The Lower Plants of Cwm Rhaeadr Forest
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
- 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 .
- 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
- 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.
- 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|
|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
- 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.
- 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
|Arthonia radiata||Q CO|
|Cladonia coniocraea||AG Q|
|Cladonia furcata subsp. furcata||TER|
|Cladonia polydactyla var. polydactyla||CO|
|Cyrtidula quercus ##||Q|
|Evernia prunastri||LA Q FX|
|Flavoparmelia caperata||FX LA Q|
|Graphis elegans||AG Q LA|
|Graphis scripta||Q LA|
|Hypogymnia physodes||AG Q CO FX LA|
|Hypogymnia tubulosa||AG Q|
|Hypotrachyna laevigata||AG CORT|
|Hypotrachyna revoluta||Q FX|
|Lecanora chlarotera||FX CO|
|Lecanora conizaeoides f. conizaeoides||PSM|
|Lecanora expallens||PSM Q|
|Lecidella elaeochroma f. elaeochroma||Q FX|
|Lepraria incana s. lat.||PSM Q|
|Melanelia fuliginosa subsp. glabratula||Q FX|
|Micarea prasina s. lat.||CORT Q|
|Normandina pulchella||Q FX|
|Opegrapha vulgata||Q CO|
|Parmelia saxatilis||LA CO AG Q SX|
|Parmelia sulcata||Q FX AG SC|
|Pertusaria amara f. amara||Q FX LA|
|Phlyctis argena||Q SC|
|Physcia tenella subsp. tenella||FRX|
|Platismatia glauca||Q FX LA CO AG|
|Porpidia macrocarpa f. macrocarpa||SX|
|Ramalina farinacea||Q LA|
|Trapelia corticola||CORT LA|
|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|
|Puccinia caricina||Binerved sedge|
|Puccinia circaeae||Enchanter’s nightshade|
|Pucciniastrum circaeae||Enchanter’s nightshade|
|Erysiphe circaeae||Enchanter’s nightshade|
|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).