Beach and Dune - Gower - page 157

FIG 86. Southern marsh-orchid, a plant of the dune slacks. (Harold Grenfell)
ThefloraoftheduneslacksatOxwichandWhitefordisparticularlyrichandthesouthernmarsh-orch-
id Dactylorniza praetermissa (Fig. 86), early marsh-orchid D. incarnata and marsh helleborine Epipactis
palustris , the horsetail Equisetum variegatum and the sedge Carex serotina grow at both sites. The bee
orchid Ophrys apifera (Fig. 87) and green-flowered helleborine Epipactis phyllanthes are also occasion-
ally found in this habitat.
Many of the rarer plant species found at these sites are linked to specific phases in the early develop-
ment of dune-slack communities, but the larger dune systems in Gower such as Whiteford and Oxwich
are now highly stabilised with only a small proportion of bare sand, little wind-generated erosion and ex-
tensive areas of dune grassland and scrub. For instance the fen orchid (Fig. 88) is confined in Britain to
damp calcareous dune slacks and fens, and the dune slacks of South Wales hold more than 90 per cent of
the British population, the number ofBritish sites having declined fromoverthirty tojust eight. Evidence
suggests that the major reason for the decline in fen orchid populations is the loss of young dune-slack
habitats due to undergrazing and stabilisation and lowering of water tables. It means that the populations
at Whiteford and at Kenfig Dunes (to the east of Gower) are the largest and most important in Britain.
While in the fens of eastern England the fen orchid consists of the typical comparatively narrow leaved
form, the form found in the Gower dune is shorter and broader-leaved.