Exposed Crags and Scree (usually above the line of enclosure)

Upland crags and scree in West Glamorgan are mostly confined to the higher ground of the South Wales Coalfield in Neath Port Talbot where the predominant exposed rock is Pennant Sandstone. Large amounts of scree often accumulate below old, disused sandstone quarries where the large siliceous boulders become populated with acid loving crustose lichens, particularly species of Stereocaulon, Porpidia, Lithophila and Rhizocarpon. Mosses like Andreaea rothii subsp. falcata, Racomitrium lanuginosum, Racomitrium fasciculare and Ptychomitrium polyphyllum are ubiquitous in these habitats.  

At the head of Vale of Neath, the ground rises to 600m above sea level, the highest point in Glamorgan. Here, the Rhigos Mountain road climbs along the boundary between West Glamorgan and Rhondda Cynon Taff to reveal the dramatic Pennant Sandstone escarpment of Craig y Llyn. Part of the scarp lies in Rhondda Cynon Taff, but a large portion which partly encloses the lake named Llyn Fach is in West Glamorgan. The north-facing cliff face is cool and moist even in summer and it supports an assemblage of bryophytes and vascular plants with northern (boreal-montane) and arctic-alpine affinities, many of which are rare or absent elsewhere in the county. The rocky scree that has accumulated below the cliffs has Fir Clubmoss (Huperzia selago) and Polytrichum alpinum plus all the mosses and lichens mentioned above. But the cliffs above support a much more diverse flora that includes a number of uncommon fern species e.g. Wilson's Filmy-fern (Hymenophyllum wilsonii), Mountain Male-fern (Dryopteris oreades), Brittle Bladder-fern (Cystopteris fragilis), Oak Fern (Gymnocarpium dryopteris) and Beech Fern (Phegopteris connectilis). Amoung the long list of significant upland and montane bryophytes found here are the mosses Andreaea rupestris, Anoectangium aestivum, Blindia acuta, Bartramia ithyphylla, Entoshodon obtusus, Isopterygiopsis pulchella, Orthothecium intricatum, Pohlia elongata, Pohlia flexuosa and Seligeria incurvata with Barbilophozia floerkii and Saccogyne viticulosa amoung the more conspicuous liverworts.

Of the notable flowering plants that have been recorded on Craig y Llyn in the past are Stone Bramble (Rubus saxatilis), Cowberry (Vaccinium vitis-idaeus) and Serrated Wintergreen (Orthilia secunda), but none of these have been found there in recent decades. However, Cowberry has been recorded recently on the north-facing outcrop of Craig y Pant which lies a short distance further west of Craig y Llyn. Rock Stonecrop (Sedum forsteranum) was last recorded at Craig y Llyn in 1890, but Roseroot (Sedum rosea), a notable arctic-alpine species, still occurs in reasonable amounts on the cliffs above Llyn Fawr, which is just outside the West Glamorgan border.

Exposed, north-facing crags like Craig y Llyn are rare in West Glamorgan but investigation of smaller, upland outcrops can be rewarding. For example, a recent exploration of a small sandstone outcrop above Cymmer in the Afan Valley revealed populations of Babilophozia floerkii, Barbilophozia attenuata, Lophozia sudetica and Isopterygiopsis pulchella.