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Key sites and key habitats for rare bryophytes

by Sam Bosanquet

 

 

Key sites and key habitats

Rare and scarce bryophytes have been recorded at numerous localities across the Vice-county and are doubtless present at many others. Five sites, two of them very large, stand out as being particularly important for bryophyte conservation in Pembrokeshire; all are, entirely or partially, protected by SSSI and/or SAC designations. They are listed below in alphabetical order. Many other sites are also of significant bryophyte conservation importance and their exclusion from this list certainly does not mark them as unimportant. The most interesting species at each site are listed, with their National Status given in bold (e.g. NT=Near Threatened, NS=Nationally Scarce, RDB(VU)=Vulnerable).

SR89 Brownslade & Broomhill Burrows
Dr David Holyoak’s survey in 2002 showed that Brownslade Burrows in the most important site in the UK for the European RDB liverwort Petalophyllum ralfsiiNS, S8, BAP; only a few Irish sites support larger populations. The dunes also hold Amblystegium serpens var. salinumNS, Didymodon acutusNS, Drepanocladus polygamus NS, D. sendtneriNS, Gymnostomum viridulumNS and Pleurochaete squarrosaNS, but none of the Red Data Book dune-slack Bryum species has been recorded. Base-rich rocks at Gravel Bay, just north-west of Broomhill Burrows, support Grimmia lisae NS, Porella obtusataNS and Pterogonium gracile.

SN03 Carn Ingli
This range of hills - incorporating Mynydd Dinas, Mynydd Melyn, Mynydd Caredog and Mynydd Carn Ingli - is separated from the main Preseli massif by Cwm Gwaun. Its bryological importance centres on two habitats that are shared with Preseli: its flush complexes are less well-developed, whilst its igneous tors are comparable and include Carn Ingli itself, the most extensive block-field in the Vice-county. A spring-head above Pont Ceunant holds Hamatocaulis vernicosusNS, S8, BAP, with a second colony in a flush nearby; Splachnum ampulaceum also grows near Pont Ceunant. Twenty one of the 22 tufts of Glyphomitrium daviesii NS currently known in Wales are on Garn Fawr, Mynydd Dinas, a tor that also supports Lophozia excisa and L. sudetica; a deep hole in Carn Ffoi hides the only colony of Douinia ovata known from the Vice-county, whilst other holes there have Bazzania trilobata and Rhabdoweisia fugax; Polytrichum alpinum and Rhabdoweisia crispata are rare at Carn Edward; the extensive block-field of Carn Ingli holds B. trilobata, Gymnomitrion crenulatum and Andreaea megistosporaNS but it is too acidic for its rocks to support the Grimmiales present on Mynydd Preseli. Several other flush complexes and a few tors on Carn Ingli remain unexplored.

SM92 Esgyrn Bottom
Esgyrn Bottom, Pembrokeshire’s only more or less intact bog, lies to the south of Cwm Gwaun near Llanychaer. This private site has been visited by Roy Perry, the BBS and Martha Newton, and is the only known site for several bryophyte species in the Vice-county. Jean Paton found Calypogeia sphagnicola, Cephaloziella elachistaNS and Riccardia latifrons during the BBS visit, whilst Matt Sutton collected Pallavicinia lyelliiRDB(VU), BAP during a training course run by Martha Newton. Sphagnum magellanicum is scattered on the bog, but a recent record of S. fuscum has yet to be confirmed. Pohlia lutescens and Rhabdoweisia crispata grow in the oak woodland between the two arms of the bog.

SN03/13 Mynydd Preseli
Like its outlier, Carn Ingli, Mynydd Preseli’s bryological interest lies in its flushes and tors. The Brynberian flush complex, on the northern side of the mountain, has been explored by the BBS, Martha Newton and several other bryologists and holds Barbilophozia floerkei, Calypogeia neesiana, Riccardia latifrons, Hamatocaulis vernicosus NS, S8, BAP (in springheads), Sphagnum flexuosum NS, S. molle, S. platyphyllum NS, S. russowiiand S. subsecundum. Other colonies of H. vernicosus have been found on the slopes of Cerrig Lladron and in Cwm Garw, but this species is very local and is absent from large parts of the Preseli hills. More regular components of the Preseli flushes, especially the most base-enriched, include Jungermannia exsertifolia var. cordifolia, Blindia acuta, Calliergon sarmentosum, Fissidens osmundoides and Scorpidium scorpioides, whilst Jungermannia pumila and Philonotis calcarea appear to be rare but may be widely scattered.

