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Vice-county 35

Monmouthshire

Ysgyryd Fawr (The Skirrid) near Abergavenny

 

BBS Vice-county recorder:

Mr Sam Bosanquet,
Dingestow Court,
Monmouth,
Monmouthshire
NP25 4DY

sambbryo@aol.com

 

Accounts of previous meetings in the County:

Click on the links below for the meeting reports:

 

Current status of recording

The bryophytes of Monmouthshire are currently being mapped on a tetrad basis. Please send any new records you may have to the vice-county recorder.

 

A bryological tour through Monmouthshire

Read Sam Bosanquet's travelogue

 

Key sites and key habitats for rare bryophytes


Rare and scarce bryophytes have been recorded at numerous localities across the entire Vice County and are doubtless present at many others. Five locations stand out as being especially important for bryophyte conservation in the county; all are, entirely or partially, protected by SSSI and/or SAC designations. Many other sites are also of significant bryophyte conservation importance and their exclusion from this list certainly does not mark them as unimportant.

ST59 Blackcliff, Wyndcliff & Chepstow Woods
The steeply sloping woods of the lower Wye Valley, which hold several tall crags of Carboniferous Limestone, stretch from Tintern to Chepstow, a distance of more than 6km. Two cliffs are of particular importance for their calcicolous bryophytes: the northeast-facing Black Cliff and the south-facing Wynd Cliff. Numerous other outcrops are known to support interesting species, despite the difficulty of accessing many of them. Three of the four Nationally Rare species that have been recorded from this area appear to be extinct: Anomodon longifolius RDB(EN), Schedule 8 was last recorded from “near Tintern” in 1925; Bryum turbinatum RDB(CR) was collected from a roadside in 1891; Ditrichum flexicaule RDB(DD) was found in two places in 1891 and 1906. A fourth Nationally Rare moss, Seligeria campylopoda RDB(DD), remains a widely scattered rarity of small pieces of limestone between Black Cliff and Apostles Rocks. Despite much recent searching, there remains a possibility that A. longifolius persists in the area, and the same may be true of the critical D. flexicaule; B. turbinatum has surely vanished, indeed it has not been recorded in Britain since 1947.

Despite these losses, the calcareous woods of the lower Wye Valley are home to a number of uncommon bryophytes. Most notable is the S. campylopoda mentioned above - 9 of the 12 known extant British colonies of this species are in the area (the other 3 are elsewhere in VC35!). Limestone provides the habitat for a few scattered patches of Cololejeunea rosettiana NS and C. calcarea, as well as an abundance of Marchesinia mackaii; Amblystegium confervoides NS, Campylophyllum calcareum NS, Eurhynchium striatulum NS and Leptobarbula berica NS also occur, usually in rather small quantity, on shaded limestone. An exposed section of the Wynd Cliff supports a colony of Schistidium elegantulum ssp. elegantulum, a critical species currently known from very few British sites; the quarry below the cliffs holds Gymnostomum viridulum NS; the stream running through Cave Wood is lined with Fissidens rivularis NS and provides sufficiently humid conditions for Lophocolea fragrans and Trichocolea tomentella. Away from the Wye Valley, the limestone west of Chepstow is also of conservation importance. Great Barnets Woods holds Thuidium recognitum NS, the Mounton area has Anomodon longifolius RDB(EN), Schedule 8 and Scorpiurium circinatum NS, whilst Daggers Hill supports Seligeria campylopoda RDB(DD) and Amblystegium confervoides NS.

SO20/21 The Blorenge, Cwm Ifor & Gilwern Hill
This large area - stretching for about 8km from Gilwern Hill to Mynydd-y-garn-fawr - forms a geological entity connected by the Carboniferous limestone that outcrops at several places along its northern and eastern sides. Above this limestone is a capping of Millstone Grit, which forms beds of block-scree on the Blorenge and Mynydd-y-garn-fawr ridges. The geological diversity of the area means that it has an exceptionally long bryophyte list, and three of its component tetrads have the highest totals of any in the county. The area’s bryophytes fall into two camps: the limestone supports many Nationally Scarce species, whilst the sandstone and Millstone Grit support upland and Atlantic species of biogeographical interest.

The natural limestone outcrops on the eastern edge of the Blorenge, the gorge of Cwm Ifor, and a few other crags nearby, are known to support a rich bryophyte flora; those on Gilwern Hill have not been explored in such detail. The tiny Seligeria mosses are well-represented on almost all of the natural limestone: S. pusilla NS is locally frequent on most outcrops; S. acutifolia NS is occasional on three; whilst S. donniana NS appears to be restricted to one outcrop on Gilwern Hill. The sheltered limestone of the Cwm Ifor gorge holds Platydictya jungermannioides NS and Bartramia ithyphylla, whilst Funaria muhlenbergii NS is at its only VC locality on a limestone boulder nearby. Most of the limestone at Gilwern Hill has been quarried and the resultant calcareous spoil heaps provide suitable conditions for Scapania cuspiduligera NS and Rhodobryum roseum. The Scapania also occurs in small quantity in a quarry at Garn-ddyrys, a kilometre to the east. Thuidium philibertii is frequent on calcareous quarry spoil on both sides of the Blorenge ridge.

