks sheltered from direct rain. Lecanora epanora is often dominant, also Lepraria incana, Leproloma membranaceum and Rhizocarpon reductum (Lecanoretum epanorae, James et al. 1977). Other species include Acarospora sinopica, Rhizocarpon furfurosum and Lecanora handelii (Purvis 1996). Examples: This is nodum SX14, Orange & Fryday (1998) (one relevé). 6.3 A community with Lecidea inops constant; occurring on rocks with copper mineralization (Lecideetum inopis, Purvis 1996). This community is a species-poor facies of an association found also in Scandinavia. COMMISSIONED REPORT F01AC201/1  SCOTTISH NATURAL HERITAGE 2002 Facies: There is a species-poor facies dominated by Psilolechia leprosa, which is widespread in Britain in copper enriched environments; it also occurs rarely on natural exposures. 7 Aquatic communities 7.1 A community occurring on periodically inundated rocks by rivers and lakes. Species present are Hymenelia lacustris, Dermatocarpon luridum, D. meiophyllizum, Rhizocarpon lavatum, Staurothele fissa and Verrucaria aethiobola (Aspicileetum lacustris, James et al. 1977). Facies: A facies occurring on less frequently inundated rocks. It has the species of 7.1. with in addition Porpidia macrocarpa and P. tuberculosa (James et al. 1977). A facies occurring on l shaded rocks. This facies has the additional species Bacidia inundata, Catillaria chalybeia, Aspicilia laevata and Verrucaria praetermissa (James et al. 1977). A facies occurring on very shaded and humid rocks. There are increased amounts of Verrucaria hydrela and V. margacea (James et al. 1977). A facies occurring on very shaded mica schist rocks in small streams. Species occurring include Chromatochlamys larbalestieri, Porina grandis and often Thelidium pyrenophorum. It occurs in western Scotland and Ireland (James et al. 1977). Porpidia hydrophila is present in this facies; also with Porina guentheri var. lucens, P. interjungens (rare), Porocyphus kenmorensis, Hymenelia lacustris, Catillaria chalybeia, Porpidia cinereoatra, P. macrocarpa, Rhizocarpon spp. (James et al. 1977). These are species poor assemblages comprising mainly Porpidia hydrophila, P. macrocarpa, Hymenelia lacustris and Rhizocarpon lavatum and are common on hard acid rocks in upland rivers (pers. obs.). Other freshwater noda, often based on few samples, are given below. A nodum found on submerged, rarely exposed rocks, in nutrient poor woodland streams. This is dominated by bryophytes: Rhynchostegium alopecuroides and Hygrohypnum ochraceum; also Scapania undulata and Racomitrium aciculare (North Wales, Orange 1999). This is a nodum of occasionally inundated rocks. The mosses Racomitrium aciculare, R. aquaticum and R. affine are present, with the lichen Massalongia carnosa (North Wales, Orange 1999). A nodum developed on boulders by woodland streams. This is dominated by the moss Isothecium holtii and is rarely inundated (North Wales, Orange 1999). A bryophyte dominated nodum of shaded seasonal waterfalls on basic rocks. The species include Rhynchostegium riparioides, Calliergon cuspidatum, Brachythecium plumosum, Fissidens adianthoides, Thamnobryum alopecurum and Saccogyna viticulosa (Group 1 of Yarranton 1962). COMMISSIONED REPORT F01AC201/1  SCOTTISH NATURAL HERITAGE 2002 A nodum developed on basic, inundated rocks. The mosses of the nodum include Rhynchostegium riparioides and Brachythecium rivulare, and the lichen Verrucaria aquatilis is present (Graham 1988, relevés 1503, 1504, 492, 357, 358). 7.2 A community occurring on river and lake margins and by seepages. Species present are Aspicilia caesiocinerea, Ephebe lanata, Rhizocarpon geminatum (rare), R. reductum and Trapelia involuta. Cyanobacteria are also represented and the mosses Bryum alpinum and Racomitrium aquaticum (Ephebetum lanatae, James et al. 1977). 7.3 A community occurring in montane streams. Characteristic species present are Ionaspis suaveolens, Placynthium flabellosum and Polyblastia cruenta; while others include Hymenlia lacustris, Bacidia inundata, Catillaria chalybeia, Dermatocarpon luridum, Rhizocarpon lavatum, Staurothele fissa and Verrucaria margace. Rare species include Dermatocarpon rivulorum, Gyalidea fritzei and Polyblastia quartzina. This is best developed in Cairngorms, usually above 910 m (Ionaspidetum suaveolentis, James et al. 1977). Examples: These occur on calcareous boulders with Ionaspis epulotica, I. Odora and I. cyanocarpa, as well as more widespread freshwater species (Gilbert et al. 1988). 