Seed bank and its restoration potential in Estonian flooded meadows

Questions What is the overall restoration potential of the persistent soil seed bank of abandoned flooded meadows? To what degree does the share of typical flooded meadow species in the soil seed bank change during secondary succession from traditionally managed hayfields to stages overgrown by woody vegetation? Location Flooded meadows in Alam-Pedja Nature Reserve, central Estonia (26 degrees 14 ' E, 58 degrees 33 ' N). Methods The species composition of above-ground vegetation and the persistent soil seed bank were investigated with PerMANOVA and non-metric multidimensional scaling in mown, 25-yr abandoned and 50-yr abandoned sedge and tall forb meadows subjected to annual flooding. Particular attention was given to typical flooded meadow species in the persistent soil seed bank. General linear models and non-parametric tests were used to assess successional trends in seed bank richness, density, similarity to target vegetation and percentage of flooded meadow species to assess the restoration potential of the soil seed bank. Results The cessation of traditional management has led to considerable changes in both above-ground and seed bank communities, differences between successional stages being more pronounced in the soil seed bank. The density of the seed bank was higher in abandoned meadows. Diversity in the vegetation and soil seed bank was lowest in the 25-yr abandoned tall forb meadows. Although the soil seed bank similarity to above-ground mown meadows (locally defined target vegetation) was relatively low across different successional stages, the proportion of flooded meadow species in the seed bank remained high - even after 50-yr abandonment, on average 42% of emerged seeds from sedge meadow and 34% from tall forb meadow were typical flooded meadow species. Conclusions Abandoned floodplain meadows in central Estonia still contain a relatively large grassland community species pool, including a large and effective soil seed bank. The soil seed bank could thus play an important role in the restoration of abandoned and overgrown meadow communities. Targeted experiments addressing the optimal techniques for activating the soil seed bank in flooded meadow soil are needed.