Yanal Bog
Encyclopedia
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.
s and clay alluvium. Above this sits a layer of peat
. This results in a high water table
, creating a distinct domed landscape feature.
, and support two species, Black Bog-rush (Schoenus nigricans) and Blunt-flowered Rush (Juncus subnodulosus), 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 (Molinea caerulea) and Carnation Sedge (Carex panicea) 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 (Carex acutiformis) and Greater Pond-sedges (C. riparia). Common Reed (Phragmites australis) and Marsh Horsetail (Equisetum palustre) 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 (Carex pulicaris), Saw-wort (Serratula tinctoria), Meadow Thistle (Cirsium dissectum), Marsh Valerian (Valeriana dioica), Dyer’s Greenweed (Genista tinctoria), Marsh Arrowgrass (Triglochin palustris), Southern Marsh-orchid
(Dactylorhiza praetermissa), Fen Bedstraw (Galium uliginosum), Devil’s-bit Scabious (Succisa pratensis) and Tawny Sedge (Carex hostiana) and Tufted-sedge (Carex elata).
Hectare
The hectare is a metric unit of area defined as 10,000 square metres , and primarily used in the measurement of land. In 1795, when the metric system was introduced, the are was defined as being 100 square metres and the hectare was thus 100 ares or 1/100 km2...
biological Site of Special Scientific Interest on the southern edge of the North Somerset Levels
North Somerset Levels
The North Somerset Levels is a coastal plain, an expanse of low-lying flat ground, which occupies an area between Weston-super-Mare and Bristol in North Somerset, England...
, just north of the village of Sandford
Sandford, Somerset
Sandford is a village between Churchill and Banwell on the A368 in North Somerset, England.The Parish of Winscombe and Sandford, centred around the Parish Church of Saint James, includes the villages of Barton, Oakridge, Sandford, Sidcot and Woodborough....
, North Somerset
North Somerset
North Somerset is a unitary authority in England. Its area covers part of the ceremonial county of Somerset but it is administered independently of the non-metropolitan county. Its administrative headquarters is in the town hall in Weston-super-Mare....
. It was notified as an SSSI in 1988.
Site description
Yanal Bog is a calcicolous lowland mire. Underlying the site are gravelGravel
Gravel is composed of unconsolidated rock fragments that have a general particle size range and include size classes from granule- to boulder-sized fragments. Gravel can be sub-categorized into granule and cobble...
s and clay alluvium. Above this sits a layer of peat
Peat
Peat is an accumulation of partially decayed vegetation matter or histosol. Peat forms in wetland bogs, moors, muskegs, pocosins, mires, and peat swamp forests. Peat is harvested as an important source of fuel in certain parts of the world...
. This results in a high water table
Water table
The water table is the level at which the submarine pressure is far from atmospheric pressure. It may be conveniently visualized as the 'surface' of the subsurface materials that are saturated with groundwater in a given vicinity. However, saturated conditions may extend above the water table as...
, creating a distinct domed landscape feature.
Biological Interest
The plant communities of the mire are nationally rare in BritainGreat Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...
, and support two species, Black Bog-rush (Schoenus nigricans) and Blunt-flowered Rush (Juncus subnodulosus), 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 (Molinea caerulea) and Carnation Sedge (Carex panicea) are abundant species, and this part of the mire is characterised by the presence of a number of species which favour base-rich
Base-rich
Base-richness in ecology is the level in water or soil of chemical bases, such as calcium or magnesium ions. Many organisms are restricted to base-rich or base-poor environments. Chemical bases are alkalis, and so base-rich environments are neutral or alkaline...
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 (Carex acutiformis) and Greater Pond-sedges (C. riparia). Common Reed (Phragmites australis) and Marsh Horsetail (Equisetum palustre) 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 (Carex pulicaris), Saw-wort (Serratula tinctoria), Meadow Thistle (Cirsium dissectum), Marsh Valerian (Valeriana dioica), Dyer’s Greenweed (Genista tinctoria), Marsh Arrowgrass (Triglochin palustris), Southern Marsh-orchid
Southern Marsh-orchid
The Southern Marsh Orchid or Leopard Marsh Orchid is acommonly occurring species of European orchid....
(Dactylorhiza praetermissa), Fen Bedstraw (Galium uliginosum), Devil’s-bit Scabious (Succisa pratensis) and Tawny Sedge (Carex hostiana) and Tufted-sedge (Carex elata).
Source
- English Nature citation sheet for the site (accessed 15 July 2006)