Vice-county 45 (Pembrokeshire)

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The tors of Mynydd Preseli are home to numerous upland bryophytes

The following account has been taken from The Mosses and Liverworts of Pembrokeshire (2010) with updated names and a few additional sites and species.

Sam Bosanquet, December 2020

Broad bryophyte habitats

Almost every habitat above the high spring tide level in Pembrokeshire has its characteristic common bryophytes, as well as a range of uncommon and rare species.  The most logical way to cover these common species in a broad-brush way is to use a habitat classification and discuss the typical species within each habitat.  BRYOATT used the EUNIS classification to divide the British bryophyte flora by habitats, so this classification is followed here.  It differs very slightly from the UK BAP Broad Habitats Classification used in the Carmarthenshire Flora, but there are significant similarities.  The first two levels of the EUNIS classification are employed here: 10 categories (A–J) are then subdivided into between two and nine additional classes.  The NVC is also used here as a signpost for recognition of grassland and peatland communities, despite some people’s scepticism over its value.

A2 Littoral sediment

Hennediella heimii and Tortella flavovirens are the only mosses recorded from estuarine saltmarsh in Pembrokeshire.  Both are uncommon and restricted to the upper saltmarsh, especially where tracks cross it.  The map in Adam (1976) confirms that Pembrokeshire saltmarshes are not as diverse as those further north in Britain, as two of his three samples held 1–5 species (perhaps just 1) and the other held zero, whereas some saltmarshes in Scotland may hold 10 or more bryophyte species.

As well as true estuarine saltmarsh, the Pembrokeshire coast holds scattered stands of superficially similar vegetation that have developed on salt-sprayed clay deposits overlying rocky shores, often some 15 or 20 m above spring tide level.  This ‘perched saltmarsh’ is usually dominated by Festuca rubra and may hold Agrostis stolonifera, Armeria maritima, Juncus gerardii, Plantago maritima or Puccinellia maritima.  Its bryophyte flora includes Amblystegium serpens var. salinum, Archidium alternifolium, Kindbergia praelonga and Tortella flavovirens, with Bryum sp. at three sites.  A Bryum colony at Ceibwr Bay (SN108458) was provisionally identified as B. intermedium, and both it and others at St Bride’s (SM803111) and West Angle Bay (SM852033) deserve a return visit in late summer.

B1 Coastal dunes and sandy shores

There is a series of lime-rich dune systems along the south Pembrokeshire coast between the Castlemartin Range (SR89Y–Z) and Tenby (SS19J), and these contrast with less calcareous systems in the north at Whitesands (SM7326–7327), Newport (SN0540) and Poppit Sands (SN1548).  The southern dunes are both derived from limestone and overlie limestone, so their flora is dominated by calcicoles such as Campylium chrysophyllum, Tortella squarrosa and Trichostomum crispulum, as well as the more widespread Syntrichia ruraliformis.  The most extensive system occupies the west end of the Castlemartin Peninsula, between Linney Burrows (SR8997) and Kilpaison Burrows (SM8900).  This comprises mobile and fixed dunes, large disused sand quarries in Brownslade Burrows (SR8998) and Broomhill Burrows (SM8800) that now hold dune slack vegetation including thousands of plants of Petalophyllum ralfsii, a few natural slacks, and a fen dominated by Juncus subnodulosus.  The richest fixed dune vegetation is on thin sand overlying limestone, both here and further east at Stackpole Warren (SR9794–9895) where Bryum canariense and Didymodon acutus grow.  Other dune bryophytes found at these sites and at Freshwater East (SS0197–0298), Manorbier (SS0697), Penally Burrows (SS1298–1299) and Caldey Island (SS1496) include Brachythecium albicans, Bryum spp., Homalothecium lutescens, Rhynchostegium megapolitanum and Tortella flavovirensBryum cf. algovicum, Brachythecium albicans, R. megapolitanum, S. ruraliformis and T. flavovirens all grow in the northern dunes, but they lack strong calcicoles like Tortella.

Tortella squarrosa

B2 Coastal shingle

Most of the coastal shingle in Pembrokeshire – for example the spectacular storm beaches at Newgale and Aber Mawr – is too unstable to support bryophytes.  The more stable Pickleridge at the head of the Gann Estuary, Dale (SM8107) held Brachythecium albicans, Bryum cf. caespiticium, Campylopus introflexus, Ceratodon purpureus and Dicranum scoparium in 2001, whilst Dalby (1965) also noted Polytrichum juniperinum and Pseudoscleropodium purum there.  This mix of calcifuge species is probably typical of the dry, leached environment provided by coastal shingle.

B3 Rock cliffs, ledges and shores

Pembrokeshire’s long and convoluted coast spans every aspect and degree of slope and is home to a tremendous range of bryophytes from the southern calcicole mosses of the Castlemartin Range, like Dicranella howei and Tortula protobryoides, to northern calcifuge liverworts of the Newport area, such as Gymnomitrion concinnatum and Marsupella emarginata.  A total of 217 species have been recorded specifically on coastal slopes, cliffs, rocks or in coastal gullies in Pembrokeshire, a high proportion of the 269 assigned to this habitat in BRYOATT.  Probably the easiest way to examine such a varied flora is to look at four contrasting coasts: examples of the southern limestone on the Castlemartin Range, south-facing Old Red Sandstone slopes near Dale, north-facing igneous slopes on Strumble Head, and the tall, north-facing siliceous cliff slopes near Newport.  The most characteristic B3 species are six that are restricted to the county’s coast but are widespread around it: Frullania microphylla, F. teneriffae, Schistidium maritimum, Tortula atrovirens, T. viridifolia and Weissia perssonii, although the abundant Trichostomum brachydontium is almost as typical.

Much of the limestone coast is very exposed and supports few bryophytes apart from the ubiquitous Trichostomum brachydontium and locally frequent Tortula viridifolia and Weissia controversa var. crispata.  It is at its richest either on northeast-facing slopes, or where thin soil overlies limestone: a combination found on St Govan’s Head (SR9792), Stackpole Head (SR9994) and Lydstep Head (SS0897–0997).  The north-easterly aspect favours pleurocarpous mosses, such as Calliergonella cuspidata and Homalothecium lutescens, whilst thin soil supports Riccia sorocarpa, Fissidens dubius and Microbryum species.  Schistidium maritimum is absent from the limestone.

Carn Ogof cliffs on the Strumble Peninsula

South-facing sandstone supports warmth-lovers such as Grimmia lisae, Nogopterium gracile and Zygodon viridissimus var. stirtonii, and coastal slopes derived from it hold locally abundant Tortula atrovirens as well as the more widespread T. viridifolia.  The ubiquitous Trichostomum brachydontium is often joined by the similar-looking Tortella flavovirens, and Frullania spp. and Schistidium maritimum share boulders low down on the coastal slopes.  The grazed coastal slopes on the north side of Westdale Bay (SM7906) typify the sandstone flora apart from holding the rare Tortula wilsonii.  They also illustrate the flora that might be present more widely on the north side of Milford Haven if grazing was returned to the coastal slopes and scrub was controlled better.

Cell Howell (SN0843) is a series of cliffs and coastal slopes 150 m tall in the north-east of the county between Newport and Ceibwr Bay.  The rock here is a mixture of hard sandstone and very friable shale, and the cliffs have extensive jumbles of boulders and slabs on steep ground below them.  The height of the cliffs couples with the northerly aspect and rocky undercliffs to provide a cool microclimate reminiscent of montane areas, so it is perhaps unsurprising that upland species such as Gymnocolea inflata, Barbilophozia sudetica, Marsupella emarginata and Racomitrium fasciculare grow here.  The bryophytes of Cell Howell are typical of the tallest cliffs of north Pembrokeshire, and many are also found at Carn Ogof (SM8837) and Dinas Head (SN04A), as well as between Newport and Cemaes Head (SN04–14).  Coscinodon cribrosus is particularly characteristic of the north Pembrokeshire coast, growing in dense, hoary cushions on friable shale near the cliff edge, as well as on boulders on coastal slopes.  The base-poor, humid conditions also favour liverworts such as Diplophyllum albicans, Lophozia ventricosa, Saccogyna viticulosa and Scapania gracilis, all of which are locally abundant, as well as the mosses Dicranum majus, Hypnum jutlandicum, Cynodontium bruntonii and Rhytidiadelphus loreus, which lend a feeling of a western oak woodland to the flora.  This flora is repeated on the north coast of Cornwall in the Boscastle area (Paton, 1969).

C1 Surface standing waters

Ponds and bog pools are the two habitats considered to belong to C1.  There are numerous ponds, small lakes and reservoirs around Pembrokeshire, but they are not important bryophyte habitats when their water levels are high.  Some have notable species in their littoral zone when water levels drop (see C3), and a few have Fontinalis antipyretica or Leptodictyum riparium growing semi-submerged on rocks or logs on their margins.  The floating liverworts Riccia fluitans and Ricciocarpos natans have never been recorded in the county, although the former grows reasonably close by in Carmarthenshire and might be expected in ponds in lowland eastern Pembrokeshire.

Sphagnum cuspidatum and Warnstorfia fluitans are both frequent in oligotrophic pools on Mynydd Preseli, both on the ridge and on low-lying land either side of it.  Odontoschisma fluitans sometimes floats among the SphagnumW. fluitans was also dominant below an open canopy of Carex rostrata in a pool on Rhos Fawr (SN0227).

C2 Surface running waters

The rocky streams and rivers that drain Mynydd Preseli support a rich bryophyte assemblage that includes the liverworts Chiloscyphus polyanthos, Marchantia polymorpha subsp. polymorpha and Scapania undulata, and the mosses Fontinalis antipyretica, F. squamosa, Hygroamblystegium fluviatile, Hygrohypnella ochracea, Platyhypnidium riparioides, Racomitrium aciculare, Schistidium rivulare and Sciuro-hypnum plumosumPorella pinnata joins them in the Eastern Cleddau downstream from Waun Isaf (SN1430) and in the Afon Anghof downstream from Sealyham (SM9628), reaching its maximum abundance on the Western Cleddau at Treffgarne (SM92M).  It is a feature of most rivers of central and northern Pembrokeshire and is one of the county’s most characteristic bryophytes.  The uncommon Jubula hutchinsiae grows on rocks by the Afon Gwaun below Kilkiffeth Wood (SN0134) and on the Syfynwy at Farthing’s Hook (SN0427) alongside the more widespread Lejeunea lamacerina and Riccardia chamedryfolia.  The Riccardia is sometimes found forming bright green patches on stones in deep, clear water.  Dichodontium sp., Hyocomium armoricum, Rhizomnium punctatum, Schistidium apocarpum and Thamnobryum alopecurum appear to be more characteristic of rocky middle reaches of the rivers, especially in wooded valleys, as does Fissidens pusillusCinclidotus fontinaloides and Hygroamblystegium tenax are found in neutral streams and rivers in the lowlands, although the Cinclidotus extends all the way up the Eastern Cleddau to Mynachlog-ddu (SN13F), whilst Fissidens monguillonii grows on silty rocks in four of the county’s rivers.  The rare Fissidens fontanus joins a typical lowland assemblage of F. antipyretica, Leptodictyum riparium, Leskea polycarpa and Orthotrichum cupulatum on rocks and walls by the Western Cleddau in Haverfordwest (SM9515).

C3 Littoral zone of inland surface waters

Steep earth river banks in lowland Pembrokeshire develop a diverse bryophyte flora that includes many species which reproduce asexually and so can recolonise after spates.  Lunularia cruciata, Bryum dichotomum, B. gemmiferum, Pohlia annotina and P. camptotrachela all reproduce with gemmae, whilst Bryum rubens, B. sauteri, Dicranella schreberiana, D. staphylina, Epipterygium tozeri and Pohlia melanodon grow from tubers.  An alternative approach is to produce abundant sporophytes very rapidly, as demonstrated by Pseudephemerum nitidum and Tortula truncataFossombronia pusilla, Atrichum undulatum, Oxyrrhynchium hians, Physcomitrium pyriforme and Pleuridium subulatum are also characteristic species of open lowland river banks, and Anthoceros punctatus is sometimes found in this habitat.  Wooded rivers tend to support a slightly different range of species, including Pellia endiviifolia or P. epiphylla according to pH, Calypogeia arguta, Conocephalum conicum, Dicranella heteromalla, D. rufescens, Fissidens bryoides var. caespitans, F. celticus, Kindbergia praelonga, Plagiothecium nemorale and P. succulentum.

