Thursday, 29 January 2015

Cefn Onn

On Sunday morning I took a quick stomp from Parc Cefn Onn up to the old limestone quarry on the ridgeway north of Cardiff. Virtually the whole walk fell within tetrad ST18S, which must be one of the richest for bryophytes in south-east Glamorgan - a mixture of wooded country park, acid woodland on the lower slopes and limestone woodland and exposed outcrops at the ridgetop. I had a cursory look at the bryos back in 2011, and a few others (including Peter Sturgess, who's now signed up to this blog - hello Peter!)  have done some recording too, but it's never had a thorough survey. There's also some conifer plantation within the same tetrad, on the Caerphilly side of the ridgeway, which hasn't been looked at.

The wooded limestone outcrops below the quarry support some impressive carpets of Anomodon viticulosus (see photo above), plenty of Neckera crispa and Tortella tortuosa, and smaller quantities of Eucladium verticillatum and Cirriphyllum crassinervium.
Neckera crispa
The quarry itself looked fairly horrific on first impression - it was being used for overwintering cattle and you can see the effect this has had in the photo below.

The quarry sides were undamaged, however, and produced a good range of calcicoles including Aloina aloides (fruiting), Ditrichum gracile and Trichostomum crispulum.
Ditrichum gracile
An area of short limestone turf above the quarry produced Brachythecium glareosum, Campylium protensum, Rhytidiadelphus triquetrus and, more surprisingly, a small patch of Hylocomium splendens (presumably in an area that has been leached).

Finally, an area of hilltop limestone outcrops to the west of the quarry (photo below) added Pseudocrossidium revolutum as well as more Ditrichum gracile. I found Dicranum bonjeanii in this area in 2011 but couldn't relocate it on Sunday.

Thanks to Peter Sturgess for suggesting the ID of Ditrichum gracile, which he'd found in the same area. I was put off the scent by the small size of the patches at Cefn Onn (only 2cm tall), but am pretty sure this is what they are.


  1. I agree that is likely to be Ditrichum gracile; I'll post a couple of pics of D flexicaule soon.

  2. Thanks Sam, and for posting the pics of flexicaule. There were quite a few patches of Ditrichum at Cefn Onn, all lacked the short-leaved shoots and were quite wavy when dry. Under the microscope, the leaf margins towards the base of the leaf had hyaline cells - listed as a distinguishing feature in Smith though it sounds from what you say like differences between this pair are not always clear cut.

  3. Very nice selection of habitats and species George.

  4. Very nice selection of habitats and species George.