Lower Plants of Cwm Rhaeadr

The Lower Plants of Cwm Rhaeadr Forest

R.G.Woods BSc


Over two days in September 2006 an extensive survey of mosses, liverworts, lichens and fungi was undertaken in this large conifer forest. Due to resource constraints the survey concentrated on areas likely to support the most species rich assemblages. The macrofungi present particular survey problems requiring repeated visits throughout the year to secure anything approaching a complete list. The list of fungi presented here is the result of casual observation over two days early in the fruiting season for most species and is consequently far from complete.

With no historical landuse background data available to the author at the time of survey he consulted early OS maps. The survey concentrated on areas shown as broadleaved woodland prior to coniferous afforestation, the Nant y Rhaeadr, areas of wetland and any ancient trees. From experience such areas are likely to be richer in lower plants. Coniferous plantations established on former grassland sites whilst supporting large quantities of lower plants, tend always to be poor in species diversity.

The site was extensively walked and driven over and any of the above habitats once located were subject to detailed survey. Any other species noted in passing in additional habitats were listed.

The names I have used for most fungi follows R. Phillips (2006), Mushrooms . Macmillan, London; for lichens B.J. Coppins (2002) Checklist of Lichens of Great Britain and Ireland , British Lichen Society, London and for mosses and liverworts T. L. Blockeel and D. G. Long (1998), A Checklist and Census Catalogue of British and Irish Bryophytes . British Bryological Society, Cardiff.

Mosses and Liverworts

Fifty-two species of moss and twenty-one species of liverwort were noted. No species of national or even county conservation concern were located. There were, however, a number of areas where mosses and liverworts formed a significant part of the vegetation.

Ground Layer species in woodland

  1. Conifer BlocksWithin the lower parts of the forest on shaded banks and under the conifer canopy on former field sites a range of widespread pleurocarpous (creeping, weft-forming) mosses dominated. The more widespread species were the common tamarisk-moss Thuidium tamariscinum , the common feather-moss Eurhynchiumpraelongum and with fatter, more worm-like stems, the neat feather-mossScleropodium purum . The springy turf-moss, Rhytidiadelphus squarrosus with its spiky bent-back leaves was particularly widespread whilst its larger relative, the big shaggy-moss Rhytidiadelphus triquetrus formed dense stands locally. The leafy liverwort, the bifid crestwort Lophocolea bidentata was widespread. Common tuft-forming species included the bank haircap moss Polytichum formosum and the common smoothcap moss Atrichum undulatum .

    In the upper parts of the forest on probably former heathland, more acid soil-loving mosses dominated such as the red-stemmed feather-moss Pleurozium schreberi, the glittering wood-moss Hylocomium splendens and the heath plait-moss Hypnum jutlandicum . Throughout the forest wherever soil and clay is exposed such as in ditch banks and on the root plates of wind-thrown trees the tiny liverworts white earwort Diplophyllum albicans and ladder flapwort Nardia scalaris were abundant amongst lesser amounts of pouchworts Calypogeia species together with the silky forklet- moss Dicranella heteromalla . Wet clay on ditch sides supported a more specialised flora including the rufous forklet-mossDicranella rufescens and the marsh forklet-moss D. palustre and the thalloid liverwort the overleaf pellia Pellia epiphylla , whilst the wet ditch bottoms were in places dominated by the cow-horn bog-moss Sphagnum denticulatum .

    In shaded areas close to the Nant Rhaeadr extensive stands of the lustrous bog-moss Sphagnum subnitens occurred, with, about small tributary streams, lesser amounts of the fringed bog-moss S. fimbriatum .

  2. Broad-leaved woodland and former broad-leaved woodland sites.In freely-drained areas currently under a canopy of mature sessile oak or on sites marked on earlier editions of the OS maps as broad-leaved woodland many of the species listed from conifer blocks are frequent. In addition extensive cushions of the little shaggy-moss Rhytidiadelphus loreus occurs in these areas together with cushions of the greater fork-moss Dicranum majus and smaller amounts of the whitish, ribbon-like waved silk-moss Plagiothecium undulatum . On the north facing banks at the head of the Nant Rhaeadr below the falls and adjacent to an existing sessile oakwood were found stands of the five-ranked bog-mossSphagnum quinquefarium . This is a local ancient woodland species in Carmarthenshire occurring elsewhere only rarely amongst sheltered block scree.

