Environmental determinants of variation in Czech Calthion wet meadows:: a synthesis of phytosociological data

A comprehensive data set of Czech wet meadow vegetation (Calthion alliance) and relevant environmental data were collected and published by E. Balatova in 1972-1997. This paper presents a synthesis of this phytosociological data set with the aim of (i) finding the main gradients in Calthion wet meadow vegetation and relating them to soil chemistry factors, (11) comparing soil chemistry within different soil depths and various vegetation types and (ill) evaluating each soil chemistry variable with respect to its ability to explain variation in wet meadow vegetation. Correspondence analysis revealed that vegetation changes along two major gradients of the same importance: (1) from species-rich communities to the species-poor, tall-forb communities of highly-productive habitats and (ii) from neutrophytic communities to acidophytic communities, mostly of mountain habitats. The first PCA axis of environmental variables is clearly identified as the axis of acidity, the second one as the axis of nutrients. The factors connected with soil acidity and base saturation (e. g. pH, H+, Al3+, Ca2+) are inter-correlated, and they are the most important of the measured factors for vegetation composition. This is also reflected in traditional phytosociological classification. Nutrients (N, P, K) are also inter-correlated and explain less, but still a very significant part of vegetation variation. However, the Filipendulenion communities, which often developed after cessation of mowing or as a result of eutrophication, are only weakly differentiated according to the amount of available soil nutrients. This apparent paradox is presumably caused by nutrient depletion during the development of these highly-productive stands. A relationship between their development and calcium concentration in the topmost soil layer has also been found.