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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 [...]

Because of their extreme environment and vulnerability, mires are well able to reflect the ongoing climate change. Northern mires are presently being studied intensively from this point of view. But little is known about the effect of climate change on peatlands in temperate zone. Monitoring of mires in sensitive montane regions of continental Europe can provide valuable information in this regard. This article uses more than 10 years of data from our monitoring to show hydrological and vegetation changes in well-preserved mountain mires. Primary attention has been paid to mire hydrology, especially the water table and its fluctuations, and vegetation, as they are among the key drivers for carbon cycling and ecological processes in peatlands. The results presented reveal a decreasing mean water table level in the studied mires, particularly in ombrotrophic bogs where their distinct microtopographic features show different responses. Minerotrophic fens well supplied by upwelling groundwater present a more hydrologically stable picture. Changes in mire vegetation were also found, the most significant shifts recorded being among wet microtopographic features related to open bog expanses (sedge hollows, lawns). For example, the cover of Warnstorfia fluitans and sedges (mainly Carex limosa) was considerably reduced. In contrast, the vegetation of hummocks (representing the drier end of the moisture gradient) proved to be relatively stable, including the species composition of Sphagnum mosses. [ABSTRACT FROM AUTHOR]