A base-rich sandstone crag on the north face of the Blorenge supports Encalypta ciliata NS and Plagiobryum zieri at their most southeasterly British locality; Bartramia ithyphylla, Mnium marginatum and Pohlia cruda near their southeasterly limit; and a number of interesting associates including Cololejeunea calcarea, Lejeunea patens, Bryum ‘subelegans’, Platydictya jungermannioides NS and Tortula subulata var. graeffii NS. Scree beds have developed along the length of the main ridge - from the Blorenge summit to the southern end of Mynydd-y-garn-fawr (and on to Mynydd Garnclochdy to the south). The only Nationally Scarce species they support is Leucobryum juniperoidum, but this is of much less interest than the assemblage of bryophytes that reach the south-eastern edge of their core British ranges here. Two patches of Anastrophyllum minutum and five of Lepidozia cupressina have been found so far; Bazzania trilobata and Dicranum fuscescens are slightly more widespread. Only the deepest holes in the block scree beds provide sufficiently humid conditions throughout the year for these species to occur.

SO22 Cwmyoy
Cwmyoy Graig is the county’s best example of dry, south-facing, Old Red Sandstone slopes, an unusual habitat that is also found at the southern ends of Bryn Arw and Ysgyryd Fawr. The most notable species here is Grimmia longirostris NS, which grows on a sandstone block in the central valley and is currently known from only one other site in Wales. Nearby, Leucodon sciuroides and Pterogonium gracile are abundant on sandstone blocks, whilst Rhodobryum roseum and Bryum donnianum NS occur in calcareous turf. The dry, south-facing slopes of the Graig support strong colonies of Microbryum curvicolle and Tortula lanceola, as well as smaller quantities of T. modica, M. davallianum and M. rectum. Other species recorded here include Bartramia ithyphylla, Cephaloziella stellulifera NS, Scleropodium tourettii and Tortula subulata var. graeffii NS. A BBS visit to the sandstone block-field below the nearby Cwmyoy Darren revealed Porella arboris-vitae, Leucodon sciuroides, Pterogonium gracile and Didymodon ferrugineus. Grimmia longirostris NS was found here in 1998 but has not been seen since.

SO23 Tarren yr Esgob
Two thirds of Tarren yr Esgob, a 4km long, east-facing series of Old Red Sandstone crags, lies in Breconshire (VC42). Despite looking rather insignificant on the map, the Monmouthshire section of the Tarren is sufficiently extensive to support most of the species that occur across the border (Jungermannia sphaerocarpa, Seligeria trifaria, Scapania calcicola and S. subalpina are the principal exceptions). The site is particularly notable as the most southeasterly locality in Britain for three scarce upland calcicoles - Bartramia halleriana NS, Plagiopus oederianus NS and Scapania aequiloba NS - as well as being at the edge of the range of other upland mosses such as Anomobryum julaceum, Distichium capillaceum, Isopterygiopsis pulchella and Pohlia elongata. Brachydontium trichodes NS and Tortula subulata var. graeffii NS are both scattered on the crag, whilst Blepharostoma trichophylla, Entosthodon obtusus, Fissidens osmundoides, Frullania fragilifolia and Tetrodontium brownianum remain unrecorded elsewhere in the Vice County.

SO51 Lady Park Wood
The principal bryological interest of this National Nature Reserve is the presence of six small patches of Anomodon longifolius RDB(EN), Schedule 8 on one part of the east-facing limestone cliff. This species is slightly commoner just across the border in England (despite having been collected in large quantity in 1954 and preceding years) but is known from just one other site in Wales (Mounton). Two thriving colonies of Seligeria campylopoda RDB(DD) occupy small pieces of limestone between the NNR and Hadnock Quarry. Numerous scarce species occur in and arround the NNR, most of them associated with limestone. Amblystegium confervoides NS, Campylophyllum calcareum NS and Eurhynchium striatulum NS are found on rocks and stones on the woodland floor; Apometzgeria pubescens (at its most southerly British site), Cololejeunea rosettiana NS, Gymnostomum calcareum NS, Seligeria donniana NS and S. acutifolia NS grow together on wet limestone by the Wippington Brook; Platydictya jungermannioides NS is probably restricted to the drier main cliff. Other habitats nearby hold Fissidens rufulus NS, Gymnostomum viridulum NS, Octodiceras fontanum NS, Orthotrichum sprucei NS and Platygyrium repens NS.

