As Heideweiher be natural or semi-natural, weakly acidic and nutrient-poor (oligotrophic) shallow lakes within the primarily saaleglazialen Altmoränen -Sandgebiete in the northwestern Central Europe , respectively.
Origin and development
The origin of the vast majority of the heathland ponds are likely to have been periglacial wind blowouts (deflation troughs): the fine sediments were blown away over the non-drifting and water-impermeable or damming soil layers made of loam , clay or stone , leaving shallow hollows. Some heather ponds also owe their existence to ice bursts at the end of the last ice age , which led to the formation of a dead ice hole or Solls . Others go to a sinkhole ( Valle Moor back). In some rare cases, heather ponds can also have emerged from a constricted oxbow lake, such as B. the Sudendorfer Vennepohl (old arm of the Bever ) or the Blanke Flat (old arm of the Leine ). Many of these ponds have recently been created or restored as open water through anthropogenic use (peat cutting, cattle troughs). An important prerequisite for the development of heath ponds the presence of a water storage layer in the substrate ( Podsol -Ortstein, clay lenses). In the course of time, heather ponds can develop into small heather bogs ( intermediate bogs ) through silting up , which often have raised bog-like vegetation. Under certain circumstances (high precipitation rate or clearly humid climatic conditions) these heather bogs can turn into real, rainwater-fed raised bogs .
Within Germany, heather ponds, which are regionally also known as Schlatt , Flat (t), Päule or Pool, or Pohl ( Low German for "Pfuhl"), are limited to the climatically Atlantic-dominated old moraine sand areas of northwest Germany . They are mainly in the Münsterland ( Kletterpoth , Lasthauser Moor ), in the Senne ( Kampeters Kolk , Langenbergteich , Weckers Heideteich ), on the Lower Rhine ( Black Water ), the Lüneburg Heath ( Stichter See , Ahlftener Flatt ), the Emsland ( Ahlder Pool , Süd-Tannen-Moor , Mickelmeer ) and the Wildeshauser Geest . Heather ponds can also be found in the corresponding landscapes of Denmark , Belgium and the Netherlands . One of the largest in the state of North Rhine-Westphalia is the Black Water near Wesel on the Lower Rhine .
Heather ponds have a specific flora adapted to the nutrient-poor environment. Many of the species found here, such as B. Strandling ( Littorella uniflora ), multi-stemmed swamp rush ( Eleocharis multicaulis ) and the endangered water lobelia ( Lobelia dortmanna ) are dependent on sandy subsoil. They disappear as soon as a layer of mud develops. At the edge of the waters rarely find in need of strong Atlantic climate conditions Marsh St. John's Wort ( Hypericum elodes ) and regularly the bog myrtle ( Myrica gale ), a graze like bushes containing essential oils. The ponds are often surrounded by damp heather , the character of which is the bell heather ( Erica tetralix ), as well as by pipe grass ( Molinia caerulea ). The lung gentian ( Gentiana pneumonanthe ), the marsh bear moss ( Lycopodiella inundata ) as well as round-leaved and mean sundew ( Drosera rotundifolia and D. intermedia ) also grow here . The narrow-leaved cottongrass ( Eriophorum angustifolium ), which is white-fruity in large numbers in early summer , gives the heather dwarfs a peculiar charm.
Because of their mostly small size and low vegetation, heather ponds are of subordinate importance for the avifauna . Little grebes and teal are more common. Fish are completely absent in the rather acidic waters. Among the amphibians , moor and pond frogs and small water frogs are very typical; of reptiles , adder , smooth snake , slow worm and forest lizard inhabit the area around the heather ponds.
Hazard and protection
The existence of the heather ponds is threatened today, particularly by increasing nutrient enrichment from agriculture (including diffuse inputs via the air) and the general lowering of the groundwater.
- Tobias Böckermann : “In search of the old heavenly ponds” (PDF; 599 kB) . Published in: Neue Osnabrücker Zeitung , March 2010
- Claus-Peter Hutter (ed.): Lakes, ponds, ponds and other still waters. Recognize, define and protect biotopes. (Biotope determination books). Stuttgart 1993, p. 13 and 81
- Klaus Kaplan (1993): Risk of heather pond through immissions. On the situation of nutrient-poor still waters and their plant species. - LÖLF-Mitteilungen No. 1/93, pp. 10-17.
- Hans-Gerhard Kulp u. a. (Ed.): Oligotrophic still waters in the north-west German Geest - importance and protection of the Wollingster lake and the Farger Heideweiher (Bremen contributions for natural history and nature conservation, volume 11). Bremen 2019
- Hans-Christoph (1990): Basics for the protection of oligotrophic still waters. - Nature conservation and landscape management in Lower Saxony 22. Hanover.
- Hans-Christoph Vahle (1995): Oligotrophic heather ponds as anthropogenic ecosystems. - Nature and Landscape 70 (7): 295-301.
- Rüdiger Wittig (1980): The protected moors and oligotrophic waters of the Westphalian Bight: vegetation, flora, botanical protection efficiency and care suggestions. - Series of publications by the State Institute for Ecology, Landscape Development and Forest Planning North Rhine-Westphalia, Volume 5. Münster-Hiltrup.