The bryological interest of the tors varies with exposure as well as chemical composition; prominent Carnalw is much less interesting than the small but sheltered Carn Breseb and Craig Talfynydd. The latter, on the south side of Preseli, supports Hedwigia integrifolia NS and Glyphomitrium daviesiiNS, the Hedwigia at its only south Wales site. Gymnomitrion crenulatum, which occurs on several tors, is also known from Dartmoor and Carn Ingli but is otherwise absent in Britain south of Plynlimmon. The igneous rocks are home to a good range of notable grimmiales, rare or absent in the rest of south Wales. Grimmia incurvaNS grows on Carnau Ysfa, many miles from its nearest known sites in Shropshire and north Wales; Grimmia decipiens NS has recently been collected from one igneous rock on the ridge of the mountains; and Grimmia curvata (Dryptodon patens) is abundant on single rocks at Carn Afr and Carnau Ysfa.

The nivation hollow at the head of Cwm Wern had more of an upland feel than any other part of Preseli. Marsupella emarginata var. aquatica and Nardia compressa are abundant in the streams, with M. e. var. pearsonii, Jungermannia obovata and Anomobryum julaceum on dripping rocks. Despite previous quarrying, Polytrichum alpinum, Pohlia elongata and Rhabdoweisia crispata persist at Craig y Cwm. Grimmia donniana and Racomitrium affine both grow on the quarry spoil.

There are at least ten colonies of Fossombronia foveolataNS on damp ground near Brynberian and a few plants of F. fimbriataNT grow in three of these; two other tiny colonies of F. fimbriata occur without F. foveolata. Pohlia bulbifera and Ephemerum serratum also occur on damp, poached ground in the Brynberian area, whilst Haplomitrium hookeriNS has been found on a damp track-side further east. Historic Preseli records of Blasia pusilla and Cladopodiella francisciNS have not been repeated.

SR99 Stackpole NNR
The Stackpole National Nature Reserve protects a wide range of calcicolous habitats, including the limestone headlands of Stackpole Head and Saddle Point, sheltered and exposed outcrops in the Mere Pool Valley, dunes at Broad Haven, Stackpole Warren and Barafundle Bay, the Bosherston Lily Ponds and steep-sided woodlands. A large number of uncommon species have been recorded in the NNR, the most notable being Cololejeunea rosettianaNS, Reboulia hemisphaerica, Riccia cavernosaNS, Aloina ambiguaNS, Bryum canarienseNS, Didymodon acutusNS, Grimmia orbicularisNS and Pleurochaete squarrosaNS. The only Pembrokeshire record of Porella cordeana comes from the Lily Ponds, where E.F. Warburg found it in 1958. Although, some parts of the NNR have been explored in reasonable detail many others are almost unknown. Weissia longifolia var. angustifolia grows just outside the NNR on the north side of Stackpole Quay and is also from the Castlemartin Ranges to the west; it seems likely to be present somewhere at Stackpole. Further survey is advisable as other rare and scarce species known from further east on the South Wales coast, including Cephaloziella calyculata, Funaria muhlenbergii, F. pulchella, Tortula protobryoides or even Weissia levieri, may await discovery.

Other localities
The importance of arable habitats for bryophyte conservation in Britain is still not fully understood, but the Survey of Bryophytes of Arable Land (SBAL) currently being carried out by the BBS should provide much useful information. SBAL recording in Pembrokeshire in 2003 turned up colonies of Fossombronia caespitiformisNS near Angle and Weissia longifolia var. longifolia NS near Johnston. Phaeoceros carolinianus, currently listed as RDB(EN) but probably only NS, has not yet been recorded in the county but any arable Phaeoceros should be checked carefully as all fruiting Phaeoceros from arable fields in V-cs 35 and 44 has proved to be monoicous and therefore P. carolinianus. The BAP Priority species Didymodon tomaculosus has not yet been recorded in Pembrokeshire, but recent records from Ireland and Shropshire suggest that it may have been overlooked here.

