Abstract
Abstract. Raising safety levees and reinforcing dykes is not a sufficient and sustainable solution to the intense winter and summer floods occurring with increasing frequency in Eastern Europe. An alternative, creating permanently flooded floodplain wetlands, requires improved understanding of ecological consequences. A 9 month mesocosm study (starting in January), under natural light and temperature conditions, was initiated to understand the role of previous land use (fertility intensity) and flooding water quality on soil biogeochemistry and vegetation development. 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 and biodiversity in river floodplains.
Highlights
In riverine regions in Eastern Europe, both the frequency and the severity of flooding have increased in the last decades (Bronstert, 2003), in regulated rivers systems and in more pristine rivers such as the Vistula and Odra in Poland (Kundzewicz et al, 2005)
We showed that permanent inundation of floodplain sediments significantly influenced both soil biogeochemistry and vegetation development, but that the severity of these redoxrelated changes appeared to be strongly determined by the interactions between soil characteristics, as determined by land use, and water quality
Banach et al.: Effects of long-term flooding our earlier findings on short-term flooding during summer, where flooding itself rather than water quality determined the biogeochemical response and the vegetation development (Banach et al, 2009b)
Summary
In riverine regions in Eastern Europe, both the frequency and the severity of flooding have increased in the last decades (Bronstert, 2003), in regulated rivers systems and in more pristine rivers such as the Vistula and Odra in Poland (Kundzewicz et al, 2005). Because flood prevention by raising dykes seems to be insufficient in the future, new strategies have been proposed which allow creating more space for floodwater by dyke/levee displacement and creation of wetlands and secondary channels. These aim to combine several goals including safety, the restoration of other floodplain functions (land accretion, recreation, water storage), and nature restoration of both riparian wetlands and permanently flooded marshes (Smits et al, 2000; van Stokkom et al, 2005). It is a problem to restore peat forming vegetation (e.g. Carex species) in marshes, which is important to counteract the effects of land subsidence (mechanical compression and oxidation) resulting from agricultural drainage and eutrophication (Wösten et al, 1997; Schipper and McLeod, 2002), this will decrease the hydrological retention capacity
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