Fen Management Handbook - Scottish Natural Heritage

Bog bean growing in a
transitional fen on Orkney
(A. McBride).
Brown mosses are absent from fens receiving water with little or no baseenrichment,
and bog-moss species dominate, particularly Sphagnum fallax, S.
squarrosum, and S. palustre, commonly accompanied by bottle sedge (Carex
rostrata), common sedge (C. nigra) and common cotton-grass (Eriophorum
angustifolium). These fens can be very wet, with a quaking surface. In some
situations, usually in confined basins, a floating raft of Sphagnum and sedges,
sometimes known as a ‘schwingmoor’, develops over water and sloppy peat. At
Wybunbury Moss in Cheshire (see case study at the end of Section 6), the raft
floats over a basin 14 m deep. In some fens, this floating mat grows above the
influence of the groundwater and surface water, and develops vegetation more
characteristic of raised bogs, with species such as round-leaved sundew (Drosera
rotundifolia), cranberry (Vaccinium oxycoccus), and ombrotrophic bog mosses such
as Sphagnum papillosum and S. capillifolium.
Round-leaved sundew and
Sphagnum fallax on the
edge of a pool, Wybunbury
Moss, Cheshire (I. Diack).
Single-species dominated swamps tend to occur in permanent standing water,
ranging from those in base-poor conditions dominated by bottle sedge (Carex
rostrata) or bladder sedge (C. vesicaria), to those characteristic of more nutrient- or
base-enriched conditions dominated by great fen-sedge (Cladium mariscus), large
sedges including tufted-sedge (Carex elata), greater tussock-sedge (C. paniculata),
greater and lesser pond sedges (C. riparia and C. acutiformis), common reed
(Phragmites australis), bulrush and lesser bulrush (Typha latifolia and T. angustifolia).
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