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In 1958, 85% of the peat-bog complex Kyselovsky les, in the Czech Republic, was flooded with water from the Lipno reservoir. A new vegetation pattern has spontaneously developed in the newly established shoreline and replaced the original peat-bog vegetation dominated by bog pine (Pinus rotundata Link) forest. This vegetation pattern consists of zonal strips with relatively sharp borders. This zonation is a mosaic of sedge fens, reed canary grass (Phalaris arundinacea L.) beds, tussock cottongrass (Eriophorum vaginatum L.) stands, and a community dominated by ericaceous shrubs. The study focused on the vegetation development of this zonal vegetation. Measurements of the water table level, groundwater pH, and conductivity, together with terrain microtopography, were done to estimate the ways in which the water reservoir influences the mire vegetation. The most important factor is lake water fluctuation, which explained most of the vegetation gradient variability. Lake water fluctuations were represented by lake water levels, which directly flooded a certain part of the gradient from 1990 to 2006 for a known number of days. Key words: sedge fen, raised bog, waterlogging, flooding, Eriophorum vaginatum, Pinus rotundata. Le complexe tourbeux de Kyselovsky en Republique Tcheque a ete inonde sur 85 % de sa surface originale par l'eau du reservoir Lipno, en 1958. Un nouveau patron de vegetation s'est spontanement developpe sur la nouvelle bordure riveraine et a remplace la vegetation de tourbiere originale dominee par une foret de pin des tourbieres (Pinus rotunda Link). Ce patron de vegetation comporte des bandes zonales avec des bordures relativement abruptes. On trouve dans ces zones une mosaique de tourbieres basses a carex, de plages de phalaris roseau (Phalaris arundinacea L.), de peuplement de linaigrettes en touffes (Eriophorum vaginatum L.) et une communaute dominee par des ericacees arbustives. Les auteurs ont etudie specifiquement le developpement de ces zones de vegetation. Ils ont mesure le niveau de la nappe phreatique, le pH et la conductivite des eaux souterraines, ainsi que la microtopographie, afin d'evaluer les facons selon lesquelles le reservoir d'eau influence la vegetation de la tourbiere. La fluctuation de l'eau du lac constitue le facteur principal qui explique la majeure partie de la variabilite du gradient de vegetation. Les fluctuations des eaux du lac s'effectuent selon des niveaux d'eau qui ont inonde certaines portions du gradient, de 1990 a 2006, pendant un nombre de jours connu avec precision. Mots-cles : tourbiere basse a carex, tourbiere haute, saturation en eau, inondation, Eriophorum vaginatum, Pinus rotundata., Introduction The floristic variation of mire vegetation is closely related to ecological gradients. The most serious attempt for classification and synthesis of variation along such gradients was a comprehensive study [...]