Poor fen

Poor fen occurs where the ground is permanently wet with nutrient-poor water which is somewhat acidic. It occurs around springs on mountain slopes, in places where neutral water enters more acidic bogs, and in complex with wet acidic grassland.[1]

The organic soils of poor fens are composed of peat.[2] As with all peatlands, the rate of plant decomposition is slower than accumulation under wetland conditions. As the peat surface thickens, the plant community changes in response to lower nutrient availability, and increasingly acidic and anaerobic chemistry.[3]

Poor fen is usually grazed by wild animals or livestock, which prevents ecological succession to wet woodland.

Natural disturbance factors influencing poor fens include fire, flooding, windthrow, and insects. Similar to grazing, a natural fire regime can prevent succession to woodland. In the absence of fire, a thick layer of leaf litter can encroach on the open mire which in turn stifles fen vegetation.[2]

The marsh cinquefoil (Potentilla palustris)

Poor fens are covered with peat-forming Sphagnum mosses[3] such as Sphagnum angustifolium, Sphagnum fallax and Sphagnum magellanicum, while other brown mosses can also be frequent, such as Polytrichum strictum. Mosses combine with a high abundance of sedges such as Carex canescens, Carex echinata, Carex nigra, Carex lasiocarpa, Eriophorum scheuchzeri (white cottongrass) and Trichophorum cespitosum (tufted bulrush). Other abundant plants are Andromeda polifolia (bog-rosemary), Betula nana (dwarf birch), Dactylorhiza maculata (heath-spotted orchid), Eriophorum vaginatum (hare's-tail cottongrass), Potentilla erecta (common cinquefoil), and Vaccinium oxycoccos (bog cranberry).[1]

• Bog
• Fen
• Marsh
• British National Vegetation Classification
• Mires in the British National Vegetation Classification system (see especially M5 to M14, and M31 to M38)