The Atlantic element of the Pembrokeshire woodland flora is less well developed than that of Cardiganshire and Carmarthenshire woods. This is probably because of a combination of Mediterranean influences in the Pembrokeshire climate and a general lack of deep gorges. Coed Ty Canol is the best example of an Atlantic woodland in the Vice-county, with its rockier sections holding humidity demanders such as Frullania fragilifolia, Harpanthus scutatus, Plagiochila bifaria, P. punctata, P. spinulosa, Dicranum scottianum and Dicranodontium denudatum. Hanging oak woodlands on the north-facing cliffs above the Goultrop Roads hold a similar hepatic flora, although Harpanthus is absent. The BBS recorded Lepidozia cupressina in reasonable quantity in Lawrenny woods and it is likely that other oak woodlands by the Cleddau estuary hold humidity demanding bryophytes. Further exploration of Pengelli Forest and the Cwm Gwaun woodlands is also needed.

Carboniferous Limestone forms much of the southern coast of Pembrokeshire, from Tenby in the east to Linney Head in the west. The south-facing rocks of Giltar Point are very exposed and support few bryophytes, whilst the headland’s flat top is covered by coarse grassland; a few gaps at the junction of these two habitats are suitable for Tortula protobryoidesNS and T. viridifoliaNS. T. protobryoides also grows a few miles further west: on Lydstep Head. The limestone here is more folded, so conditions are more sheltered; as a result, a rich bryophyte flora, including Southbya tophaceaNT, Bryum canariense NS, Encalypta vulgaris and Pleurochaete squarrosaNS, occurs. Nearby, south-west of Lydstep, Funaria pulchellaNT was collected by P.W. Richards in 1958. Stackpole (see above) is the next limestone area to the west, and this is the beginning of a 10km long stretch of limestone coast. Most lies in the MOD’s Castlemartin Ranges and has not been explored; a brief visit to the coast at Stack Rocks in 2003 revealed Weissia longifolia var. angustifolia and another to Crickmail Down revelaed Microbryum davallianum f. commutata. A second band of limestone, a few miles north of the coast, is mostly exposed in quarries. It meets the Daugleddau Estuary at the old quarry complex of West Williamston, which is owned by the National Trust and includes some natural limestone exposures. A visit by the BBS produced Bryum torquescens NS, Encalypta vulgaris, Gymnostomum calcareumNS and G. viridulumNS.

Recording coverage on the north Pembrokeshire (non-limestone) coast is patchy, but is much better than that for inland parts of the county. Many coastal bryophytes are widely distributed around the coast: Tortula viridifoliaNS is almost ubiquitous on coastal slopes, whilst Frullania fragillifolia, F. microphylla, F. teneriffae, Tortula atrovirensNS and Weissia perssoniiNS, BAP are widespread. The most humid coastal slopes, such as those of Carn Ogof, support locally abundant Saccogyna viticulosa and Scapania gracilis and occasional Bazzania trilobata, Cephalozia lunulifolia or Plagiochila bifaria. Coscinodon cribrosusNT is found on shattered sandstone in at least 9 localities around the coast between Cemaes Head and Trewent Point and has also been noted on igneous rocks at Pwll Deri. Pwll Deri, on the west side of Strumble Head, also supports a colony of Campylopus polytrichoidesNT, whilst the north-facing coast of Strumble Head holds Riccia beyrichianaNS and Tritomaria exsectiformis. Fossombronia maritimaNT was collected from thin soil on the top of a rock on the coast just west of Porthclais, one of only two Welsh localities from which it is known. Fossombronia angulosaNS has been known from the islands of Skomer and Skokholm for some years and has recently been located in two places on the Pembrokeshire mainland. Skomer also supports Porella obtusata NS, a liverwort of neutral sandstone that also grows at Freshwater West and formerly at West Dale Bay, Grimmia laevigataNS and R. beyrichianaNS.

The coastal slopes around the Milford Haven Waterway and on the south coast between Stackpole and Manorbier have a different character to the rest of the Vice-county and are most notable for their Mediterranean-Atlantic species. Cephaloziella turneriNT and Ditrichum subulatumNT grow with Epipterygium tozeri on very friable, south-facing soil around tree roots in at least 3 localities on the north shore of the Haven. The Ditrichum is at the northern limit of its world range. Grimmia lisae NS is a poorly understood Mediterranean-Atlantic species that appears to favour sandstone rocks on south-facing coastal slopes; records come from the south side of the St David’s Peninsula, the north shore of Milford Haven, the coast south of Angle, Trewent Point and Manorbier. Tortula canescensNS and T. cuneifoliaRDB(VU) are part of the same floristic element (Hill & Preston, 1998) but it is feared that both have been lost to scrub encroachment or construction of the Oil Refineries; T. wilsonii RDB(EN) persists at Westdale Bay, where grazing levels are still high, and south of Waterston.

