Invertebrate survey at Gunpowder Park, the former Royal Ordnance Site in the Lee Valley
Other particularly interesting areas of older grassland include a triangular area at the northwestern
edge of the osier area, the area to its west on the opposite side of the track where foundations remain
and the northern edge of the Osier Marsh.
New grasslands
A lot of the substrate appears poor, with a sand and gravel component. There is also a calcareous
influence from the presence of flints. Both these features will help in the establishment of diverse
vegetation long term.
The new developing grasslands currently contain a good proportion of sparsely vegetated ground.
Arca B2 is a good example of grassland that should become increasingly important for invertebrate
populations, as long as some form of disturbance management is used to maintain a proportion of
bare ground. There are varying amounts of White and Red Clover, some Bird's-foot-trefoil, Kidney
Vetch, melilots and a reasonable amount of Carrot and Bristly Ox-tongue, all important resources
to different species of invertebrate. Any regular cutting regime of these grasslands, unless on a
rotational basis, will drastically reducing their value, both in terms of forage and in terms of leaf,
stem, pollen and seed resources etc.
Slopes, especially south facing, are valuable features, especially if they contain areas with bare
ground (Plate 12). The mini 'river valley1 systems also currently have a large proportion of bare
ground. Winter flooding of these should help prevent their loss to rapid colonization, and their
seasonal wetland nature is likely to develop a valuable fauna.
Osier Marsh
The PFA ponds (Plate 14) are a key feature of this area and the whole site as it presently stands. The
seasonally exposed edges and algal mats are an extremely important habitat for many ground beetles,
including for example Bembidion obliquum new to Essex (Harvey 2002). By the end of the season
the two ponds become almost completely dry and it could become a problem in the future to
control succession to woodland.
The marshy vegetation developing beyond the pond edges is an important habitat. There arc useful
plants present here including Angelica Angelica sylvestris, Purple Loosestrife Lythrum salicaria.
Willowherb Epilobium, Gipsywort Lycopus europaeus, figwort Scrophularia and mint Mentha.
A creek area joining the two PFA ponds is valuable habitat whilst it remains open - there was
plenty of mint in flower and a large willow with a trunk in the sun on the north side of the creek
could have good bark fauna. The western pond has interesting raised gravelly islands and northern
edge.
The ride that has been cut into the woodland between the northern edge of Osier Marsh and the
eastern PFA pond provides a valuable ground flora far richer than the more shaded adjacent
woodland. This is a habitat that could usefully be increased.
The older osier and birch provides a large extent of wet woodland habitat, but the open edge
habitat is crucial to many species, including the adults of dead wood feeders such as the Musk
Beetle Aromia moschata. It should therefore be a priority to maintain as much open and woodland
edge habitat as possible.
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Essex Naturalist (New Series) 21 (2004)