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| The Culm |
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| Habitat: Purple moor-grass and rush pastures (of national significance) |
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Occur on poorly-drained, usually acidic soils, in lowland areas of high rainfall. The distinctive vegetation is dominated by purple moor-grass and rushes.
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Culm grasslands are species-rich pastures, typical of poorly-drained acid soils, supporting asuite of purple moor-grass and rush communities. They typically form a mosaic of vegetationcommunities together with heathland, other species-rich grasslands and wet woodland. Because the habitat type is quite unlike any other habitat found in England they have come tobe called Culm grasslands, named after the Carboniferous Culm Measures on which they arefound.
Nationally this habitat type is known as Rhôs pasture and the UK probably has more of thishabitat than the rest of Europe (with the possible exception of the Republic of Ireland). TheNatural Area is one of the four most important areas for it along with southern Wales (Dyfed,Powys and Glamorgan), south-west Scotland (Dumfries and Galloway) and Northern Ireland(County Fermanagh).
The extent of the habitat in the Natural Area represents more than 8% of the UK resource and80% of that in England. Remaining areas of the habitat in the Natural Area are but a fractionof what once existed. In the Devon section of the Natural Area the habitat now only coverssome 2% of the land area, having been reduced from about 29,500 ha in 1900. The rate ofloss has been particularly acute during the last couple of decades, with overall some 48% byland area lost between 1984-89, of which 87% was due to agricultural improvement, 3% dueto afforestation and 1% due to scrub invasion. In Cornwall the loss is estimated at between64-86% between 1983-1989.
Two of the plant communities (M24c and M16b) commonly encountered within Culmgrassland sites are, within the UK, virtually restricted to south-west England and areconsidered to be of particular conservation significance.
Rush pasture, which may be on seasonally to permanently wet sites, typically supports softrush and sharp-flowered rush with lesser spearwort, marsh bedstraw, greater bird's-foottrefoil, meadowsweet and water mint. Purple moor-grass dominated communities usuallyeither have a tussocky fen character with tormentil, devil's-bit scabious, wild angelica or aheathy character with such species as cross-leaved heath, bog asphodel, common cotton-grassand a range of sedge species. These communities grade in places to bog-type communitiescharacterised by bog-mosses, bog pimpernel, marsh St. John's-wort, marsh pennywort,round-leaved sundew and bog pondweed. Adjacent to rivers and streams, particularly wherethe ground may be waterlogged, tall-fen vegetation is generally prevalent with the distinctivespecies meadowsweet, wild angelica, yellow iris and ragged-robin.
A number of distinctive and often attractive plant species can be found some of which are ofsomewhat restricted distribution. These include heath spotted-orchid, southern marsh-orchid,lesser butterfly orchid, bogbean, saw-wort, meadow thistle, marsh lousewort, pale butterwortand petty whin.
Characteristic butterfly species include the marbled white and small pearl-bordered fritillary,which in a national context are rather uncommon species. Typical bird species includebreeding grasshopper warbler, a nationally declining species and willow tit both of whichhave a regional stronghold in Culm grassland sites. In addition, these sites are noted forbreeding reed bunting and tree pipit and wintering snipe and woodcock.
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