Floodplain corridor and slope effects on land mollusc distribution patterns in a riverine valley

The aim of this study was to assess the role of river floodplains as biocorridors for terrestrial snail dispersal. We hypothesised that assemblages in the river alluvium should be more homogeneous in species composition than those in the forest slopes above the river. We also studied the effect of rivers as barriers on the assemblage composition of snail species inhabiting slopes of riverine valleys. The study was conducted on 33 woodland plots arranged in three parallel transects in the Tichá Orlice river valley (E Bohemia, Czech Republic). One transect was in an altered river floodplain and the remaining two on the slopes of the river valley.As expected, the median value of the Jaccard similarity coefficient was highest in the floodplain (50%), although significant difference was obtained in comparison with assemblages of only one slope transect. Further analysis showed that snail assemblages were mostly affected by environmental factors such as humidity and soil calcium content; connectivity played rather minor role.