The Afon Teifi at Cilgerran

The characteristic epiphyte flora that develops on tree trunks by silty rivers is poorly represented in Pembrokeshire compared with Carmarthenshire, as there are just single records of Orthotrichum sprucei by the Eastern and Western Cleddaus and the Afon Teifi, and sparse Leskea polycarpa and Syntrichia latifoliaHomalia trichomanoides and Thamnobryum alopecurum are often abundant on tree boles by rivers.

The county’s two main reservoirs both have well-developed draw-down zones from time to time, although Rosebush Reservoir (SN0629) at least was brim-full for most of the 2000s.  This may be a factor in its relatively impoverished flora compared with the larger Llys-y-fran Reservoir (SN0324–0426), further downstream on the Afon Syfynwy.  Only Bryum dichotomum, Ephemerum stoloniferum (formerly E. serratum), Fissidens sp., Fontinalis antipyretica and Pseudephemerum nitidum grow on the margins of Rosebush Reservoir, whereas Llys-y-fran holds additional Fossombronia sp., Aphanorrhegma patens, Bryum klinggraeffii, Dicranella rufescens, D. schreberiana, Ephemerum crassinervium subsp. sessile (formerly E. sessile), Fissidens taxifolius, F. viridulus, Leptodictyum riparium, Tortula truncata, Trichodon cylindricus, Weissia controversa and W. rostellataRiccia cavernosa and Aphanorrhegma patens sometimes grow in great abundance on the margin of Bosherston Lake (SR99) when water levels drop in late summer.

D1 Raised and blanket bogs

There are only two extant raised bogs in Pembrokeshire, at Esgyrn Bottom (SM9734) and Cors Llanerch (SN0534), but there were probably one or two others that have now been lost, for example the wooded mire at Corsydd Llangloffan (SM9031) is reported to have very deep peat deposits that suggest it has a raised bog dome.  There is still a reasonably intact dome at Esgyrn Bottom, which supports Erica tetralix Sphagnum papillosum raised mire (M18) where the bryophytes Odontoschisma fluitans, Kurzia pauciflora, Mylia anomala, Odontoschisma denudatum, O. sphagni, Dicranum scoparium, Leucobryum glaucum, Sphagnum capillifolium subsp. rubellum, S. cuspidatum, S. magellanicum, S. papillosum and S. tenellum grow.  Cors Llanerch was deep ploughed and planted with conifers since a 1965 visit by Francis Rose and now supports an impoverished flora.

The CCW lowland grassland survey recorded Trichophorum cespitosumEriophorum vaginatum mire (M17) at scattered sites in the county from near Hayscastle in the west (SM9124) to Crymych in the north-east (SN1832).  This has a similar bryophyte flora to raised bog, but lacks Sphagnum magellanicum and, in Pembrokeshire, Odontoschisma denudatum, but usually retains a high frequency of S. capillifolium subsp. rubellum and S. papillosum.  Other regular bog species include the liverworts Calypogeia fissa, Cephalozia bicuspidata and C. connivens, and the mosses Aulacomnium palustre, Hypnum jutlandicum and Pleurozium schreberi.  There are more extensive stands of M17 on Mynydd Preseli, but blanket bog is uncommon even there.  It is floristically similar to the lowland stands, but holds a few additional species.

D2 Valley mires, poor fens and transition mires

Most of the poor fen and transition mire in Pembrokeshire is on the lower slopes of Mynydd Preseli, but there are scattered stands elsewhere in the north, usually in basin mires.  The main vegetation types are Carex rostrataSphagnum fallax mire (M4), Carex rostrataSphagnum squarrosum mire (M5) and Narthecium ossifragumSphagnum papillosum valley mire (M21).  M4 is usually very species-poor, with few other bryophytes except Polytrichum commune var. commune growing in the S. fallax carpet.  M5 may be richer, and there are records of Chiloscyphus pallescens, Rhizomnium pseudopunctatum, Sphagnum contortum, S. flexuosum, S. subnitens, S. teres and Straminergon stramineum from this community.  M21 resembles a bog in its abundance of S. papillosum, but lacks Eriophorum vaginatum.  It is the richest form of poor fen for hepatics and often supports Calypogeia spp., Cephalozia connivens, Cephaloziella hampeana, Kurzia pauciflora and Odontoschisma sphagni, with Odontoschisma fluitans in wetter stands.

The acid flush community Carex echinataSphagnum fallax/denticulatum mire (M6) also belongs in this category.  Its bryophyte flora differs little from that of the poor fen, but the predominance of Sphagnum fallax, S. denticulatum and Polytrichum commune, all poor substrates for liverworts, leads to a limited hepatic flora in this community.  Acid flushes are often fed by springs that have very high covers of bryophytes, probably because of the constant movement of water through them.  Some belong to Philonotis fontana Saxifraga stellaris spring (M32), others do not fit the NVC.  Hamatocaulis vernicosus is a characteristic component of springs with neutral water, and sometimes grows in the flushes emanating from them.  Other regular spring bryophytes include Brachythecium rivulare, Calliergonella cuspidata, Dichodontium palustre, Philonotis fontana and Sarmentypnum exannulatum.

D4 Base-rich fens and calcareous spring mires

Although limestone is restricted to southern Pembrokeshire, the county’s base-rich fens are almost all in the north.  Most of the small number of exceptions are reed-dominated (see D5), but there are reed-free examples at Frainslake (SR8997), where Plagiomnium ellipticum is abundant, east of Bangeston (SM9903), and in the Ritec valley (SN1001).  The St David’s Peninsula (SM72–82) has a series of important rich-fen sites where Calliergon giganteum is locally abundant alongside the sedge Carex diandra in Carex rostrataCalliergonella cuspidata/Calliergon giganteum fen (M9).  Campylium stellatum, Palustriella falcata, Scorpidium cossonii and S. scorpioides add to the diversity here, whilst Calliergon cordifolium replaces its relative in areas with raised water tables or nutrient enrichment.  Carex dioicaPinguicula vulgaris mire (M10) is widespread from here eastwards to Frenni Fawr (SN2135), but is extremely rare everywhere except on Mynydd Preseli.  The middle of M10 flushes is often markedly calcareous, with species such as Ctenidium molluscum and S. cossonii prominent, whilst the base-richness drops off towards the edge of runnels and base-tolerant sphagna including Sphagnum contortum, S. inundatum and S. platyphyllum become frequent.

Sphagnum platyphyllum in a flush on Mynydd Preseli

Palustriella falcata-dominated calcareous springs belonging to Palustriella commutataFestuca rubra spring (M37) are restricted to the north side of Mynydd Preseli and are very rare even there.  Other species recorded in these springs and the stony flushes that they feed include Aneura pinguis, Pellia endiviifolia, Blindia acuta, Ctenidium molluscum, Philonotis calcarea, Schistidium apocarpum and Scorpidium cossonii.

D5 Sedge and reed beds, normally without free-standing water

Sedge and reed beds were excluded from BRYOATT as being “of rather marginal interest”.  This is partly true, especially of dense, species-poor sedge beds belonging to Carex riparia swamp (S6) and Carex acutiformis swamp (S7) – both of which are mercifully rare in Pembrokeshire – but not of some reed beds.  Reed beds with standing water, belonging to Phragmites australis reed-bed (S4) are bryologically dull, but the reed-fen communities Phragmites australisPeucedanum palustre tall-herb fen (S24) and Phragmites australisEupatorium cannabinum tall-herb fen (S25) hold a reasonable array of bryophytes.  All of the best examples of reed-fen are coastal: at Pwllcrochan Fen (SM9102–9202), Goodwick Moor (SM9437), Castlemartin Corse (SR8999), Freshwater East reedbed (SS0197), Ritec Fen (SN0901–1100) and Cors Penally (SS1198).  The humidity of the first three is indicated by locally abundant Riccardia chamedryfolia growing up reed stems alongside Pseudocampylium radicale, Brachythecium rivulare, Calliergonella cuspidata, Leptodictyum riparium and Oxyrrhynchium speciosum.  This is more or less the sum total of bryophyte species present in Pembrokeshire reed fen, but it includes a high proportion of notable species.

Tussock sedge-dominated Carex paniculata sedge swamp (S3) is more widespread than the other sedge communities and is also slightly more bryophyte-rich, although that stems partly from its tendency to take over from more open, and even more diverse, fen vegetation.  The sides of the Carex tussocks are often covered with Kindbergia praelonga, Plagiothecium denticulatum or Pseudotaxiphyllum elegans, and Brachythecium rivulare, Hookeria lucens, Plagiomnium undulatum and Rhizomnium punctatum may grow in wet runnels between the tussocks.

E1 Dry grasslands

Lophocolea bidentata, Atrichum undulatum, Brachythecium rutabulum, Calliergonella cuspidata, Kindbergia praelonga, Pseudoscleropodium purum, Rhytidiadelphus squarrosus and Thuidium tamariscinum are the most regular bryophytes in unimproved Centaurea nigraCynosurus cristatus grassland (MG5), but neutral grassland is not a naturally rich bryophyte community.  Its diversity is increased by soil gaps on steep slopes, where Anthoceros punctatus, Fossombronia pusilla, Bryum rubens, Fissidens spp., Pseudephemerum nitidum and Tortula truncata can find a niche, or in slightly heathy forms with affinities to acid grassland.

Hylocomium splendens, Hypnum jutlandicum, Pleurozium schreberi and sometimes a few scraps of Rhytidiadelphus loreus or Sphagnum sp. characterise the acid swards of Festuca ovinaAgrostis capillarisGalium saxatile grassland (U4) and Nardus strictaGalium saxatile grassland (U5).  Parched Festuca ovinaAgrostis capillarisRumex acetosella grassland (U1) characteristically supports abundant Polytrichum juniperinum alongside Cladonia and Peltigera lichens.

Calcicolous grasslands are naturally the most species-rich of the dry grassland communities, although they are so easily damaged by enrichment and ploughing that they have almost vanished from Pembrokeshire.  Festuca ovinaCarlina vulgaris grassland (CG1) and Festuca ovinaHelictotrichon pratensis grassland (CG2) remain only on the Castlemartin Range (SR89–99), where most show significant coastal influences or have developed on blown sand, further east on the south coast.  The bryophyte-rich grassland at the west end of West Williamston (SN0206) was also mapped as CG2.  Most of the bryophytes recorded from calcareous grassland in Pembrokeshire could equally be placed in the coastal category B3 because neutral grassland mostly replaces calcareous swards inland of the coast.  They include Ctenidium molluscum, although it is surprisingly uncommon in grassland on Castlemartin Range, Lophocolea bidentata, Calliergonella cuspidata, Dicranum scoparium, Didymodon fallax, Eurhynchium striatum, Fissidens dubius, Homalothecium lutescens, Hypnum cupressiforme var. lacunosum, Hylocomiadelphus triquetrus and in more open swards Trichostomum brachydontium, T. crispulum and Weissia controversa var. crispata.

E2 Mesic grasslands

Nutrient-rich Lolium perenneCynosurus cristatus grassland (MG6) and Lolium perenne leys (MG7) are even more impoverished than semi-natural neutral grassland.  Brachythecium rutabulum, Kindbergia praelonga and Oxyrrhynchium hians are regular components of more open swards, whilst arable mosses such as Bryum rubens and Tortula truncata are often found on soil gaps.  Rhytidiadelphus squarrosus is often abundant in mown lawns, but usually indicates remnant patches of semi-improved dry grassland rather than true mesic grassland.  Calliergonella cuspidata is perhaps more tolerant of enrichment, but other dry grassland species such as Pseudoscleropodium purum and Thuidium tamariscinum tend to be absent from MG6 and MG7.  Both Pembrokeshire colonies of Weissia squarrosa are in reseeded MG7 with Lolium and Trifolium.