    On the valley floor close to the Nant Rhaeadr is an extensive ribbon of wet woodland developed along a line of springs. Few trees in this area appear to be of great age and the development of this woodland may at least in places be quite recent in origin. However on the right bank below the footbridge at the southern boundary of the forest at small block of ash/hazel woodland has developed around a number of small springs and flushes. This area supports a number of cushions of the attractive and local leafy liverwort, the handsome woolywort Trichocolea tomentella, possibly indicating a more ancient status for woodland in this area. Other moisture loving mosses in this area include the shining hookeria Hookera lucens and hart’s-tongue thyme-moss Plagimnium undulatum .

Epiphytic (tree dwelling) species

  1. On ConifersConifers with their acidic and non porous bark support few mosses and liverworts. The mamillate plait-moss Hypnum andoi is the most common species with its relative the cypress-leaved plait-moss Hypnum cupressiforme being largely confined to the most mature trees.

    Old cut stumps that have begun to decay support a more diverse flora including mosses such as the rusty swan-neck moss Camplopus flexuosus, the heath star-moss C. introflexus, the swan’s-neck thyme-moss Mnium hornum and the liverworts crestwort Lophocolea spp., wood-rust Nowellia curvifolia and two-horned pincerwort Cephalozia bicuspidata.

  2. On Broadleaved treesMosses and liverworts cover large areas of the bark of trees and shrubs and are a notable feature of the woodland, contributing much to its character. As with the conifers the wefts of the mamillate plait- moss Hypnum andoi are common, as are cushions of the moss the crisped pincushion Ulota crispa . The tiny thalloid liverwort the forked veilwort Metzgeria furcata covers large areas as do colonies of the purplish leafy liverwort the tamarisk scalewort Frullania tamarisci . Overgrowing these species are the tiny colonies of the leafy liverwort called fairy beadsMicrolejeunea ulicina , with its bead-like leaves. Also widespread but less abundant was the thalloid liverwort, the whiskered veilwort Metzgeria temperata with its elongated thallus lobes covered in minute plantlets (gemmae). Around the base of most trees the minature shrub-like stems of the slender mouse-tail mossIsothecium myosuroides was abundant.

    On the more base-rich bark of ash and on the few ancient oak trees the golden silky patches of the silky wall feather-moss Homalothecium sericium were noted in several places. The small liverwort Micheli’s least pouncewort Lejeunea cavifoliatended to also be most frequent on these trees as were the tuft-forming park yoke-moss Zygodon rupestris and the wood bristle-moss Orthotrichum affine .

    Old, bark-free logs were rare but in the humid air close to the stream they supported a notable moss and liverwort flora. The liverworts wood-rust Nowellia curvifolia and creeping fingerwort Lepidozia reptans were common, whilst the liverworts grove earwort Scapania nemorosa and lesser featherwort Plagiochila porelloides occurred in much smaller quantities with the pellucid four-tooth mossTetraphis pellucida .

Species of banks and rock outcrops beside streams

Rocks beside the Nant Rhaeadr are covered by the golden-green cushions of the flagellate feather-moss Hyocomium armoricum almost to the exclusion of all other species. This moss is absent from east Wales but becomes the dominant streamside moss in the Cambrian Mountains and in west Wales and is a good example of a plant with an “Atlantic” distribution. Such species reach their greatest abundance along the Atlantic seaboard of Europe, favoured perhaps by cool, moist summers and relatively mild winters. Another Atlantic species recorded only from the largest, north-facing rock outcrops beside the stream is the leafy liverwort straggling pouchwort Saccogyna viticulosa . These outcrops also supported the tiny weft-forming wry-leaved tamarisk-moss Heterocladium heteropterum . On sunnier rocks on the NE bank of the stream above the flood zone the cushion forming variable crisp-mossTrichostomum brachydontium occurred whilst on rocks in the flood zone the yellow fringe-moss Racomitrium aciculare and the liverwort notched rustwort Marsupella emarginata were noted. These are common species in Mid Wales.


