More around St David's

Almost any patch of clay ground appears to hold Ephemerum crassinervium ssp. sessile 

It's hard to believe that Ephemerum crassinervium ssp. sessile is Nationally Scarce, or that Bosanquet (2010) only listed two Pembrokeshire sites for it. Perhaps it's having a good year, but there are dozens of patches of it in any open clay ground in grassland, heath and pond edge on sites around St David's. It's often accompanied by Ephemerum stoloniferum, and sometimes closely admixed, but it can be reliably picked out by the longer, narrower perichaetel leaves even before a hand-lens reveals a nerve.

Another species apparently gaining ground is the Nationally Rare Acaulon mediterraneum, with a new site - the fourth in the county - found on St David's Airfield. This is the first that's not on an exposed headland, and in the same open clay patches as the Ephemerum.  In contrast, the Acaulon quickly colonising the new heathland creation field nearby was muticum.

After finding Cephaloziella integerrima new to the St David's area on the airfield heaths last week, checking the gemmae on various samples turned up another patch on the northern side of the runway. This one was in similar open clay / subsoil and also shaded by a gorse bush (a feature noted on a couple of Cornish records too). I also found a third population on a pile of clay-rich subsoil in Middle Mill Quarry near Solva.

Cephaloziella integerrima location, Waun Llechell

Acaulon mediterraneum spores

On the Bug Farm at Harglodd-isaf, a streamside boulder in rough pasture held a patch of Grimmia laevigata, like the Acaulon mediterraneum only otherwise known in the county from exposed coastal slopes. A good find here was a non-fruiting Physcomitrium in a recently created winter-wet scrape, which appears to be Physcomitrium sphaericum under the microscope. I would have expected the first county record of this to come from the reservoir at Llys y Fran, but it illustrates how good these things are at dispersing. 

Grimmia laevigata

apparent Physcomitrium sphaericum and habitat

 St David's Commons

Middle Pond on Dowrog Common

Thanks to Sarah Beynon at the Bug Farm, I've just started some work surveying commons and some associated land near St David's. Only two days in, but already some surprises.....

I'll confess I wasn't expecting much from Dowrog Common, as under-grazing has left much of it as a sea of rank heath and moor-grass pasture. Pleasing then to find Cladopodiella francisci by a cattle path near the northern fenceline, and some Ephemerum crassinervium ssp. sessile on the stone track to Trefadog. Both are Nationally Scarce - the latter is proving to be almost predictable in the right damp habitats in the county, but the former is only known from single locations on Carn Ingli and Mynydd Preseli.

The star find on Dowrog was a good population of Micromitrium tenerum on the dried-up bed of an ancient clay pit, 'Centre Pond', on the north side of the road. 'Turfs' of this tiny moss, complete with ripening capsules, dominate the silty-clay centre, and smaller patches are interspersed with Juncus bulbosus around this. It is absent from the Scirpus fluitans dominated fringe.  The only associated bryophyte is a small amount of Pseudephemerum nitidum. This represents the only extant Welsh population of this red-listed moss, the two tiny patches recorded at Wyndrush Pastures SSSI a couple of years ago having proved to be a transient occurrence from a long-buried spore bank. The several square metres occupied here may perhaps represent the strongest UK population. There are plenty of other ponds on Dowrog, but all appear to either be overly-trampled clay, or too strongly vegetated. It will be important to maintain the right grazing levels here, and to resist over-deepening or other works. Australian Swamp Stonecrop Crassula helmsii is now rife on parts of the nearby St David's Airfield Heaths, so poses a real threat here too. 

Millimetre Moss - Micromitrium tenerum

Over on the Airfield Heaths, I had no luck refinding the Drepanocladus sendtneri in the small fen-hollow on Waun Llandruidion, although the associates originally noted by Sam Bosanquet (Calliergon giganteum, Scorpidium scorpioides and Scorpidium cossonii) are still present under the Carex lasiocarpa. A small patch of open clay below a gorse bush on an old causeway around Waun Llechell held a tiny patch of Cephaloziella integerrima, which represents a third Welsh site for this rare liverwort, only recently found new to Pembs on the Castlemartin range. The biggest surprise, however, came from the edge of the limestone chip path a few metres away. Growing with Aloina aloides and common ruderal species such as Barbula unguiculata, Pseudocrossidium hornschuchianum and Bryum ruderale I collected four shoots of a non-fruiting Ephemerum. Under the microscope, the broad leaves, strong costa, prominent 'shoulders' and some cells in divergent lines all point to Ephemerum cohaerens. This would represent the first Welsh record (and an atypical habitat), so will shortly go to the referee for confirmation (subsequently confirmed by Sharon Pilkington)

Ephemerum cf. cohaerens and location

Lastly, I had a crawl about on the Bug Farm heathland creation project area that I designed and 'built' last winter. Pleasing to see plenty of open, damp clay as well as heather and gorse germinating well from the mowings from the adjoining Waun Fachelich. Ephemerum crassinervium ssp. sessile and Acaulon muticum were good early results here, amongst the abundant Trichodon cylindricus, Tortula truncata, Pseudephemerum nitidum and other pioneer species.

Heathland Creation field at the Bug Farm