OR/14/043 Site description - Pont Clydach (Sites 1, 2 and 3)
| Farr, G, Graham, J, and Stratford, C. 2014. Survey, characterisation and condition assessment of Palustriella dominated springs 'H7220 Petrifying springs with tufa formation (Cratoneurion)' in Wales. British Geological Survey Internal Report, OR/14/043. |
Introduction
Pont Clydach (Clydach Bridge) is the name given to the sites located along the Afon Clydach upstream and downstream of the road bridge, and less than 800 m to the north of Foel Fawr/Herbert’s Quarry. The streams that drain from Foel Fawr/Herbert’s Quarry also join the Afon Clydach along its course. Three sites were assessed along the ‘Pont Clydach’ section including one, upstream of Pont Clydach (SN7396519551) and two downstream (SN7338319189 and SN7364319860), all within a 500 m stretch of the Afon Clydach.
Geological and hydrogeological data
The area is underlain by Lower Devonian Brownstones Formation and there are Devensian Glacial Till deposits mapped within the valley. Large boulders of conglomeratic Devonian Old Red Sandstone occur throughout this part of the Afon Clydach and form parts of all three sites. Hand auguring at Site 1 proved about 5 cm of mineral ground underlain by unconsolidated sandy material with silicate material >1 cm derived principally from the Devonian bedrock. The deposit was tested with HCI and there was no reaction, confirming that the shallow ground was dominantly silicate rich material. There was no evidence of tufa deposition at either Sites 1, 2 or 3.
All three sites are located on the eastern, or right hand bank of the Afon Clydach which flows to the north. Each of the three sites is fed by areas of diffuse seepage or by discrete springs or a combination of both. The water from the seepages and springs forms the runnels and shallow channels that flow towards and discharge into the Afon Clydach. It is not known if the Devonian bedrock or the unconsolidated superficial deposits provide the main source of water for the springs and flushes although a combination of both is possible.
A discrete spring near the base of Site 1 (SN7396519551) was estimated to be flowing at 0.5l/s however this water and the short runnel which it feds bypasses the main part of the site and did not support Palustriella. It can be very difficult to estimate flow from diffuse seepages in the field, however runnels fed by seepages do offer some potential to estimate the combined flow in certain areas. At Site 3 the flow in a runnel (downstream from several seepage areas) was estimated at 0.25 l/s.
Four water quality samples were collected; two at Site 1 (SN7397319559 and SN7396519551) and one each at Sites 2 (SN7338319189) and 3 (SN7364319860). Nutrient levels are low or below the level of detection in all four samples with calcium and bicarbonate the dominant ions. pH values in the main parts of the sites range from 5.63–6.67 (Site 1), 6.74–7.3 (Site 2) and 7.07–7.5 (Site 3).
Land use and pressures
All three sites are located within a short distance from the road and there is open access for walkers and the public although there does not appear to be a heavy footfall in the area. Grazing from sheep and horses and associated poaching occurs but is not excessive. There is no evidence of burning or obvious signs of nutrient enrichment at any part of the site. There is nothing to suggest that there are any groundwater or surface water abstractions in the immediate area. Sites 2 and 3 (downstream from Pont Clydach) may both receive run off from the adjacent road and associated drainage.
© Ordnance Survey.
Vegetation (spring) of Pont Clydach Site 1
Palustriella falcata dominated short vegetation between 1–3 cm height following the margins of a central runnel. The immediate margins of the central runnel have locally dominant patches of Campylium stellatum with Scorpidium revolvens and occasional Riccardia multifida. Palustriella commutata occurs as scattered patches in the upper part of the site.