E3 Seasonally wet grasslands

The commonest form of marshy grassland in lowland Pembrokeshire is Juncus effusus/acutiflorus Galium palustre rush-pasture (M23).  This varies in appearance from dense stands of species-poor J. effusus to open, herb-rich communities with abundant J. acutiflorus.  The pleurocarpous mosses Brachythecium rivulare, B. rutabulum, Calliergonella cuspidata and Kindbergia praelonga are all common components of rush-pasture, and they are often joined by Anthoceros punctatus, Fossombronia wondraczekii, Pellia neesiana, Physcomitrium pyriforme, Pohlia annotina, P. camptotrachela and Pseudephemerum nitidum in open, cattle-grazed stands, especially by streams.  Wet hollows and ditches in rush-pasture approach fen vegetation and can hold abundant Calliergon cordifolium, whilst flushed stands may support patchy Sphagnum fimbriatum, S. inundatum, S. palustre or S. subnitens.

Anthoceros punctatus in poached marshy grassland. Sporophytes are still immature and antheridial cavities can be seen as small pits on the thallus in the centre of the photo

Seasonal flushing in acid grassland encourages a different suite of Sphagna, especially S. denticulatum and S. fallax, to grow among Agrostis canina, Carex nigra, C. panicea and Nardus strictaDiplophyllum albicans, Aulacomnium palustre, Campylopus flexuosus, C. introflexus, Polytrichum commune var. commune and Rhytidiadelphus squarrosus are also frequent in flushed grassland around Mynydd Preseli.

E7 Sparsely wooded grasslands

Pembrokeshire parkland seems to be of minimal note for its epiphytes and of no bryological interest for its grassland.  The epiphyte flora on old Fraxinus and Quercus at Picton Park (SN0113) includes little more than Frullania dilatata, F. tamarisci, Metzgeria furcata, Cryphaea heteromalla, Lewinskya affinis, Ulota bruchii, U. phyllantha, Zygodon conoideus and Z. viridissimus – in other words a fairly mundane assemblage.  The county’s other parklands, at Slebech Park (SN0214) in the south and Cilwendeg (SN2238) and Ffynnone (SN2438) in the north, remain bryologically unknown and might be worth exploring, although all are in quite intensively farmed areas and so may be enriched.

F3 Temperate scrub

The main scrub formers in Pembrokeshire are Crataegus monogyna, Prunus spinosa, Sambucus nigra, Rubus fruticosus agg. and Ulex europaeus, with some Corylus avellana scrub on woodland edges in the south, dense Hippophae rhamnoides scrub in dunes near Tenby (SS19), and very small areas of Myrica gale around Mynydd Preseli (SN13).  Rubus is a poor epiphyte host and bramble thickets seldom hold many bryophytes at all, whereas Ulex can trap humidity and often supports liverworts such as Frullania dilatata, Metzgeria consanguinea, M. violacea and Microlejeunea ulicinaCorylus, Sambucus and P. spinosa are roughly equal as epiphyte hosts, but the base-poor bark of Crataegus is generally clothed with Hypnum spp. and seldom holds other epiphytes.  Epiphyte hosts were routinely recorded in Pembrokeshire, but no attempt was made to distinguish scrub from woodland or Corylus growing as an understorey or as the dominant species in a block of scrub.

Salix is the best host for obligate epiphytic bryophytes in Pembrokeshire.  This is a different conclusion to that reached by the 1997 BBS epiphyte survey, who found Fraxinus and Sambucus to be the main epiphyte hosts in a transect across southern Britain.  This difference is partly because the BBS survey measured a different factor to the Pembrokeshire survey: mean bryophyte diversity on tree species in tetrads rather than total counts of bryophyte-host records.  However, Fraxinus does come second in the Pembrokeshire survey, whilst Salix came third for the BBS.  The difference partly reflects the greater abundance of Salix compared with Sambucus in the far west (unfortunately the BBS transect ended in Devon and central Glamorgan and thus missed westernmost Britain), and partly the water retentive nature of Sambucus bark which makes it a particularly rich host tree in eastern England.  Certainly Sambucus can support a diverse flora in Pembrokeshire, but Salix stands usually feel intrinsically more diverse.  Mean species counts by site appear to reinforce this – Salix has a mean species count of 5.3 whereas Sambucus manages just 2.7 – but the Pembrokeshire data were not collected sufficiently systematically to allow such detailed comparison between host species.  Overall, however, it is clear that Salix spp., Fraxinus and the much-maligned Acer pseudoplatanus, all of which have base-rich bark, are key epiphyte hosts in Pembrokeshire, with Corylus, Sambucus and Prunus scrub holding well-developed communities and Quercus and Ulmus being locally important.  As noted by Bates et al., the main host trees do not necessarily account for all records of notable species, so Zygodon rupestris has only been noted on Quercus in Pembrokeshire, Pulvigera lyellii has been found on Quercus, Tilia and Ulmus, and Lewinskya striata grows on at least 10 host trees, including cultivated Acer sp. and Sorbus aucuparia.  Most of the commonest epiphytes favour Salix and/or Fraxinus, but Neckera pumila is almost as frequent on Corylus, Orthotrichum tenellum uses Sambucus and Ulmus regularly, and Metzgeria consanguinea is notably frequent on the acid-barked Alnus.  Although data collection was slightly haphazard and perceived poor host trees were often ignored if a good stand of Salix or Fraxinus had already been scrutinised on a site, it is clear that the epiphyte flora of Pembrokeshire is both varied and reasonably rich.

The ground layer in scrub is reminiscent of woodland but usually more species-poor.  Lophocolea bidentata, Atrichum undulatum, Brachythecium rutabulum, Dicranella heteromalla, Didymodon insulanus, Fissidens bryoides, F. taxifolius, Kindbergia praelonga and Plagiomnium undulatum are typical scrub bryophytes, and all can be locally dominant.  Which species dominates is perhaps somewhat stochastic, as many scrub communities are of too recent origin to have developed semi-stable bryophyte communities.

F4 Temperate shrub heathland

Heathland is concentrated in coastal Pembrokeshire and Mynydd Preseli, but there are blocks of dry and wet heath throughout the county, especially on common land.  The widespread dry heath community Calluna vulgaris Ulex gallii heath (H8) and the coastal Calluna vulgarisScilla verna heath (H7) are usually too dense for many bryophytes to grow, although Hypnum jutlandicum is usually present, sometimes as etiolated scraps below leggy ericoids, and Pleurozium schreberi abounds on upland-edge stands, for example on Parc Mawr (SN03I).  Dicranum scoparium, Hylocomium splendens, Polytrichum formosum and Rhytidiadelphus squarrosus are all locally frequent, and Campylopus introflexus is especially abundant in burnt heathland or near the coast.  Calluna vulgaris Erica cinerea heath (H10) and Calluna vulgarisVaccinium myrtillus heath (H12) both occur on Preseli and are bryologically similar to the Ulex heaths.

Wet heath has a much richer bryophyte flora than dry heath, especially when superficial flushing encourages soligenous fen species to join the typical wet heath components.  Trichophorum cespitosum Erica tetralix wet heath (M15) is much the commoner of the two wet heath communities in Pembrokeshire, with Erica tetralixSphagnum compactum wet heath (M16) occurring with it on the St David’s Peninsula (SM72–82), south of Strumble Head (SM93), and on the north side of Mynydd Preseli (SN03–13).  Sphagnum compactum and S. tenellum are the main markers of M16, which is otherwise very similar to its commoner counterpart.  Sphagna are usually prominent in all but the driest forms of M15 and often include S. denticulatum, S. fallax, S. inundatum, S. papillosum and S. subnitens.  Other regular wet heath mosses include loose patches of Aulacomnium palustre, dense cushions of Leucobryum glaucum, wefts of Hylocomium splendens, Hypnum jutlandicum, Pleurozium schreberi and Rhytidiadelphus loreus, and tufts or carpets of Campylopus flexuosus, C. introflexus, C. pyriformis and Dicranum scoparium.  Liverworts such as Calypogeia fissa, C. muelleriana, Cephalozia connivens, Diplophyllum albicans and Kurzia sylvatica may grow through the sphagna or over exposed peat.  Flushing adds dramatically to the flora, encouraging Aneura pinguis, Riccardia multifida, Breutelia chrysocoma, Campylium stellatum, Campylopus atrovirens, Polytrichum commune, Sarmentypnum sarmentosum, Scorpidium revolvens and Straminergon stramineum.

Sphagnum compactum in M16 wet heath

This category also includes Molinia caerulea Potentilla erecta mire (M25) – some of which is akin to wet heath but has a very high cover of Molinia, while other forms are more similar to rush-pasture (M23) – as well as heathy forms of Molinia caerulea Cirsium dissectum fen-meadow (M24).  Aulacomnium palustre, Hylocomium splendens, Pseudoscleropodium purum, Sphagnum inundatum, S. subnitens and Thuidium delicatulum are all regular species in heathy forms of M24 and M25, and the former often supports base-tolerant mosses such as Calliergonella cuspidata, Campylium stellatum and Sarmentypnum exannulatum.  Rank Molinia forms a substrate for Calypogeia arguta, C. fissa, Cephalozia bicuspidata, Mnium hornum, Pseudotaxiphyllum elegans and, on the St David’s Peninsula, Entosthodon obtusus.

F9 Riverine and fen scrubs

This category includes wet Salix woods but not, according to BRYOATT, the epiphyte flora of trees by rivers.  The floor of wet woodland usually has permanently wet, muddy patches alternating with drier ground around tree bases.  Chiloscyphus pallescens, Pellia epiphylla, P. neesiana, Brachythecium rivulare, Calliergon cordifolium, Calliergonella cuspidata, Hookeria lucens, Leptodictyum riparium, Plagiomnium undulatum, Rhizomnium punctatum, Sphagnum squarrosum and Thuidium tamariscinum are regular components of the woodland floor, with C. cordifolium typically occupying the wettest pools and P. undulatum often dominating slightly drier areas.  Fallen wood lying on the wet woodland floor is one of the typical habitats of the large Aneura.  Wet Salix woodland is often a rich habitat for epiphytes, and Salix is the most popular host tree in the county.  Most of the epiphytes mentioned above under F3 Temperate scrub are common in wet woodland, with the most characteristic being Frullania dilatata, Metzgeria violacea, Hypnum andoi, Neckera pumila, Lewinskya affinis, Orthotrichum pulchellum, Ulota bruchii, U. phyllantha and Zygodon conoideus.

FA Hedgerows

The bryophyte flora of hedgerows is similar to that of F3 Temperate scrub, but regular cutting or laying allows more light in and favours certain species.  Radula complanata, Bryum capillare, Cryphaea heteromalla, Lewinskya affinis, Orthotrichum diaphanum, Ulota bruchii and U. phyllantha are characteristic of layed hedges, whilst Frullania dilatata, Metzgeria furcata, Lewinskya striata and Orthotrichum tenellum tend to grow on the sunny trunks of hedgerow trees.  The pleurocarpous mosses Brachythecium rutabulum, Homalothecium sericeum, Isothecium alopecuroides and Kindbergia praelonga often cover layed trees and branches, and Neckera complanata is strikingly abundant in hedges in the southern half of the county.  The hedge bank itself is home to various woodland mosses, such as Atrichum undulatum, B. rutabulum, K. praelonga, Mnium hornum, Hylocomiadelphus triquetrus, Thamnobryum alopecurum and Thuidium tamariscinum, with Calypogeia arguta, Dicranella heteromalla, Epipterygium tozeri, Fissidens spp., Pogonatum aloides and Weissia controversa on earth gaps.  Dicranum scoparium, Hylocomium splendens, Pleurozium schreberi and Rhytidiadelphus squarrosus are locally abundant hedgerow mosses in the north, where their presence sometimes represents the last remnant of cleared heathland.

G1 Broadleaved deciduous woodland

Oaks (Quercus petraea & Q. robur) are the dominant trees in most of Pembrokeshire’s dry semi-natural woodlands, although Ash (Fraxinus excelsior) dominates locally in the south and may be abundant in the north as well.  Sycamore (Acer pseudoplatanus) dominates many coastal woodlands and is generally abundant, whilst beech (Fagus sylvatica) is reasonably widespread and dominates some plantings.  The understorey often holds Hazel (Corylus avellana) and sometimes Wych Elm (Ulmus glabra), Holly (Ilex aquifolium) or Rowan (Sorbus aucuparia).  Wet Alder (Alnus glutinosa) woodland follows streams and picks out other wet areas, and Willow (Salix cinerea & S. caprea) is widespread and often abundant (see F9).  Oak trunks are often clothed with Isothecium myosuroides or Hypnum andoi, with Homalothecium sericeum and Isothecium alopecuroides joining or replacing them on Ash trunks.  The epiphyte flora of the woodland understorey is essentially the same as that described under F3, although Frullania tamarisci, Microlejeunea ulicina and Neckera pumila are noticeably more frequent in woodland than scrub.

