Reed beds are a natural habitat found in floodplains, waterlogged depressions and estuaries. Reed beds are part of a succession from young reed colonising open water or wet ground through a gradation of increasingly dry ground. As reed beds age, they build up a considerable litter layer which eventually rises above the water level, and ultimately provides opportunities for scrub or woodland invasion. Artificial reed beds are used as a method of removing pollutants from grey water.
Reed beds vary in the species they can support, depending on water levels within the wetland system, climate, seasonal variations, and the nutrient status and salinity of the water. Those that normally have 20 cm or more of surface water during the summer are referred to as reed swamp. These often have high invertebrate and bird species use. Reed beds with water levels at or below the surface during the summer are often more complex botanically and are known as reed fen. Reeds and similar plants do not generally grow in very acidic water, and so in these situations reed beds are replaced by other vegetation such as poor-fen and bog.
Although common reed is characteristic of reed beds, not all vegetation dominated by this species is reed bed. It also occurs commonly in unmanaged damp grassland and as an understorey in certain types of damp woodland.
Many animals are adapted to living in and around reed-beds. These include mammals such as Eurasian otter, European beaver, water vole, harvest mouse and water shrew, and birds such as Great Bittern, Purple Heron, European Spoonbill, Water Rail (and other rails), Purple Gallinule, Marsh Harrier, various warblers (Reed Warbler, Sedge Warbler etc), Bearded Reedling and Reed Bunting.
Treatment ponds are small versions of constructed wetlands which uses reed beds or other marshland plants to form an even smaller water treatment system. Similar to constructed wetlands, water trickling through the reed bed is cleaned by microorganisms living on the root system and in the litter. Treatment ponds are used for eg the water treatment of a single house or a small neighbourhood.