| Anagallis tenella | F |
| Aneura pinguis | O |
| Bryum pseudotriquetrum | R |
| Calliergonella cuspidata | R |
| Campylium stellatum | O |
| Cardamine pratensis | R |
| Carex demissa | R |
| Carex flacca | O |
| Cirsium palustre | R |
| Cratoneuron filicinum | R |
| Cynosurus cristatus | R (<1%) |
| Festuca rubra | R (<1%) |
| filamentous algae (Chlorophyta) | O |
| Galium palustre ssp. palustre | R |
| Holcus lanatus | R (<1%) |
| Juncus acutiflorus | O |
| Juncus effusus | O |
| Myosotis sp. | R |
| Nostoc sp. | R |
| Palustriella commutata | O |
| Palustriella falcata | A |
| Philonotis fontana | O |
| Plantago lanceolata | R |
| Ranunculus flammula | O |
| Rhytidiadelphus squarrosus | O |
| Riccardia multifida | R |
| Rumex acetosa | R |
| Sagina cf nodosa | R (<1%) |
| Scorpidium revolvens | O |
| Stellaria media | R (<1%) |
| Taraxacum sp. | R |
| Thuidium tamariscinum | R |
| Trifolium repens | R (<1%) |
A neutral rush dominated flush adjoining to the left of the main runnel with Palustriella falcata but with a different spring head source. Below the Juncus stems are abundant Calliergonella cuspidate and frequent Hamataucalis vernicosus. Chrysosplenium oppositifolium and Warnstorfia sarmentosa occur locally.
| Aneura pinguis | O |
| Calliergonella cuspidata | F |
| Cardamine pratensis | R |
| Chrysosplenium oppositifolium | O |
| Cynosurus cristatus | R (<1%) |
| Festuca rubra | R |
| Galium palustre ssp. palustre | R |
| Hamatocaulis vernicosus | F |
| Holcus lanatus | R (<1%) |
| Juncus acutiflorus | F |
| Juncus effusus | O |
| Lotus pedunculatus | R |
| Myosotis sp. | R |
| Philonotis fontana | F |
| Rhytidiadelphus squarrosus | O |
| Rumex acetosa | O |
| Scorzoneroides autumnalis | R |
| Trifolium repens | R (<1%) |
| Warnstorfia sarmentosa | R (<1%) |
An acid rocky deep water spring which joins the main spring channel from the right low down and in close proximity to the Afon Clydach. It is dominated by Brachythecium rivulare, Calliergonella cuspidata, Chrysosoplenium oppositifolium, Conocephalum conicum and the central channel has patches of Fontinalis antipyretica attached to submerged stones.
| Brachythecium rivulare | O |
| Calliergonella cuspidata | O |
| Chrysosplenium oppositifolium | O |
| Conocephalum conicum | O |
| Cratoneuron filicinum | O |
| Dichodontium pellucidum | R |
| Fontinalis antipyretica | O |
| Galium palustre ssp. palustre | R |
| Lophocolea bidentata | R |
| Plagiomnium undulatum | O |
| Rhizomnium punctatum | R |
| Rumex acetosa | O |
| Scapania undulata | R |
| Thuidium tamariscinum | R |
Upland acid grassland to 20 cm height (Nardus stricta, Galium saxatile) with regular hummocks of Aulocomnium palustre, Polytrichum commune and Sphagnum subnitens.
| Aulocomnium palustre | R |
| Dicranum scoparium | O |
| Galium saxatile | O |
| Hypnum jutlandicum | R |
| Juncus effusus | R |
| Nardus stricta | A |
| Polytrichum commune | R |
| Potentilla erecta | R |
| Rhytidiadelphus squarrosus | O |
| Sphagnum subnitens | R |
| Vaccinium myrtillus | R |
Vegetation (spring) of Pont Clydach Site 2
Palustriella falcata dominated short vegetation between 1–3 cm height following the margins of several runnels that converge into one. The immediate margins of the central runnel have locally dominant patches of Campylium stellatum with Scorpidium cossonii, Scorpidium cossonii, occasional Philonotis calcarea and Jungermannia exertifolia ssp. cordifolia. Larger central runnels support aquatic flowering plants including Nasturtium officinale s.l, Mentha aquatica, Ranunculus flammula while Palustriella falcata becomes less frequent towards the base of the flush (adjoining the Afon Clydach) being replaced by more frequent Cratoneuron filicinum and Philonotis fontana.
