Gro Ystwyth

Site of Special Scientific Interest · 52.3349, -3.9142

Open in the interactive map →

Also within

Dyfed County

Climate exposure

This is about exposure to a nationwide pressure this habitat type carries — not a verdict on this site's own management.

Coastal

Coastal habitats are exposed to sea-level rise and storm erosion. Where hard sea defences sit behind them, there's nowhere landward to retreat to — a squeeze that keeps compressing the habitat no matter how well it's managed.

Habitats

Coastal vegetated shingle, Fast flowing river and stream, Mixed scrub, Montane scrub

Geology & landscape

Landscape processes: Coastal, Fluvial

Description

Description Gro Ystwyth is of special interest for both its fluvial geomorphological and biological features. The site comprises six discrete areas along the middle and upper reaches of the Afon Ystwyth, the largest of which is 2 km west of Pontrhydygroes and known as Grogwynion. This area contains a particularly fine example of an actively braiding river system, a feature which is now quite rare in Wales. Throughout the site, the alluvial deposits on the valley floor support a mosaic of riverside habitats, including rare ‘shingle heath’ communities which are known from only one other river in England and Wales. A rich and unique assemblage of lichens is found at Grogwynion, including species associated with metal-rich habitats. Fluvial Morphology The reach of the Afon Ystwyth at Grogwynion is one of the finest examples of an actively braiding river in Wales and is important for studies of processes and form in gravel-bed rivers. Changes in planform have been reconstructed over the last hundred years, during which time the river has moved across the valley floor creating a series of abandoned chutes. This pattern of behaviour may reflect the high toxicity of the sediments, associated with past mining activity, impeding vegetation development and, therefore, bank stability, rather than the input of coarse sediment to the system. Recent studies have shown rapid contemporary change in the channel section in response to high magnitude floods. Biology Lateral movement of the river channel has led to the deposition of shingle and finer sediments on which has developed a mosaic of habitats, ranging from unstable shingle beach communities to grassland, heathland and scrub. The vegetation communities tend to occur in bands, reflecting the presence of a series of shingle ridges and depressions underlain by sediments of varying grain size. The ecological setting and types of heathland communities which have developed on the shingle of the rivers Rheidol and Ystwyth are highly distinctive and very unusual in southern Britain; the only known examples showing any close similarity are found in central and northern Scotland. Grogwynion has the largest area of such communities in England and Wales. They are characterised by the presence of heather Calluna vulgaris, with wavy hair-grass Deschampsia flexuosa, purple moor-grass Molinia caerulea, sheep’s-fescue Festuca ovina, and sheep’s-bit Jasione montana. In the more grassy areas, common bent Agrostis capillaris is frequent and sheep’s sorrel Rumex acetosella is common on less stable shingle banks. The metal-tolerant sea campion Silene uniflora is an unusual feature of the communities. Some of these heathland communities include an extensive cover of mosses and lichens, with mounds of Pleurozium schreberi moss and prominent clumps of Cladonia lichens. At Grogwynion, the lichens include the uncommon C. fragilissima and C. uncialis ssp. uncialis. The latter is rare in Scotland and unknown elsewhere in Britain south of the Scottish border. Lichen species which are normally montane, such as Stereocaulon condensatum and Epilichen scabrosus [LF], are present at low altitudes on these river gravels and contribute to making this lichen assemblage unique. Parts of the now abandoned Grogwynion and Gwaithgoch metal mines are included in the site. On the abandoned spoil heaps and remains of buildings there has developed a rich metallophyte lichen flora, including a number of nationally scarce species such as Vezdaea acicularis, Gyalidea subscutellaris and Thelocarpon impressellum. Tree regeneration on the flood plain is probably restricted by the nutrient-poor, porous substrate and the high concentrations of heavy metals which have resulted from past mining activity. Gorse Ulex europaeus is common, and in places forms thick bands of scrub, with occasional western gorse Ulex gallii. Damp scrub-woodland of grey willow Salix cinerea has developed in places alongside backwaters, the latter dominated in parts by broad-leaved pondweed Potamogeton natans and floating sweet-grass Glyceria fluitans. Large areas of marshy grassland dominated by purple moor-grass occur where drainage is impeded, such as in areas of fine silt, and there are patches of great wood-rush Luzula sylvatica. Large areas of unstable river shingle at Grogwynion support a number of nationally scarce species of beetle, including the five-spot ladybird Coccinella quinquepunctata. Frequent signs of otter activity can be found at the site. Remarks: The majority of Grogwynion is managed as a nature reserve by the Wildlife Trust West Wales. Otter is listed in Schedule 5 of the Wildlife and Countryside Act 1981 (as amended) and in Annexes II and IV of the European Council Directive 92/43/EEC on the conservation of Natural Habitats and of Wild Fauna and Flora.

