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| Breckland |
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| Habitat: Standing open water and canals (of national significance) |
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Includes natural water bodies (e.g. lakes and meres) and man-made water bodies (e.g. canals, reservoirs and gravel pits) and their adjacent wetland habitats.
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There are twelve semi-permanent meres in Breckland with a fluctuating water level, all inNorfolk. The best known are Ringmere and Langmere at East Wretham Heath, the firstNature Reserve in Breckland, the Devil's Punch Bowl and Fowlmere in the Stanford TrainingArea. These unique hydro-geological features are also biologically important systems fed bybase-rich groundwater with no in-flow or out-flow streams. The direct connection with theaquifer leads to seasonal fluctuations in water levels in the meres, low in mid-winter andhigher in the summer, reflecting a lag in recharge from winter rains. Longer climatic cycleslead to the meres drying completely in some years as has happened up to seven times thiscentury. In the dry years of 1859-1862 and 1900-1903 crops were grown in the beds ofLangmere and Fowlmere.
Unlike almost all other inland freshwater bodies the meres are naturally self-sustaining withno tendency to grow over with swamp, reedbed or woodlands. Instead the fluctuating waterlevel constantly destroys established vegetation and creates bare mud for fresh colonisationby a number of rare and local plant species which require low competition and low nutrientlevels.
In the flooded state the meres are characterised by pondweeds and stoneworts. In the dryphase the vegetation occurs as concentric rings of different plant communities with two rarebryophytes (a moss and a liverwort) living on exposed bare mud. The invertebrate fauna alsoincludes rare species and a highly characteristic group of species which can survive dryperiods either by burrowing into damp soil or because they form a desiccated egg stage whichawaits the re-wetting of the system. Two such species are known in Britain only from themeres. The bird life of the Meres is rich in wildfowl in the water-filled years, especially littlegrebe, tufted duck, gadwall, pochard, and the occasional shelduck.
A number of other water bodies are called meres in Breckland but these differ fromfluctuating meres in being rainwater-fed. These meres, for example those in Wretham Parklie on lenses of clay and are not primarily groundwater fed nor show the marked rise and fallin water levels. As a consequence they lack the characteristic species of the fluctuatingmeres. Meres were a focus of early human settlement and frequently have archaeologicaldeposits around, and sometimes in them.
Three open pingo systems, extensive areas of pits and pools, survive in the natural area today,relicts of tundra-like conditions 20,000 years ago. These are at Thompson, Foulden and EastHarling Commons. Similar systems occur at five or more other sites such as Hills and Holes(Great Hockham), Breckles Heath and Frost's Common which are now covered inplantations, making interpretation difficult. Pingos also occur extensively in the StanfordTraining Area, some in open grassland but many obscured by a dense scrub woodland. Another fine system occurs at East Walton Common just outside Breckland.
Pingos at the three main sites in Breckland contain varying amounts of water. Some areover-grown, filled with willows and nearly dry, whilst others are permanently wet with openwater and fen vegetation. Water supply from below varies from one pingo to the next. Openpingos with marked fluctuations in water level have low growing vegetation with mints,marsh pennywort, bogbean and carpets of mosses. Others have tall fen vegetation of reed,saw sedge, and tussock sedges. Water violet fills some of the pingos producing a floatingpink flowered spectacle in May and June, whilst bladderwort, fen pondweed and amphibiousbistort are other characteristic aquatic species. Damp areas are flower-rich too, and includethe lovely marsh helleborine and other marsh orchids.
These features have a remarkable range of invertebrates, especially water beetles more typicalof far northern latitudes, which may therefore be glacial relicts in a glacial relict landscape. These are "mini mammoths" alive and well in Breckland as long as their pools remain fedwith nutrient poor water. These sites, Thompson Common especially, are vibrant withdragonflies and damselflies in summer. Pingos are excellent breeding sites for amphibiansand are especially notable for their populations of great crested newts, toads and commonfrogs.
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