The woodland floor in most of Pembrokeshire is dominated by vascular plants, although bryophytes can be locally abundant and rise to dominance on steep slopes and boundary banks.  Common mosses of neutral to acid ground in woodland include the ubiquitous pleurocarps Brachythecium rutabulum and Kindbergia praelonga, along with Atrichum undulatum, Cirriphyllum piliferum, Eurhynchium striatum, Mnium hornum, Plagiomnium undulatum, Polytrichum formosum, Hylocomiadelphus triquetrus and Thuidium tamariscinumLophocolea bidentata is the commonest liverwort, although the larger Plagiochila asplenioides can be very eye-catching in the east of the county.  Steep banks suit Calypogeia arguta, C. fissa, Dicranella heteromalla, Didymodon insulanus, Fissidens bryoides, F. taxifolius and Oxyrrhynchium pumilum, and these are joined by Cephalozia bicuspidata and Diplophyllum albicans on leached areas, for example on ancient boundary banks.  A suite of large mosses, including Dicranum majus, D. scoparium, Plagiothecium undulatum and Rhytidiadelphus loreus give the humid valley woodlands of the north-east a distinctly moss-dominated feel, although the oceanic flora of the ‘western oak woodland’, including species such as Bazzania trilobata and Sphagnum quinquefarium, is restricted to a few banks, for example in Cwm Cŷch (SN23).  Base-rich woodland on limestone, for instance at Stackpole (SR99), has characteristically abundant Neckera complanata and Thamnobryum alopecurum, although other prominent mosses such as Brachythecium rutabulum, Eurhynchium striatum and Plagiomnium undulatum are just as common on neutral ground.

Rock outcrops and boulders greatly enrich the woodland flora, and the rocky woodlands of Coed Ty Canol (SN03Y) and Cwm Gwaun (SN03) are among the most bryophyte-rich habitats in the county.  Diplophyllum albicans is often the dominant species on acid rock outcrops, with Heterocladium heteropterum joining or replacing it in shade.  Other frequent species on siliceous or igneous rock in woods include Calypogeia fissa, Lepidozia reptans, Campylopus flexuosus, Cynodontium bruntonii, Dicranella heteromalla, Diphyscium foliosum, Hypnum andoi and Racomitrium aquaticumMarsupella emarginata is more typical of boulders, as are Scapania nemorea and Grimmia hartmanii.

Hylocomiadelphus triquetrus in base-rich woodland

Limestone outcrops and boulders are more or less restricted to a few sites on the south coast and are at their best at Stackpole NNR (SR99) – where the Mere Pool Valley (SR9793–9794) and North Hill (SR9794) are the most natural examples – Park Farm, Manorbier (SS0698), Lydstep (SS0897), and Little Hoyle Cave (SN1100).  The bulky mosses Anomodon viticulosus, Fissidens dubius, Homalothecium sericeum, Neckera complanata and Thamnobryum alopecurum and the leafy liverwort Porella platyphylla are usually the most striking feature of these rocks, but a closer look may reveal creeping Rhynchostegiella tenella, the black liverwort Marchesinia mackaii or the minute Cololejeunea rossettianaScorpiurium circinatum is locally abundant, especially in more open woodland, Plasteurhynchium striatulum clothes limestone boulders at five sites, and the subtle Taxiphyllum wissgrillii grows on half-embedded rocks in the woodland floor at four.

Logs and stumps provide another substrate for woodland bryophytes and often support a few species that are absent elsewhere.  Lophocolea bidentata, L. heterophylla, Brachythecium rutabulum, Hypnum cupressiforme and Kindbergia praelonga are usually the only bryophytes on logs in dry, southern woods.  Further north, Lepidozia reptans, Campylopus flexuosus, Pseudotaxiphyllum elegans and Tetraphis pellucida exploit this habitat.  A few sites are humid enough to hold Cephalozia curvifolia, albeit seldom in abundance, and only the valley at Dwfr Dysgynfa Cwm-du in the Gwaun Valley (SN0433) is humid enough for Odontoschisma denudatum to join the log flora.

Unsurfaced rides in broadleaved woodland can hold species such as Chiloscyphus pallescens, Fossombronia pusilla, Pellia endiviifolia and Calliergonella cuspidata, but most rides are now surfaced with gravel or shale.  The characteristic flora of surfaced tracks is discussed under G3.

G3 Coniferous woodland

Conifer plantations are found throughout Pembrokeshire, but are concentrated around Mynydd Preseli in the north.  The bryophyte flora is reasonably capable of surviving under a first conifer crop, when it resembles the assemblage that grew in that area prior to planting (Hill & Jones, 1978), albeit with some changes in abundance, especially a rise to dominance of pleurocarpous species.  The disturbance caused by felling and replanting is usually enough to profoundly alter an area’s flora.  Spruce (Picea) and Larch (Larix) are the two main plantation trees, and the latter’s deciduous nature allows a richer bryophyte flora to survive than the dense shade of the former.  Dicranum majus, Dicranum scoparium, Hypnum jutlandicum, Plagiothecium undulatum, Rhytidiadelphus loreus, Sphagnum quinquefarium and Thuidium tamariscinum dominated the floor of a Larch plantation at 260 m altitude on Frenni Fawr (SN2035), whilst Pellia epiphylla, Mnium hornum, P. undulatum, Polytrichum commune var. commune, Pseudotaxiphyllum elegans, Sphagnum palustre, Sphagnum subnitens and T. tamariscinum were under Spruce at 185 m altitude at Estinog (SM9930).  Kindbergia praelonga is the only other moss that regularly dominates the floor of plantations, especially in the south of the county.

The bark of conifers is usually too acid to support a diverse epiphyte flora, but conifers provide more humid conditions than deciduous trees and epiphytes that can tolerate the low pH often grow in profusion.  10 species of liverwort and two species of moss have been recorded as epiphytes on the principal plantation trees.  In addition, Dicranoweisia cirrata has been found on Pinus, Myriocoleopsis minutissima on Chamaecyparis, and the mature Cupressus on Caldey held Frullania dilatata, Brachythecium rutabulum, Hypnum cupressiforme var. resupinatum, Orthotrichum diaphanum, Rhynchostegium confertum, Syntrichia laevipila, Ulota phyllantha and Zygodon viridissimus.  Willows (Salix) set within conifer plantations are now a well-known host for the liverwort Colura calyptrifolia, as well as Metzgeria consanguinea, Microlejeunea ulicina, Orthotrichum pulchellum, Ulota crispa and others.

Decaying logs and stumps are the other major habitat within plantations.  Twelve species have been noted specifically on stumps in plantations throughout the county: Lepidozia reptans, Lophocolea heterophylla, Lophozia ventricosa var. ventricosa, Cephalozia curvifolia, Campylopus introflexus, Hylocomium brevirostre, Hypnum jutlandicum, Kindbergia praelonga, Plagiothecium denticulatum var. denticulatum, Polytrichum formosum, Rhytidiadelphus loreus and Tetraphis pellucida, but other locally common species on this substrate include Lophocolea bidentata, Hypnum cupressiforme and Orthodontium lineare.

Conifer plantations are usually blessed with a network of tracks to aid timber extraction, some of which have been constructed recently, whilst others were extant before coniferisation and have merely been upgraded.  The tracks often support a rich bryophyte flora because they are surfaced with stone rather than tarmac, have little traffic except during forestry operations, have damp microclimates because of the shade of the conifers, and often slope down into shallow ditches.  The species composition depends primarily on the surfacing stone, so a track surfaced with limestone at Shipping Hill Plantation (SN1310) supports calcicoles such as Aneura pinguis, Barbula unguiculata, Cratoneuron filicinum, Dicranella varia, Didymodon fallax and Trichostomum crispulum.  In contrast, most of the north Pembrokeshire plantation tracks are surfaced with base-poor local shales and hold calcifuge plants that are also found on the tracks of Mynydd Preseli.  Characteristic bryophytes on these northern tracks include the mosses Archidium alternifolium, Atrichum undulatum, Bryum alpinum, Calliergonella lindbergii, Campylopus introflexus, Ceratodon purpureus, Ditrichum heteromallum, Hypnum jutlandicum, Oligotrichum hercynicum, Philonotis fontana, Pogonatum aloides, P. urnigerum, Pohlia annotina, P. wahlenbergii, Polytrichum commune var. commune, Polytrichum commune var. perigoniale and P. juniperinum, as well as the liverworts Nardia scalaris, Pellia neesiana, Riccardia chamedryfolia and Solenostoma gracillimum.  Earth banks by these tracks are subject to periodic major disturbance and their flora includes several early colonists that are gradually replaced by bulky pleurocarpous mosses as the banks mature.  Calypogeia arguta, C. fissa, Diplophyllum obtusifolium, Solenostoma gracillimum and Ditrichum heteromallum are typical of sparsely vegetated, iron-stained earth banks; they are then replaced by Diplophyllum albicans, Dicranella heteromalla and Pogonatum aloides; and later Hypnum jutlandicum, Hylocomium splendens, Rhytidiadelphus loreus and others take over.

H2 Screes

The scree in Pembrokeshire is predominantly igneous and is associated with the tors of Mynydd Preseli, Carn Ingli and various other places in the north.  There is also an outlying bed of Millstone Grit scree in the south-east, but the county does not hold any screes of limestone or other base-rich rock.  The largest bed of block scree is on Carn Ingli (SN03T), and there are other significant ones at Rhestr Gerrig (SN1331), on Carn Menyn (SN1432) and on Foel Drygarn (SN1533).  10 species of liverwort and 29 moss taxa have been specifically noted in scree on Carn Ingli and Preseli, but the distinction between scree and tors (see H3) is not always clear.  This is the classic habitat for species of Andreaea and Racomitrium, which usually grow on rock surfaces, whilst gaps in the scree are often filled with Diplophyllum albicans, Campylopus flexuosus, Hypnum jutlandicum, Pohlia nutans and Pseudotaxiphyllum elegans.

Block scree on Carn Alw, Preseli

The Millstone Grit scree at Garness Farm, Llanteg (SN1809) lies at just 70 m altitude and is more than 25 km from the nearest comparable habitat in Pembrokeshire, although there is a similar area of Millstone Grit scree less than 5 km away on Ragwen Point (SN2207) in Carmarthenshire.  19 bryophyte species were recorded growing on rock in the Garness Farm scree: Frullania tamarisci, Lejeunea lamacerina, Lophozia ventricosa var. silvicola, Plagiochila bifaria, Scapania gracilis, Campylopus flexuosus, C. introflexus, C. pyriformis, Dicranum fuscescens, D. scoparium, D. scottianum, Hypnum jutlandicum, Isothecium myosuroides, Pleurozium schreberi, Pseudotaxiphyllum elegans, Racomitrium lanuginosum, Rhytidiadelphus loreus, Thuidium tamariscinum and Ulota crispa.

H3 Inland cliffs, rock pavements and outcrops

Mynydd Preseli is not a particularly rocky area of hills, although it is crowned by a series of tors and its slopes are strewn with innumerable igneous boulders.  The only significant natural outcrop of siliceous rock is in the nivation hollow at the head of Cwm Wern (SN03V), and much of the rock there has been quarried away leaving just a low series of natural rock faces above the quarry.  Despite its limited extent, this site is home to the only Pembrokeshire colony of Pohlia elongata, which grows alongside more prosaic upland saxicolous species, such as Diplophyllum albicans, Gymnocolea inflata, Barbilophozia sudetica, L. ventricosa var. silvicola, Andreaea rothii subsp. falcata, Dicranum scoparium, Polytrichastrum alpinum, Racomitrium aquaticum, R. fasciculare, R. heterostichum and Rhabdoweisia crispata.