Species mentioned

English name
search for this in other sites		 Latin name
search with Google		 IUCN / Red List Type Family
ladybird Scymus schmidti Not listed in GB list beetle ladybird coccinellidae
5 spot ladybird Coccinella quinquepunctata Not listed in GB list beetle ladybirds coccinellidae
Phalacrocorax aristotelis Not listed in GB list bird phalacrocoracidae
common bent Agrostis capillaris LC grass poaceae
wavy hair grass Deschampsia flexuosa Not listed in GB list grass poaceae
sheep's fescue Festuca ovina LC grass poaceae
floating sweet grass Glyceria fluitans LC grass poaceae
purple moor grass Molinia caerulea LC grass poaceae
sheep's bit Jasione montana VU herb campanulaceae
broadleaved pondweed Potamogeton natans LC herb potamogetonaceae
sheep's sorrel Rumex acetosella NT herb polygonaceae
sea campion Silene uniflora LC herb carophyllaceae
rugged-shielded sulphur lichen Epilichen scabrosus [LF] Not listed in GB list lichen no common name
lichen Vezdaea acicularis LC lichen vezdaeaceae
red stemmed feather moss Pleurozium schreberi LC moss hypnales
great wood rush Luzula sylvatica LC rush juncaceae
gorse Ulex europaeus LC shrub leguminosae
western gorse Ulex gallii LC shrub leguminosae
bell heather or ling Calluna vulgaris NT shrub dwarf ericaceae
grey willow Salix cinerea LC tree shrub salicaceae

Plant communities

A9 — Fast flowing river and stream, Marginal and inundation, Pond ditch and canal, Sluggish river and stream

Potamogeton natans community

Schoenoplectus lacustris, Juncus bulbosus, Sparganium angustifolium, Sparganium erectum, Sparganium minimum, Alisma plantago-aquatica, Lobelia dortmanna, Equisetum fluviatile, Myriophyllum alterniflorum, Elodea canadensis, Lemna minor, Lemna trisulca, Nymphaea alba, Callitriche platycarpa, Callitriche stagnalis, Littorella uniflora, Potamogeton natans, Ranunculus trichophyllus, Glyceria fluitans, Chara subspinosa

A14 — Fast flowing river and stream

Myriophyllum alterniflorum community

Isolepis fluitans, Juncus bulbosus, Fontinalis antipyretica, Lobelia dortmanna, Equisetum fluviatile, Myriophyllum alterniflorum, Lemna minor, Callitriche stagnalis, Littorella uniflora, Potamogeton filiformis, Potamogeton gramineus, Potamogeton natans, Ranunculus peltatus, Chara spp., Nitella hyalina

A17 — Chalk river and stream, Fast flowing river and stream

Ranunculus penicillatus ssp. pseudofluitans community

Berula erecta, Nasturtium officinale, Elodea canadensis, Lemna minor, Callitriche stagnalis, Veronica beccabunga, Polygonum amphibium, Polygonum hydropiper, Potamogeton crispus, Potamogeton pectinatus, Ranunculus penicillatus ssp. pseudofluitans

A18 — Fast flowing river and stream

Ranunculus fluitans community

Fontinalis antipyretica, Fontinalis squamosa var. curnowii, Myriophyllum alterniflorum, Myriophyllum spicatum, Elodea canadensis, Mentha aquatica, Lemna gibba, Lemna minor, Potamogeton perfoliatus, Ranunculus fluitans, Glyceria fluitans, Phalaris arundinacea

MC6 — Coastal vegetated shingle, Hard cliff and cliff slope

Atriplex prostrata-Beta vulgaris ssp. maritima sea-bird cliff community

Daucus carota, Sonchus oleraceus, Taraxacum officianalis, Tripleurospermum maritimum, Cochlearia officinalis, Silene uniflora, Spergularia rupicola, Atriplex hastata, Malva arborea, Plantago coronopus, Armeria maritima, Polygonum aviculare, Rumex crispus, Bromus hordeaceous, Catapodium marinum, Dactylis glomerata, Festuca rubra

