Fen Management Handbook - Scottish Natural Heritage

emoval or soil stripping, both of which remove the litter, plant material (including
roots) and top layers of peat. Either of these operations can simultaneously make
the surface wetter by lowering it relative to the groundwater and create conditions
suitable for the development of more diverse nutrient-poor vegetation. A 360
degree tracked excavator is most commonly used, with preference for relatively
lightweight (12t) machines, ideally on wide tracks. This approach is being used by
the Little Ouse Headwaters Project, http://www.lohp.org.uk.
Area of turf stripping on
Anglesey, where a nutrient
rich rank vegetation was
removed to expose the
base rich and relatively
nutrient poor strata which
can then support a more
diverse range of fen
species (A. McBride).
Turf stripping is to a shallower depth than soil stripping, with only the moss, litter
layer and top few centimetres of peat being removed. Both techniques can also
be useful in bringing the surface level of the peat closer to the current water
table level, re-creating wetter conditions at the peat surface, along with removing
the seed bank of any unwanted plant species. It may, however, also remove any
remnant seed bank of fen species and it is often beneficial to combine soil stripping
with the addition of cut material from a ‘target’ habitat type to encourage rapid
re-establishment. The latter operation is unlikely to cause further enrichment given
that the major nutrient pool is likely to be in the soil, and only a thin covering of cut
material is likely to be needed. This combination of techniques has been shown
to be particularly useful for fen meadow restoration on former agricultural land,
where up to 70% of the target species from the ‘donor’ fen site established on
areas where top soil stripping had occurred before hay spreading, although at small
abundances in some cases (Kilmkowska et al, 2007).
To help gauge the depth of top soil strip, some basic information on nutrients
should be gathered across the site and down the peat profile. Assessing NPK
concentrations at 10cm intervals to a peat depth of 30 to 50cm will help indicate
what depth of top soil needs to be removed to recreate nutrient poor conditions. In
this case, analysis of soil samples for both bio-available (i.e. extractable) and total
N and P, along with pH are useful. These data allow an assessment as to whether
a ‘flush’ of nitrogen or phosphorus might be expected on any associated exposure
to air and re-wetting, respectively. Sampling across the site will help identify if there
are ‘hot spots’ of nutrients or areas of lower nutrient status that might be able to
be retained intact. Chemical analysis of peatland soils should be undertaken on
samples of known volume and the results expressed volumetrically.
The technique is successful even on highly enriched sites such as former arable
land. For example, during fen meadow restoration on mineral soils, removal of
the top 10 to 20 cm of soil depleted total phosphorus concentration by around
85% and also reduced bio-available phosphorus (Tallowin & Smith, 2001). As the
technique actually physically removes nutrients it should only need to be undertaken
once, assuming major nutrient inputs are prevented from building up again. There
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