Moss and Liverwort Species List

Artichum undulatum Common smoothcap
Calliergonella cuspidata Pointed spear-moss
Campylopus flexuosus Rusty swan-neck moss
Campylopus introflexus Heath star moss
Dicranella heteromalla Silky forklet-moss
Dicranella palustris Marsh forklet-moss
Dicranella rufescens Rufous forklet-moss
Dicranum majus Greater fork-moss
Dicranum scoparium Broom fork-moss
Eurhynchium praelongum Common feather-moss
Eurhynchium striatum Common striated feather-moss
Fissidens bryoides Lesser pocket-moss
Fissidens taxifolius Common pocket-moss
Heterocladium heteropterum Wry-leaved tamarisk-moss
Homalothecium sericium Silky wall feather-moss
Hookeria lucens Shining hookeria
Hylocomium splendens Glittering wood-moss
Hyocomium armoricum Flagellate feather-moss
Hypnum andoi Mamillate plait-moss
Hypnum cupressiforme Cypress-leaved plait-moss
Hypnum jutlandicum Heath plait-moss
Hypnum resupinatum Supine plait-moss
Isothecium myosuroides Slender mouse-tail moss
Mnium hornum Swan’s-neck thyme-moss
Orthotrichum affine Wood bristle-moss
Plagiomnium undulatum Hart’s-tongue thyme moss
Plagiothecium succulentum Juicy silk-moss
Plagiothecium undulatum Waved silk-moss
Pleurozium schreberi Red-stemmed feather-moss
Pogonatum aloides Aloe haircap
Pogonatum urnigerum Urn haircap
Polytrichum formosum Bank haircap
Polytrichum piliferum Bristly haircap
Pseudotaxiphyllum elegans Elegant silk-moss
Racomitrium aciculare Yellow fringe-moss
Racomitrium heterostichum Bristly fringe-moss
Rhizomnium punctatum Dotted thyme-moss
Rhytidiadelphus loreus Little shaggy-moss
Rhytidiadelphus squarrosus Springy turf-moss
Rhytidiadelphus triquetrus Big shaggy-moss
Scleropodium purum Neat feather-moss
Sphagnum denticulatum Cow-horn bog-moss
Sphagnum fimbriatum Fringed bog-moss
Sphagnum quinquifarium Five-ranked bog-moss
Sphagnum subnitens Lustrous bog-moss
Sphagnum teres Rigid bog-moss
Tetraphis pellucida Pellucid four-tooth moss
Thamnobryum alopecurum Fox-tail feather-moss
Thuidium tamariscinum Common tamarisk-moss
Trichostomun brachydontium Variable crisp-moss
Ulota crispa agg. Crisped pincushion
Zygodon rupestris Park yoke-moss
Calypogeia arguta Notched pouchwort
Calypogeia fissa Common pouchwort
Cephalozia bicuspidata Two-horned pincerwort
Diplophyllum albicans White earwort
Frullania dilatata Dilated scalewort
Lejeunea cavifolia Micheli’s least pouncewort
Lepidozia reptans Creeping fingerwort
Lophocolea bidentata Bifid crestwort
Marsupella emarginata Notched earwort
Metzgeria furcata Forked veilwort
Metzgeria temperata Wiskered veilwort
Microlejeunea ulicina Fairy beads
Nardia scalaris Ladder flapwort
Nowellia curvifolia Wood-rust
Pellia epiphylla Overleaf pellia
Plagiochila asplenoides Greater featherwort
Plagiochila porelloides Lesser featherwort
Saccogyna viticulosa Straggling pouchwort
Scapania nemorea Grove earwort
Scapania undulata Water earwort
Trichocolea tomentella Handsome woolywort



Sixty eight species of lichen were recorded, the majority being found on the trunks and branches of broadleaved trees. No species of conservation concern were located, though an interesting flora is beginning to develop on the few mature to ancient trees present in the woodland.