SD1 — Coastal vegetated shingle, Sand dune

Rumex crispus-Glaucium flavum shingle community

Solanum dulcamara, Crithmum maritimum, Cirsium arvense, Cirsium vulgare, Helminthotheca echioides, Hypochaeris radicata, Jacobaea vulgaris, Lactuca serriola, Leontodon saxatilis, Senecio viscosus, Sonchus arvensis, Sonchus asper, Tripleurospermum maritimum, Crambe maritima, Cerastium fontanum, Honckenya peploides, Sagina apetala, Silene uniflora, Atriplex prostrata, Sedum acre, Euphorbia paralias, Lathyrus japonicus, Geranium robertianum, Glaucium flavum, Plantago coronopus, Plantago lanceolata, Rumex crispus, Potentilla anserina, Ammophila arenaria, Arrhenatherum elatius, Elytrigia atherica, Elytrigia juncea, Festuca rubra, Holcus lanatus, Lolium perenne

SD2 — Coastal vegetated shingle, Sand dune

Honkenya peploides-Cakile maritima strandline community

Salsola kali, Achillea millefolium, Cirsium arvense, Eryngium maritimum, Hypochaeris radicata, Senecio vulgaris, Sonchus arvensis, Tripleurospermum maritimum, Cakile maritima, Cerastium diffusum, Honckenya peploides, Silene uniflora, Stellaria media agg., Atriplex glabriuscula, Atriplex laciniata, Atriplex littoralis, Atriplex patula, Atriplex prostrata, Sedum acre, Polygonum oxyspermum subsp. Raii, Rumex crispus, Potentilla anserina, Agrostis stolonifera, Ammophila arenaria, Arrhenatherum elatius, Elytrigia juncea, Elytrigia repens, Festuca rubra, Leymus arenarius, Poa annua

SD3 — Coastal vegetated shingle, Sand dune

Matricaria maritima-Galium aparine strandline community

Bolboschoenus maritimus, Juncus bufonius, Juncus gerardii, Ligusticum scoticum, Matricaria discoidea, Sonchus arvensis, Sonchus asper, Tripleurospermum maritimum, Mertensia maritima, Cakile maritima, Cochlearia officinalis, Honckenya peploides, Stellaria media agg., Atriplex glabriuscula, Atriplex patula, Atriplex prostrata, Triglochin maritimum, Plantago maritima, Armeria maritima, Rumex crispus, Glaux maritima, Galium aparine, Agrostis stolonifera, Elytrigia repens, Festuca rubra, Holcus lanatus, Leymus arenarius, Poa annua

W20 — Montane scrub

Salix lapponum-Luzula sylvatica scrub

Salix arbuscula, Salix cinerea, Salix lapponum, Salix myrsinites, Salix phylicifolia, Salix reticulata, Empetrum nigrum, Calluna vulgaris, Salix lanata, Vaccinium myrtillus, Vaccinium uliginosum, Carex atrata, Carex bigelowii, Carex binervis, Carex flacca, Luzula multiflora, Luzula sylvatica, Huperzia selago, Selaginella selaginoides, Aulacomnium palustre, Mnium hornum, Philonotis fontana, Plagiomnium undulatum, Rhizomnium punctatum, Dicranum bonjeanii, Dicranum majus, Dicranum scoparium, Fissidens adianthoides, Racomitrium lanuginosum, Calliergonell cuspidatum, Ctenidium molluscum, Hylocomium splendens, Hypnum callichroum, Hypnum cupressiforme, Palustriella commutatum, Plagiothecium denticulatum, Plagiothecium undulatum, Pleurozium schreberi, Ptilium crista-castrensis, Rhytidiadelphus loreus, Rhytidiadelphus squarrosus, Rhytidiadelphus triquetrus, Sanionia uncinata, Scorpidium revolvens, Thuidium tamariscinum, Atrichum undulatum, Polytrichastrum alpinum, Sphagnum capillifolium, Sphagnum fallax, Sphagnum girgensohnii, Sphagnum palustre, Sphagnum russowii, Sphagnum squarrosum, Sphagnum subnitens, Sphagnum teres, Barbilophozia barbata, Chiloscyphus polyanthos, Diplophyllum albicans, Lophocolea bidentata, Plagiochila porelloides, Ptilidium ciliare, Scapania undulata, Cladonia squamosa, Peltigera canina, Angelica sylvestris, Caltha palustris, Hieraclium spp., Saussurea alpina, Solidago virgaurea, Campanula rotundifolia, Succisa pratensis, Valeriana officinalis, Rhodiola rosea, Vaccinium vitis-idaea, Thymus praecox, Epilobium anagallidifolium, Dactylorhiza viridis, Euphrasia officinalis, Rhinanthus minor, Oxalis acetosella, Oxyria digyna, Polygonum viviparum, Rumex acetosa, Anemone nemorosa, Ranunculus acris, Thalictrum alpinum, Alchemilla alpina, Alchemilla glabra, Filipendula ulmaria, Geum rivale, Galium boreale, Galium saxatile, Saxifraga aizoides, Saxifraga hypnoides, Saxifraga oppositifolia, Saxifraga stellaris, Viola riviniana, Agrostis canina, Agrostis capillaris, Anthoxanthum odoratum, Deschampsia cespitosa, Deschampsia flexuosa, Festuca ovina, Festuca rubra, Nardus stricta, Dryopteris dilatata, Phegopteris connectilis

