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.