There are more than 20 tors on Mynydd Preseli and its outlier Carn Ingli.  Most of those in western Preseli are composed of fine-grained, basic Dolerite, whereas those further east are mostly Rhyolitic lavas and tuffs.  Carn Ingli is Rhyolite again.  These tors support nearly 80 bryophyte species, including some such as Glyphomitrium daviesii, Grimmia funalis, G. incurva and Hedwigia integrifolia that are at the southern limit of their British distribution.  The most abundant bryophytes here include Diplophyllum albicans, Lophozia ventricosa, Marsupella emarginata, Andreaea rothii subsp. falcata, A. rupestris, Campylopus flexuosus, Heterocladium heteropterum, Hypnum jutlandicum, Pseudotaxiphyllum elegans, Racomitrium fasciculare and R. heterostichum, with the tiny Rhabdoweisia crispata and R. fugax hiding in deep holes and a few calcicoles, such as Frullania tamarisci, Fissidens adianthoides or F. dubius, picking out slightly base-enriched damp patches.  Most of the bryophytes of igneous scree are also found on tors and the distinction between the two habitats is often blurred.  There are other tors further west in the county, most notably at Treffgarne Rocks (SM92M), which includes the prominent landmark of Maiden Castle.  This site demonstrates the oceanic flora that can develop on the sheltered north side of tors, as it holds Bazzania trilobata, Lepidozia cupressina, Saccogyna viticulosa, Scapania gracilis and Dicranum scottianum.  Thin soil on peat both here and on Plumstone Rock (SM9123) supports the uncommon Odontoschisma denudatum and Leptodontium flexifolium.  Tors on the north coast between St David’s Head (SM72J) and Fishguard (SM93) are floristically similar to those inland and often have outlying colonies of A. rothii subsp. falcata, Hedwigia stellata or R. heterostichum.

A colony of Grimmia curvata on igneous rock at Carnau Ysfa, Preseli

Most rock outcrops further south are in woodland or are on the coast.  Perhaps the only naturally outcropping limestone without woodland cover or coastal influences is in Stackpole NNR (SR99).  The flora on rocks and thin soil on ledges here includes Frullania tamarisci, Porella platyphylla, Reboulia hemisphaerica, Riccia sorocarpa, R. subbifurca, Scapania aspera, Dicranella varia, Fissidens dubius, Homalothecium sericeum, Scorpiurium circinatum, Syntrichia montana, Tortella nitida, Tortula lanceola, T. muralis, Trichostomum brachydontium, T. crispulum and Weissia controversa var. crispata.  Many of these species are equally at home on worked rock and limestone walls, but Reboulia, R. subbifurca, S. aspera and T. lanceola appear to be restricted to natural outcrops.

The cuttings through which the A477 passes east of Kilgetty (SN10) have now had enough time to revegetate with bryophytes.  The Pen-y-bont cutting (SN1509) is through Coal Measures shales and supports both the acidophiles Campylopus introflexus, Hypnum jutlandicum, Polytrichum juniperinum and P. piliferum, and the calcicoles Dicranella varia and Trichostomum crispulum.  The Crunwere cutting (SN1810) is through sandstone and now holds a remarkably rich flora that includes Frullania tamarisci, Radula complanata (on rock), Pogonatum urnigerum, Polytrichum juniperinum, Ptychomitrium polyphyllum and Rhytidiadelphus loreus.  Two cuttings for the A40 east of Llanddewi Velfrey (SN11) appear, from a moving car, to be almost entirely covered with C. introflexus.

Quarries are dealt with under J3 rather than splitting recently worked sites from long-abandoned sites.

H5 Miscellaneous inland habitats with very sparse or no vegetation

This catch-all category includes various habitats where bryophytes play a significant role or are the principal plant cover.  It is typified by the flora of unsurfaced tracks and the banks by them.  This includes Bryum rubens and several of its tuberous relatives, B. dichotomum, Dicranella schreberiana, Pogonatum urnigerum, Pohlia annotina, P. camptotrachela and Polytrichum juniperinum, with Fossombronia wondraczekii and Pseudephemerum nitidum in damper areas.  Funaria hygrometrica is another typical member of the category as it colonises nutrient-rich bare ground, including fire sites.

Road verges are among our least well-regarded bryophyte habitats, but periodic disturbance by considerate tractor drivers provides suitable conditions for a range of mosses and liverworts.  A temporary glut of habitat is also provided by tree plantings on verges, although these are a double-edged sword as they soon transform nice, open verges into clumps of dull, unsuitable and often non-native trees.  The highways department have systematically planted up most of the better verges by the A40, A477 and A487, but a few remain, notably at Pelcomb Cross (SM921177), Keeston Bridge (SM908186) and the Jordanston turn-off (SM940303).  The key in these areas is that road straightening has separated off an ‘island’ of grassland surrounded on one side by the new road and on the other by a layby.  The vegetation on this ‘island’ seems to escape the nutrients that drench most of the countryside, providing ideal conditions for such notable species as Cephaloziella stellulifera, Lophozia excisa, Archidium alternifolium, Calliergonella lindbergii, Weissia brachycarpa, W. longifolia, W. rutilans and a tall form of Fissidens incurvus.

I1 Arable land and market gardens

The flora of arable land was studied throughout the British Isles between 2003 and 2005 by the BBS Survey of the Bryophytes of Arable Land (SBAL) (Preston et al., 2010); some market gardens were included.  40 fields in Pembrokeshire were included in the 820 recorded throughout Britain and Ireland, despite Pembrokeshire (and indeed the whole of Wales) being considered so poor for arable that none of the 200 randomly selected fields were in the county.  It turned out that Wales’ marginal position makes it rather good for arable bryophytes, if not for arable farming, with Wales and Scotland holding the majority of fields with the species- and liverwort-rich assemblages. Preston et al. (2010) propose six bryophyte assemblages that are typical of British arable: two with predominantly north-western distributions, two that are mostly south-eastern, and more widespread weedy and setaside assemblages.  The Tortula truncataAnthoceros assemblage (A) and Dicranella staphylinaRiccia glauca assemblage (B) are found mostly in Wales, western England, Scotland and Ireland and are the most bryophyte-rich forms of arable.  They have constant Bryum rubens, Dicranella staphylina, Tortula truncata and Trichodon cylindricus and often hold liverwort and hornwort species.  Assemblage A has a higher frequency of hornworts (Anthoceros & Phaeoceros) and Fossombronia spp. than assemblage B, which is characterised by more frequent Riccia spp. and Bryum violaceum.  Most sampled Pembrokeshire fields belong to one or other of these categories.  In contrast, no Pembrokeshire fields were considered to represent the species-poor Barbula unguiculataBryum klinggraeffii assemblage (C), and only two were assigned to the Tortula acaulonMicrobryum davallianum assemblage (D).  Both are more characteristic of eastern England and both are marked by constant B. unguiculata, B. klinggraeffii and P. cuspidatum as well as the absence of the liverwort markers of A and B.  Most of the preferentials for C and D do occur in Pembrokeshire, indeed P. cuspidatum grows in 30 of the 40 sampled fields, but they are seldom abundant and are generally associated with obvious markers for other assemblages.  The weedy Bryum dichotomumMarchantia polymorpha assemblage (E) is present in a few field entrances in Pembrokeshire but not entire fields.  Its most characteristic species are Bryum argenteum, B. dichotomum, Funaria hygrometrica and M. polymorpha.  Fallow rotations favour the Brachythecium rutabulumFissidens taxifolius assemblage (F) in which the pleurocarpous mosses B. rutabulum, Kindbergia praelonga and Oxyrrhynchium hians are abundant amongst a crowded vascular cover.  Fissidens taxifolius rises to abundance in this community as well, often forming clonal patches that have developed from tubers.  Weissia longifolia is listed among the species that are most frequent in this assemblage but that may just be because a fallow year allows time for it to develop the sporophytes necessary for identification.  Much non-fertile Weissia sp. in Pembrokeshire’s A and B fields was thought likely to be W. longifolia.

Entosthodon fascicularis in cereal stubbles at Great Nash

Forty Pembrokeshire fields were included in SBAL and a further 39 were surveyed subsequently using SBAL methodology, albeit without detailed soil analysis or pH testing.  The mean diversity of the 40 SBAL fields was 15 taxa, the maximum 23 from a cereal field at Great Nash (SM9709), and the minimum 6 from a potato field at Johnston (SM9209).  Four cereal crops – barley, wheat, oats and rye – were surveyed, along with fields of beans, maize, potatoes, rape and setaside.  Little variation was noted between the cereal crops and setaside was generally quite species-rich, but the four alternative crops all proved bryologically poor.  The majority of Pembrokeshire fields (59 of the 79 studied) hold assemblage B, which varies in appearance from diverse forms with frequent Riccia spp. and Bryum violaceum to species-poor forms with little more than Bryum rubens, Dicranella staphylina, Tortula truncata and Trichodon cylindricum.  Assemblage A is much less frequent than B (16 fields), a picture that contrasts with the maps presented by Preston et al. for the two assemblages.  This is unsurprising given how infrequent Anthoceros, Phaeoceros and Fossombronia spp. are in Pembrokeshire arable, but may be because the present analysis has been over-cautious over assigning fields to A.  Alternatively, there may be variation between years according to climate and the ease of autumn ploughing, in which case some mapped B could be poorly-developed A.  The paucity of arable fields above 100 m altitude in the county is clear on the map, but the lack of fields in the central lowlands (SM91–SN11) is surprising and may just be a facet of recording.  There are certainly some maize fields in this area, but it is predominantly pastoral.

Records from the 40 SBAL fields span a pH range from 4.8 to 7.2.  Most of the bryophytes recorded show a pH tolerance of about 1 unit (mean 1.1), with a maximum tolerance of 2.4 units shown by 12 ubiquitous mosses: Brachythecium rutabulum, Bryum rubens, Bryum violaceum, Dicranella staphylina, Ephemerum serratum (formerly E. minutissimum), Kindbergia praelonga, Oxyrrhynchium hians, Tortula acaulon, Pseudephemerum nitidum, Tortula truncata, Trichodon cylindricus and Weissia sp., which typically form the core of the Pembrokeshire arable assemblage.  The 12 ubiquitous species also have mean pH at the acid end of the spectrum (6.0), and only the uncommon Bryum sauteri, Didymodon tomaculosus and Pohlia melanodon show a lower mean pH (5.3–5.9).  At the other end of the spectrum are species such as Bryum ruderale, Dicranella varia, Microbryum davallianum, M. rectum and, perhaps surprisingly, Weissia longifolia var. longifolia, which are somewhat calcicolous (6.7–7.0).

I2 Cultivated areas of parks and gardens

The cultivated areas of parks and gardens are, presumably, flowerbeds.  These are often too regularly cultivated to develop a distinct bryophyte flora, and only 14 species were noted from flowerbeds during recording.  These include Phaeoceros laevis, which is frequent in the walled garden at Picton Castle (SN0013) alongside Ephemerum serratum (formerly E. minutissimum), and Bryum rubens, Dicranella schreberiana and Pohlia melanodon finding shelter from high winds at Dale Fort (SM8205).  The ubiquitous pleurocarps Brachythecium rutabulum, Kindbergia praelonga and Oxyrrhynchium hians are probably the most regular bryophytes of flower beds.

J1 Buildings of cities, towns and villages

Pembrokeshire is a rural county by British standards.  It includes just one city and seven towns, none of which covers more than 3×3 km.  There are, however, numerous villages and nowhere is truly remote, so there is plenty of J1 habitat in the county.  There appears to be little difference between the bryophyte flora of buildings in towns and in villages, although Orthotrichum diaphanum is perhaps slightly commoner in the six town/city centres than elsewhere.  Wall tops usually sport Didymodon rigidulus, Grimmia pulvinata, Orthotrichum anomalum, Schistidium crassipilum, Syntrichia montana, Tortella nitida and Tortula muralis, whilst their sides may have Streblotrichum convolutum var. commutatum, Bryum radiculosum, Homalothecium sericeum, Neckera complanata, Orthotrichum diaphanum, Pseudocrossidium revolutum, Rhynchostegiella tenella, Rhynchostegium confertum or Zygodon viridissimus.  Roofs remained an endlessly inaccessible source of frustration, sated occasionally by tufts that had fallen on to the street.  In all, 14 moss species were recorded from roofs made of corrugated asbestos, slate or artificial tiles: Bryum argenteum, B. capillare, Campylopus introflexus, Dicranoweisia cirrata, Didymodon luridus, D. rigidulus, D. tophaceus, G. pulvinata, O. diaphanum, S. crassipilum, S. montana, T. nitida, T. muralis and Z. viridissimus.

Didymodon nicholsonii on tarmac in Steynton

As well as buildings, the urban environment includes roads, pavements, gardens, parks and wasteground.  All six urban areas in Pembrokeshire include a water feature – generally a river, stream or pond – and three of the six have sea fronts.  Although these habitats do not belong to J1, it is easiest to include two quick analyses of urban bryophytes in this section.

