ASPECTS OF THE POPULATION BIOLOGY OF LIPARIS-LOESELII (L.) RICH. VAR.OVATA RIDD. EX GODFERY (ORCHIDACEAE) IN THE DUNE SLACKS OF SOUTH WALES, UK

Demographic techniques have been employed to study populations of the rare orchid Liparis loeselii var. ovata across a range of dune slack h abitats at a South Wales site. The study has shown that vrey large num bers of shoots (>300) may occur within a single 1 x 1 m quadrat and th at the vegetative production of side shoots is common. Regular populat ion surveys over time have shown that individuals represented by a sin gle shoot can live for 8 years. Subsequent analyses of the Aoristic co mposition of the study quadrats has revealed the presence of subtle va riations in species composition and vegetation structure in relation t o age and hydrology, although all of the plots still fall within the S D14 Salix repens-Campylium stellatum dune slack community defined by t he British National Vegetation Classification. When attributes of popu lation flux are analysed in relation to floristic composition, one sig nificant trend to emerge is that the appearance of new genets is most prevalent in successionally young slacks. As the natural formation of new slacks by sand blow is now a rare event in the South Wales dune fi eld, the management of Liparis loeselii var. ovata is currently aimed at attempting to ensure the persistence of suitable communities throug h biomass reduction techniques. (C) 1998 The Linnean Society of London .