The sand dunes at Penally Burrows are lime-rich and hold frequent Didymodon acutusNS and abundant Pleurochaete squarrosaNS. The eastern part of The Bennet, Newport, has Rhynchostegium megapolitanum, but most of the site is scrub-infested and bryologically poor. Other small dune systems on Caldey Island and at Freshwater East, Poppit and Whitesands Bay have not been surveyed for their bryophytes but they are probably too damaged to support more than a few common species. The sand quarry at Monington holds a small colony Fossombronia incurvaNS, whilst the one at Brawdy has Anthoceros punctatusNS.

Flush complexes similar to those on Mynydd Preseli occur near Crymych at Gweunydd Blaencleddau, Caeau Gafel and Caeau Pentre Galar. Neutral flushes hold Drepanocladus exannulatus, Sphagnum contortum and S. teres, whilst more base-rich ones are dominated by Drepanocladus cossonii, D. revolvens or Scorpidium scorpioides and sometimes support Rhizomnium pseudopunctatum. Haplomitrium hookeri NS was found in one of the flushes at Pentre Galar, whilst another holds Jungermannia exsertifolia subsp. cordifolia. Cephalozia plenicepsNS grows through Sphagnum subnitens at Caeau Gafel and in at least 6 other localities in the Vice-county. Hamatocaulis vernicosusNS, S8, BAP is also widely scattered away from its Preseli stronghold, although it appears to be absent from the Crymych flush complexes. Strongly base-rich flushes, typically dominated by Palustriella commutata, are rare on Mynydd Preseli and very rare elsewhere in Pembrokeshire; those at Llambed Moor, which also support Philonotis calcarea, are therefore notable.

The tors at Treffgarne Rocks are the only ones away from Carn Ingli and Mynydd Preseli that are known to support a notable bryophyte flora. Bazzania trilobata, Lepidozia cupressina, Odontoschisma denudatum, Dicranum fuscescens and D. scottianum are the most interesting species that have been recorded by the numerous bryologists who have visited the tors. Plumstone Rock holds Dicranum fuscescens but is too exposed to be of more bryological interest.

Peatlands are scattered around the lower slopes of Mynydd Preseli, but none support the interesting bryophytes of Esgyrn Bottom. Calypogeia sphagnicola and Cephalozia macrostachyaNS were collected from a bog in Cwm Gwaun in the 1960s but it is not known whether the bog is still extant, let alone the bryophytes.

The specialities of the Afon Teifi - Cryphaea lamyana RDB(VU), S8, BAP and Orthotrichum spruceiNS, BAP - have been recorded from the short section of the river’s southern bank that is in Pembrokeshire. Two other Nationally Scarce mosses that have been recorded on the Cardiganshire bank, Fissidens rivularis and Grimmia lisae (of the form previously known as G. retracta), should be looked for on the Pembrokeshire section of the river. Neither of the Teifi specialities has been found on Pembrokeshire’s principal rivers, the Eastern and Western Cleddaus, despite survey work by David Holyoak. The Western Cleddau has a slightly richer bryophyte flora than the Eastern, including Fissidens monguilloniiNT at Treffgarne and Crow Hill and Octodiceras fontanum NS in the centre of Haverfordwest. Porella pinnataNS is locally abundant by both rivers and on some of their tributaries. Anthoceros punctatusNS grows on vertical soil by the Eastern Cleddau in at least one place; Schistidium platyphyllum has been found on the Carmarthenshire bank of the Eastern Cleddau but remains unknown from Pembrokeshire. There are no large rivers on the Old Red Sandstone south of Haverfordwest, which may be the reason why the sandstone specialist Dialytrichia mucronata is so rare in the Vice-county.

The key habitats for bryophyte conservation in Pembrokeshire are:

  • arable habitats
  • Atlantic woodlands
  • coastal limestone
  • coastal slopes
  • dunes
  • flushes
  • igneous tors
  • peatlands
  • riparian habitats

Abbreviations:

CR Critically Endagered
EN Endangered
VU Vulnerable
DD Data Deficient
NT Near Threatened
NS Nationally Scarce
RDB Red Data Book

Sam Bosanquet

 
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