[Characteristics of soil seed banks in backwater area of Three Gorges Reservoir water-level-fluctuating zone at initial stage of river-flooding].

A germination test was made to study the characteristics of soil seed banks in the backwater area (including the flooded, non-flooded, and control areas of secondary bush and abandoned farmland) of Three Gorges Reservoir water-level-fluctuating zone. There existed significant differences in the soil seed banks between secondary bush and abandoned farmland, with an average seed density being 6991 +/- 954 seed per m2 and 26193 +/- 6928 seed per m2, respectively. Flooded area had the lowest seed density, while non-flooded area had the highest one. The seed density decreased with soil depth. A total of 118 species belonging to 45 families and 97 genera were detected in the soil seed banks of secondary bush and abandoned farmland, most of which were annual and perennial herbage species, belonging to Asteraceae, Poaceae, Scrophulariaceae, and Cruciferae. Among the 118 species, there were 34 species (occupying 28.8%) whose individuals accounted for less than 0.01% of the total. In the soil seed banks of secondary bush and abandoned farmland, the species number was similar, species diversity index and evenness index were relatively high, but the dominant species differed greatly, and the ecological dominance was relatively low. The species diversity in non-flooded area and the ecological dominance in flooded area were the highest, and the similarity index between the flooded and non-flooded areas was the highest.