W21 — Hedgerow scrub, Mixed scrub

Crataegus monogyna-Hedera helix scrub

Hedera helix, Salix cinerea, Acer pseudoplatanus, Ilex aquifolium, Betula pendula, Corylus avellana, Fagus sylvatica, Quercus robur, Fraxinus excelsior, Malus sylvestris, Sorbus aria, Taxus baccata, Ulmus glabra, Ulmus procera, Sambucus nigra, Viburnum lantana, Euonymus europaeus, Cornus sanguinea, Juniperus communis, Ligustrum vulgare, Clematis vitalba, Rhamnus cathartica, Crataegus laevigata, Crataegus monogyna, Prunus spinosa, Juncus effusus, Plagiomnium undulatum, Brachythecium rutabulum, Kindbergia praelonga, Rhynchostegium confertum, Tamus communis, Heracleum sphondylium, Torilis japonica, Arum maculatum, Arctium minus, Cirsium arvense, Lonicera periclymenum, Moehringia trinervia, Silene dioica, Stellaria graminea, Stellaria holostea, Stellaria media agg., Calystegia sepium, Mercurialis perennis, Geranium robertianum, Iris foetidissima, Glechoma hederacea, Lamium purpureum, Origanum vulgare, Stachys sylvatica, Teucrium scorodonia, Allium ursinum, Hyacinthoides non-scripta, Circaea lutetiana, Rumex sanguineus, Anemone nemorosa, Ranunculus repens, Fragaria vesca, Geum urbanum, Potentilla sterilis, Poterium sanguisorba, Rosa arvensis, Rosa canina, Rubia peregrina, Rubus fruticosus agg., Galium aparine, Urtica dioica, Viola riviniana, Anisantha sterilis, Arrhenatherum elatius, Brachypodium pinnatum, Brachypodium sylvaticum, Bromopsis erecta, Dactylis glomerata, Elytrigia repens, Holcus lanatus, Holcus mollis, Poa trivialis, Asplenium scolopendrium, Pteridium aquilinum, Dryopteris filix-mas

W22 — Hedgerow scrub, Mixed scrub

Prunus spinosa-Rubus fruticosus scrub

Hedera helix, Acer campestre, Corylus avellana, Ulex europaeus, Prunus spinosa, Plagiomnium undulatum, Brachythecium rutabulum, Eurhynchium striatum, Kindbergia praelonga, Thuidium tamariscinum, Atrichum undulatum, Lophocolea bidentata, Achillea millefolium, Cardamine flexuosa, Lonicera periclymenum, Moehringia trinervia, Silene dioica, Silene uniflora, Stellaria media agg., Mercurialis perennis, Geranium robertianum, Stachys sylvatica, Teucrium scorodonia, Hyacinthoides non-scripta, Oxalis acetosella, Digitalis purpurea, Plantago lanceolata, Veronica chamaedrys, Armeria maritima, Rumex acetosa, Filipendula ulmaria, Geum urbanum, Rosa canina, Rubus fruticosus agg., Rubus idaeus, Galium aparine, Urtica dioica, Viola riviniana, Agrostis capillaris, Brachypodium sylvaticum, Dactylis glomerata, Festuca rubra, Holcus lanatus, Holcus mollis, Poa trivialis, Asplenium scolopendrium, Pteridium aquilinum, Dryopteris borreri, Dryopteris filix-mas