Individual study: Creation of small pools for colonisation by white-faced darter Leucorrhinia dubia dragonflies at Chartley Moss NNR, Staffordshire, England
Beynon T.G. (2001) Colonization by white-faced darter Leucorrhinia dubia (Vander Linden) of the East-West Ditch at Chartley Moss NNR, Staffordshire, with notes on its status at other pools. Journal of the British Dragonfly Society, 17, 20-30
In Britain the white-faced darter Leucorrhinia dubia is a rare dragonfly with a disjunct distribution. It has declined in the last 35 years and it is now present at only half of the localities at which it occurred in the mid 20th Century. In Britain it is found at isolated sites from the English Midlands to northern Scotland. Currently there are only five breeding sites in England and it is a UK Biodiversity Action Plan species. Chartley Moss is the most southerly known extant site in the UK and increasing the number of breeding pools on its peatland bog habitat was undertaken in 1988 in an attempt to bolster the population.
Creation of additional breeding pools: The white-faced darter Leucorrhinia dubia, requires relatively deep, oligotrophic, acidic bog pools with semi-submerged rafts of Sphagnum moss at the edges in which to breed. They are confined to waters without fish. Larvae also occur among waterlogged Sphagnum in depressions devoid of open standing water. In an attempt to increase the available breeding habitat, management work was undertaken by English Nature and conservation volunteers at Chartley Moss. In 1988, three small pools (size approx. 1 m x 2 m to 1 m x 3.5 m) were dug out with spades, enlarging cavities that were created during the removal of felled Scot's pine Pinus sylvestris stumps and roots. The new pools were located in the middle of the peat raft on the moss. An additional 10 path-side pools were also excavated.
Colonisation of pools by white-faced darters: Initial success was noted with territorial L.dubia males, copulating pairs and ovipositing females seen in 1989. In 1990, egg-laying was observed at one pool, and three larvae were found in September. However, no adults were seen emerging from any of the pools, though occasional males held territories in some years.
Colonisation of pools by Sphagnum moss: By early 1989, all pools had an almost complete cover of semi-submerged Sphagnum moss. Sphagnum very rapidly filled the pools, which now dry out each summer (too dry for dragonfly larvae to persist).
Conclusions: It is thought that the pools that were dug were too small and shallow, with natural succesion leading to infilling by Sphagnum within two years. This could be perhaps countered with regular moss clearance (by hand-raking) though this would lead to a new problem i.e. the potential removal of L.dubia larvae at the same time. Overall the action was deemed to be unsuccesful.
For further information see:
Bailey M.P. (1992). The White-faced dragonfly Leucorrhinia dubia at Chartley Moss National Nature Reserve. Journal of the British Dragonfly Society, 8, 1, 1-3.
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