Upper reaches of the Afon Tywi

The rocky upper reaches of Afon Tywi, north of Lynn Brianne, couldn't be more different from the lowland, meandering section of the river with which I'm familiar from winter Brown Hairstreak egg surveys.

 

A couple of weekends ago we stayed a night at Dolgoch Hostel in Ceredigion, just a field away from the Tywi (which here forms the boundary between VC46 and VC42). Sam had provided me with a list of rare bryos to look out for, and though I failed to find any of these there was still plenty of interest - for me at least. Most notable, perhaps, was the abundance of Atrichum crispum, here growing on the thin soil layer on top of large river boulders.

I was also impressed by the quantity of Andraea rothii ssp falcata on the in-channel rocks, sometimes growing not far above the water level. A small patch of the lichen Lasallia pustulata (please correct my ID if wrong!) was growing in the same habitat.

The river itself was full of great wefts of Fontinalis squamosa, and Oligotrichum hercynicum was frequent on steep gravelly banks.

I'm a little puzzled by this falcate Campylopus, which had the nerve filling about a third of the leaf base. It might just be C. flexuosus, but is almost lacking in tomentum and doesn't have any obvious coloured cells in the basal angles of the leaf.

Sam tells me this part of the Tywi has been little studied bryologically. It surely warrants a proper look.