Fen Management Handbook - Scottish Natural Heritage

8.3.4 Bund creation
In some cases it is possible to prevent the input of eutrophic water by isolating the
fen from the source with a surface bund. Bunds built from clay-rich soils are likely
to be relatively impermeable and will also help retain any nutrients which do seep
through. This is only possible:
– if there is another cleaner water source available, such as from a second river
source or from a borehole. This latter approach was taken at Strumpshaw Fen.
Here, the borehole was used for summer water deficit, and river water was
allowed to flood onto the fen into holding areas during the winter when nutrient
concentrations were diluted by higher flow. This technique is presented as a
case study in Hawke and José (1996);
– if the fen is already sufficiently supplied with water from other sources and will not
be severely affected by the loss of this water source;
– If the severed pathway does not fundamentally change the hydrological character
of the site.
In general, bunding should be seen as a last resort to be considered when the
preferable option of improving water quality at source has failed.
8.4 Impact management to reduce the effects of enrichment on fens
Various techniques can be used on the fen itself to reduce the effects of nutrient
enrichment. Depending on the degree of enrichment, the accessibility of the
site and the management budget available, enriched fens may benefit from a
combination of different techniques.
8.4.1 Grazing
Nutrient reduction by grazing relies on transferring nutrients out of the fen system
in the form of dung and urine. In order to achieve nutrient removal, stock is moved
regularly off the fen (preferably daily) to another dry enclosure or pen. This movement
mimicks the traditional infield/outfield system, typical of many heathlands. See
Section 6: Fen Vegetation Management for further guidance on grazing.
8.4.2 Cutting vegetation and litter removal
Nutrients accumulate in the plant tissue as vegetation grows and at the end of the
growing season the above-ground material of herbaceous plants (herbs, grasses,
sedges) dies back. The nutrients within this material may be translocated to the
roots for over-winter storage and re-used the following spring, released back to
the fen system via decomposition or accumulated in fen peat development. On
many sites, all three processes occur simultaneously. The principle of cutting and
removing vegetation off-site is to remove the nutrients in the live plant material
before they are lost/recycled back into the fen habitat.
Cutting should therefore be done at the end of the maximum growth period but
before die-back, which for most species is late July or August. Where accessibility
allows, machinery such as a brush-cutter can be used, and mechanical rakes
are also available. However, on many sites hand cutting or strimming is required
along with hand raking to remove cut material. This can therefore be a very labour
intensive management technique.
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