The most accessible form of the built environment is the church or chapel yard.  These share walls, flower beds and some trees with gardens (see I2), but have the unique feature of graves, which provide bare earth, gravel or stone substrates according to their age and design.  Reasonably comprehensive lists were prepared for 65 churches, 33 chapels and 24 cemeteries distributed across the county.  These showed little difference between the three categories, with mean species counts of 24 for churches, 26 for cemeteries and 27 for chapels.  The slightly higher chapel score is counter-intuitive, as many chapels are ultra-neat and have a minimal yard.  However, it may reflect the concentration of chapels in the north of the county in more bryophyte-rich areas, or may be an artefact of the relatively larger number of churches sampled.  A total of 171 species was recorded from these 122 sites.  The three most ubiquitous were Brachythecium rutabulum, Bryum capillare and Tortula muralis, all of which were recorded in more than 100 of the sites, whereas nearly 40 taxa were only found at a single site.  Orthotrichum anomalum turned out to be Pembrokeshire’s holiest moss, with the highest percentage (37 %) of all its records in the county coming from consecrated ground.

Stevenson & Hill (2008) looked at the bryophyte flora of King’s Lynn in Norfolk and used the results of Robin Stevenson’s surveys to challenge various generalisations about urban bryofloras.  None of Pembrokeshire’s six towns/cities was surveyed in the detail of King’s Lynn, but SDSB recorded in the county town of Haverfordwest, his home town of Milford Haven, and his work town of Pembroke Dock on several occasions; Fishguard, Narberth, Pembroke, St David’s and Tenby were only visited a handful of times.  Seven of the attributes looked at by Stevenson & Hill are repeated here (Table 18) for the three towns Haverfordwest (SM91, including Albert Town, Merlin’s Bridge & Prendergast), Milford Haven (SM80–90, including Hakin, Hubberston & Steynton) and Pembroke Dock (SM90, including Llanion & Pennar).  All are considerably smaller than the King’s Lynn study area, and records deliberately excluded surrounding non-urban habitats, only including parks, churchyards and the coast/river on to which the town faces.

The species richness of the three Pembrokeshire towns appears at first glance to be less than that of the King’s Lynn study area, but that is more than three times the size of any of the towns and includes blocks of ancient woodland and farmland, which were excluded in the Pembrokeshire analysis.  The overall species-richness is rather good compared with Pembrokeshire as a whole, where the average species count for the 34 10×10 km (100 km²) recording units is 210, especially given the small size of each town.  There is no more indication of toxitolerance in Pembrokeshire towns’ bryophytes than in those of King’s Lynn.  Both Haverfordwest and Milford Haven support few annual bryophytes compared with King’s Lynn, but Pembroke Dock appears to hold a higher number.  This might be a reflection of SDSB’s keener recording in Pembroke Dock during lunch breaks in winter, when annual mosses are at their most apparent, but could equally be a reflection of Pembroke Dock’s extensive wasteground, calcareous soils and warm climate.  Pembroke Dock’s bryophytes also show slightly higher mean Ellenberg values for Light and Reaction, thanks to the presence of species such as Microbryum rectum and Trichostomum crispulum.  Salt tolerance is slightly higher for the seafront towns of Milford Haven and Pembroke Dock than for Haverfordwest, although Schistidium maritimum was only noted in Milford Haven.  Uncommon species recorded in the three towns are Targionia hypophylla, Gymnostomum calcareum, Fissidens fontanus and Scorpiurium circinatum in Haverfordwest, Dialytrichia mucronata, Ditrichum subulatum, Gymnostomum viridulum and Syntrichia virescens in Milford Haven and G. viridulum in Pembroke Dock.  Haverfordwest’s score was boosted by four species of Racomitrium, Grimmia trichophylla, Hedwigia stellata and Ptychomitrium polyphyllum that survive on imported rocks at County Hall.  As Stevenson & Hill concluded, the urban bryophyte flora is not impoverished, does not appear to be toxitolerant, and is not significantly thermophilous.  It is encouraging that these observations seem to hold true in western Britain as well as in the east, although further analyses would help to put this into context.

J2 Low density buildings

This category includes “scattered residential buildings, agricultural buildings, fences, field walls and rural churchyards” and is therefore one of the most widespread in the county.  Rural churchyards were not distinguished from those in villages in the analysis in J1, but there was no sign that they differ bryologically.  Cottages, farm houses and the walls around them are home to Didymodon rigidulus, Grimmia pulvinata, Schistidium crassipilum, Tortula muralis and the rest of the typical wall flora, and again show no difference from J1.  26 moss species were specifically recorded from farmyards.  These show a distinct tendency towards nutrient tolerance, or a high Ellenberg N value, as many farm walls are enriched by fertiliser drift or slurry-derived ammonia.  The 26 farmyard species have a mean Ellenberg N value of 4.7 (on a scale of 1 to 7), whereas the county’s entire bryophyte flora has a mean N of 3.2.

Campylopus introflexus, Ceratodon purpureus and Dicranoweisia cirrata can often be found growing in the rotting top of fence posts, and a few other species sometimes exploit this habitat, including Lophocolea bidentata, L. heterophylla and Dicranum scoparium.  Concrete fence and gate posts are the easiest place to find Didymodon rigidulus, Orthotrichum diaphanum, Schistidium crassipilum and Tortula muralis in the wider countryside, and they provide and alternative host for a few epiphytes on the tree-less Mynydd Preseli, including Cryphaea heteromalla and Lewinskya affinis.  Dry stone “field walls” are not a typical Pembrokeshire habitat, and most boundaries are hedgerows (see FA) or rocky banks akin to ‘Cornish hedges’.  Bryophytes recorded on the stone-faced clawdd wall separating Mynydd Preseli Common from the surrounding ‘clean’ land include 28 listed in Table 20, although it is unclear whether these really belong to J2 or not.

Ruined buildings are another example of J2.  There are many ruined cottages and farms in north Pembrokeshire; rather fewer in the south.  More than 70 bryophyte species have been found growing on and inside these ruins, and they provide a ready locus for calcicoles of mortar in the generally acid ground around Mynydd Preseli.  The most regular ruin mosses are Aloina aloides, Streblotrichum convolutum var. commutatum, Barbula unguiculata, Brachythecium rutabulum, Bryoerythrophyllum recurvirostrum, Bryum capillare, Didymodon rigidulus, Encalypta streptocarpa, Homalothecium sericeum, Plagiomnium undulatum, Polytrichum juniperinum, Pseudocrossidium revolutum, Rhynchostegiella tenella, Rhynchostegium confertum and Tortula muralis, most of which grow on crumbling mortar or on the faces of rocks in the ruins’ walls.  P. juniperinum is a notable exception that usually grows on thin soil on the tops of decaying walls.  It seems highly likely that the mortar mosses, especially A. aloides and P. revolutum, would have been imported to the buildings with mortar rather than arriving unaided.  Lime kilns are widespread around the county’s coast.

J3 Extractive industry sites

Quarrying is the most widespread extractive industry in Pembrokeshire and is the only one that continues actively both on the southern limestone and on the igneous rocks south of Haverfordwest.  Coal mining ceased in the 20th century and there is now little sign of the small-scale pits that once dotted the coalfield, whilst the 35 metal mines were all of minimal extent except for the Llanfyrnach lead mine.  Extractive industry sites usually have abundant disturbed ground where early successional species can colonise, and bryophytes in the genera Nardia, Scapania, Solenostoma, Bryum, Dicranella, Didymodon, Pogonatum, Pohlia, Polytrichum and Tortula often play a significant role in their floras.   Variation in pH and wetness couple with a supply of both saxicolous and terricolous habitats to provide a rich array of niches.  Succession usually leads to a gradual transition from open habitats to scrub or woodland as it is seldom feasible for grazing to take place in disused quarries.  The humidity of quarry woodlands encourages liverworts such as Colura calyptrifolia and Radula complanata, but quarry woodlands are little different to woodlands elsewhere in the countryside.  The tendency for ‘environmental restoration’ in disused quarries to involve woodland planting is unfortunate because it replaces an unusual habitat rich in specialists with a mundane habitat that is much more widespread.

Carboniferous Limestone has been quarried in Pembrokeshire for centuries thanks to easy sea transport both on the south coast and inland near the Daugleddau estuary.  The only working limestone quarries in the 21st century are at Carew (SN0404) and Ludchurch (SN1510), but disused quarries are widespread inland between Monkton (SM9701) and Llanteg (SN1610), and on the coast from Bosherston (SR9595) to Tenby (SN1200).  The typical bryophyte flora of a disused limestone quarry includes Aloina aloides, Dicranella varia, Didymodon fallax and Trichostomum crispulum, as illustrated in a list from Bosherston Quarry (SR9595).  The ancient limestone quarries at West Williamston (SN0205–0206) are now largely wooded, but hold calcareous grassland on spoil near their western end.  The rich flora here includes Bryum torquescens at its only county site, Gymnostomum viridulum, Microbryum rectum and M. starckeanum.  This is an indication of what can colonise disused limestone quarries many decades after they ceased working.

Slate quarries are a feature of north Pembrokeshire, although they do not have anything like the profound effect on the landscape that those of Snowdonia do.  Much the largest is at Rosebush (SN0729–0730), where Bellstone Quarry operated between 1825 and 1891 and Rosebush Quarry immediately to the south between 1842 and the late 1890s.  Other significant disused slate quarries are at Llanychaer (SM9835), Mynydd Du (SN0831), Craig y Cwm (SN0931), Groesffordd (SN1729), by the Teifi at Cilgerran (SN1944), and at Glogue (SN2132–2232).  Floors of broken slate mixed with clay support Solenostoma gracillimum, Dicranella heteromalla, Pogonatum urnigerum and Polytrichum juniperinum, but it is the heaps of old, lichen-encrusted uncut slate that hold the richest elements of the flora, including up to five species of Racomitrium.  The 19 liverworts and 53 mosses recorded in the northern part of Rosebush Quarry (SN0730) illustrate the typically rich flora of the slate quarries, although it is the only one where Coscinodon cribrosus, Dicranella subulata and Schistostega pennata have been found, and is one of four sites in the county with Grimmia donniana.  There is an active road stone quarry in igneous rocks near Tier’s Cross (SM9111), but this has never been checked for bryophytes.  A quick foray into the disused Syke Quarry at Walwyn’s Castle (SM8710) revealed Pogonatum nanum and Schistidium apocarpum.  There are other reasonably large quarries with Racomitrium spp., P. urnigerum and other typical quarry bryophytes at Gignog (SM8824), Red Hill (SM9417), Scleddau (SM9433), Treffgarne (SM9524), Triffleton (SM9724), Llandilo (SN1027) and Llangolman (SN1226), and many smaller quarries and pits throughout the county.  None of these rivals the slate quarries for bryophyte diversity.

The site of Coscinodon cribrosus in Rosebush Quarries

Sand is still being quarried at Trefigin, Monington (SN1343), where the owners let SDSB and two CCW colleagues in to record the flora in 2006.  The five species of liverwort and 25 mosses recorded on revegetating sand include both the calcifuge Pogonatum urnigerum, Polytrichum juniperinum and P. piliferum and the calcicole Aneura pinguis, Aloina aloides, A. ambigua, Bryum algovicum, Dicranella varia and Pseudocrossidium hornschuchianum, suggesting significant variation in the pH of the glacial sands and gravels being extracted.  In contrast, the disused sand quarry in Brownslade Burrows (SR8998) is extremely lime-rich and its flora comprises 21 typical dune slack bryophytes including Petalophyllum ralfsii, Calliergonella cuspidata, Didymodon tophaceus and Drepanocladus aduncus.

The only bryophytes recorded on the large spoil tip at the disused lead-silver mine at Llanfyrnach (SN2231) are Cephaloziella divaricata, Bryum pallescens, Dicranella varia and Weissia controversa var. densifolia.  Two visits have failed to reveal Ditrichum plumbicola or other more notable metalophytes.

