Fen Management Handbook - Scottish Natural Heritage

The temptation to burn large areas is considerable. Natural England does not
consent fen management by burning in the Broads, except when it is considered an
appropriate part of restoration to commercial cutting regimes.
Mowing
A variety of rotations have been used, from annual cutting up to about once every
ten years.
Annual or biennial cutting can produce a type of species-rich fen meadow (M13,
M22) where the Phragmites canopy is replaced by Juncus subnodulosus, albeit
at the cost of losing the prized S24 communities. Species-rich fen meadow is
now a rare vegetation type within the Broads. However, regular cutting is required
to prevent the formation of a thick mat of Juncus litter, which can suppress many
smaller species. Disadvantages include:
– Frequent cutting can destroy tussock structure; in low-lying fens, this can result
in a reduction in species richness.
– Disposal of arisings – apart from the lack of demand, disposal of the material
off-site is seldom possible, due to physical difficulties of moving the material
over soft, wet peat soils without causing considerable structural damage,
as well as the resource needs for these labour-intensive operations. On-site
disposal, whether by burning in bonfires or composting, produces local nutrient
enrichment and consequent vegetation changes.
– Lack of continuity and physical structure due to frequent cutting is
disadvantageous to invertebrate communities.
– Operation is labour-intensive.
Despite these disadvantages, the rarity of these fen meadow communities
means that this form of management is still considered worthwhile in small, more
manageable patches. It is worth noting that once established by cutting, these
communities can largely be maintained by low-level grazing as described below,
which can allow the tussock structure to recover.
Longer-rotation cutting (5 – 10 years) maintains the S24 communities by
periodically opening up the surface to allow many component species to germinate
from seed, while removing woody growth and hence retarding succession to scrub
and woodland.
Disadvantages include:
– Disposal of arisings: leaving cut material on the fen can produce a dense litter
mat which suppresses germination and growth of many species, while on-site
disposal can cause local nutrient enrichment problems. Machinery such as the
Broads Authority’s fen harvester can blow chopped litter some distance, but the
ultimate disposal problem may just be moved to another part of the floodplain.
– Quantities of woody material from 5-10 years of scrub growth can also present
disposal problems.
– Large-scale catastrophic management: because of the areas involved (typically
compartments of up to 5 ha), operations involving machinery tend to be on
a fairly large scale. This presents problems for many invertebrates which
can be slow to recolonise, while the uniformity of habitat which results may
disadvantage some species. This can be overcome by techniques such as
cutting in strips.
– Labour-intensive.
Low-level grazing, using traditional breeds, seems to be an effective way of
managing these areas. At Woodbastwick Marshes, part of Bure Marshes NNR,
four Highland cattle have been grazing 25ha of tall-herb fen since 2000.
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