Lichen communities in the British Isles: A preliminary conspectus

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360 P. W. James, D. L. Haz.okszoorth and tr,. Rose 10. Lichen Commwities in the British Isles coerulea ar'd V. dufourii are par_ . A facies not unlike the Tonini)ttnn tia candida is replacecl by T. aromatica s recognition at the association level as it is n mossy limestone rocks in woodland, a facies ouriculatum' C' crispum, polyblastia Cladonia 1>ocillum, t ruriher speci ::'""i-Xf,'J^"r1",: I-ike the ntgri is able to extend from calcareous walls. In churchyards its difierent ecological ,.Tfrr|.l".T::ll e.asily be seen by, for example, comparing the lichen communities on trre driest and dampest walls of the church, or those on verticar tombstones and around the basal parts of horizontal tops of chest-tombs. similar contrasts can be seen in comparing limestone boulders in turf and u,iclc expanscs of limestone rock faces. The placynthietum nigri is conspicuouslv rarer in churchyards in the low-rainfall areas of East Angria th""'i;:;;;; and west England. Allied to this community is one sometimes encountered in depressions in limestone which often hold water fc r considerable periods of ii-. ancr in osum predominates; this may represent a is in need of further study it is noi formally reated as a "nodum" (see Fig. 7). Free_living in such hollows when it is or has just becn All. 13. Xonthorion parietinae Xanthorion parietinae Ochsn.-see p. 342 for nomenclature. Physciehtm ascendentis Frey & Ochsn. See p, 344 for nomenclature. A community not s association (sec p. 344) occasionally occurs on nutrie us rocks urrd *ullr, particularly in farmyards. In thi scens, physcia tribaclia and, Ramalina duriaei are particularly characteristic of it. Physcietum caesiae Mot. Bull. int. Acad. pol. Sci. Lett. lCracoaie], ser. B,1924, g43 (1925). This association is widespread on nutrient_enriched sites perching stones) but, while it is particularly frequent on (e.g. birds' limestones (espccially the Jrorizontal faces on the tops of gravestoncs and concrete posts), it is lcss specific to rock type than nutrient availability. In moderately pollutecl areas the association is especially well developed
362 P. W. James, D. L. Hawksuorth and F. Rose Scotland (e.g. Ben Hope, Ben Lawers, Caenlochan and Glen Clova). The community spreads from rock on to adjacent rock debris, bryophytes and mica schist-rich soils and thus can be treated as both terricolous ancl saxicolous. Detailed lists of the species of this nodum on Ben Lawers have been provided by James (1965). On Ben Hope the communities are similar but Pannaria hooheri is dominant on rock. Many of the lichens in this nodum are extremely rare and restricted to it in the British Isles. The following may be mentioned as characteristrc: Belonia russula, Biatorella fossarum, Caloplaca stillicidiorum (on mosses), Euopsis granatina, Gyalidea fritzei, Pannaria hookeri, Pertusaria glomerata, Placynthium dolichoterum, P. pannariellum, Polyblastia cupularis, P. inumbrata, P. scotinospora, P. tlteleodes, Protoblastenia siebenhaarina, Sporopodium fuscolutewn, Thelopsis melathelia and Thyrea radiata. This nodum is apparently distinct from the Aspicilietum oerrucosae Frey (see Klement, 1955) although it has a number of species in common with it. Its syntaxonomic position is in need of further study but it has clear affinities with some communities of alpine habitats in Norway of which it probably represents a species-poor facies. Rhizocarpon petraeum nodum (Table X) Siliceous rocks at the margins of limestone outcrops support a very characteristic assemblage of species (Table X) whose presence is indicativc of the site being somewhat calcareous. This is essentially a transitional nodum occurring chiefly in highland Britain and in which "substrateswitch" species arc an important component. Some species of this community (".g. Caloplaca flaoocirescens, Buellia alboatra, Rhizocarpon petraeum) occur, for example, on granite stones in a stone and calcareous mortar u'all in lowland Britain. Species found in this nodum include Bacidia sabuletorum, B. umbrina, Caloplaca aurantiaca, Candelariella aitellina, Lecanora muralis, Lecidea illita, L. speirea, L. umbonata, Lecidella stigmatea, Lithographa tesserata, Polyblastia theleodes, Protoblastenia monticola, P. rupestris (not usually as "var. caloa"), Rhizocarpon petraeum and Thelidium pyrenophorum. This community is not accorded the status of an association here as it is essentially transitional betwcen limestone and siliceous rock associations and is usually very limited in extent. Ability to recognize this nodum is of considerable importance to ecologists as it enables base-rich rocks in essentially siliceous rock areas to be recognized and thus indicates sites of potential importance for their phanerogamic floras. Species Acaros\or a glattcocarPa Bacidia sabuletorum B. anbrina Buellia aethalea CaloPlaca aurantiaca C. citrina C andelariella oitellina C atil laria lenticul, ar is C lathr oPor ina c alc ar e a CoIIema cristatum C. PolycarPon Gyalecta jen'ensis H uili a alb o c a er u I e s c ens IonasPis ePulotica Lecanora crenulata L. disPersa L. muralis Lecidea il.lita L. lithoPhila L. pelobotryon L. speirea L. umbonata Lecidella scabra L. stigmatea LithograPha tesserata Pertusari.a amara P. pseudocorallina P lacynthium lis mor en s e Polyblastia scotinosPor a P. theleotles P r ot obl a s t enia monticol a P. ruPestris Rh i z oc a r Pon ob s cur atum R. Petraeum Thelidiutn deciPiens T. pyrenoPhorum TraPeka coarctata Verrucat'ia coerulea Test,n X. Rhixttc arP on Petr aeunt' nodum' t-,2 t, +.0 1.2 1.0 L') 2.2 1.2 tC 1-.L 1.2 r.2 1.2 2.3 )-) )-) l', -r.L 1.3 -)- ? 1,.2 -L') 1.2 J,) )-7 )-) +.0 )-) L-') 1.2 +.0 +.0 1.3 L) )-) 1.2 1.3 z.J 7.2 1.3 1.3 -J- ) 1.2 t2 ),') l.z Stand L2 L.J t.z +.2 +.0 ), ') rO 1.3 ), ') ), ') t.2 -L) 1.2 1.2 =), ) ),) +.0 1.3 f.0 1.2 t.2 - 4.0 L) - t.r +.2 1.2 1.3 1.3 +.0 +.2 ta 1-.L tC - ta tn 1.3 r.2 -L) -L) 1.3 1.2 -L)
Page 1 and 2: TO PETER W. IAMES, DAVID ANd FRANCI
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Lichen communities in the British Isles: A preliminary conspectus

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