Effects of long-term flooding on biogeochemistry and vegetation development in floodplains – a mesocosm experiment to study interacting effects of land use and water quality
Abstract. The frequent occurrence of summer floods in Eastern Europe, possibly related to climate change, urges the need to understand the consequences of combined water storage and nature rehabilitation as an alternative safety measure instead of raising and reinforcing dykes, for floodplain biogeochemistry and vegetation development. We used a mesocosm design to investigate the possibilities for the creation of permanently flooded wetlands along rivers, in relation to water quality (nitrate, sulphate) and land use (fertilization). Flooding resulted in severe eutrophication of both sediment pore water and surface water, particularly for more fertilized soil and sulphate pollution. Vegetation development was mainly determined by soil quality, resulting in a strong decline of most species from the highly fertilized location, especially in combination with higher nitrate and sulphate concentrations. Soils from the less fertilized location showed, in contrast, luxurious growth of target Carex species regardless water quality. The observed interacting effects of water quality and agricultural use are important in assessing the consequences of planned measures for ecosystem functioning (including peat formation) and biodiversity in river floodplains.