| Summary: | The vegetation of calcareous rock fissures and crevices, marble screes, and snow-beds on granite, marble and lime-rich schists was studied in the Pirin Planina Mts., SW Bulgaria. Three plant communities of the rock-fissure vegetation were described, including the Hi-eracio pannosi-Caricetum, Leontopodio-Potentilletum stojanovii, and the Silene pusilla-Saxifraga oppositifolia community (both in subalpine and alpine altitudes). The syntaxonomic relations of the communities to the Ramondion nathaliae were discussed. The scree vegetation on marble in the alpine belt is represented by the Papaveri-Armeri,etum (with several subassociations and variants) which populates shady and moist habitats, and the Veronico kellereri-Silenetum prostratae growing on sunny, dry, South-facing screes. They were classified within a new alliance, the Veronico-Papaverion degenii, an endemic unit for Bulgaria. The low-altitude screes were classified within the Bromo lacmonices-Geranietum macrorrhizi (Silenion marginatae). Snow-bed vegetation on silicate bedrock belongs to the Salicion herbaceae. The Ligustico - Plantaginetum gentianoidis (concave relief forms,long-lasting snow cover) and the Omalotheco-Alopecuretum gerardii (convex relief forms, short-lasting snow cover ), were described from this alliance. The marble snow-beds in the Pirin Planina Mts. are classified within the Salicion retusae which includes two associations such as the Bartsio-Salicetum reticulatae and Gentiano-Plantaginetum atratae, characteristic of the long-lasting and short-lasting snow patches,respectively. All of the associations, but the Leontopodio-Potentilletum stojanovii and Ligustico-Plantaginetum gentianoidis, were described as new. All of the communities house many species endemic to the Pirin Planina Mts., Bulgaria and Balkan Peninsula.
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