Marvellous Merthyr Mawr

Prior to undertaking a search of the scraped slack habitats at this beautiful NNR, Sam's NRW colleagues, Duncan Ludlow and Emma Brown kindly showed me one of the known Petalophyllum ralfsii colonies at Merthyr Mawr yesterday, plus we also visited the spot where George made his nocturnal observation a week or two back. Given the very dry conditions at these locations, I was pleasantly surprised by how large and verdant the Petalophyllum plants were.

We also looked at one of this year's Portland Moth locations, where George recently discovered Riccia cavernosa and we estimated there must have been a few thousand small rosettes developing. As far as I'm aware this is a new species for the reserve. The largest specimens we could find are depicted below, but most were much smaller. Given the right conditions, there could be quite a display here. Duncan informed me that this area has been subjected to some scrub clearance work and its use as a bridleway stopped, so the occurrence of the moth and the liverwort highlights at least two significant benefits of the work and controls implemented here. I've marked the extent of the Riccia colony on the photo below.

Unfortunately there was no Petallophyllum or Riccia to be found in the two scraped areas I examined, though the larger slack is at a very early stage of colonisation and was well populated with non-fruiting Bryum species. In addition to frequent dichotomum and argenteum and occasional gemmiferum, there were patches of putative dyffrynense (photo below), which may be worth sending off to David Holyoak? At least two other Bryum leaf forms were present, so a site well worth revisiting as succession takes place...

...PS. does anyone know what causes these rings in the wet sand? I'm guessing it's fungal, but I never collected any to look under the miscroscope.