Vegetation hardly affected by extreme fl...( This release is available in A HREF ...)

Dessau. Extreme flood events in floodplain grasslands affect carabid beetles and molluscs more than plants. This is the finding of a study by biologists from the Helmholtz Centre for Environmental Research (UFZ), TU Berlin, the German Federal Institute of Hydrology (BfG), KON Kallmnz and the ILN Bhl, following several years of observations before and after the Elbe floods of August 2002. Flow variations are known to be most important drivers in structuring riverine communities. However, until now, the effects of extreme flood events on the flora and fauna of floodplains have been largely unknown, despite the fact that such events are likely to become more frequent as a result of climate change, say the researchers, writing in the latest issue of the journal "Ecology". They surveyed plants, carabid beetles and molluscs in spring and autumn at 36 plots on an Elbe floodplain grassland that was flooded in 2002. Data from 1998 and 1999 were compared with data from 2003 and 2004.

The samples were taken from marked plots in riverine grassland near Dessau (UNESCO-Biosphere Reserve Riverine Landscape Elbe - Saxony-Anhalt) measuring almost one square kilometre which is flooded seasonally by the Elbe. During the 2002 flood these plots were submerged for at least two weeks, with the water height ranging from 2.4 to 5.4 metres above soil level.

"Our findings show that the mollusc and carabid beetle communities were the most severely affected by the floods," explains Christiane Ilg of the UFZ. "This disproves the hypothesis that groups with lower mobility are more severely affected by floods being less able to escape, and that they recolonise the flooded habitat only after some delay." The number of carabid beetles fell from 117 species before the flood to 88 immediately after the flood, but had recovered by 2
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