Etymology

The word "fen" is derived from Old English fenn. from Proto-Germanic *fanja. Cognates include Gothic (fani), Old Frisian(fenne), Dutch (veen) and German (Fenn(e), Venn, Vehn, Feen, Fehn).^[2]

Fen vegetation

Fen was once thought to be a phase in the natural succession from open lake, through reedbed, fen and carr, towoodland, or as the peat develops and its surface rises, to bog. Now, it is more generally recognised that fens are persistent habitats whose existence is dependent on the availability of water.^{[citation needed]}

Carr is the northern European equivalent of the wooded swamp of the south-eastern United States.^[3] It is a fen overgrown with generally small trees of species such as willow (Salix spp.) or alder (Alnus spp.). A list of species found in a fen therefore covers a range from those remaining from the earlier stage in the successional development to the pioneers of the succeeding stage.

Fen also merges into freshwater marsh, when it develops more in the direction of grassland. This is most likely to occur where the tree species of carr are systematically removed by man for the development of pasture (often together with drainage), or by browsing wild animals, including beavers.

The water in fens is usually from groundwater or flowing sources (minerotrophic) with a fairly high pH (base-rich, neutral to alkaline). Where the water is from rainwater or other sources with a lower pH (more acidic), fen is replaced by vegetation dominated by Sphagnum mosses, known as bog.

Where streams of base-rich water run through bog, these are often lined by strips of fen, separating "islands" of rain-fed bog.

References

• 1. ^ UK Biodiversity Action Plan

  2. ^ Etymonline

  3. ^ Bug Life

Rose, F. Grasses, Sedges, Rushes and Ferns of the British Isles and north-western Europe (1989) ISBN 0-670-80688-9

External links

• Great Fen Project

Categories: Landforms | Soil | Wetlands