Y Glyn-diffwys

Site of Special Scientific Interest · 52.9864, -3.5012

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Also within

Clwyd County

Habitats

Bracken scrub

Geology & landscape

Geological Feature: Gorge / Ravine · Geological Period: Ordovician

Landscape processes: Fluvial

Description

Description This site is notified as an example of a semi-natural ancient broadleaved woodland situated in the steeply incised section of the Afon Ceirw. Such wooded sections are rare in the former county of Clwyd. The woodland which occurs on acidic Ordovician rocks, has a canopy dominated by native tree species. Sessile oak Quercus petraea together with wych elm Ulmus glabra and less commonly ash Fraxinus excelsior are the principal species. The well-developed shrub layer is characterised by hazel Corylus avellana. The field layer is variable, reflecting the different steepness, aspect and soil conditions in the gorge. On the north side of the gorge, dog's mercury Mercurialis perennis, bluebell Hyacinthoides non-scripta, bramble Rubus fruticosus and ramsons Allium ursinum occur whilst to the south, ferns including several Dryopteris species are widespread together with bracken Pteridium aquilinum. Ericaceous shrubs are locally present. The gorge itself is singularly the most important feature supporting a number of uncommon higher plant and fern species including national rarities together with several species of Atlantic bryophytes. Atlantic bryophyte assemblages tend to be uncommon in Clwyd woodlands because of the lower rainfall and hence humidity. Important bryophyte species include the liverworts Porella pinnata and Plagiochila spinulosa together with the mosses Isothecium holtii and Hypnum callichroum.

Species mentioned

English name
search for this in other sites		 Latin name
search with Google		 IUCN / Red List Type Family
bracken Pteridium aquilinum LC fern dennstaedtiaceae
ramson Allium ursinum LC herb liliaceae
bluebell Hyacinthoides non-scripta LC herb liliaceae
dog's mercury Mercurialis perennis LC herb euphorbiaceae
bramble Rubus fruticosus LC herb rosaceae
prickly featherwort Plagiochila spinulosa LC liverwort jungermanniales
pinnate scalewort Porella pinnata LC liverwort jungermanniales
downy plait moss Hypnum callichroum Not listed in GB list moss hypnales
Holt's mouse-tail moss Isothecium holtii LC moss hypnales
hazel Corylus avellana LC tree corylaceae
ash Fraxinus excelsior LC tree oleaceae
sessile or durmast oak Quercus petraea LC tree fagaceae
wych elm Ulmus glabra LC tree ulmaceae

Plant communities

W25 — Bracken scrub

Pteridium aquilinum-Rubus fruticosus underscrub

Hedera helix, Acer pseudoplatanus, Fagus sylvatica, Quercus robur, Fraxinus excelsior, Sambucus nigra, Ulex europaeus, Crataegus monogyna, Prunus spinosa, Luzula multiflora, Mnium hornum, Brachythecium rutabulum, Kindbergia praelonga, Angelica sylvestris, Conopodium majus, Heracleum sphondylium, Arum maculatum, Cirsium arvense, Lonicera periclymenum, Silene dioica, Stellaria holostea, Mercurialis perennis, Geranium robertianum, Glechoma hederacea, Teucrium scorodonia, Hyacinthoides non-scripta, Chamerion angustifolium, Circaea lutetiana, Digitalis purpurea, Rumex acetosa, Anemone nemorosa, Ficaria verna, Potentilla erecta, Rosa arvensis, Rosa canina, Rubus fruticosus agg., Rubus idaeus, Galium aparine, Galium mollugo sens.lat., Galium saxatile, Urtica dioica, Viola riviniana, Agrostis capillaris, Anthoxanthum odoratum, Arrhenatherum elatius, Dactylis glomerata, Festuca rubra, Holcus lanatus, Holcus mollis, Poa trivialis, Pteridium aquilinum, Dryopteris dilatata, Dryopteris filix-mas