7.4 A community occurring in streams and lakes that is submerged for much of the year. Species present are Verrucaria aquatilis, V. rheitrophila and V. funckii; also the moss Fontinalis antipyretica and the algae Hildenbrandia rivularis and Lemanea spp. (Verrucarietum siliceae, James et al. 1977). Verrucaria rheitrophila and Hildenbrandia appear to indicate slightly base-rich conditions (pers. obs). 8 Flushed rocks Communities of flushed rocks are often closely related to other communities. Some rocks of these communities may be flushed for much of the time, or they may be very dry in summer, so that drought sensitive species are absent. 8.1 This community has abundant Andreaea alpina, with Marsupella emarginata as the only other constant. It occurs on dripping north-facing cliffs with a very slight base influence at 580-750 m altitude in Eryri (Nodum SX1, Orange & Fryday 1998). 8.2 A community that has Marsupella emarginata, Ephebe lanata or Campylopus atrovirens, with Andreaea rothii absent or less frequent than the other species. It occurs on seasonally flushed, acid upland rocks (Nodum SX2, Orange & Fryday 1998). 8.3 A community occurring on flushed acid upland rocks which are seasonally dry, dominated by Andreaea rothii, with constants Cladonia subcervicornis and C. diversa. Other frequent or preferential species include Lepraria caesioalba and Lecidea pycnocarpa f. pycnocarpa. It is abundant in upland areas of the north and west (Nodum SX3, Orange & Fryday 1998). The same community is recorded as nodum C1 by Orange (1998), with Porpidia contraponenda as another constant species. 8.4 This community occurs on exposed, seasonally flushed, base-rich upland rocks. The moss Amphidium mougeotii is constant, and the mosses Blindia acuta and COMMISSIONED REPORT F01AC201/1  SCOTTISH NATURAL HERITAGE 2002 Racomitrium ellipticum, and the crustose lichens Porpidia glaucophaea and Thelidium papulare are frequent (nodum SX16, Orange & Fryday 1998). Other examples: A community described from wet calcareous rock faces at an altitude of 950 m on Ben Lawers. Species present are Koerberiella wimmeriana, Collema auriforme, C. glebulentum, Placynthium nigrum, P. asperellum, Thelidium pyrenophorum, Trapelia coarctata, T. involuta, T. placodioides, Ephebe lanata and Hymenelia lacustris Gilbert et al. (1988). A community developed on flushed montane mica schist. Species present are Koerberiella wimmeriana, Dermatocarpon miniatum, D. luridum, Hymenelia lacustris, Polyblastia theleodes and Thelidium fumidum (Gilbert et al. 1988). A community occurring on occasionally flushed montane mica schist. Species present are Acarospora rhizobola and Psora rubiformis (Gilbert et al. 1988). 8.5 A community occurring on flushed limestone rock and tufa. Often Eucladium verticillatum and Palustriella commutata are present, but it grades into spring and flush communities that are outside the scope of this project, for instance M37 Cratoneuron commutatum-Festuca rubra spring (Rodwell 1991). Lichens are rare; the only characteristic one appears to be Thelidium fontigenum on the drier parts of tufa, which are not actively growing. Examples: These include tufa and calcareous stream bank where the species include Palustriella commutata, Eucladium verticillatum, Pellia endiviifolia and Jungermannia atrovirens (Graham 1988, relevés 356 and 636). 9 Snow beds Much snow bed vegetation is terricolous and outside the scope of this survey. 9.1 A community occurring on the upper surface of rocks in snow-beds. Species present; include the lichens Ameliella andreaeicola ined., Lecanora leptacina, L. formosa, Miriquidica griseoatra, Frutidella caesioatra, Poepidia contraponenda, Rhizocarpon jemtlandicum and Micarea paratropa, and the mosses Andreaea spp. and Rhizocarpon heterostichum agg. (Fryday 2001). 9.2 A community developed on small rocks and pebbles in snow beds. The species present include Stereocaulon tornoense, S. plicatile, Micarea marginata, M. paratropa, Rhizocarpon cinereonigrum, Ionaspis odora, Frutidella caesioatra, Protothelenella corrosa and Rhizocarpon anaperum (Fryday 2001). 10 Bryophyte dominated terrestrial communities They are developed in overhangs and crevices. 