Fen Management Handbook - Scottish Natural Heritage

Smaller excavations are preferable because they produce more edge per unit
area than a single large excavation over the same footprint. The length of the
edge is important, as it provides a niche for the establishment of species-poor
swamp communities dominated by lesser bulrush and common reed. A further
consideration is that excavation may impede carbon sequestration through
conversion to open water, and produce dry peat which will oxidise and release
carbon.
Clear conservation objectives will help decide whether species-poor or speciesrich
swamp is required. A species-rich swamp will require management of tall
species such as reed by mowing or grazing. Smaller excavations are also better
because there is less material to be disposed of, and less risk of wave erosion, so
allowing emergent vegetation to re-establish more rapidly from the margins, from
rhizomes and from the newly-exposed seed bank.
New turf ponds have been dug at Woodbastwick Fen and other
localities in the Norfolk Broads using a 360º excavator with wide tracks
and mats to avoid damage to the peat. Smaller (1 ha) excavations, which have been very slow to establish
emergent vegetation.
Removing the accumulated litter and peat to just above the level of the
rhizomes of reed or other species (e.g. reedmace and common clubrush)
will also allow for more rapid re-establishment without creating
large areas of open water. However, Natural England have found in
the Norfolk Broads that re-worked cuttings have been slow to develop
a submerged or emergent vegetation cover, probably because a
significant depth of loose unconsolidated organic silt makes it difficult
for aquatic macrophytes to establish. The restoration of diverse fen
vegetation has been much more successful where the cuttings have
been carried out in ‘virgin’ fen peat. Cutting peat from intact areas in
the Norfolk Broads resulted in relatively rapid re-vegetation with swamp
species such as saw sedge, especially where the water depth was
less than 30 cm deep. It is important to note that creation of the turf
ponds coincided with dry summers in the mid-1990s and there was
little inundation with water whilst the vegetation established. Care
should be taken in areas of virgin peat as this could destroy a unique
archaeological record of that locality.
All turf ponds created in the Norfolk Broads since 1983 have been
monitored, and the results of all surveys during that time reviewed.
These findings are available in a report held by the Broads Authority
“Broadland Turf Pond Surveys 2005 and Analysis of Data 1983-2005”.
Creating shallow areas with water depths of 15 - 20 cm (max 30 cm) will favour
more rapid re-vegetation with reedswamp or other pioneer vegetation.
Removal of the top layers of degraded peat from Redgrave and
Lopham Fen (see case study 5.2) has successfully regenerated
the botanical diversity of areas (Exell 2003). Species that have reappeared
include common butterwort, bog mosses, round-leaved
sundew, black bog-rush, cross-leaved heath (Erica tetralix) and marsh
lousewort. Turf removal has been used successfully at Cors Geirch in
Wales, where localised areas of rich-fen vegetation have established
in association with seepage areas.
151