| Agrostis stolonifera | R (<1%) |
| Anagallis tenella | O |
| Aneura pinguis | F |
| Bryum pseudotriquetrum | R |
| Calliergonella cuspidata | R |
| Campylium stellatum | O |
| Cardamine pratensis | O |
| Carex demissa | R |
| Carex flacca | O |
| Cirsium palustre | R |
| Cratoneuron filicinum | O |
| Ctenidium molluscum | R |
| filamentous algae (Chlorophyta) | R |
| Fissidens adianthoides | R |
| Hydrocotyle vulgaris | R |
| Juncus acutiflorus | O |
| Jungermannia exsertifolia ssp. cordifolia (non fertile) | O |
| Mentha aquatica | R |
| Nasturtium officinale s.l. | R |
| Palustriella commutata | O |
| Palustriella falcata | A |
| Philonotis calcarea | O |
| Philonotis fontana | R |
| Plagiomnium undulatum | R |
| Ranunculus flammula | R |
| Scorpidium cossonii | O |
| Thuidium tamariscinum | R |
| Trifolium repens | R (<1%) |
| Veronica beccabunga | R |
Vegetation (adjoining spring) Pont Clydach Site 2
Upland acid grassland to 20 cm height (Nardus stricta, Agrostis capillaris) with scattered extensive rush pasture dominated by Juncus effusus, occasional Juncus acutiflorus.
| Agrostis capillaris | R |
| Calliergonella cuspidata | F |
| Juncus acutiflorus | R |
| Juncus effusus | A |
| Nardus stricta | R |
Vegetation (spring) of Pont Clydach Site 3
Particularly species-rich Palustriella falcata dominated short vegetation between 1–3 cm height following the margins of a number of runnels eminating from several spring heads. The immediate margins of the central runnels have luxurious growth of Campylium stellatum with Fissidens adianthoides, Bryum psedotriquetrum, Scorpidium cossonii, Philonotis calcarea and notable stands of Scorpidium scorpioides occur in several places. Larger central runnels support aquatic flowering plants including Nasturtium officinale s.l, Myosotis sp., Ranunculus flammula, Potamogeton polygonifolius and locally Hypericum elodes, Eriophorum cf latifolium.
| Agrostis stolonifera | R (<1%) |
| Anagallis tenella | O |
| Bellis perennis | R |
| Bryum pseudotriquetrum | O |
| Calliergonella cuspidata | R |
| Campylium stellatum | F |
| Cardamine pratensis | R |
| Carex demissa | O |
| Carex flacca | O |
| Chrysosplenium oppositifolium | R |
| Cirsium palustre | R |
| Cratoneuron filicinum | O |
| Ctenidium molluscum | R |
| Didymodon fallax | R |
| Equisetum palustre | R |
| Eriophorum cf latifolium | R (<1%) |
| Festuca ovina | R (<1%) |
| filamentous algae (Chlorophyta) | R |
| Fissidens adianthoides | R |
| Hypericum elodes | R |
| Juncus acutiflorus | R |
| Juncus bulbosus | R (<1%) |
| Juncus effusus | R |
| Lotus pedunculatus | R (<1%) |
| Myosotis sp. | R |
| Nasturtium officinale s.l. | R |
| Palustriella commutata | O |
| Palustriella falcata | A |
| Philonotis calcarea | F |
| Philonotis fontana | O |
| Potamogeton polygonifolius | R |
| Preissia quadrata | R |
| Prunella vulgaris | R |
| Ranunculus flammula | R |
| Scorpidium cossonii | O |
| Scorpidium scorpioides | R |
| Scorzoneroides autumnalis | R |
| Succisa pratensis | R (<1%) |
| Taraxacum sp. | R |
Vegetation (adjoining spring) Pont Clydach Site 3
Heavily sheep grazed acid grassland to 20 cm height (Nardus stricta, Agrostis capillaris, Potentilla erecta) often associated with quarry spoil and infill associated with repairs to the adjoining road (A4069). The sward has regular patches of Hylocomium splendens, Rhytidiadelphus squarrosus.
| Agrostis capillaris | R |
| Hylocomium splendens | O |
| Hypnum cupressiforme | O |
| Juncus effusus | O |
| Nardus stricta | F |
| Pleurozium schreberi | R |
| Potentilla erecta | R |
| Rhytidiadelphus squarrosus | R |
| Sphagnum inundatum | R |
| Sphagnum subnitens | R |
Condition assessment
The overall assessment is that Pont Clydach (Sites 1–3) should be classified as being in favourable ecological and hydrogeological condition. However, Sites 2 and 3 shown some signs of over grazing and poaching by sheep. In addition, Sites 2 and 3 are situated immediately below the A4069 and have related issues of soil creep, littering and trampling (close proximity of parking place).