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.

Humid dune slack at Kenfig NNR

dune slack vegetation supporting Drepanocladus sendtneri, overtopped by Salix repens and Carex nigra tussocks

The small slack south of the bird hide floods quite deep (~80cm) during the winter, although yesterday it was bone dry. The composition and structure of higher and lower plants in this slack is very different to that found in the scraped slacks across the reserve, in fact I have been surprised by the range of vegetation variation there is between slacks at Kenfig. Interestingly, the most abundant bryophyte species in the western half of the slack I was looking at yesterday (in compartment 4a) was Fontinalis antipyretica (four photos below). In places it replaced Calliergonella cuspidata as the dominant underscrub species, forming thick wefts beneath Salix repens scrub, as-well-as carpeting areas of open ground and growing as pendant drapes off the lower limbs and trunks of Salix cinerea. I can see Sam noted similar growths in nearby slacks too, but it's the first time that I have encountered it as a major component of slack vegetation.

 

More significant vegetation in the slack included some good patches of Drepanocladus sendtneri (at SS79628103 - top photo - and SS79568102), which are to be safeguarded from proposals to rejuvenate parts of the slack. A robust form of D. aduncus was also frequent in the slack and some some material seemed indeterminate to my eye, even after examining it under the microscope.

D. sendtneri

Miscellaneous observations of less the familiar taxa included Puccinia cancellata on Juncus acutus and Tuberolachnus salignus (Large Grey Willow Aphid) noted crawling around the lower limbs of Salix cinerea.