A fen is a type of peat-accumulating wetland fed by mineral-rich ground or surface water. It is one of the main types of wetlands along with marshes, swamps, and bogs. Bogs and fens, both peat-forming ecosystems, are also known as mires. The unique water chemistry of fens is a result of the ground or surface water input. Typically, this input results in higher mineral concentrations and a more basic pH than found in bogs. As peat accumulates in a fen, groundwater input can be reduced or cut off, making the fen ombrotrophic rather than minerotrophic. In this way, fens can become more acidic and transition to bogs over time.
Avaste Fen, Estonia. Sedges dominate the landscape, woody shrubs and trees are sparse.
Wicken Fen, England. Grasses in the foreground are typical of a fen.
Spaulding Fen, Wisconsin.
Small extreme rich fen in southwestern Minnesota. The white flowers, Parnassia glauca, are a fen indicator species in Minnesota.
Peat is an accumulation of partially decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, moors, or muskegs. Sphagnum moss, also called peat moss, is one of the most common components in peat, although many other plants can contribute. The biological features of sphagnum mosses act to create a habitat aiding peat formation, a phenomenon termed 'habitat manipulation'. Soils consisting primarily of peat are known as histosols. Peat forms in wetland conditions, where flooding or stagnant water obstructs the flow of oxygen from the atmosphere, slowing the rate of decomposition. Peat properties such as organic matter content and saturated hydraulic conductivity can exhibit high spatial heterogeneity.
A lump of peat
Peat stacks in Südmoslesfehn (district of Oldenburg, Germany) in 2013
Peat gatherers at Westhay, Somerset Levels in 1905
Peat extraction in East Frisia, Germany