On the beautiful diverse Danube? Danubian floodplain forest vegetation and flora under the influence of river eutrophication

The aim of this study was to investigate and compare the flora and vegetation of three well‐preserved hardwood floodplain forest areas along the river Danube and to discuss whether possible differences between the floodplain forests can be linked to river eutrophication. Flora and vegetation data from three study areas located on the Upper, Middle and Lower Danube in Central and Eastern Europe were compared using univariate and multivariate statistical methods. Special attention was paid to floristic composition, plant functional types, and ecological indicator values. We found that the three studied hardwood floodplain forests appeared to be rather different regarding floristic composition and herb‐layer vegetation. Despite the high beta diversity, the distribution of the plant functional types indicated generally equal habitat conditions, which were quite stable. The diversity of herb‐layer vegetation decreased downstream, while the indicators of nutrient availability pointed to increasing nutrient supply. The factor light apparently played a minor role for herb‐layer diversity. There is a remarkable congruence between the results of our floodplain vegetation analysis and the longitudinal river eutrophication patterns as described in the literature. We conclude that the nutrient input into Danubian hardwood floodplain forests increased downstream, resulting in higher nutrient availability for plants. This promoted especially the growth of tall and competitive forbs, which outcompeted other plant species. Even if the importance of the various eutrophication patterns is difficult to quantify, our study provides evidence that anthropogenic eutrophication has a distinct effect on the flora and vegetation of Danubian hardwood floodplain forests. Copyright © 2010 John Wiley & Sons, Ltd.