Thursday, 2 February 2017

Glamorgan 2016

These are some extracts from the Glamorgan Botany Group 2016 Excursion Report - with thanks to David Barden (main author), Karen Wilkinson and Julian Woodman.

Cwm Dare & Daren y Dimbath – Saturday 26 March 

There are two species of filmy-fern in Glamorgan, Hymenophyllum wilsonii (Wilson’s Filmy-fern) and H. tunbrigense (Tunbridge Filmy-fern), and our aim on this excursion was to survey their populations at two sites – the first discovered in 2014 by Tim Rich, and the second known for about 100 years.

The recent site is in Dare Valley Country Park, so it was here that nine of us met on a cloudy and occasionally drizzly morning. After a brisk walk up through the park, Tim indicated to us the area high on the screes where four patches of H. wilsonii had been found in 2014 (see Wild flowers of Dare Valley Country Park by T. Rich and C. Gait).

Having listened to Tim describe what we were looking for, Caroline Langdon said “is this it?” and pointed down at the rocks in front of us, where to the astonishment of all some fronds were present! We quickly found lots more, giving us a total of 52 patches, even though we only covered about a third of the area of scree in the time available.

The delicate fronds of Hymenophyllum wilsonii (Wilson's Filmy-fern) at Cwm Dare

The initial idea had been to measure the size of every patch to assess the population dynamics (patches increase radially by about 1–2 cm a year). However, it was very hard to define an individual because the ferns crept through moss, plants and leaf litter between and around boulders, so a crude census was made by plotting GPS locations. Most patches were fertile, and ranged from dense mats on edges of exposed rocks with dwarf fronds 1–2 cm long, to more luxuriant plants with fronds 3–5 cm long in the deep crevices. The patches ranged widely in size too, indicating a long-established and healthy population, and the largest known one in Glamorgan. Other interesting plants seen on the screes, also previously recorded by Tim, were Dryopteris oreades (Mountain Male-fern) and Huperzia selago (Fir Clubmoss). Moving on to the well-known site at Daren y Dimbath, our group of eight botanists contended with some heavy rain to examine the populations of both species there. These appear to be doing well, with a combined total of 22 patches of H. wilsonii and 29 of H. tunbrigense being seen.

A range of sizes of plants were recorded, both species showing the classic exponential declines in numbers of patches with increasing size. However, one medium-sized
patch of H. wilsonii and one huge patch of H. tunbrigense were peeling off the rocks under their own weight, leaving fragments of rhizome in crevices, which were then regrowing. As a result, small patches may not necessarily indicate regeneration from spores. Also found on the rocks were the rare ferns Dryopteris aemula (Hay-scented Buckler Fern) and the gametophytes of Trichomanes speciosum (Killarney Fern) in dark shaded crevices.

Newton Burrows - Sunday 15 May

Fourteen enthusiastic botanists gathered in the car-park at Newton Burrows on a sunny but breezy day, and soon set about investigating the area of rough grassland to the immediate north, where according to online photos, large rocks for sea-defences had been stored in the not-too-distant past. Trifolium scabrum (Rough Clover) was abundant here, and there was also a little Trifolium arvense (Hare’s-foot Clover), Fumaria bastardii (Tall Fumitory) and F. muralis (Common Ramping Fumitory), but a greater prize awaited! A tufted grass with very diffuse panicles got the attention of Tim Rich, and realisation rapidly dawned that we were looking at Poa bulbosa (Bulbous Meadowgrass).

Quite possibly the find of the year! Poa bulbosa (Bulbous Meadow-grass) was frequent-abundant over a substantial area on sandy gravel near Newton Burrows car-park. Unusually for this species, none of the plants were producing plantlets within the spikelents (proliferation). The abundance of the plant meant that we had no qualms about detatching a few of the destinctive basal bulbils for examination. 

Dunes and woodland provided a range of species, and even the lunch stop provided Botrychium lunaria (Moonwort). At the end of the day the coastal shingle just landward of the dune edge provided easier botanising, with the highlight being Valerianella locusta var. dunensis (Common Cornsalad) to round off an enjoyable day.

Valerianella locusta var. dunensis (Common Cornsalad) 

Morfa Ystradowen - Sunday 5 June

On a warm summer’s day with light winds, our group of eight met to examine the western part of Morfa Ystradowen (a former SSSI), with the permission of the landowner at ‘Vale Holiday Homes’. Almost immediately, we found Trifolium micranthum (Slender Trefoil) on a track, but we were forced to pick up speed through the fields to the north-east because of the presence of some rather
curious horses! 