J4 Transport networks and other constructed hard-surface areas

The most abundant substrate in the transport network is tarmac (or asphalt), which is widely used to surface roads, paths, pavements and carparks.  If tarmac is reasonably damp for part of the year and is not subject to constant traffic it can develop a rich moss flora: a remarkable 63 species of moss have been recorded from tarmac in Pembrokeshire, but there are no records of liverworts from this substrate.  Tarmac has numerous small holes in which silt can gather and thus provides conditions relatively similar to those found on riverside rocks.  Thus the traditionally riparian mosses Didymodon nicholsonii and Syntrichia latifolia are far more common on tarmac in Pembrokeshire than in their more traditional haunts.  A gentle slope, allowing a regular flow of water, seems particularly beneficial to these two species.  Bryum argenteum, B. dichotomum, Ceratodon purpureus and Cratoneuron filicinum are almost constant on undisturbed tarmac and are often joined by Barbula unguiculata, Brachythecium mildeanum, B. rutabulum, Didymodon insulanus, Funaria hygrometrica, Orthotrichum diaphanum or Syntrichia montana if there has been a slight build-up of silt.  Syntrichia ruralis (of one form or another) can become locally dominant in the middle of roads, and Tortula truncata often encroaches on to the edge of a road from the muddy verge.  Among the more remarkable species recorded from tarmac in the county are gemmiferous Bryum pseudotriquetrum in the middle of a road at Pont Wedwst (SN2835), Rhytidiadelphus squarrosus and R. triquetrus on an old layby at Pont yr Haiarn (SN1428), and Scorpiurium circinatum on tarmac paths in churchyards at Bosherston (SR9694) and Stackpole Cheriton (SR9897).

The flora of concrete paths, pavements, tracks and carparks is similar to that of tarmac, but is less diverse and has closer ties to the flora of limestone or walls rather than rivers.  Didymodon nicholsonii and Syntrichia latifolia have only been recorded twice each from concrete, but instead there are more records than on tarmac for Didymodon luridus, D. sinuosus, Schistidium crassipilum and Tortula muralis.

Difficulty of access and general dangers associated with railways led to very little recording on railway ballast.  The only semi-complete list came from a footpath crossing the railway at Pant-y-crwyn (SM9318), where Cephaloziella sp., Streblotrichum convolutum var. commutatum, Barbula unguiculata, Bryum capillare, Bryum ruderale, Campylopus introflexus, Ceratodon purpureus, Funaria hygrometrica, Polytrichum juniperinum, Pseudocrossidium hornschuchianum, Rhytidiadelphus squarrosus and Pseudoscleropodium purum grew.  This list includes both calcicoles, such as B. ruderale and P. hornschuchianum, and calcifuge species like C. introflexus and P. juniperinum and suggests there is either significant variation in the pH of the clinker here, or that leaching of minerals is taking place.  Tracks surfaced with shale or limestone are discussed under G3 and H5.

Key sites for bryophyte conservation in Pembrokeshire

In 2010 when the Flora was written, Pembrokeshire held 19 Nationally Rare (NR) bryophyte species (Preston, 2010), all but one of which have been assigned a threat status and are listed in the Red Data Book (RDB CR, EN, VU, DD & NT), and 68 Nationally Scarce species (Preston, 2006).  These Nationally Rare and Scarce bryophytes are found almost throughout the county, at least in the river valleys, but are focussed in certain hotspots where the geology, topography and management history have produced ideal conditions.  Most hotspots are also rich in locally rare taxa, defined as those known from five or fewer tetrads in the county.  160 taxa are thought to be locally rare according to recent recording.

A coincidence map of all notable taxa – both those that are Nationally Rare or Scarce and those which are locally rare – highlights the hotspots of bryophyte diversity in the county.  Many of these have been known to bryologists for generations, including Treffgarne Gorge and Tors, Esgyrn Bottom and Coed Ty Canol, but others were completely unknown or were under-valued.  Despite A.H. Brinkman’s recording around St Ishmael’s (SM80), the diversity of the bryophyte flora of Milford Haven Waterway was not appreciated until very recently, probably too late for some of its rarities such as Tortula canescens and T. cuneifolia.  The Eastern Cleddau Valley was an unknown Mediterranean hotspot, although the BBS had visited a few parts of it.  Mynydd Preseli proved to be much richer than anyone had appreciated despite numerous previous visits, with species such as Grimmia incurva and Glyphomitrium daviesii on its tors and a population of Fossombronia fimbriata on flat ground to the north.  Stackpole NNR and the coastal limestone had also been examined many times before, but detailed surveys revealed gems like Cephaloziella calyculata and Southbya tophacea that mean its bryophyte flora is at least as important as its well-known lichens.  More information on the key sites for bryophyte conservation in Pembrokeshire follows.

Coincidence map of notable bryophytes in Pembrokeshire

St David’s Peninsula coast (SM72–82)

The coast between St David’s Head and Newgale holds a rich array of habitats including heathland, tors and south-facing coastal slopes.  The Head itself is composed of basic igneous rocks, which feed mineral- and base-rich flushes.  Periodically flushed thin soil over igneous rock is home to a large population of Fossombronia maritima mixed with Riccia beyrichiana, an association repeated on the nearby Ramsey Island (SM72).  F. maritima is also found on the south side of the peninsula at Portlysgi and Porthclais, whilst R. beyrichiana is scattered across the heathy commons inland.  Sunny south-facing rocks support several colonies of Grimmia lisae, with G. laevigata at Penycwm and Campylopus pilifer at Ninewells and The Gribin.  Coscinodon cribrosus is found on St David’s Head, in the Solva area and near Newgale.  Frullania microphylla var. microphylla, F. fragilifolia and F. teneriffae are all widespread, as are Tortula atrovirens, Weissia perssonii and Scleropodium tourettii, making this a good example of the county’s coastal flora.

Droughted rocks on the coast adjacent to Solva

Angle Peninsula coast (SM80)

Carboniferous Limestone outcrops on the north side of the Angle Peninsula, but it is the extensive exposure of Old Red Sandstone on its south side that makes this an important stretch of the Pembrokeshire coast.  Outcrops behind Gravel Bay provide the most accessible locus in the county for Porella obtusata, which grows alongside Grimmia lisae, Nogopterium gracile and Zygodon viridissimus var. stirtonii.  The Grimmia is frequent along the coast as far as South Studdock, and is joined by a very hoary form of G. laevigata near Black Cave.  The South Studdock valley is one of just two mainland Pembrokeshire sites for Fossombronia angulosa and also supports Frullania microphylla var. microphylla and Drepanocladus polygamus.

Old Red Sandstone on the Angle Peninsula

Milford Haven Waterway (SM80–90)

Creek banks on the north side of the ria of Milford Haven Waterway are the key area in Wales for Ditrichum subulatum and Cephaloziella turneri, both of which grow on crumbly soil just above the spring tide level.  Tortula wilsonii has one very few extant Welsh colonies at Wear Point, alarmingly close to the one of only two south Wales sites for the invasive alien Lophocolea semiteres, which has colonised a section of the coast path.  A.H. Brinkman recorded Tortula canescens and T. cuneifolia near St Ishmael’s and Antitrichia curtipendula near Milford Haven, but none can be refound.  There is a good chance that the development of a string of oil refineries and the expansion of Milford Haven in the 1960s destroyed at least some bryologically rich open ground, although 1950s aerial photographs show much of their footprint was pasture.  Some woodlands further up the estuary have Dicranum scottianum and Plagiochila bifaria in them, and Lepidozia cupressina was recorded from Lawrenny Wood in 1980.

Castle Pill – home to Cephaloziella turneri and Ditrichum subulatum

Treffgarne Gorge & Tors (SM92)

H.H. Knight appears to have been the first person to collect bryophytes from the tors just north-east of the village of Treffgarne.  He found Lepidozia cupressina and Dicranum scottianum there in 1909, and the Lepidozia is still present on the north side of Maiden Castle.  Other notable species recorded from the tors include Bazzania trilobata, Odontoschisma denudatum and Leptodontium flexifolium.  A BBS visit to the adjacent gorge in 1958 produced the first ever specimen of Fissidens celticus, as well as the aquatic F. monguilloniiPorella pinnata is more abundant in the river here than anywhere else in the county.

Esgyrn Bottom (SM93)

Esgyrn Bottom, Pembrokeshire’s most intact raised bog, lies to the south of Cwm Gwaun near Llanychaer.  It is the only known site for several bryophyte species in the Vice-county.  Jean Paton found Calypogeia sphagnicola, Cephalozia macrostachya, Cephaloziella elachista and Riccardia latifrons during a BBS visit, and the Cephaloziella remains extant at this, its only known Welsh locality.  Matt Sutton collected Pallavicinia lyellii in peat cuttings in 1999, and later showed it to be reasonably widespread on the site.  Sphagnum magellanicum is scattered on the least damaged part of the bog, and the bog liverwort flora remains among the best in the county, with Odontoschisma fluitans, Mylia anomala, Odontoschisma denudatum and others, although three of JAP’s most uncommon species appear to have been lost.

Eastern Cleddau Valley, Llawhaden (SN01)

The Llawhaden area is a previously unheralded hot-spot for Vice-county rarities.  The roadside crag behind the church supports the only Radula lindenbergiana known in south Wales, along with Philonotis arnellii and the slightly commoner Plagiochila bifaria, Reboulia hemisphaerica and Rhabdoweisia fugax.  Mature ash and oak trees in the valley nearby hold the uncommon Leucodon sciuroides, Nogopterium gracile and Zygodon rupestrisOrthotrichum sprucei has its only Eastern Cleddau colony here, Fissidens monguillonii grows on silty tree roots by the river, and Porella pinnata is present for some distance both upstream and downstream.  Scorpiurium circinatum is on the church walls.

Rosebush Quarries (SN02–03)

Grimmia donniana is the most obvious county rarity in Rosebush Quarries because it grows in profusion on the ancient slate waste there and is much more plentiful than at its other three local sites.  Other local rarities here include Marsupella sprucei, Nardia compressa, Dicranella subulata and Racomitrium affine, whilst Coscinodon cribrosus has its only inland site in the county on one rock face and Schistostega pennata grows in a cave.  Martha Newton regularly visited the quarries on FSC courses and made most of the significant discoveries here.

Slate waste in Rosebush Quarries

Carn Ingli massif (SN03)

This upland block lies north-west of Mynydd Preseli and stretches from Carn Ingli in the east to Mynydd Dinas in the west.  Its habitats are similar to those on Preseli and include several tors, a large bed of block scree, extensive stands of upland heath in varying condition, and low-lying flush complexes on the northern flank.  The block scree of Carn Ingli itself is the most striking part of the site, but although it holds Andreaea megistospora and Gymnomitrion crenulatum it is generally rather dry and bryophyte-poor.  Other tors further west on the massif include Carn Ffoi, with Douinia ovata, and Garn Fawr, with 21 cushions of Glyphomitrium daviesiiSplachnum ampullaceum and Hamatocaulis vernicosus grow in flushes near Pont Ceunant, and Fossombronia fimbriata, Haplomitrium hookeri and Riccardia incurvata are on trampled ground on Mynydd Melyn.  The uncommon Leptodontium flexifolium is locally abundant in burnt heathland on the Carn Ingli ridge.

Coed Ty Canol (SN03)

The rocky woodland in this National Nature Reserve on the north-west side of Mynydd Preseli is the most significant site for oceanic bryophytes in Pembrokeshire, although its relatively exposed position means that it is less rich than some woods in north-eastern Carmarthenshire and eastern Cardiganshire.  Among the humidity-demanding or western species here are Bazzania trilobata, Harpanthus scutatus, Kurzia trichoclados, Plagiochila bifaria, P. punctata and P. spinulosa, Scapania umbrosa, Dicranodontium denudatum and Dicranum scottianum, most of which are rare in the county.  Rose (1975) considered this one of the most important sites for Atlantic bryophytes in west Wales.  Aneura mirabilis has twice been uncovered from below Sphagnum in the wood.