Lichens on trees

  1. On ConifersConifer plantations tend to support few lichens. Densely grown evergreen conifers such as firs and spruces cast too deep a shade and only a few shade tolerant lichens such as Lepraria species occur on their trunks. Following thinning and as the trees mature and the lower limbs die back light levels increase and a somewhat greater range of species occur. Few, however are of any note (in contrast to the native pinewoods of Scotland which support an exceptionally rich lichen flora) being mostly common acid bark-loving species eg Cladonia coniocraea, Lecanora conizaeoides and L. expallens such as were found on the large Douglas firs around the car park.

    Larch provides an exception. Shedding its needles in winter, it also casts a lighter shade in summer and permits the growth of lichens. The small larch plantation to the north of the camping barns is festooned in a wide range of lichens, including the shrubby growths of the beard lichens Usnea florida and U. subfloridana , the oak “moss” Evernia prunastri and a range of foliose and crustose species.

  2. On Broadleaved TreesThe most diverse lichen communities occur on ancient or veteran trees. Most of the plantation forestry is in consequence unsuitable since trees are felled long before they develop niches such as old dead, bark-free wood, large crevices out of direct rainfall and the sort of base-rich bark, only found on old trees. It is fortunate that a few ancient trees survive, particularly about the camping base and its associated meadows. Here two ancient oaks provide the only sites for lichens such asLeptogium teretiusculum, Anisomeridion biformis, Bacidia rubella and Catillaria atropurpurea . Other notable species, uncommon elsewhere in the community woodland include Dimerella lutea and Normandina pulchella . These latter two species occur on maiden oaks in the one surviving significant block of seminatural oakwood close to Craig-y-Rhaiadr. Trees here are just beginning to develop a more noteworthy lichen flora with, in addition to the above, Arthonia spadicea andArthopyrenia ranunculospora occurring on the larger and possibly most ancient specimens. These are typically the first lichen species confined to ancient trees. Holly appears to be rapidly invading this block of woodland. Some control may be required to prevent the bases of the more noteworthy trees becoming too heavily shaded. Every effort should be made to retain all of the largest and most ancient trees in the woodland, keeping their trunks relatively open and free of smothering growths of evergreens such as ivy and holly.

    Branches and twigs support a diverse lichen flora of common and widespread species such as the grey-green foliose lichens Parmelia saxatilis P. sulcata, Hypotrachyna revoluta, Hypogymnia physoides, H. tubulosa and Platismatia glauca and the yellow Flavoparmelia caperata .

    The wet woodland beside the Nant Rhaeadr supports an interesting, if limited range of lichens confined to the dampest of woodlands in western Britain. Fragmentary examples of the Parmelion laevigatae community occur on alder, characterized by the presence of the blue-grey strap-like lobes of the foliose lichenHypotrachyna laevigata and the grey crusts of Megalaria pulverea . On bark-free wood the foliose cup-lichen Cladonia caespiticia and the green gelatinous crusts of the crustose lichen Micarea prasina are common. It is important to retain this old fallen wood in this area as with time a richer flora may develop.

Lichens on other Substrates

There are few rock outcrops, the most extensive being in the bed of the stream. Due to the deep shade lichen growth is poor on these rocks. Elsewhere a limited flora of widespread species occurs on stones, small outcrops and soil exposed beside the forestry tracks. On these banks the commonest lichens are acid soil-loving species of the cup lichen genus (Cladonia spp.). Dry underhangs support the yellow crusts of Chaenotheca furfuracea andLecidea orosthea .


Lichen Species List

Q= on oak; FX= on ash; CO= on hazel; AG= on alder; PSM= on Douglas fir; LA= on larch; SC= on grey willow TER= on soil; CORT= on logs; SX= on rock

