These are springs in low humus soil layers influenced by chalk This habitat is characterised by the formation of preponderantly small pools on a chalky subsoil. Although the phenomenon often seems unimpressive, a very special habitat with characteristic flora has developed here.
The crucial factor here is the property of the chalk to precipitate out of the water when it emerges from the soil layer and then to form solid structures. Over long periods terraces can form from the chalk deposits over which water flows into a series of small pools down the slope. A distinction is made between the chalk precipitation predominantly caused by abiotic factors (sinter formation) and the biogenic chalk precipitation caused by the extraction of carbon dioxide during the growth of algae and mosses (calcareous tufa).
A thick natural cover of mosses of many species is usually found on calcareous tufa. The high CO2 requirement of the mosses significantly facilitates the precipitation of the chalk as little carbonic acid can form in the water. Tufa springs with colonies of cratoneurions are priority FFH habitats and are therefore under special protection. Areas where such flora are established are often home to rich macrozoobenthos (animal micro-organisms) communities. The sinter springs are normally typified by an almost complete absence of plant and animal life.
These valuable and rare micro-organism habitats which are in an almost unspoilt condition are still not completely understood in terms of their complexity and integration into surrounding habitats; they are therefore the subject of intensive research and protection.