Conservation biology of an endangered grassland plant species, Pseudorchis albida, with some references to the closely related alpine P-straminea (Orchidaceae)

Pseudorchis albida s.s. is today a rather rare grassland orchid with a declining distribution in Scandinavia, as well as in other parts of Europe. This paper presents (a) ecological site descriptions from 30 Norwegian and Swedish sites, and (b) vegetation analyses from five Swedish populations of the closely related, alpine R straminea, which enable sonic, comparisons between taxa. A Detrended Correspondence Analysis ordination of vegetation data separated sites of P. albida rather well according to their geographical location. The Swedish south-west coast sites were particularly distinct. The Norwegian mid inland region constituted a transition zone between sites from the Norwegian west coast and sites from the Swedish eastern mountains. About 10 vascular plant species form a core group, common to nearly all sites. About 150 species occur in lower total frequencies than 50%. It is concluded that P. albida can occur in a wide array of plant communities. A Kendall correlation matrix for environmental variables for the R albida sites and the site's scores along the three first axes in the DCA ordination showed significant correlations between altitude, soil-pH, grazing, precipitation, mowing, ignition loss, and soil-potassium, with vegetation clusters. (C) 2002 The Linnean Society of London.