Anisomeridium biforme Q
Anisomeridium ranunculosporum Q
Arthonia cinnabarina Q
Arthonia radiata Q CO
Arthonia spadicea Q
Bacidia rubella Q
Baeomyces rufus TER
Caloplaca ulcerosa FX
Candelariella reflexa FX
Catinaria atropurpurea Q
Chaenotheca furfuracea TER
Cladonia coniocraea AG Q
Cladonia diversa TER
Cladonia fimbriata Q
Cladonia floerkeana Q
Cladonia furcata    subsp. furcata TER
Cladonia polydactyla  var. polydactyla CO
Cladonia portentosa TER
Cladonia ramulosa CO
Cyrtidula quercus ## Q
Dimerella lutea Q
Dimerella pineti SC
Evernia prunastri LA Q FX
Flavoparmelia caperata FX LA Q
Graphis elegans AG Q LA
Graphis scripta Q LA
Hypocenomyce scalaris BPE
Hypogymnia physodes AG Q CO FX LA
Hypogymnia tubulosa AG Q
Hypotrachyna laevigata AG CORT
Hypotrachyna revoluta Q FX
Lecania erysibe FX
Lecanora chlarotera FX CO
Lecanora confusa LA
Lecanora conizaeoides  f. conizaeoides PSM
Lecanora expallens PSM Q
Lecanora jamesii FX
Lecidella elaeochroma f. elaeochroma Q FX
Lepraria incana s. lat. PSM Q
Leptogium teretiusculum Q
Melanelia fuliginosa subsp. glabratula Q FX
Melanelia subaurifera Q
Micarea prasina s. lat. CORT Q
Mycoblastus fucatus Q
Normandina pulchella Q FX
Ochrolechia androgyna LA
Ochrolechia parella Q
Opegrapha vulgata Q CO
Parmelia saxatilis LA CO AG Q SX
Parmelia sulcata Q FX AG SC
Peltigera praetextata FX
Pertusaria amara f. amara Q FX LA
Pertusaria hymenea FX
Pertusaria leioplaca Q
Pertusaria multipuncta FX
Phlyctis argena Q SC
Physcia aipolia FX
Physcia tenella subsp. tenella FRX
Platismatia glauca Q FX LA CO AG
Porpidia crustulata SX
Porpidia macrocarpa f. macrocarpa SX
Psilolechia lucida SX
Ramalina farinacea Q LA
Trapelia coarctata SX
Trapelia corticola CORT LA
Trapeliopsis granulosa CORT
Usnea florida LA Q
Usnea subfloridana LA Q



As indicated above only an incomplete list of fungi can be provided due to the short time available for survey. The following 32 taxa were noted. Most species were either mychorrhizal on tree roots (=M), in leaf litter +L or on dead wood +D. A few rust, smut and powdery mildew species were noted as parasites of higher plants.

Amanita rubescens Blusher M
Boletus badius Bay bolete M
Boletus chrysenteron Red cracking bolete M
Calocera viscose Yellow stagshorn D
Clavulina coralloides White coral L
Clitocybe dealbata Ivory funnel L
Clitocybe rivulosa Fool’s funnel L
Collybia maculata Spotted toughshank L
Hygrophoropsis aurantiaca False chanterelle L
Hypholoma fasciulare Sulphur tuft D
Hymenochaetae tabacina A bracket fungus on oak stumps
Laccaria laccata Tawny deceiver L
Lactarius quietus Oakbug milkcap M
Lactarius tabidus Birch milkcap M
Mycena haematopus Burgundydrop bonnet D
Mycena sanguineolenta Bleeding bonnet D
Paxillus involutans agg. Roll rim M
Pleuteus cervinus agg. Deer shield D
Psathyrella sp. A brittlestem D
Russula spp. Brittlegill species M
Scleroderma citrinum Common earthball M?
Suillus grevillei Larch bolete M
Trametes versicolor Turkey tail D
Naohidemyces vacciniorum Bilberry
Phragmidium violaceum Bramble
Puccinia caricina Binerved sedge
Puccinia circaeae Enchanter’s nightshade
Pucciniastrum circaeae Enchanter’s nightshade
Taphrina tosquinetii Alder
Erysiphe circaeae Enchanter’s nightshade
Microsphaera alphitoides Oak
Sphaerotheca fuliginea Germander speedwell


Conspicuous orange coloured patches on the shaded trunks of trees, particularly the large Douglas firs near the car park, were caused by the filamentous alga Trentepohlia . This is a widespread alga. Tiny circular spots looking like spots of rust on ivy leaves close to the car park were caused by a near relative of Trentopohlia called Phycopeltis . This latter alga was first recorded from the British Isles from south west Ireland in 1965. It is a mostly tropical and subtropical genus probably only recently colonizing the British Isles as the climate has warmed (see attached illustration).

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