COUNTRYSIDE COUNCIL FOR WALES
SITE OF SPECIAL SCIENTIFIC INTEREST: CITATION
YNYS MÔN CAEAU TALWRN
National Grid Reference: SH487764 & SH476773
Site Area: 24.8 ha
Caeau Talwrn are of special interest for their neutral grassland and mire vegetation. The site comprises a complex of small enclosures to the south and west of the village of Talwrn situated on glacial drift in the upper catchment of the Afon Cefni. The heterogeneous nature of the drift and topography together with the local occurrence of base-rich springs and seepage lines has given rise to a complex mosaic of vegetation types varying with the impedance of the drainage. The vegetation of this site is of particular interest as it includes not only dry neutral grasslands and various types of mire especially rich-fen, fen-meadow and rush pasture, but also shows the transitions between the various types particularly well.
The dry grasslands are largely restricted to the enclosures to the south of the village. These are of the crested dog's-tail Cynosurus cristatus - black knapweed Centaurea nigra type and include two different sub-communities: meadow vetchling Lathyrus pratensis and the heath grass Danthonia decumbens. These grasslands support a profusion of grasses and herbs. Amongst the most prominent grasses are common bent Agrostis capillaris, crested dog's-tail and red fescue Festuca rubra while herbs include black knapweed, autumn hawkbit Leontodon autumnalis, common bird's-foot trefoil Lotus corniculatus and red clover Trifolium pratense. The locally uncommon fern adder's tongue Ophioglossum vulgatum is found within the meadow vetchling sub-community while smooth brome Bromus racemosus occurs locally within both sub-communities. These grasslands gradually merge into wetland communities as species such as ragged robin Lychnis flos-cuculi, rushes Juncus spp, purple moor-grass Molinia caerulea and meadowsweet Filipendula ulmaria become more prevalent.
There are extensive areas of purple moor-grass - meadow thistle Cirsium dissectum fen-meadow in the east of this site; these are dominated by purple moor-grass with frequent small sedges such as tawny sedge Carex hostiana and flea sedge Carex pulicaris. Despite the name of this community, meadow thistle is not found here. Where the ground is flushed with base-rich water, particularly in the north-western fields, black bog-rush Schoenus nigricans is found in stands of black bog-rush - blunt-flowered rush Juncus subnodulosus mire. Locally uncommon species such as fragrant orchid Gymnadenia conopsea and marsh helleborine Epipactis palustris can be found in this area.
The wetter areas of land with a high water table are dominated by blunt-flowered rush which forms the main component of blunt-flowered rush - marsh thistle Cirsium palustre fen-meadow. Within these areas meadowsweet is locally abundant and species such as wild angelica Angelica sylvestris and sneezewort Achillea ptarmica are frequent.
Other forms of rush pasture within this site, are dominated by soft rush Juncus effusus and, more locally, hard rush Juncus inflexus with a wide range of other species including greater bird's-foot trefoil Lotus uliginosus fleawort Pulicaria dysenterica and purple loosestrife Lythrum salicaria.
In the southern part of this site the hedge banks support excellent populations of Aquilegia vulgaris.