10.1 These are communities of moist, base-rich overhangs in upland areas. Constant species are Amphidium mougeotii, Anoectangium aestivum, Tortella tortuosa, Ctendium molluscum and Plagiochila porelloides. The lichens are on small areas of bare rock, or grow on moss cushions. This community contains numerous COMMISSIONED REPORT F01AC201/1  SCOTTISH NATURAL HERITAGE 2002 uncommon species of bryophyte (nodum SX17, Orange & Fryday 1998). This a widespread but very local community in upland areas, and it is of particular conservation value. Facies: Stands with the ferns Asplenium viride and Cystopteris fragilis were distinguished as OV40 by Rodwell (2000). 10.2 These are communities of base-rich well-lit crevices. The constant species are the ferns Asplenium trichomanes and A. ruta-muraria, and the bryophytes Porella platyphylla and Homalothecium sericeum (community OV39 of Rodwell 2000). In sub-community OV39a the mosses Tortula intermedia and Trichostomum crispulum are also frequent. This community was defined largely on its vascular plants, but related stands containing only bryophytes are likely to be frequent. Averis (1998) provides the basis of a classification of bryophyte dominated communities in Highland woods, but this work is unpublished and is not reproduced here. Other examples: This community consists of a thick carpet of tall bryophyte species. Rhytidiadelphus loreus, Thuidium tamariscinum and Hylocomium brevirostre are dominant. Other species also present are Dicranum majus, Plagiothecium undulatum, Polytrichum formosum, Hylocomium splendens, Plagiochila spinulosa and the fern Hymenophyllum tunbridgense. The community is described from sandstone boulders in woodland (the Closed Boulder Associule, Richards 1938) and similar stands are very frequent in north and west Britain. This is a community of small hepatics and pleurocarpous mosses. Diplophyllum albicans, Heterocladium heteropterum and Sematophyllum micans are the most abundant; others at least locally abundant include Fissidens adianthoides, Calypogeia arguta, Cephalozia bicusoidata, Harpanthus scutatus, Lepidozia reptans, Saccogyna viticulosa and Scapania umbrosa. The community is described from sandstone boulders in woodland (the Open Boulder Associule, Richards 1938). The community is probably widespread and frequent in facies lacking the rarer species. This community is developed on steep, north-facing rocks of ‘intermediate’ pH. Important species of the community include Amphidium mougeotii, Eurhynchium praelongum, Bartramia pomiformis, Diplophyllum albicans, Fissidens dubius, Lejeunea lamacerina and Mnium hornum (Group II of Yarranton 1962). This community occurs on deeply shaded, acid, soily cliff bases. Species described from the community include Diplophyllum albicans, Hypnum cupressiforme agg. (likely to be H. andoi), Isothecium myosuroides and Mnium hornum (Group III of Yarranton 1962). This community occurs on dry, partly shaded cliff bases of ‘intermediate’ pH. Species described from the community include Brachythecium rutabulum, Bryum capillare, Homalothecium sericeum, Frullania tamarisci, Hypnum cupressiforme agg., Lophocolea bidentata, Isothecium alopecuroides, Metzegeria furcata and Pterogonium gracile (Group IV of Yarranton 1962). COMMISSIONED REPORT F01AC201/1  SCOTTISH NATURAL HERITAGE 2002 This community occurs on partly shaded, acid cliff faces with some soil. Species present are Dicranum majus, Lophocolea bidentata, Pleurozium schreberi, Polytrichum formosum and Thuidium tamariscinum (Group VI of Yarranton 1962). This community occurs on acid boulders in oceanic woodland. It is dominated by the common moss Isothecium myosuroides, but with macrolichens such as Parmelia taylorensis, P. laevigata and Sphaerophorus globosus also present. The community is also found on acid bark (Parmelion laevigatae) and is of conservation interest (pers. obs.). This community is similar to the Hypnum andoi-Isothecium myosuroidesFrullania tamarisci association mentioned by Averis (1998) 4 REFERENCES Averis, A.B.G. 1998. A Classification of Bryophyte Communities in Scottish Highland Woods and Some Related Heaths and Mires. Unpublished manuscript, May 1998. Averis, A.B.G. 1998b. Bryophyte Survey of Coed Rheidol NNR. Unpublished report to Countryside Council for Wales. Averis, A.B.G. & Averis, A.M. 1998c. Vegetation Survey of Beinn Eighe, Wester Ross, 1997. 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