Fen Management Handbook - Scottish Natural Heritage

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Case Study 6.3
Fen Vegetation Management
– Bure Marshes
Bure Marshes is a 736 ha fen NNR on the Norfolk Broads (OSGR TG337166).
Past management
Prior to the second half of the 20 th century, many areas of the Norfolk Broads
floodplain fens which were not able to be cut for commercial reed and sedge
for thatching were economically important for marsh hay. This was used as feed
and bedding for cattle and horses, and was a valuable resource, due to the high
productivity of the marshes. Changes in agricultural practices, notably the ability
to produce high-nutrient hay from fertilised grass leys and the reduction in the
agricultural labour force with increased mechanisation (not an option on these soft
wet peat soils) meant that most of these areas were no longer cut.
Successional processes and the winter-wet summer-dry water regime allowed
Bure Marshes to develop as a species-rich tall-fen vegetation type (NVC S24,
Peucedano-Phragmitetum australis fen) dominated by reed with the Broads
rarity milk parsley Peucedanum palustris, foodplant of the swallowtail butterfly.
In contrast, lower areas within the floodplain remain wet for more of the year,
inhibiting many plant species other than large monocots and producing speciespoor
reedbeds. Lack of mowing also allows the formation of tussocks, often of
tussock sedge Carex elata, which provides habitat and refuges for plants (and
animals) intolerant of prolonged flooding. These same conditions, however, also
favour colonisation by woody species, particularly alder Alnus glutinosa and grey
sallow Salix cinerea, which, left unchecked, can rapidly convert open fen into wet
woodland.
Management rationale
While wet woodland has its virtues (and much of that found in the Broads is a
feature of European importance), recently-colonised areas of fen are in the process
of losing the open fen interest (swallowtail butterflies being a good example) and
have not yet acquired the wet woodland interest which comes with age and a high
deadwood component. Past conservation efforts have therefore concentrated on
reducing the extent of wet woodland, clearing areas of recent (post Second World
War) scrub and maintaining open fen interest, especially S24 NVC communities.
Techniques
Open fen maintenance initially took the form of large-scale mowing, on the
reasonable grounds that this was the agricultural technique which had formerly
maintained the habitat. Commercial reed and sedge cutting will not be considered
here – they have their own rationale and deal successfully with well-defined
communities.
Burning
While burning standing vegetation can be very effective in regenerating the plant
community, its effect on invertebrates is unlikely to be beneficial across the range
of species. Strip burning can reduce the problem, but requires extensive cutting
of firebreaks, sometimes to the extent that burning the remainder is superfluous.