CHOBHAM COMMON NNR - Surrey Wildlife Trust

Mowing
Regular mowing creates an even sward and can favour grass dominance over dwarf
shrubs. As mowing removes only the taller parts of plants, leaving the lower layers of
vegetation and litter layer intact, the effect on the accumulated nutrient stores is
modest. Mown material must be removed off site to reduce nutrients. In one study
the amount of nitrogen removed from the system was equivalent to about five years
of atmospheric input with 44% of the above ground nitrogen removed (Hardtle et al.,
2006) and calculations from inputs and stored nitrogen levels in south east England
suggest that mowing and litter removal could remove about 22% of stored nitrogen or
6-7 years of inputs (Power pers. comm.). Mowing and removal of cut material is
impractical on many parts of Chobham Common, especially on low lying areas and
steep and uneven ground. Mowing uses machinery which is less sustainable than
grazing and burning, and also risks the possibility of soil compaction and possible
erosion, particularly on wetter ground.
Turf stripping
Turf stripping removes the remaining vegetation, the litter and organic layers and
depending how low the machinery is set, part of the A horizon of the underlying soil.
This is an extremely effective way of reducing nutrients, as high levels of nitrogen are
stored in the organic layer and soil A horizon and so the removal of these, as well as
above ground vegetation constitutes a substantial removal of nutrients. This has
been calculated as the equivalent of between 37 and 176 years of nitrogen input.
(Hardtle et al., 2006). Turf stripping can increase species richness and reduce the
cover of Molinia (Backx, El-Kahloun & Meire, 2005). However it can also result in
restoration of a species poor heathland, due to depletion of seed banks from the
stripping process, acidification of groundwater and increases in soil ammonium
concentrations which can inhibit seed germination and reduce seedling survival
There is strong historical evidence that extensive turf stripping was one of the main
traditional practices on Chobham Common (Letter from Bisley churchwardens to the
Poor Law Commissioners, 1838; Agriculture in Surrey, Stevenson W. 1809).
Turf stripping creates bare ground, early successional habitats and areas of open
water which are important components of heathland communities and support a
range of species including woodlark, Formica rufibarbis, water vole, sand lizard,
marsh club moss and the communities found in depressions in the substrates of the
Rhynchosporion. The creation of new areas of bare ground, scrapes pools and
ponds as part of the cycle of management will benefit and maintain biodiversity.
Turf stripping is expensive and produces large volumes of material for disposal,
although this can be offset if turves are used in restoration projects. If carried out on
a large scale or in an insensitive manner turf stripping can be unsightly. There are
also indications that in the long term, use of mowing and turf stripping can lead to
loss of phosphorus and that P limited areas may favour Molinia, but that phosphorus
loss is limited when burning is used. as more P is retained in the ash (Hardtle et al.,
2006). All donor turf sites must also be carefully checked for potential sites of historic
environment value, including Mesolithic flint deposits.
From the point of view of nutrient stripping only, management by occasional burning
or cutting followed by grazing, and a long term programme of turf stripping are
probably the best options for heathland restoration and maintenance.
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