Type 2 - Calcareous Fen
Calcareous fens are a rare and distinctive category of Type 2 wetlands. They are characterized by non-acidic peat soil and dependent on a constant supply of cold, oxygen-poor groundwater rich in calcium and magnesium bicarbonates. This calcium-rich environment supports a plant community dominated by "calciphiles", or calcium-loving species, several of which are state-listed as endangered, threatened or special concern.
- Soil: Non-acidic, sedge-derived peat; saturated or nearly saturated during most of the growing season
- Hydrology: Constant, upwelling groundwater; waterlogged within at least a few inches of the surface with scattered small pools and rivulets
- Vegetation: Grasses, sedges, rushes, shrubs, various broad-leaved plants; many rare species
- Common sites: Calcareous fens are found throughout much of Minnesota, with the general exception of the northeast part of the state. They occur at the base of river terraces and glacial lake beach ridges and in other areas where confining layers force mineral-rich groundwater to the surface.
- NWI Symbols: PEMB, PSSB
Because they are so rare, calcareous fens are afforded special protection under the Minnesota Wetlands Conservation Act (Minn. Statutes 103G.223). The DNR maintains an official list of known calcareous fens 
that fall under these regulations. The locations (map points) of these fens are also available as a GIS layer through the DNR Data Deli. Many of the fens are on private land and are not open to public access, however, several are located on DNR Scientific and Natural Areas.
For more information on calcareous fens, see the calcareous fen fact sheet , and the Native Plant Community descriptions for Prairie Extremely Rich Fen (OPp93) and Northern Extremely Rich Fen (OPn93) .