Beyond the old railway, we saw Verbena officinalis (Vervain), a small amount of Adoxa moschatellina (Moschatel), and some typical woodland species, including a range of ferns that permitted a quick training session! Here too, Karen noticed the signs of Ash Dieback, which seems to have become considerably more frequent this year.

The old railway itself was clearly regularly mown, affording a pleasantly shady walk. The wet woodland to the west looked promising (but, we reckoned, probably better in spring), while Berula erecta (Lesser Water Parsnip) was noticed in a ditch on the eastern side. Scrambling down the bank, we emerged into an area of very tussocky grassland that had been subject to a light burning, probably early in the year. Dryopteris carthusiana was again abundant here, but more interesting was plenty of Ulex gallii (Western Gorse), a 2m × 2m patch of Comarum palustre (Marsh Cinquefoil), and a tiny remnant of Sphagnum ‘bog’ with typical acid-loving species.

Comarum palustre (Marsh Cinquefoil) 

Moving off the old railway, a shady track took us through woodland back up to our starting point, where we came across a variant of Blechnum spicant (Hard Fern). Some of the group returned to their  ars at this point, but the rest decided to finish off by examining a field adjacent to the main road. This had presumably been heavily grazed by sheep in the past, because the flora was rather poor and also remarkably uniform. However, Rhinanthus minor (Hayrattle) was abundant, while a few Dactylorhiza fuchsii (Common Spotted Orchid) were found, and the southern end held a population of Myosotis discolor (Changing Forget-me-not) amongst a stand of Bracken.

A lobed variant of Blechnum spicant  (Hard Fern)

Merthyr Common - Sunday 18 September

Meeting at Morlais Top on a largely fine day, our group of eight headed briskly north along a rough track, in order to waste no time in getting to one of our target monads... but we had time enough to notice a clump of flowering Sanguisorba officinalis (Great Burnet) on a roadside, and a few ruderal/waste-heap weeds including Brassica juncea (Chinese Mustard) on the way through Pengarnddu.

Beyond this, the ditch on the eastern side of the track provided some good botanising, with plenty of Triglochin palustris (Marsh Arrow-grass). A stream feeding into this from the east yielded more marsh plants, with highlights being a small quantity of Veronica scutellata (Marsh Speedwell) and more remarkably a population of Persicaria minor (Small Water-pepper). We followed the track up as far as the Nant Morlais, then turned up into the ravine cut by this stream. The cliffs on the southern side looked promising at first, but there was only a very limited tall-herb community here, which included small quantities of Valeriana officinalis (Valerian) and Succisa pratensis (Devil’s-bit Scabious) amongst abundant Luzula sylvatica (Great Wood-rush).

Persicaria minor (Small Water-pepper)

Our next stop was ‘Pitwellt Pond’, which contrary to what the OS map said, we knew to have been drained many years ago. Disappointingly, however, the whole area was a sea of Juncus effusus (Soft Rush), and so we did not spend any time here – instead, we headed west out onto the main area of Merthyr Common. Although not turning up much variety specieswise, this was pleasantly heathery, and in addition we were pleased to find Empetrum nigrum (Crowberry), previously recorded on the Common on just one occasion.

Having previously examined the geological map, we were expecting a transition in rock type as we headed northwest, and passing a couple of ‘shake holes’, it was clear that the limestone was not far below the surface. When it came, the change was remarkably abrupt (see photo), and we then spent some time examining the long-abandoned quarries of Twynau Gwynion. Here we found upland specialities including locally frequent Saxifraga hypnoides (Mossy Saxifrage), and smaller quantities of Cystopteris fragilis (Brittle Bladder Fern), Asplenium viride (Green Spleenwort), and   (Limestone Bedstraw).

Had time allowed, we would have spent longer here, as there was plenty of good habitat in these quarries and on the slopes down to the vice-county boundary. However, we had quite a long walk to get to our cars, so headed back south, crossing the limestone–gritstone boundary again. On the way, we came across a curiously small area of calcareous turf (with typical species) on an embankment next to the cutting of the old tramway that served the quarry. This resulted in the unusual sight of Calluna vulgaris and Cirsium acaule (Dwarf Thistle) growing side by side!

All in all, it was an enjoyable day, with a surprising variety of habitats and some interesting plants too – a good end to the botanical year!

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