Variability and classification of Carpathian calcium-rich fens

Calcareous and rich fens harbour the unique biodiversity of plants invertebrates. They are extremely sensitive to landscape changes because their island nature. In Carpathians, they still well-preserved, but number has substantially decreased. Knowledge about variability classification into vegetation units, a baseline for efficient nature conservancy, is insufficient in Eastern where phytosociology used different methodologies than Western Carpathians. It resulted artificial boundaries distribution types low compatibility with modern European habitat schemes. Here we gathered large set vegetation-plot records, sampled by unified sampling protocol. The aim was uncover principal variation compositional data, identify resulting clusters hitherto reported create system adjusted entire Carpathian territory. line previous ecological studies, unsupervised classifications (Twinspan, beta-flexible clustering method) largely mirrored base saturation gradient distinguished between relict younger fen grasslands. We defined formally cores 10 units well reproduced them as prototypes semi-supervised k-means clustering. final essentially correspond phytosociological associations, five being first time Romania. These were well-separated coordinate analysis, whose axis separated from grasslands, while second followed water level largely. Groundwater pH conductivity contributed forming significant gradients. Climate (temperature, precipitation, hot days above 30 °C) specific edaphic conditions diversification types. Our analyses supported grasslands both tufa-forming peat-forming ones, belonging associations Habitat Directive occurring all countries including Romania, rather having single separate Eastern-Carpathian association. provide strong evidence distinguishing Sphagno warnstorfii-Tomentypnetalia order its alliances warnstorfii-Tomentypnion nitentis, Stygio-Caricion limosae Saxifrago hirculi-Tomentypnion latter missing other countries. will make calcareous applicable continental