Other localities
Limestone quarry spoil supports Scapania cuspiduligera NS on Gilwern Hill and at Garn-ddyrys, Rhodobryum roseum on Gilwern Hill, Racomitrium canescens NS and Thuidium philibertii in Cwm Sychan, T. philibertii and Tortula lanceola on The Blorenge and Aloina ambigua NS near Risca. Mounds of colliery spoil often have a rich and varied hepatic flora, including Barbilophozia floerkei, Lophozia bicrenata and Ptilidium ciliare, and appear to be ideal for Buxbaumia aphylla NS (which has yet to be discovered in south Wales). Uncommon colonists of colliery spoil include Anthoceros punctatus NS at Blaen Bran, Didymodon ferrugineus in Cwm y Glyn and Plagiomnium cuspidatum in Cwm Lickey.

Most of the county’s bogs have been lost through drainage or neglect, but a few key sites remain. Cleddon Bog’s Cladopodiella francisci NS has surely been lost, but Cephalozia connivens, Kurzia pauciflora and Mylia anomala remain; two mounds of Polytrichum strictum, at Garn-yr-erw and on The Blorenge, have somehow escaped burning; Waun Afon holds a little Splachnum ampulaceum and deserves a more detailed survey; a bog on Rhymney Hill has S. ampulaceum, Scapania paludicola NT and Cladopodiella fluitans. Acid-flushed Molinia near Maesycwmmer supports Barbilophozia kunzeana NT (at its most southerly British site) and S. paludicola NT; there must be other suitable habitat for these rare species elsewhere in the west of the county.

A rich assemblage of epiphytes occurs on alders and willows by slow, silty rivers, and is well-developed by the Usk, Monnow, Trothy, Wye and a few of their tributaries. The rarest member of this assemblage, Myrinia pulvinata NS, has been noted twice on the Usk, whilst more regular components include O. sprucei NS and, probably, Tortula subulata var. subinermis. The vertical banks of eroding sections of the river are a key habitat for Hennediella stanfordensis (now excluded from the Nationally Scarce list because it is thought to be introduced), Epipterygium tozeri and Pohlia lescuriana NS. The rare bryophytes of fluctuating reservoir margins have not been investigated in most of Monmouthshire due to a lack of recent droughts; the exception is Llandegfedd Reservoir, which supports several million plants of Riccia cavernosa NS and several thousand of Ephemerum sessile NT when water levels are low.

The church roofs of Monmouthshire are a key bryophyte habitat that has been ignored by conservationists for many years. South-facing Old Red Sandstone tiles, here and in neighbouring Herefordshire, support Grimmia decipiens NS, G. laevigata NS, G. ovalis RDB(VU) and Hedwigia ciliata RDB(DD). Two of the Grimmia spp. are widespread in the county, G. decipiens has been recorded on one roof and H. ciliata is known from three. Re-roofing of buildings with slate or artifical tiles continues to destroy colonies of these rare mosses and an inevitable conclusion is that all four species have undergone catastrophic declines in recent history, as locally-quarried tiles have been replaced as the most readily available roofing material.

The bryophytes of arable land remain relatively poorly understood, although the Survey of Bryophytes of Arable Land (SBAL), being run by the BBS from 2001 to 2005, has filled in many gaps in our knowledge. Monmouthshire’s arable fields appear to be a key locus for Phaeoceros carolinianus RDB(EN); five of the eleven post-1950 British records come from the area between Abergavenny, Usk and St Maughan’s. Anthoceros agrestis NS is a constant companion of P. carolinianus in Monmouthshire fields and is a little more widespread in the county. Weissia rostellata NT was recorded near Dingestow in 2003, at its first Monmouthshire and third Welsh site. Two other rare Weissia spp. have been recorded from the county and may occur in arable fields. Weissia squarrosa RDB(EN) was found on a field bank near Cwmyoy by Augustin Ley in the late 19th century but has not been recorded since; W. multicapsularis RDB(VU) was found on a hedgebank next to an arable field near Dingestow by George Garlick in 1981 and also has not been relocated.

The key habitats for bryophyte conservation in Monmouthshire are (in the order mentioned above):

• limestone in woodland
• upland limestone crags & gorges
• sandstone crags & blocks
• block scree
• south-facing unimproved dry grassland
• quarry spoil
• bog and flush
• tree-lined rivers
• margins of fluctuating reservoirs
• stone-tiled roofs
• arable habitats

Abbreviations:

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

Sam Bosanquet

Local Flora

BOSANQUET, S.D.S. (2003) Monmouthshire register of rare bryophytes. Unpublished report, Dingestow Court, Monmouth.

 
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