Invertebrate survey at Gunpowder Park, the former Royal Ordnance Site in the Lee Valley
Cutting just once a year even in the autumn, winter or early spring period will knock out invertebrates
that nest and overwinter in dead herbaceous stems and flowerheads. On the other hand these and
other species often favour habitat with open areas and bare and sparsely vegetated ground.
A management mechanism is therefore needed which can deliver a continuity of all these resources
in as much abundance as possible, but at the same time retain a varied sward height, and periodically
renew bare ground and disturbed areas. Where low level grazing is not an available option then
some form of cutting and/or disturbance regime will become essential. However it should be
recognized that cutting during the summer season will remove forage at a critical time for some
species, and cutting during the autumn-winter-spring period will remove over wintering resources.
This means that on grasslands managed for their invertebrate interest cutting should be undertaken
on a rotational basis, preferably leaving some areas uncut for at least 3-5 years or longer to allow
dependent invertebrate populations to flourish. At the same time deliberate disturbance of a
proportion of the substrate will maintain the presence of bare and sparsely vegetated ground essential
for ground nesting and warmth loving species.
Old grasslands
It is recommended that the old flower rich grasslands are not cut even on a rotational basis, since
these are key reservoirs at the site of grassland invertebrates dependent on plant diversity and
resources such as stems, leaves, pollen, seeds, etc and for species that overwinter in tussocks.
Periodic small-scale disturbance may need to take place in order to maintain a proportion of bare
and sparely vegetated ground. If succession and scrub development takes place, then occasional
scrub removal may be required. The recommended method would be to physically pull up the
scrub, exposing valuable bare substrate, or to use spot painting of a glyphosatc weedkiller such as
Roundup to kill the scrub.
New grasslands
Every opportunity should be taken to create banks, steep slopes and disturbed areas, especially
where there is a higher sand/gravel component to the substrate. This could valuably include the
occasional furrowing of areas within substrate poor grasslands to expose bare ground and
produce a varied topography.
Some areas of grassland developing on poor substrate should be left uncut to encourage a tussocky
structure that might encourage colonization from the nearby Rammey Marsh. As succession and
scrub development eventually takes place, then occasional scrub removal may be required. The
recommended method would be to physically pull up the scrub, exposing valuable bare substrate,
or to use spot painting of a glyphosatc weedkiller such as Roundup to kill the scrub. The rate of
scrub development at Rammey Marsh suggests this kind of management would only become
necessary after at least 10-15 years.
Whilst regular cutting is necessary on amenity areas, it is recommended that most of the grasslands at
the site on poor substrate should be managed with compartments cut on a rotational basis, and some
areas left uncut for at least 3-5 years. This is essential for species that overwinter in dead flowerheads
and stems. These uncut areas could be in the form of wide margins as well as 'islands'. It would not
be especially important where these were placed, or the proportion of grasslands left uncut, as long as
efforts were made to maintain habitat continuity in the form of corridors and a patchwork.
Essex Naturalist (New Series) 21 (2004)
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