Phytogeographical boundary between the Pannonicum and Hercynicum: a multivariate landscape analysis in the Podyjí/Thayatal National Park, Czech Republic/Austria

The phytogeographical boundary between two major Central European floristic regions is analysed at the landscape scale in the border area between the Czech Republic and Austria. A database of floristic records, potential natural vegetation types, selected environmental variables, and mean Ellenberg indicator values was compiled for a grid of 172 quadrats of approximately 1.2×1.1 km. The data on flora and vegetation were subjected to detrended correspondence analysis to reveal the main gradients, and to cluster analysis to suggest a regional land classification. The patterns revealed by these analyses were related to environmental variables, and cluster analysis of environmental variables was used to produce an environmental land classification. The results indicate that the Pannonicum and Hercynicum are separated by a transitional zone, located on the prominent deforested slope at the edge of the Bohemian Massif. Floristically, this zone is more closely related to the Hercynicum, but according to the environmental land classification it rather belongs to the Pannonicum. This zone possesses some additional unique features not shared with the two main regions, e. g. low proportion of nitrophilous species and occurrence of several species restricted to it. The Dyje/Thaya river valley, which runs roughly perpendicular to the main phytogeographical boundary, does not influence the regional phytogeographical subdivision and belongs to the same phytogeographical region as the adjacent landscape.