Thursday, 22 September 2016

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.


  1. Excellent. The red highlighted area is exactly where I saw the Riccia, though there is probably more of it by now than when I was there a few weeks ago. Incidentally we didn't catch Portland Moth there - Paul had one in the petalwort slack and another nearer the car park.

  2. Thanks George. I think a Portland moth session should be arranged for next year. I'll book to set my taps in this area as this patch looks like it should have P.M. ;-)

  3. I'm glad you've finally caught up with Petalwort, Barry! I have seen similar Bryum to that at Pembrey, but never such a well-grown patch. Yours looks a good candidate for B dyffrynense, but mine never passed muster. Good luck!

  4. Yes, I was thrilled to finally catch up with it and have both Emma and Duncan for getting me there! It was bigger than I expected, but more helpful was seeing the habitat it's found in, which will make me rethink where to search more intensively. Can you pass on David's email please as I'm suspecting the one on the BBS website is no longer in use?