Cwm Marydd - the best of Brechfa

Less than 10 minutes' drive from Cwnc y Llwyn is the steep-sided valley of Cwm Marydd (SN5031).  It doesn't look like much on OS maps or aerial photos, but very steep sides, rock outcrops, a series of cascades, relatively old Oak & Ash, and even a mine adit (not marked on any map I've seen) make it a perfect site for bryophytes.  The bryophyte species list stands at 120, and includes Tritomaria exsecta at its only recorded site in VC44, Cephalozia catenulata, Plagiochila exigua, P. punctata, P. spinulosa, Jubula hutchinsiae and Platyhypnidium alopecuroides.  I have visited on 6 occasions before, and spent an hour there this afternoon to stretch my legs during Half Term.

Highlight was locating two trees with Plagiochila exigua alongside a waterfall at SN50383202 and SN50363199: finally getting GPS readings for this, the only known population in Brechfa Forest.  Alongside both were patches of a toothier Plagiochila with scarcely decurrent leaves that I assume is P. punctata, although its non-deciduous leaves and brown colour make me a little suspicious and I need to investigate further [I did and it still looked odd, but I'm certain it's P. punctata, with the non-papillose cuticle ruling out the far-fetched Macaronesian P. stricta].  A lot of staring at Lejeuneaceae failed to reveal anything notable, which was a surprise.

Plagiochila exigua

Interesting Plagiochila punctata with slightly decurrent leaf bases, a brown colouration like P. bifaria, and non-deciduous leaves

Two nice lichens were also present: the pink-fruited Mycobilimbia pilularis (spores checked today) was on an old Ash alongside P. exigua, and the tiny Graphina pauciloculata grew with G. ruiziana on a Hazel (microscope checking needed).  Three patches of a large lichen in the canopy of the Ash need a revisit with a telescope...

Homage in the Hepste

It's nearly 18 years since Graham and I visited Sgwd yr Eira to pay homage to the southernmost British population of Sphenolobopsis pearsonii - found by Martha Newton in 1994 and 'twitched' by us in 1999.  We were glad to see that this Nationally Scarce liverwort is still present on one rockface (we assume it's the same one where Martha found it, though we haven't yet checked), but were worried to see that most of the patch looks moribund.

On our way to the Sphenolobopsis we searched the ravine downstream - where Plagiochila bifaria was present in a classic mist-zone location - and some south-facing cliffs where putative Ctenidium molluscum var robustum (or perhaps var condensatum) grew close to var molluscum and looked convincingly different (if un-nameable).  Nearby there was some Dicranum montanum on a log.

Then we reached Sgwd yr Eira, with its classic walk-behind waterfall and extensive mist zone.  Most Ash trunks were plastered with algae - too humid for anything else perhaps - but eventually we found some Plagiochila exigua at the base of an Ash.  Unlike the small Lejeuneaceae this species lacks propagules, so it's a sure-fire indicator of long-term Atlantic bryophyte richness in the valley.

The first stretch upstream of Sgwd yr Eira was a bit dull, but frequent Anastrophyllum hellerianum on logs and a few patches of Filmy Ferns kept us going until we reached a set of low cascades.  At long last there was some Aphanolejeunea - 30+ patches on a Willow and 1 on a massive boulder - the first record for the Hepste-Mellte catchment.  Careful scrutiny revealed a single shoot of Drepanolejeunea growing alongside one Aphanolejeunea patch, but we couldn't find any more.

Happy with our lot we continued upstream in the fading light, where a yapa (Bolivian word for an added bonus) came in the form of Hygrobiella laxifolia on a riverside rock shelf.  The godfather of south Wales bryology HH Knight found this species in "Hepste Glen" in the early 20th century, but nobody had seen it since.  This was a fitting end to an outstanding final day of our Coedydd Nedd a Mellte survey!

Wonderful Waterfalls Country

The Nedd and Mellte valleys in southern Breconshire have long been known as a bryological hotspot: they are SAC for their Old Sessile Oakwood and Tilio-Acerion habitats and hold many miles of deeply-incised valley woodland.  Over the last 20 years, the valleys have produced many bryological gems, including Aphanolejeunea microscopica new for Glamorgan, Plagiochila exigua new for Breconshire, and the largest known British population of Rhytidiadelphus subpinnatus.  Despite many visits by different people, included a funded bryophyte survey lasting several weeks, there remain several areas with no records of notable species at all: is this because they are dull or just inaccessible?  The visit Graham and I made to an unknown section of the Mellte earlier in the year suggested that hotspots remain undiscovered; a day in the Nedd valley below Glan-yr-afon (SN9009) redoubles that feeling!

This area really is outstandingly rich in oceanic bryophytes, especially in a south Wales context.  Photos of highlights follow:

Aphanolejeunea microscopica - on one slender Ash downstream of the downstream-most major waterfall on this section of the river.  The second record for the SAC and new for Breconshire, following a colony on the Pyrddin in Glamorgan about 1.5 km to the west.

Plagiochila exigua - a large patch on a slender Oak overhanging the river, just downstream of the 2nd major waterfall as I worked my way upstream.  Very clearly associated with mist from the waterfall.  The second record for Breconshire and the SAC, following a colony found by Graham in 2011 on base-rich rocks about 3km to the north.

Plagiochila bifaria - sharing the Oak with P. exigua, where it formed a patch nearly 1m long.  The third record for Breconshire and the SAC, following colonies Graham and I spotted by the Nedd 2km to the north and on dry cliffs above the Mellte earlier this year.

Anastrophyllum hellerianum - on at least 7 Oaks above the 2nd waterfall and on 1 Oak above the 3rd major waterfall as I went upstream.  I looked at many, many other Oaks in the valley and the clustering of Anastrophyllum, Jamesoniella autumnalis and Blepharostoma trichophyllum around these 2 waterfalls was really obvious.

Rhytidiadelphus subpinnatus - 2 colonies seen: 1 on a boundary bank near Glan-yr-afon looked rather scrappy and intermediate, but this 1x1m patch on an Ash bole just above the river was absolutely classic!

Hymenophyllum tunbrigense - an honorary bryophyte that occurs in remarkable abundance in this part of the Nedd valley.  I took GPS readings for at least 20 different patches, most of which were >1x1m in extent.  Plagiochila spinulosa was alongside most of them.

A mystery liverwort - this is probably Kurzia trichoclados on humus on a Hymenophyllum crag, but it was very glistening and looks 'wrong'.  It is possible that this could be Telaranea europaea... annoyingly my compound microscope has bust, so I can't be sure.  If it is 'just' the Kurzia then it is new for Breconshire and the SAC, but if my dreams came through it would be the 3rd British record of the Telaranea!

There are still several completely unknown sections of the SAC and I have no doubt that more rare bryophytes await discovery.  Graham and I will be writing a report covering the bryophyte interest of the SAC this winter, which will help identify the gaps and should prompt a couple more expeditions.