Yanal Bog


Yanal Bog is a 1.6 hectare biological Site of Special Scientific Interest on the southern edge of the North Somerset Levels, just north of the village of Sandford, North Somerset. It was notified as an SSSI in 1988.

Site description

Yanal Bog is a calcicolous lowland mire. Underlying the site are gravels and clay alluvium. Above this sits a layer of peat. This results in a high water table, creating a distinct domed landscape feature.

Biological Interest

The plant communities of the mire are nationally rare in Britain, and support two species, Black Bog-rush and Blunt-flowered Rush, which have restricted distributions in south-west England, and a number of species which are localised in the Avon area. Surrounding the raised mire is a belt of grassland, and although this is included within the SSSI, it is largely made up of common grass and herb species.
In the community in the western part of the mire, Blunt-flowered Rush, Purple Moor-grass and Carnation Sedge are abundant species, and this part of the mire is characterised by the presence of a number of species which favour base-rich conditions. Black Bog-rush is locally abundant along a wet drainage ditch in this western part of the site. In the eastern part of the mire Purple Moor-grass and Blunt-flowered Rush are again abundant, but the abundant sedge species here are Lesser Pond-sedge and Greater Pond-sedge. Common Reed and Marsh Horsetail are also frequent. This part of the site supports plant species associated with more neutral conditions.
The site has a species-rich flora; species which occur here but are localised or confined to specialised habitats in the Avon are Flea Sedge, Saw-wort, Meadow Thistle, Marsh Valerian, Dyer’s Greenweed, Marsh Arrowgrass, Southern Marsh-orchid, Fen Bedstraw, Devil’s-bit Scabious and Tawny Sedge and Tufted-sedge.