Mynydd Preseli massif (SN03–13)

The hills of Mynydd Preseli only reach an altitude of 536 m and lack any exposures of really base-rich rock, but they are much the most bryologically diverse part of Pembrokeshire.  The Ordovician shales and slates that dominate their geology outcrop in the nivation hollow of Craig y Cwm, which supports the only Marsupella emarginata var. aquatica, Solenostoma obovatum and Pohlia elongata in the county, as well as Nardia compressa and Bryum julaceum.  Most of the rock exposures on the massif are igneous, rather than sedimentary, occurring as tors and block fields that hold humidity-demanding liverworts and disjunct colonies of northern mosses.  Among the most notable species here are Grimmia funalis, G. incurva, Hedwigia integrifolia and Kiaeria blyttii at the southern edge of their British ranges; the southernmost extant colony of Glyphomitrium daviesii; two populations of Grimmia decipiens and several of G. ramondii; the humidity-demanding Douinia ovata; and widespread Gymnomitrion crenulatum, Racomitrium sudeticum, Rhabdoweisia crispata and R. fugax.  Numerous flushes originate on the hillsides, and those which run past basic igneous rocks are often enriched with minerals, providing suitable conditions for frequent Sphagnum flexuosum, S. platyphyllum and one of Britain’s largest colonies of Hamatocaulis vernicosus.  As the ground levels out, the flushes feed mires in which Calypogeia sphagnicola, Cephalozia pleniceps and Odontoschisma fluitans grow, and where Cephalozia macrostachya var. macrostachya has been recorded in the past.  Hollows, stream banks and track sides provide the final important habitat on Mynydd Preseli: seasonally flooded areas in which Fossombronia fimbriata, F. foveolata, Haplomitrium hookeri, Ephemerum serratum and Pohlia bulbifera are found.  Schistostega pennata is a spectacular feature of some gaps in the stone-faced wall around the Mynydd Preseli common.

Craig Talfynydd on the south side of Preseli

Afon Teifi (SN14–24)

The protected species Dendrocryphaea lamyana has its only Pembrokeshire colonies on the Afon Teifi, in the county’s far north-east.  Our stretch of the river, which also flows through Carmarthenshire and Cardiganshire, is also notable for a population of the silt-loving Orthotrichum sprucei, as well as holding Porella pinnataPhilonotis arnellii has been collected from riverside bluffs in the Cilgerran area.

The Afon Teifi near Cilgerran

Brownslade & Linney Burrows (SR89)

Another protected species, Petalophyllum ralfsii has its largest UK population in the disused sand quarry in Brownslade Burrows, where David Holyoak estimated there were more than 400,000 thalli in 2002.  The dunes here are formed of highly calcareous sand and are therefore suitable for a suite of other notable species, including Didymodon acutus, Gymnostomum viridulum and Tortella squarrosa.

Castlemartin Range (SR89–99)

Although the exposed Linney Head (SR89) supports almost no bryophytes at all, more sheltered sections of the Castlemartin Range, including limestone outcrops above Bluck’s Pool bay and on the north-east side of St Govan’s Head, woodland in Mount Sion Covert, and damp tracks and hollows on Pen-y-holt Down, Mount Sion Down, Bulliber Down and Trevallen Down support a rich array of notable calcicolous mosses.  The Range supports a remarkable trio of Cephaloziella: C. dentata at one of two known Welsh sites, C. integerrima at one of three Welsh sites, and the only fractionally more frequent C. calyculata. Also present is the only extant Rhodobryum roseum in Pembrokeshire and the largest population of Entosthodon pulchellus in the county.  A further 13 nationally notable species include Didymodon acutus, Ephemerum recurvifolium, E. crassinervium subsp. sessile, Leptobarbula berica and Microbryum starckeanum, as well as the local rarities Microbryum curvicollum, M. davallianum var. commutatum, Weissia longifolia var. angustifolia and W. longifolia var. longifolia.

Outcropping Carboniferous Limestone on the Castlemartin Range

Stackpole and Bosherston (SR99)

Stackpole National Nature Reserve holds the greatest concentration of nationally and locally notable bryophytes in Pembrokeshire and is the only site in the county for Grimmia orbicularis and Seligeria sp., and the only extant site for Bryum canariense.  The lake at the heart of the NNR supports very large plants of Fontinalis antipyretica, and has Riccia cavernosa growing on its exposed margins in dry summers.  Thin soil on limestone outcrops by the lake and in the drier Mere Pool Valley supports Entosthodon pulchellus, Fissidens crispus, Microbryum starckeanum and the uncommon Tortula lindbergii (T. lanceola) and Reboulia hemisphaerica, whilst lime-rich blown sand on Stackpole Warren and behind Barafundle Bay is carpeted with Tortella squarrosa and holds locally frequent B. canariense, Didymodon acutus, Gymnostomum viridulum, Weissia controversa var. crispata and Bryum julaceumSouthbya tophacea grows on more humid, north-east facing slopes on Stackpole Head along with Cephaloziella integerrima, C. calyculata, Riccia subbifurca, Fossombronia caespitiformis subsp. multispira and Scapania cuspiduligera.  Limestone woodland around the lakes and in the Mere Pool Valley is home to Cololejeunea rossettiana, Marchesinia mackaii, Plasteurhynchium striatulum, Scorpiurium circinatum and Taxiphyllum wissgrillii, and there is an much-visited colony of Leptodon smithii on ash trees near the Bosherston carpark.

Bryophyte-rich blown sand near the Settlement in Stackpole NNR

Lydstep Head (SS09)

The steep, north-facing, lime-rich slopes of Lydstep Head are home to a larger colony of Southbya tophacea than the one at Stackpole, albeit without such notable associates.  However, most of Stackpole’s calcicoles are also present somewhere at Lydstep, especially on thin soil overlying limestone on the headland’s south side.  They include Fossombronia caespitiformis subsp. multispira, Riccia subbifurca, Entosthodon pulchellus, Microbryum starckeanum, Scleropodium tourettii, Tortula lindbergii (T. lanceola), T. protobryoides, Weissia controversa var. crispata and Entosthodon mourettii.  The only really reliable Pembrokeshire record of Encalypta vulgaris comes from here, but it has not yet been relocated.

Other sites

The three western islands all support Fossombronia angulosa, Weissia perssonii, Tortula atrovirens and T. viridifolia, and each has its own set of other notable species.  Skokholm (SM70) holds Marchesinia mackaii and Riccia crozalsii; Skomer (SM70–71) is home to Grimmia laevigata and Porella obtusata; whilst Ramsey (SM72) has Fossombronia maritima, Riccia beyrichiana and R. crozalsii on its damp tracks.  The south-eastern Caldey (SS19) is most notable for one of few south Wales records of Ephemerum recurvifolium.

Seasonally wet ground supporting Riccia beyrichiana on Ramsey Island

Complexes of wet heath and fen on the St David’s Peninsula, including Trefeiddan Moor (SM72), Dowrog Common (SM72), St David’s Airfield Heaths (SM72) and Ysgeifiog Moor (SM82) hold scattered colonies of Riccia beyrichiana, as well as Ephemerum stoloniferum (formerly E. serratum) and Fossombronia wondraczekii.  A fen hollow by St David’s Airfield supports Drepanocladus sendtneri, and Calliergon giganteum has its county headquarters in the peninsula’s fens.

The Mynydd Preseli Hamatocaulis vernicosus hot-spot extends south-westwards to take in other sites including Ambleston Common (SM92), Wallis Moor (SN02) and Waun Fawr Puncheston (SN03).  Wallis Moor is also important for the Fossombronia foveolata that grows near its eastern boundary.  Other uncommon flush and fen species, such as Plagiomnium elatum, P. ellipticum, Sphagnum contortum, S. flexuosum and S. teres grow on these mid Pembrokeshire commons as well.

The south-eastern outliers of Mynydd Preseli include Gweunydd Blaencleddau, Iet Goch and Caeau Pentre-galar (all SN13), all of which have species-rich flush complexes with a few notable bryophytes.  The most interesting are Haplomitrium hookeri and Jungermannia eucordifolia  (J. exsertifolia) at Pentre-galar, and Rhizomnium pseudopunctatum and Sphagnum contortum at Blaencleddau.  Splachnum ampullaceum survives in at least two places on Gweunydd Blaencleddau.

The county town of Haverfordwest (SM92) is a surprising minor hotspot, with the county’s only Targionia hypophylla on a roadside rock face and the only Fissidens fontanus in the Western Cleddau in the town centre.

Both Cwm Gwaun (SM93–SN03) and Cwm Cŷch (SN23) hold notable humidity-demanding species, including the county’s only Pseudohygrohypnum eugyrium, strong populations of Sphagnum quinquefarium, and locally abundant Jubula hutchinsiae and Plagiochila spinulosaGrimmia hartmanii has several colonies in Cwm Gwaun, as well as in the upper Eastern Cleddau valley (SN12), where Isothecium holtii has its only Pembrokeshire colony.  Plagiochila punctata and P. spinulosa have been recorded from the hanging oak wood above Goultrop Roads (SM81).

A woodland bank in Cwm Cych, NE Pembs

The remote north coast between Newport and Ceibwr Bay (SN04–14) is remarkably tall and rocky, and supports a good range of notable bryophytes including the only Gymnomitrion concinnatum in south Wales, and isolated colony of Philonotis rigida, and very large populations of Coscinodon cribrosusCynodontium bruntonii is frequent on the cliff slopes, Campylopus pilifer grows near Pen-y-bal, Drepanocladus polygamus and Philonotis caespitosa inhabit cliff-top flushes, and Weissia rutilans has been collected from two cliff-top slumps.

Pembrokeshire’s ‘Mediterranean’ coast at Manorbier (SS09) is home to large populations of Grimmia lisae and Nogopterium gracile, growing with the county’s only Tortella bambergeri, an unusual form of Porella arboris-vitae and outlying colonies of Frullania microphylla var. microphylla and F. teneriffaeRiccia subbifurca grows on thin soil overlying sandstone and Dialytrichia mucronata is on rocks on the coastal slope.  The quantity of Tortula atrovirens at the back of Manorbier Bay is impressive. Meanwhile, the coast near Trevayne Wood and Rhode Wood (SN10) is reminiscent of the north Devon coast, with Philonotis rigida and Porella obtusata among the most noteworthy species.

Didymodon acutus and Tortella squarrosa are abundant on calcareous sand at Penally Burrows (SS19), and Scorpiurium circinatum thrives in Tenby (SS19) as well as elsewhere on the south coast.

Wyndrush Pastures SSSI (SN00) holds a remarkable range of notable bryophyte species, highlighting how a resident bryologist – Matt Sutton – will find far more species by continuous ad hoc searching than any attempted tetrad survey will manage. Among the highlights in what is admittedly habitat-rich area are the only extant Welsh colony of Micromitrium tenerum, by a ditch, one of the few Welsh colonies of Bryum tenuisetum, by a pool, and Weissia rostellata.

The most interesting arable fields are near Angle (SM90), where Fossombronia caespitiformis grows; in the Steynton/Rosemarket/Nash area (SM90), where Weissia longifolia var. longifolia and the hornworts Anthoceros punctatus and Phaeoceros laevis are especially frequent; and near Loveston (SN00), where an oat field on heavy clay supports the only Didymodon tomaculosus known so far in Wales.

The Mosses and Liverworts of Pembrokeshire

by Sam Bosanquet

The Mosses and Liverworts of Pembrokeshire, ISBN 978-0-9552022-1-6, is a 316 page, card-covered book 245x175mm in size.  It includes expansive accounts for all 534 bryophyte species recorded in Vice-county 45, including tetrad distribution maps based on visits to every Pembrokeshire tetrad, and plots of altitudinal range and sporophyte timing.  The ecology of species is covered in greater depth than in most comparable county bryophyte Floras.  The introductory chapters, which account for over 100 pages, cover the history of bryophyte recording in the county, comparisons with the adjacent Vice-counties of Carmarthenshire and Cardiganshire as well as with the more distant but ecologically similar Cornwall and Caernarvonshire, the biogeography of Pembrokeshire bryophytes and their occurrence in broad habitats, accounts of declining and increasing species, and a review of SSSI bryophyte features in the county.  The book is written in an accessible and colloquial style.  Copies are available direct from the author for £20, or £15 for BBS members, plus £5.50 P&P.  Please contact sambbryo@aol.com or write to Sam Bosanquet, Dingestow Court, Monmouth, Monmouthshire NP25 4DY.  An invoice including payment details can be emailed to purchasers or posted with a copy of the book.

Local floras

Bosanquet, S.D.S. 2010. The Mosses and Liverworts of Pembrokeshire. Privately published (see details above)

Bosanquet, S.D.S & Rhind, P.M. 2004. Pembrokeshire register of rare bryophytes. CCW, Haverfordwest.

Rhind, P.M. 1999. A checklist of bryophyte species recorded in Pembrokeshire. Field Studies, 9: 469-495.