Waterfalls in the Gwaun Valley

I was in the Gwaun Valley before the harsh easterlies set in, doing some bryophyte survey for NRW. Pembrokeshire's not renowned for its waterfalls, but the steep streams of Dwfr Ddisgynfa, Cwm Du were nicely swollen. Heading upstream in waders, I found a good fruiting population of Dicranella subulata on an erosion scar created by a large beech tree which had slid into the river. This is still a rare moss in the county, but now known from three more places than the one location on the top of Preseli where Sam found it. There was a bit of Ditrichum heteromallum mixed into the small sample that I collected, which I probably wouldn't have picked out if it hadn't been fruiting.

Dicranella subulata dominates the bank here

The next section of bank had water pouring in from the wet woodland to the side, and was lined with Jubula hutchinsiae. The population here is quite large for Pembrokeshire, and some of it had sporophytes which I hadn't seen before (Sam didn't find fruiting plants during recording for his flora). I couldn't find any less common oceanic species mixed in with it, but there was some Sphagnum quinquefarium, Fissidens curnovii and Dichodontium cf. pellucidum. 

Jubula habitat

Further up, I managed to get to a promising crag next to the main waterfall which had enough spray in the area to remind me of a trip up the Rheidol with Tom in the autumn. A Trichostomum in very small quantity on the rock face here was somewhat reminiscent of the Trichostomum (Oxystegus) hibernicum that we saw that day. Tom's compared stem sections against material from Devil's Bridge and found it to have an extra zone of cells between the thin-walled medullary cells and the thick-walled cortical ones. He found the medulla proper to have 20 - 25 cells, which would place it near T. hibernicum. The leaf sheaths aren't inflated enough though, so it's Trichostomum tenuirostre var. holtii. There were also a few small shoots of Philonotis arnellii on the rock here, some Jungermannia pumila and a good sheet of Palustriella commutata. Metzgeria conjugata was on a trunk across the stream, whilst rocky ground nearby had Odontoschisma denudatum and Bazzania trilobata.

Main waterfall section

Fortunately this stream had escaped the fate of the neighbouring one to the north, which was thick with sewage fungus from a presumed recent pollution episode, not so many eyes in the countryside at the moment are there? Duly reported and quickly acted on. Lets hope the imminent new WG legislation actually makes a difference to this kind of thing.....

Not many bryophytes here